**U.S. Department of the Interior**

**U.S. Geological Survey**

**Phanerozoic Tectonic Evolution of the Circum-North Pacific**

By Warren J. Nokleberg, Leonid M. Parfenov, James W.H. Monger,

Ian O. Norton, Alexander I. Khanchuk, David B. Stone,

Christopher R. Scotese, David W. Scholl, and Kazuya Fujita

Professional Paper 1626

Abstract

The Phanerozoic tectonic evolution of the Circum-North Pacific is
recorded mainly in the orogenic collages of the Circum-North Pacific
mountain belts that separate the North Pacific from the eastern part of
the North Asian Craton and the western part of the North American
Craton. These collages consist of tectonostratigraphic terranes that are
composed of fragments of igneous arcs, accretionary-wedge and
subduction-zone complexes, passive continental margins, and cratons;
they are overlapped by continental-margin-arc and sedimentary-basin
assemblages. The geologic history of the terranes and overlap
assemblages is highly complex because of postaccretionary dismemberment
and translation during strike-slip faulting that occurred subparallel to
continental margins. We analyze the complex tectonics of this region by
the following steps. (1) We assign tectonic environments for the
orogenic collages from regional compilation and synthesis of
stratigraphic and faunal data. The types of tectonic environments
include cratonal, passive continental margin, metamorphosed continental
margin, continental-margin arc, island arc, oceanic crust, seamount,
ophiolite, accretionary wedge, subduction zone, turbidite basin, and
metamorphic. (2) We make correlations between terranes. (3) We group
coeval terranes into a single tectonic origin, for example, a single
island arc or subduction zone. (4) We group igneous-arc and
subduction-zone terranes, which are interpreted as being tectonically
linked, into coeval, curvilinear arc/subduction-zone complexes. (5) We
interpret the original positions of terranes, using

geologic, faunal, and paleomagnetic data. (6) We construct the paths of
tectonic migration.

Six processes overlapping in time were responsible for most of the
complexities of the collage of terranes

and overlap assemblages around the Circum-North Pacific, as follows. (1)
During the Late Proterozoic, Late Devonian, and Early Carboniferous,
major periods of rifting occurred along the ancestral margins of
present-day Northeast Asia and northwestern North America. The rifting
resulted in the fragmentation of each continent and the formation of
cratonal and passive-continental-margin terranes that eventually
migrated and accreted to other sites along the evolving margins of the
original or adjacent continents. (2) From about the Late Triassic
through the mid-Cretaceous, a succession of island arcs and tectonically
paired subduction zones formed near the continental margins. (3) From
about mainly the mid-Cretaceous through the present, a succession of
igneous arcs and tectonically paired subduction zones formed along the
continental margins. (4) From about the Jurassic to the present, oblique
convergence and rotations caused orogen-parallel sinistral and then
dextral displacements within the upper-plate margins of cratons that
have become Northeast Asia and North America. The oblique convergences
and rotations resulted in the fragmentation, displacement, and
duplication of formerly more nearly continuous arcs, subduction zones,
and passive continental margins. These fragments were subsequently
accreted along the expanding continental margins. (5) From the Early
Jurassic through Tertiary, movement of the upper continental plates
toward subduction zones resulted in strong plate coupling and accretion
of the former island arcs and subduction zones to the continental
margins. Accretions were accompanied and followed by crustal thickening,
anatexis, metamorphism, and uplift. The accretions resulted in
substantial growth of the North Asian and North American Continents. (6)
During the middle and late Cenozoic, oblique to orthogonal convergence
of the Pacific plate with present-day Alaska and Northeast Asia resulted
in formation of the modern-day ring of volcanoes around the Circum-North
Pacific. Oblique convergence between the Pacific plate and Alaska also
resulted in major dextral-slip faulting in interior and southern Alaska
and along the western part of the Aleutian-Wrangell arc. Associated with
dextral-slip faulting was crustal extrusion of terranes from western
Alaska into the Bering Sea.

Introduction

We interpret a Phanerozoic tectonic model of the Circum-North Pacific
(figs. 1, 2) for the orogenic collages along the eastern margin of the
North Asian Craton and the western margin of the North American Craton.
These orogenic collages are composed of tectonostratigraphic terranes
and overlap assemblages (see subsection below entitled "Key Terms...").
The tectonostratigraphic terranes consist mainly of accreted fragments
of igneous arcs, accretionary-wedge and subduction-zone complexes,
passive continental margins, and cratons. The overlap assemblages are
sequences of mainly late Mesozoic and Cenozoic continental-margin-arc
and sedimentary-basin assemblages that were deposited on subjacent
tectonostratigraphic terranes or on terranes and subjacent
cratonal-margin assemblages.

The basic data for the tectonic model are from a regional compilation
and synthesis of a new tectonostratigraphic-terrane map of the
Circum-North Pacific that includes the Russian Far East, northern Japan,
Alaska, the Canadian Cordillera, the U.S. Pacific Northwest, the North
Pacific Ocean, and the Arctic Ocean (Nokleberg and others, 1994a, 1997b,
c). This synthesis, including stratigraphic, faunal, and structural
data, enables correlation of terranes that were tectonically displaced
from one another, grouping of coeval terranes into a single tectonic
origin (for example, a single island arc or subduction zone), tectonic
reconstruction of original positions, reconstruction of paths of
tectonic migration, and interpretation of the tectonic setting of
overlap assemblages, mainly continental-margin igneous arcs, during the
Phanerozoic.

This report reviews what is known and what can reasonably be inferred
about the geology and tectonic evolution of the onshore areas of the
Circum-North Pacific. It consists of three parts: (1) an introduction
and discussion of terms and concepts applied to the components of the
Circum-North Pacific orogenic collage, (2) descriptions and
interpretations of the origins of terranes and overlap assemblages
within the collage, and (3) a model for the Phanerozoic tectonic
evolution of the Circum-North Pacific. This report concentrates on the
onshore geology and tectonics of major terranes and overlap assemblages
that can be related to igneous arcs and subduction zones. Because of the
absence of comparable geologic data, details of the geology and
tectonics of offshore areas, principally the Pacific and Arctic Oceans,
the Canada Basin, the Bering Sea, and the Sea of Okhotsk, are only
briefly summarized herein. Only the important tectonic features are
summarized for cratons and cratonal margins and the terranes derived
from those units. No attempt is made herein to provide complete
references because the literature is enormous and abundant data and
interpretations have been incorporated into numerous, excellent recent
syntheses (for example, Plafker and others, 1989b, Oldow and others,
1989; Gabrielse and Yorath, 1991; Burchfiel, 1992; Monger, 1993; Monger
and others, 1994, Moore and others, 1994; Plafker and Berg, 1994; Monger
and Nokleberg, 1996). This report draws on these syntheses and includes
previously unpublished data that were jointly compiled and interpreted
by the Russian and North American coauthors. Companion reports that
present parts of this tectonic model are those by Natal'in (1993),
Parfenov and others (1993a, b), Monger and Nokleberg (1996), and
Parfenov (1997). Previous oral versions of the paper were presented by
Nokleberg and others (1995b), Parfenov (1995a, b), and Monger and others
(1996).

This report is the result of interpretation of extensive geologic
mapping and associated tectonic studies in the Circum-North Pacific
during the past few decades. These studies suggest that most of this
region consists of a series of fault-bounded tectonostratigraphic
terranes which were accreted onto the northeastern margin of the North
Asian Craton and the northwestern margin of the North American Craton
around the Circum-North Pacific mainly during the Mesozoic and Cenozoic
(Saleeby, 1983; Parfenov, 1984, 1991, 1997; Howell and others, 1985;
Parfenov and Natal'in, 1985; Watson and Fujita, 1985; Natal'in and
others, 1986; Jones and others, 1987; Monger and Berg, 1987; Khanchuk
and others, 1988, 1990, 1992, 1996; Fujita and Cook, 1990; Zonenshain
and others, 1990; Natal'in, 1991, 1993; Silberling and others, 1992;
Sokolov, 1992; Zinkevich and Tsukanov, 1992, 1993; Monger, 1993;
Parfenov and others, 1993a, b, 1995; Moore and others, 1994a, b;
Nokleberg and others, 1994a, 1997b, c; Plafker and Berg, 1994; Tabor,
1994; Monger and Nokleberg, 1996; Sokolov and Byalobzhesky, 1996;
Khudoley and Sokolov, 1998). Earlier tectonic analyses of parts of the
region were published by Box (1985a), Howell and others (1985), Parfenov
and Natal'in (1985), and Plafker and Berg (1994).

This tectonic analysis employs six steps that have been accomplished by
a large international collaborative team for the entire Circum-North
Pacific region (Nokleberg and others, 1994a, 1997b, 1998): (1) define
and utilize a systematic set of tectonic definitions; (2) compile,
synthesize, and interpret a large number of stratigraphic, age, and
structural data to construct regional terrane and overlap-assemblage
maps, with detailed explanations, references, and stratigraphic columns;
(3) perform systematic correlations of terranes and overlap assemblages,
once parts of continuous geologic units, that were tectonically
separated by rifting and (or) strike-slip faulting; (4) perform a
systematic evaluation of correlations and tectonic linkages, as defined
below; (5) systematically evaluate and employ higher quality
paleomagnetic data (where not conflicting with stratigraphic and faunal
data); and (6) construct a tectonic model that is based on the previous
steps and in which the geologic units are scaled proportionally to those
on the regional terrane and overlap-assemblage maps of the region
(Nokleberg and others, 1994a, 1997b). This project also represents the
first attempt by a large group of geologists from Russia, Alaska, and
the Canada to interpret together the tectonic origin of this vast and
geologically complex region of the Earth. The project consists of
several geologists who have each gathered field data and observations in
their respective parts of the Russian Far East, Alaska, and the Canadian
Cordillera over many years and who have been able to work together in a
large international team.

Three groups of figures provide important illustrations for this paper.
The first group of figures (1--4) consists of four generalized
geologic/tectonic maps for the region that are page-size simplifications
of more detailed maps of major terranes, overlap assemblages, oceanic
plates, rifts, major faults, and other major geologic features of the
Circum-North Pacific. These figures are adapted from Nokleberg and
others (1994a, 1997b, c) and Monger and Nokleberg (1996). One pair of
figures (1, 2) shows major terranes; the other pair of figures (3, 4)
shows major igneous-arc-related overlap assemblages and subduction-zone
terranes, mainly of Mesozoic and Cenozoic age. The second group of
figures (5, 6) consists of plots of paleolatitude versus time for
terranes and overlap assemblages in the Russian Far East, Alaska, and
the Canadian Cordillera and for the North Asian and North American
Cratons. Figures 5 and 6 and the companion data in table 3 summarize
vital paleomagnetic data that can be used to interpret paleolatitudes
through geologic time, when not conflicting with stratigraphic and
structural data, in order to define paths of tectonic migrations through
geologic time. The third group of figures (7--20) consists of 14
time-stage diagrams that portray, in schematic plan view, the tectonic
evolution of the region from the Devonian through the present. Another
set of figures, published by Nokleberg and others (1994a) and Greninger
and others (1999), consists of 167 stratigraphic columns for major
terranes in the study area. These stratigraphic columns, along with
detailed descriptions of map units, provide base data for the
delineation of terranes and sedimentary and igneous assemblages and
permit correlations among or between terranes that have common tectonic
environments.

Acknowledgments

We thank the many geologists who have worked with us for their valuable
expertise in each region of Alaska, the Russian Far East, Hokkaido
Island of Japan, the Canadian Cordillera, and the U.S. Pacific
Northwest. In particular, we thank J.N. Aleinikoff, Yu.V. Arkhipov, H.C.
Berg, R.B. Blodgett, S.E. Box, D.A. Brew, M.D. Bulgakova, Ch. B.
Borukaev, D.C. Bradley, Howard Brooks, J. Decker, Cynthia Dusel-Bacon,
H.L. Foster, V.V. Gaiduk, B.M. Gamble, V.V. Golozubov, Arthur Grantz,
D.G. Howell, D.L. Jones, S.M. Karl, S.V. Kovalenko, W.C. McClelland,
E.M. MacKevett, Jr., A.V. Makhinin, M.V. Martynyuk, M.L. Miller, T.P.
Miller, L.Ph. Mishin, E.J. Moll-Stalcup, T.E. Moore, S.W. Nelson, V.S.
Oxman, S.A. Palanjan, I.V. Panchenko, T.L. Pavlis, L.I. Popeko, A.V.
Prokopiev, J.C. Reed, Jr., D.H. Richter, S.M. Roeske, V.I. Shpikerman,
N.J. Silberling, T.E. Smith, the late G.M. Sosunov, A.B. Till, F.F.
Tret'yakov, A.N. Vishnevskiy, I.G. Volkodav, W.K. Wallace, G.R. Winkler,
the late L.P. Zonenshain, and Yu.P. Zmievsky for their many fruitful
discussions. We thank the late Ch.B. Borykaev, the late William R.
Greenwood, Donald Grybeck, B.A. Morgan III, I.Ya. Nekrasov, A.T.
Ovenshine, P.P. Hearn, A.A. Sidorov, T.E. Smith, D.J. Templeman-Kluit,
and W.H. White for their encouragement and support of the project. We
thank T.K. Bundtzen, S.G. Byalobzhesky, A. Grantz, K.G. Mackey, B.A.
Natal'in, L.M. Natapov, G. Plafker, W.W. Patton, Jr., S.D. Sokolov, G.M.
Sosunov, R.W. Tabor, N.V. Tsukanov, and T.L. Vallier for their fine work
and discussions on the detailed terrane and overlap-assemblage map of
the Circum-North Pacific (Nokleberg and others, 1994a) and on the
tectonics of the region. We thank the North Atlantic Treaty Organization
(NATO) for their support to David B. Stone for part of his work on this
study under grant SA 12--2--02 (ENVIR.LG.930919)3912(93)LVdC. We thank
various Russian interpreters, including the late Lidiya I. Kovbas,
Tatyana L. Koryakina, Tatyana N. Velikoda, and Elena V. Alekseenko, for
their skill and assistance during long and complex scientific dialogs
and for translation of complex geologic descriptions and references. We
thank B.A. Natal'in for his participation in the compilation and
synthesis of some of the Russian Southeast part of the terrane map of
the Circum-North Pacific. We thank Stephen G. Crumley for his
compilation of paleomagnetic data. Finally, we thank Dwight Bradley,
Mikhail Kuzmin, JoAnn Nelson, and Andrei Prokopiev for their
constructive reviews of the manuscript.

Associated Studies

This study is part of a project on the major mineral deposits,
metallogenesis, and tectonics of the Russian Far East, Alaska, and the
Canadian Cordillera. The project provides critical information on
bedrock geology and geophysics, tectonics, major metalliferous-mineral
resources, metallogenic patterns, and the crustal origin and evolution
of mineralizing systems of the region for collaborators and customers.
The major scientific goals and benefits of the project are to (1)
provide a comprehensive international data base for the mineral
resources of the region that is the first extensive knowledge available
in English; (2) provide major new interpretations of the origin and
crustal evolution of mineralizing systems and their host rocks, thereby
enabling enhanced, broad-scale tectonic reconstructions and
interpretations; and (3) promote trade, scientific, and technical
exchanges between North America and East Asia. Data from the project
provide sound scientific data and interpretations for commercial firms,
governmental agencies, universities, and individuals that are developing
new ventures and studies in the project area and for land-use-planning
studies that deal with mineral-resource-potential issues. The Russian
Far East part of the project (as well as Alaska and the Canadian
Cordillera) has a vast potential for known and undiscovered mineral
deposits; however, little information existed in English in the West
until the publication of products from this project.

Published major companion studies for the project are (1) a report on
the metallogenesis of mainland Alaska and the Russian Northeast
(Nokleberg and others, 1993); (2) a tectonostratigraphic-terrane map of
the Circum-North Pacific at a scale of 1:5,000,000, with a detailed
explanation of map units and stratigraphic columns (Nokleberg and
others, 1994a; Greninger and others, 1999); (3) a summary terrane map of
the Circum-North Pacific at a scale of 1:10,000,000 (Nokleberg and
others, 1997b); (4) detailed tables of mineral deposits and placer
districts in the Russian Far East, Alaska, and the Canadian Cordillera
in paper format (Nokleberg and others, 1996) and in CD--ROM format
(Nokleberg and others, 1997a); (5) a GIS presentation of a summary
terrane map, mineral-deposit maps, and metallogenic-belt maps of the
Russian Far East, Alaska, and the Canadian Cordillera (Nokleberg and
others, 1998); and (6) a GIS compilation of geophysical, geologic, and
tectonic data for the Circum-North Pacific (Greninger and others, 1999).

A complete listing of the project goals and methods is available on the
Internet/World Wide Web at URL http://minerals.er.usgs.gov/wr/projects
/majdeps.html. Major recent articles on the project (Nokleberg and
others, 1993, 1994a, 1996, 1997a--c, 1998) are available at URL
http://wrgis.wr.usgs.gov/. This project was started at the invitation of
the Soviet Academy of Sciences to the U.S. Geological Survey in 1988.
Subsequently, several organizations and many individuals volunteered to
work on various aspects of the project, producing a large variety of
articles and maps. Other organizations participating in the project
include the Russian Academy of Sciences, ROSKOMNEDRA (now the Russian
Ministry of Natural Resources), the Alaska Division of Geological and
Geophysical Surveys, the Geological Survey of Canada, the Geological
Survey of Japan, the Exxon Exploration Co., the University of Alaska,
and Michigan State University.

Key Terms for Tectonic Analysis of the Circum-North Pacific

Three key terms for this analysis, defined in table 1 along with other
important tectonic terms, are "tectonostratigraphic terrane,"
"accretion," and "overlap assemblage."

> 1\. *A tectonostratigraphic terrane* (hereinafter referred to as
> terrane) is a fault-bounded geologic entity or fragment that is
> characterized by a distinctive geologic history which differs markedly
> from that of adjacent terranes. A terrane can also consist of an
> intensely deformed structural complex bounded by faults. Some terranes
> may be displaced facies of other terranes. Stratigraphic, faunal, and
> paleomagnetic evidence suggests that some terranes originally were
> widely separated from one another, or from the cratons of either North
> America or North Asia, by distances of as much as thousands of
> kilometers (Plafker and Berg, 1994). Other terranes, however, are
> interpreted to be displaced from one another, or from another site on
> the same continent, by distances of only hundreds of kilometers or
> less.
>
> 2\. *Accretion* is the tectonic juxtaposition of two or more terranes,
> or the tectonic juxtaposition of terranes to a cratonal margin, and
> defines a major change in the tectonic evolution of the terranes and
> cratonal margins. Geologic units formed before accretion
> (preaccretionary units) are inherent to the stratigraphy of the
> terrane. Geologic units formed after accretion (postaccretionary
> units) constitute mainly overlap assemblages that formed during a new
> stage in the tectonic evolution of the region.
>
> 3\. An *overlap assemblage* is a postaccretionary unit of sedimentary
> or igneous rocks deposited on, or intruded into, two or more adjacent
> terranes or a cratonal margin. The unit depositionally overlies, or is
> interpreted to have originally depositionally overlain, two or more
> adjacent terranes, or terranes and the cratonal margin. Overlapping
> plutonic rocks, which may be coeval and genetically related to overlap
> volcanic rocks, link or stitch together adjacent terranes, or a
> terrane and a cratonal margin. The formation of an overlap assemblage
> defines a major change in the tectonic evolution of terranes and
> cratonal margins and also provides a minimum age for terrane
> accretion.

In this tectonic model, terranes are delineated according to the
following interpreted dominant types of tectonic environment (table 1):
(1) cratonal; (2) passive continental margin; (3) metamorphosed
continental margin; (4) continental-margin arc; (5) island arc; (6)
oceanic crust, seamount, or ophiolite; (7) accretionary wedge and
subduction zone; (8) turbidite basin; and (9) metamorphic, for terranes
that are so highly deformed and (or) metamorphosed that determination of
the original tectonic environment is difficult to determine. For
terranes with complex geologic histories, the chosen tectonic
environment is the one most prevalent during the history of the terrane.

Method of Tectonic Analysis

To model such a large, widespread, and diverse set of tectonic
assemblages, this study undertakes an empirical approach to terrane
analysis. First, terranes are classified according to major tectonic
environments. Second, correlations are attempted between terranes of the
same tectonic environment, similar age, and similar paleomagnetic
latitudes (for terranes having paleomagnetic data that do not conflict
with stratigraphic and faunal data). Third, igneous-arc terranes (both
island-arc and continental-margin-arc terranes) are grouped or
tectonically linked with coeval accretionary-wedge or subduction-zone
terranes in a manner that is common around the present-day Pacific
margin. In addition, the ancient Pacific margin is interpreted as
broadly similar to the modern margin, that is, as a series of continuous
igneous arcs that separate continents and subducting oceanic plates.

This approach is supported by three lines of reasoning. First, the bulk
of stratigraphic, faunal, and some paleomagnetic data do not require
large separations of most igneous-arc terranes from either North America
or Northeast Asia. Certain exceptions are the truly exotic Tethyan fauna
that occur in the Late Permian Cache Creek subduction-zone terrane in
the North American Cordillera. Second, the ancestral Pacific Ocean is
considered to have resembled the modern one, in that it was bordered
discontinuously by paired igneous arcs and subduction zones. Third, most
igneous arcs and companion subduction-zone complexes did not migrate
across the ancestral Pacific Ocean. A notable exception to the last item
is the Wrangellia superterrane, which originated near the Late Triassic
paleoequator and was accreted to the North American Continent at a
higher paleolatitude during the Cretaceous and early Cenozoic.

Although the incompleteness of the geologic data leaves considerable
paleogeographic uncertainty that increases markedly with the age of
units, the chief result of this interpretative tectonic model is a
series of time-stage diagrams that successively depict the arrangements
of continents, active continental margins, subduction zones, spreading
ridges, and oceanic plates during the Phanerozoic. Our time-stage
diagrams are based on carefully evaluated data that were compiled from
various sources published by a large group of earth scientists. We look
forward to the accumulation of more data and refinement of the tectonic
model presented herein.

Complementary Terms: Terranes and Tectonic Components

Two types of tectonic analysis have been employed to decipher the
disorder inherent along the accretionary margins of continents, such as
the North American Cordillera. One type emphasizes the origins of parts
of the tectonic collage as distinct tectonostratigraphic terranes,
whereas the other type emphasizes the components of the tectonic
collage. These two types of tectonic analysis are complementary.
Analysis of terranes defines the basic units, whereas analysis of
components of collages adds an interpretation to the origin of units.

Analysis of Terranes

Rock associations that are characterized by the tectonic settings in
which they formed, such as cratonal margins, arcs, and ocean basins,
have been used since plate-tectonic concepts first were applied to
Cordilleran geology (for example, Hamilton, 1969). Termed "tectonic
assemblages" (Wheeler and McFeely, 1991; Wheeler and others, 1991),
"tectonostratigraphic elements" (Burchfiel, 1992), or
"tectonostratigraphic terranes" (Jones and others, 1981, 1983, 1984),
they constitute major units of new geologic and tectonic maps of the
Canadian and adjacent U.S. segments of the North American Cordillera.

Regions whose geology and, in some places, stratigraphic, faunal, and
paleomagnetic data differ from those of adjoining regions and from rocks
of the cratonal margin, and which are separated from neighboring regions
by major faults, are called "suspect" or "lithotectonic terranes" (Coney
and others, 1980; Silberling and others, 1992). Delineation of terranes
focuses attention on the nature and times of linkages between them and
shows how the tectonic collage was constructed. The concept long
predates the plate-tectonic hypothesis; terranes are analogous to Alpine
nappes or to the massifs and intervening regions in central Asia, as
described by Argand (1924). Well before terranes were widely promoted,
parts of the Cordilleran eugeosyncline had been identified as "fragments
of Asia" (Wilson, 1968, fig. 6; later the Stikinia, Alexander, and
Sonomia terranes), the "Alexander terrane" (Berg and others, 1972), and
the "Atlin terrane" (Wheeler and Gabrielse, 1972), now part of the Cache
Creek terrane.

Genetic terminology is readily married to terranes (for example,
Silberling and others, 1992). The North American Cordilleran tectonic
collage includes accreted terranes composed of juvenile arc rocks,
ocean-floor deposits and their underlying lithosphere, and
continental-margin terranes containing abundant detritus derived from a
craton (fig. 1). For example, the Cache Creek Complex is a terrane
composed of oceanic offscrapings that were accreted into an early
Mesozoic accretionary complex. Another example, in northwestern British
Columbia, contains four mid-Paleozoic through early Mesozoic arc
assemblages separated from one another by unconformities. The
paleoposition of each arc assemblage is uncertain, but together they
compose the Stikinia terrane, which was accreted during the Middle
Jurassic to form a major component of the North American Cordilleran
tectonic collage. Still other terranes contain rocks representing more
than one tectonic setting, although one setting is generally dominant;
for example, Devonian arc rocks form overlap assemblages on parts of
several passive-continental-margin terranes in the North American
Cordillera.

Analysis of Components of Tectonic Collages

The widely used terrane concept has been strongly criticized by Sengör
(1990), among others. He proposed use of the terms "primary orogenic
collage components" for fragments accreted by closing intervening ocean
basins, and "secondary orogenic collage components" for fragments
displaced within the already-accreted collage by strike-slip or other
large faults. At first sight, the location of major arc terranes (for
example, the Kony-Murgal, Stikinia, and Quesnellia terranes and the
Wrangellia superterrane; see fig. 7), oceanward of an early Mesozoic
accretionary complex, suggests that they are primary components.
However, their locations are known with some degree of certainty only
after they became part of the North American Cordilleran collage and
interacted with other terranes and cratonal-margin deposits, as they did
during the Mesozoic. We argue herein that at least the Mesozoic parts of
the oceanward arc terranes are more likely segments of the same
ancestral Pacific Ocean arc system which were displaced along the North
American plate margin, rather than being separate arcs that migrated
across oceans. Because the distinction between primary and secondary
components may be impossible in practice to make without paleogeographic
control, the term "terrane" is needed in this type of tectonic analysis.
In spite of any terminology differences, our analysis of the tectonic
collage around the Circum-North Pacific is similar in principle to that
put forward by Sengör and others (1993) for the Paleozoic tectonics of
central Asia, although we admit more paleogeographic uncertainty. His
"first-order units" of the Altaid collage are comparable to North
American Cordilleran terranes.

Methods for Correlation, Linkage, and Alignment of Major Terranes and
Overlap Assemblages

Interpretation of the geology and tectonics of the Circum-North Pacific
presents a major challenge because of the complex variety and number of
geologic units in the region and because of the complex tectonic history
of the region. The detailed and summary terrane and overlap-assemblage
maps of this region, which support our tectonic analysis, define 167
terranes, 2 cratons, 2 cratonal margins, 71 overlap assemblages, and 3
oceanic plates (summarized in figs. 1--4; Nokleberg and others, 1994a,
1997b; Greninger and others, 1999). To understand this complex array of
geology and thereby construct a relatively detailed tectonic
interpretation, three major steps are employed: (1) correlation, (2)
tectonic pairing (linking), and (3) alignment of coeval arc and
tectonically linked subduction zones into curvilinear complexes.
Previous correlations of bedrock geology and tectonic activity between
the Russian Far East and Alaska were published by Box (1985a), Howell
and others (1985), Parfenov and Natal'in (1985), and Parfenov (1997).

Correlation of Terranes and Overlap Assemblages

The first major step for this tectonic analysis is the correlation of
similar coeval terranes and overlap assemblages (table 2). Correlation
can be achieved because terranes and overlap assemblages are
working-level geologic entities that are defined by geologic mapping and
stratigraphic analysis. In this tectonic analysis, correlation is
attempted for terranes and overlap assemblages that are interpreted as
having been originally contiguous but have subsequently been
tectonically displaced during rifting or major thrusting, or displaced
along late Mesozoic and Cenozoic strike-slip and thrust faults.
Correlations are attempted for all units (both terranes and overlap
assemblages) that are interpreted to have the same tectonic origin (as
parts of a single elongate passive continental margin, island arc, or
subduction zone), at the same time and adjacent to each other. For some
units, correlated terranes and overlap assemblages do not always exhibit
identical stratigraphy but do share a common age, geographic position
(reconstructed in some cases), and tectonic environment that indicate a
tectonic origin as part of the same continental margin, island arc, or
subduction zone.

An important step for this study is the correlation, where possible, of
cratonal and passive-continental-margin terranes to either the North
Asian Craton or cratonal margin, or to the North American Craton or
cratonal margin. This type of correlation helps establish the Late
Proterozoic and Paleozoic geology of the Circum-North Pacific before
various episodes of rifting and accretion. Correlations are summarized
in table 2 and explained below. Correlations were achieved by Nokleberg
and others (1994a, 1997b) by (1) interpreting tectonic environments for
all major units (figs. 1--4); (2) comparing their geologic
characteristics, including stratigraphic, magmatic, structural,
metamorphic, paleontologic, isotopic, and paleomagnetic data (where not
conflicting with other geologic data) for units with the same tectonic
environment; and (3) comparing the stratigraphy of units as illustrated
in the 167 stratigraphic columns for major terranes and overlap
assemblages around the Circum-North Pacific (Nokleberg and others,
1994a; Greninger and others, 1999). This correlation of terranes and
overlap assemblages (1) illustrates the original continuity of rock
units in the Circum-North Pacific, (2) provides important constraints on
the past tectonics of the region, and (3) constitutes a series of
interpretations to be further evaluated by additional stratigraphic,
geochemical, isotopic, paleomagnetic, and geophysical studies.

Tectonic Pairing (Linkage)

The second major step for this tectonic analysis is tectonic pairing
(linkage) (table 2). Two types of this pairing are utilized in this
study: (1) tectonic pairing of subduction-related igneous arcs, now
preserved as various igneous-arc terranes or overlap assemblages, to
former subduction zones, now preserved as accretionary-wedge or
subduction-zone terranes; and (2) tectonic pairing of belts of
anatectically related igneous rocks and major faults (sutures) that
bound terranes. Tectonic pairings are summarized in table 2 and below.

The first type of tectonic pairing is based on (1) analyzing the
stratigraphy and structure of terranes to determine the tectonic
environment, by defining an igneous arc or subduction zone or a related
tectonic environment; (2) interpreting a physical proximity, as when
specific igneous-arc terranes were originally adjacent to specific
subduction zones; (3) interpreting linkages between collisional foreland
basins and collisional orogens; (4) determining the similarity in age of
formation of igneous-arc and subduction-zone terranes; (5) determining
subduction polarity from tectonic transport direction in a melange for
subduction-zone and accretionary-wedge terranes, where not disrupted by
later deformation; and (or) (6) recognizing the occurrence of disrupted
layers of arc-derived volcanic or volcaniclastic units from a specific
igneous arc, where possible, in the melange of the (companion)
accretionary-wedge or subduction-zone terrane.

The second type of tectonic pairing is based on the spatial and temporal
association of collisional (S type) granitic plutons and associated
volcanic rocks with (1) major fault zones (sutures) between terranes or
between a terrane and a cratonal margin, and (or) (2) belts of highly
deformed, regional-grade metamorphic rocks that occur along the fault
zones. Anatectically related igneous belts are interpreted as having
formed either during the accretion of one terrane to another or during
the accretion of one or more terranes to a cratonal margin.

Alignment of Coeval Arcs and Subduction Zones

The third major step for this tectonic analysis is the grouping of
terranes and overlap assemblages into larger entities that were probably
once continuous igneous arcs and companion subduction-zone (or
accretionary wedge) complexes. Those grouping of coeval units is based,
to varying degrees, on (1) similar stratigraphy, fauna, rock-unit age,
and structure; (2) to a lesser degree, paleomagnetic data; and (3) an
assumption of simplicity. The result of these groupings is the alignment
of coeval igneous-arc overlap assemblages and igneous-arc terranes, and
tectonically linked (companion) accretionary-wedge and subduction-zone
terranes, into coeval, curvilinear arc/subduction-zone complexes. This
philosophy results in the interpretation of single rather than multiple
continental-margin or island-arc/subduction-zone complexes. Alignment of
coeval arcs and subduction zones are illustrated below in various parts
of the tectonic model (figs. 7--20).

Problems of Correlations, Tectonic Linkages, and Alignments

Our correlations, tectonic linkages, alignments of terranes and overlap
assemblages, and the derivative tectonic model will probably change as
additional data are acquired and new ideas are created. Our tectonic
model is more highly developed for the later Mesozoic and Cenozoic
stages when correlations and linkages can be made between the units
accreted to the North Asian and North American Cratons. Some problems
are inherent to the correlation, linkage, and alignment of terranes and
overlap assemblages. For terranes that originated during rifting of
cratonal margins and have since undergone suborthogonal convergence,
terrane correlation is relatively simple. More complex problems arise
when large-scale strike-slip faults interfere with the interpretation of
terrane origin, dispersion, accretion, and postaccretionary history.

Descriptions of Geology, Correlations, and Linkages of Major Terranes
and Overlap Assemblages

A detailed description and interpretation of the geology, correlations,
and tectonic linkages of major terranes and overlap of the Circum-North
Pacific is presented here. Units are described and interpreted in the
following order: (1) continental-margin and cratonal terranes; (2) late
Paleozoic through mid-Cretaceous island-arc terranes of the Wrangellia
superterrane; (3) Triassic through mid-Cretaceous continental-margin
arcs, island arcs, and tectonically paired subduction zones; (4) Late
Cretaceous and early Cenozoic continental-margin arcs, island arcs, and
tectonically paired subduction zones; (5) middle and late Cenozoic
continental-margin arcs and tectonically paired subduction zones; and
(6) linkages between belts of anatectically related igneous rocks and
accretions of terranes. Within each group, the descriptions and
interpretations are presented in counterclockwise order, starting with
the Russian Southeast and ending with southeastern Alaska and the
southern part of the Canadian Cordillera. The correlations and tectonic
linkages of terranes and overlap assemblages for the Circum-North
Pacific are summarized in table 2.

Cratons, Cratonal Terranes, Passive Continental Margins, and
Passive-Continental-Margin Terranes

The eastern part of the North Asian Craton (NSC, NSS, figs. 1, 3, 7) and
the western part of the North American Craton (NAC, figs. 2, 4, 7) bound
the western and eastern parts of the Circum-North Pacific, respectively.
Adjacent to these cratons are two major passive continental (cratonal)
margins: the North Asian cratonal margin (Verkhoyansk fold-and-thrust
belt; NSV, figs. 1, 3, 7) to the west, and the North American cratonal
margin (NAM, figs. 2, 7) to the east. Adjacent to the passive
continental margins is a wide collage of terranes that were accreted to
the cratonal margins principally during the Mesozoic and Cenozoic (figs.
1, 2). More descriptions of, and stratigraphic columns for, the 167
accreted terranes and the cratons and cratonal margins were provided by
Nokleberg and others (1994a) and Greninger and others (1999). The growth
of continental margins by terrane accretion is an amazing facet of the
tectonic history of the region. Most of the accreted terranes are herein
interpreted as derived from various parts of the cratons, cratonal
margins, or fringing island arcs and companion subduction-zone
complexes.

Continental-Margin and Cratonal Terranes in the Russian Southeast

A complex suite of continent-related terranes in the Russian Southeast
are interpreted as tectonically derived from various parts of the North
Asian Craton and cratonal margin (NSC, NSV, NSS, figs. 1, 3, 7), the
North China Craton to the south (not shown in fig. 1), or the
Sino-Korean Craton to the south (also not shown in fig. 1). These
terranes, mainly of Archean, Late Proterozoic, and (or) early Paleozoic
age, consist of the Argun (AU), Baladek (BL), and Gonzha (GH) cratonal
terranes; the Ayansk (AY), and Oldoi (OD) passive-continental-margin
terranes; the Khanka continental-margin-arc superterrane (KA); and the
Bureya (BU) and Mamyn (MM) continental-margin-arc terranes (fig. 1).
This suite of continent-related terranes has a complex origin. Various
interpretations were proposed by Natal'in (1991, 1993), Sengör and
others (1993, 1994), Khanchuk and others (1996), and Sengör and Natal'in
(1996a, b).

Origin of the Khanka Continental-Margin-Arc Superterrane and the
Laoelin-Grodekorsk Island-Arc Terrane

The Khanka continental-margin-arc superterrane (KA, fig. 1), composed
mainly of fragments of a Late Proterozoic and Paleozoic
continental-margin arc and one accretionary-wedge complex, occurs in the
southern part of the Russian Far East. Adjacent is the Permian
Laoelin-Grodekorsk island-arc terrane (LD, figs. 1, 7). The Khanka
superterrane consists of a series of related, early and middle Paleozoic
continental-margin-arc and accretionary-wedge terranes, including the
Kabarga, Sergeevka, and Voznesenka continental-margin-arc terranes and
the Spassk accretionary-wedge terrane (predominantly turbidites)
(Nokleberg and others, 1994a; Khanchuk and others, 1996), all of which
are too small to show in figure 1. The Khanka superterrane includes
overlapping units of Devonian and Mississippian continental-rift-related
volcanic and sedimentary rocks, middle Paleozoic granitic rocks, late
Paleozoic granitic rocks, and Permian backarc-rift-related volcanic
rocks.

The Voznesenka terrane, which forms the southern part of the Khanka
superterrane, is interpreted as part of an early Paleozoic
continental-margin arc or passive continental margin that was part of
the Gondwanaland supercontinent (Khanchuk and others, 1996).
Archaeocyathids from Cambrian limestone in the Voznesenka terrane belong
to the Australian paleobiogeographic province (Belyaeva, 1998). To the
north of the Voznesenka terrane are the early and middle Paleozoic
Sergeevka and Kabarga continental-margin-arc terranes. These two
terranes, and the Bureya continental-margin-arc superterrane farther
north (fig. 1), also of early and middle Paleozoic age, are all
interpreted as parts of a single continental-margin arc (Khanchuk and
others, 1996) that formed along the margin of the paleo-Asian Ocean
along the eastern Gondwanaland margin during the latest Precambrian and
Cambrian. The Spassk accretionary-wedge terrane, containing mainly early
and middle Paleozoic oceanic rocks and turbidite deposits and also
constituting part of the Khanka superterrane, is interpreted as a
subduction-zone complex that was tectonically linked to the arc.

The Khanka superterrane is interpreted as having been rifted from the
Gondwanaland supercontinent during the Devonian, resulting in the
formation of bimodal volcanic rocks. The Permian marine and nonmarine
volcanic and terrigenous deposits that overlie most of the various
terranes of the Khanka superterrane are interpreted as having formed in
a backarc basin adjacent to the Permian island arc of the
Laoelin-Grodekorsk terrane (LD, figs. 1, 7), in a tectonic setting
similar to that of the modern Sea of Japan (Khanchuk and others, 1996).
These data and interpretations indicate that the Khanka superterrane is
a complex unit composed of fragments of diverse tectonic settings
(Khanchuk and others, 1996) and is not a part of the Sino-Korean Craton
(as interpreted by Sengör and Natal'in, 1996a, b).

In contrast, the Khanka continental-margin-arc superterrane (KA, fig. 1)
in the southern part of the Russian Southeast is interpreted by other
workers (Natal'in 1991, 1993; B.A. Natal'in, in Nokleberg and others,
1994a) as derived from part of the Sino-Korean Craton on the Korean
Peninsula (not shown in fig. 1) where similar Early Cambrian shelf
carbonates occur, and was tectonically separated from this region during
Mesozoic strike-slip faulting.

The Permian Laoelin-Grodekorsk island-arc terrane (LD, figs. 1, 7),
which occurs to the west of the Khanka superterrane (KA, fig. 1), is
tectonically linked to various Permian accretionary-wedge terranes to
the south, southwest, and southeast (Khanchuk and others, 1996). These
accretionary-wedge terranes include the Chongjin terrane (outside area
of fig. 1) which extends westward from the coast of the Japan Sea
(Chongjin city area) probably into southern Mongolia, in the area
between the Khanka superterrane and the Sino-Korean Craton. The Chongjin
terrane contains large blocks of middle and late Paleozoic ophiolites,
bedded chert, and limestone and is interpreted as having formed in a
subduction zone. Collision of the Sino-Korean Craton and the Khanka
superterrane, and closing of the ocean between the two terranes, is
interpreted as occurring during the Early Triassic (Zonenshain and
others, 1990).

Origin of the Argun, Baladek, and Gonzha Cratonal Terranes, the Ayansk
and Oldoi Passive-Continental-Margin Terranes, and the Mamyn and Bureya
Continental-Margin-Arc Terranes

Three major groups of cratonal, passive-continental-margin, and
continental-margin-arc terranes, of mainly Archean and Proterozoic age
(cratonal terranes) and mainly early and middle Paleozoic age
(continental-margin-arc and passive-continental-margin terranes), occur
in the northern part of the Russian Southeast (fig. 1). The origin of
each of these three groups is interpreted as follows. (1) The Argun (AU)
and Gonzha (GZ) cratonal terranes, the early and middle Paleozoic Oldoi
(OD) passive-continental-margin terrane, and the Proterozoic to Early
Cambrian part of the Mamyn (MM) continental-margin-arc terrane (fig. 1)
are interpreted as rifted fragments of the southern part of the North
Asian Craton and cratonal margin (NSC, NSV, figs. 1, 3, 7; Natal'in,
1991, 1993; Sengör and others, 1993, 1994; Sengör and Natal'in, 1996).
Rifting of this collage of terranes, as well as formation of similar
tectonic units in the Transbaikal region of southern Siberia and in
northern Mongolia, is interpreted as occurring during the latest
Proterozoic. (2) The Baladek (BL) cratonal terrane and the Paleozoic
Ayansk (AY) passive-continental-margin terrane (fig. 1), on the basis of
similar stratigraphy and lithology, are also interpreted as displaced
fragments of the North Asian Craton and cratonal margin (NSC, NSV, figs.
1, 3, 7), respectively (Natal'in, 1991, 1993; Sengör and others, 1993,
1994; Sengör and Natal'in, 1996a, b). (3) The early Paleozoic and older
Bureya continental-margin-arc terrane (BU, figs. 1, 7) and similar
tectonic units in northeastern China and Inner Mongolia are interpreted
as dismembered parts of the Manchurid orogenic system that formed along
the northern margin of the North China Craton (Natal'in, 1991, 1993;
Sengör and others, 1993, 1994; Sengör and Natal'in, 1996a, b).

Both the early Paleozoic and older Mamyn (MM, fig. 1) and Bureya (BU,
figs. 1, 7) continental-margin-arc terranes are interpreted as parts of
one or more continental-margin arcs that were active at various times
during the Paleozoic (B.A. Natal'in, in Nokleberg and others, 1994a).
The occurrence of large, poorly dated early and late Paleozoic granite
and granodiorite intrusions in all three terranes suggests to some
researchers that these terranes were part of a single arc (Parfenov,
1984; Parfenov and Natal'in, 1985; Zonenshain and others, 1990;
Khanchuk, 1993; Natal'in, 1993; Sengör and Natal'in, 1996). However,
differences in stratigraphy, and palinspastic reconstruction, for the
Mamyn and Bureya continental-margin-arc terranes indicate that they are
fragments of distinct arcs. The Mamyn continental-margin-arc terrane and
associated Gonzha (GZ) and Argun (AU) cratonal terranes, and the Oldoi
(OD) passive-continental-margin terrane (fig. 1), are all interpreted as
dismembered parts of the Altaid orogenic system (Natal'in, 1991, 1993;
Sengör and others, 1993; Sengör and Natal'in, 1996a, b). In contrast,
the Bureya continental-margin-arc terrane, which locally contains Late
Proterozoic to early Paleozoic igneous-arc rocks, is interpreted as
having formed along the northern part of the North China cratonal margin
as part of the Manchurid orogenic system (Natal'in, 1991, 1993; Sengör
and others, 1993; Sengör and Natal'in, 1996a, b). Disintegration of both
the Altaid and Manchurid orogenic systems into terranes occurred mainly
in the Mesozoic during the tectonic escape initiated by the convergence
of the North Asian (Siberia) and North China Cratons (B.A. Natal'in, in
Nokleberg and others, 1994a; Sengör and Natal'in, 1996a, b).

Correlation of Passive-Continental-Margin Terranes in the Russian
Northeast, Alaska, and the Canadian Cordillera and Linkage to the North
American Craton

Around the Circum-North Pacific, a suite of passive-continental-margin
terranes are correlated and interpreted as derived from the North
American cratonal margin (NAM, figs. 2, 7). These units are the Chukotka
terrane (CH) in the Russian Northeast, the Arctic Alaska superterrane
(AA) in Alaska, and the Cassiar terrane (CA) in the Canadian Cordillera
(figs. 1, 2, 7).

Eastern Part of the Chukotka Terrane and the Arctic Alaska Superterrane

Stratigraphic analysis of the North Slope terrane of the Arctic Alaska
superterrane (AA, figs. 1, 2, 7; approximately the equivalent of the
Arctic composite terrane of Plafker and Berg, 1994), the eastern part of
the Chukotka terrane (CH, figs. 1, 7; Wrangell subterrane of the
Chukotka terrane; Nokleberg and others, 1994a), and the Cassiar terrane
(CA, figs. 2, 7; Nokleberg and others, 1994a) reveal that these units,
and adjacent passive-continental-margin terranes, constitute a
long-lived Late Proterozoic, Paleozoic, and early Mesozoic,
Atlantic-type passive continental margin that faced the ancestral
Pacific Ocean (Monger and others, 1991a; Moore and others, 1994b). This
long-lived continental margin underwent two periods of
continental-margin-arc activity, one during the Late Proterozoic,
currently recognized only in northern Alaska, and another during the
Devonian and Mississippian, recognized in both northern Alaska and the
Russian Northeast. In the Russian Northeast, the Chukotka terrane
contains a Boreal fauna of Permian, Triassic, and Jurassic age (Dagis
and others, 1979; Dagis and Dagis, 1984; Zakharov and others, 1984).

The regional correlation of these passive-continental-margin terranes
(Nokleberg and others, 1994a) is based on (1) regionally similar
stratigraphy and (2) similar geologic positions around the Circum-North
Pacific. Before the opening of the Canada Basin, these terranes were
interpreted by most workers to have been part of the passive continental
margin adjacent to the North American Craton (NAC, figs. 2, 4, 7; Grantz
and others, 1990, 1991, 1998; Parfenov and others, 1993a, b; Monger and
others, 1994; Plafker and Berg, 1994; Monger and Nokleberg, 1996;
Parfenov, 1997). This grouping of terranes represents the extension of
the Paleozoic North American continental margin into the Chukotka region
of the Russian Northeast. The Arctic Alaska superterrane (AA, figs. 1,
2, 7) and Chukotka terrane (CH, figs. 1, 7) were displaced by
counterclockwise rotation, rifting, and (or) lateral translation
associated with the Early Cretaceous opening of the Canada Basin (Lawver
and Scotese, 1990; Grantz and others, 1991; Lane, 1994, 1997; Moore and
others, 1994a). Recent detrital-zircon isotopic studies in northeastern
Alaska contradict the stratigraphic correlations of Proterozoic strata
required by the rotation model, but these studies are compatible with a
transitional model involving rifting of Alaska and translation along a
major transform-fault system (McClelland, 1997).

Cassiar Terrane

The Cassiar terrane (CA, figs. 2, 7) was part of the western Canadian
margin that was displaced at least 450 km northward by dextral movement
on the Tintina-Northern Rocky Mountain Trench Fault System during the
Late Cretaceous and Early Tertiary (Gabrielse, 1985). The most complete
rock sequences in these terranes are similar to those of the North
American continental margin, namely, Late Proterozoic clastic-dominated
strata, Cambrian through Devonian carbonate rock and shale, and
Devonian-Mississippian to (locally) Triassic and Jurassic clastic rocks
with fewer carbonates. Rare magmatic rocks include Late Proterozoic and
Devonian granitic plutons and mafic and felsic volcanic-arc rocks.
Northward displacement of the Cassiar terrane by more than 2,000 km,
mostly during the Permian and Triassic, from a source in present-day
Idaho was suggested by Pope and Sears (1997).

Correlation of Metamorphosed Continental-Margin Terranes in the Russian
Northeast, Alaska, and the Canadian Cordillera and Linkage to the North
American Craton

Along the margins of the North American Cordillera and the northern part
of the Russian Northeast, outboard of the passive-continental-margin
terranes described above, are metamorphosed continental-margin terranes
of Late Proterozoic and Paleozoic age that are linked to the North
American Craton (NAC): the Seward (SD) Coldfoot (CO), Ruby (RB),
Yukon-Tanana (YT), and Kootenay (KO) terranes (figs. 1, 2, 4, 7). These
terranes are correlated because of similar ages, craton-derived
quartz-rich clastic sedimentary-rock units, and Late Devonian and Early
Mississippian continental-margin-arc sequences (Rubin and others, 1991;
Nokleberg and others, 1994a). The terranes are interpreted as having
been displaced by a combination of strike-slip and thrust movement from
loci along the North American continental margin. They exhibit broadly
similar stratigraphy, structure, metamorphism, and geographic position
between inboard passive-continental-margin terranes and outboard
island-arc and subduction-zone terranes (figs. 1, 2; Mortensen, 1992;
Foster and others, 1994; Gehrels and Berg, 1994; Moore and others,
1994b; Patton and others, 1994; Till and Dumoulin, 1994). The Seward
terrane, which occurs on both sides of the Bering Strait, forms a major
link from the Russian Northeast into northwestern Alaska (figs. 1, 2). A
long prong of the Yukon-Tanana terrane extends southeastward to lat 52°
N. near the Canadian Coast Mountains (fig. 2). Most of these terranes
were multiply penetratively deformed and metamorphosed from the middle
Paleozoic through the Mesozoic. The Yukon-Tanana terrane exhibits
several periods of regional deformation and metamorphism that range in
age from late Paleozoic through mid-Cretaceous to Late Cretaceous
(Mortensen, 1992). The Late Jurassic to mid-Cretaceous events are
interpreted as having occurred during accretion of outboard oceanic
terranes, such as the Stikinia (ST), Quesnellia (QN), and Cache Creek
(CC) terranes and the Wrangellia (WRA) superterrane (figs. 2, 7).

The metamorphosed continental-margin terranes are composed mainly of
clastic-dominated successions containing mafic to felsic volcanic rocks,
coeval granitic plutons, and local marble. Their protolith ages are
mainly early and middle Paleozoic but locally may be as old as Late
Proterozoic or as young as Triassic. Their facies, and the ages of
detrital zircons from clastic deposits within them, strongly suggest
that these units are distal, oceanward equivalents of continental-margin
strata (Smith and Gehrels, 1992). Devonian and Mississippian granitic
plutons are widely distributed within the metamorphosed
continental-margin terranes, whereas coeval volcanic successions are
more restricted in occurrence. Scattered Permian granitic plutons occur
locally, along with Devonian-Mississippian and Permian-Triassic plutonic
rocks, and associated deformational and metamorphic events (Mortensen,
1992; Smith and Gehrels, 1992). The Devonian plutons appear to be
related to coeval clastic-wedge deposits in the North American cratonal
margin to the east and to local tuff horizons in Devonian carbonate
rocks (Richards and others, 1994).

Correlation of Part of the Taymyr Peninsular Collage with the
Verkhoyansk Fold-and-Thrust Belt (North Asian Cratonal Margin)

The Taymyr Peninsula is west of the western part of the Russian
Northeast, to the west of the study area shown in figure 1. The collage
in that region is described herein because it constitutes part the
tectonic history of the Circum-North Pacific. The Taymyr Peninsula
consists of a collage of Late Proterozoic through Mesozoic terranes and
overlap assemblages (Zonenshain and others, 1990; Vernikovskiy and
others, 1998). The three major tectonic units in the region (from south
to north) are as follows. (1) The Byrranga fold-and-thrust belt contains
Ordovician to Jurassic sedimentary rocks formed in a
passive-continental-margin setting, Ordovician to middle Carboniferous
carbonate-shelf deposits, Late Carboniferous to Early Permian clastic
shallow-marine deposits, and Late Permian to Early Triassic continental
clastic coal-bearing deposits. On the basis of similar Siberian fauna
and stratigraphy, the Byrranga belt is correlated with the Verkhoyansk
fold-and-thrust belt (North Asian cratonal margin; NSV, figs. 1, 3, 7).
Middle Triassic to Jurassic sedimentary rocks on the eastern part of the
Taymyr Peninsula consist of marine clastic rocks that are also similar
to those of the Verkhoyansk fold-and-thrust belt. (2) The Central Taymyr
superterrane consists of the Fadeev and Mamont cratonal terranes, the
late Precambrian Kossovsk miogeoclinal (passive continental margin)
terrane, and the late Precambrian Shrenk island-arc terrane. The
Kossovsk and Shrenk terranes are composed of Early and Middle Riphean
units. The areas of formation of the units in the Central Taymyr
superterrane are unknown. All of the terranes in the superterrane are
overlapped by Late Riphean to Early Carboniferous deposits, including
Late Riphean to Cambrian carbonate rocks and Ordovician to Early
Carboniferous deep-water black shale. (3) The Karsk continental-margin
or turbidite terrane consists of Riphean to Ordovician turbidite. The
area of formation of the Karsk terrane is unknown. All of the terranes
of the Taymyr Peninsula collage are intruded by Permian to Triassic
granite with isotopic ages of 240 to 280 Ma, which provide a minimum age
of accretion of the terranes within the collage. Because it constitutes
an onstrike extension, the Byrranga fold-and-thrust belt is correlated
with the Verkhoyansk fold-and-thrust belt.

Correlation of Passive-Continental-Margin Terranes in the Russian
Northeast with the Verkhoyansk Fold-and-Thrust Belt

The Kula-Nera (KN), Omulevka (OV), Prikolyma (PR), and Viliga (VL)
passive-continental-margin terranes are widely separated fragments in
the central part of the Russian Northeast (figs. 1, 7). These terranes
are enclosed in a collage of accreted oceanic and island-arc terranes
that indicate rifting and migration away from a continental margin. They
share similar stratigraphy and fauna with each other and with the North
Asian cratonal margin (Verkhoyansk fold-and-thrust belt; NSV, figs. 1,
3, 7), and they are interpreted by most workers as derived from the
North Asian cratonal margin (Parfenov, 1984, 1991, 1995a--c; Parfenov
and Natal'in, 1986, 1993a, b; Nokleberg and others, 1994a; Sengör and
Natal'in, 1996a, b). The Omulevka, Prikolyma, and Viliga
passive-continental-margin terranes are also part of the Kolyma-Omolon
superterrane (KLO, fig. 7). The major terranes in this superterrane are
the Alazeya (AL), Aluchin (AC), Argatas (ARG), Beryozovka (BE),
Khetachan (KH), Munilkan (MU), Oloy (OL), Omolon (OM), Omulevka (OV),
Prikolyma (PL), Rassokha (RA), Uyandina (UY), and Yarakvaam (YM)
terranes (figs. 1, 7).

The North Asian cratonal margin (Verkhoyansk fold-and-thrust belt; NSV,
figs. 1, 3, 7) consists chiefly of a thick (max 20 km) wedge of
cratonal-margin deposits composed mainly of Carboniferous, Permian,
Triassic, and Jurassic clastic rocks and marine-littoral, deltaic, and
shelf deposits that prograde eastward (Natapov, 1984; Parfenov, 1984,
1985, 1987, 1991, 1994, 1995c; Prokopiev, 1989; Parfenov and Prokopiev,
1993; Parfenov and others, 1995). The fold belt was deposited on the
passive margin of the North Asian Continent. Major units grade
successively eastward into turbidite deposits and deep-water black
shale. The fold belt contains local Middle to Late Devonian and
Tournaisian rift-related sedimentary-rock units that are similar to
those on the Siberian platform, as well as local Early Triassic and
Early Jurassic alkalic-basalt flows and basalt dikes and sills. The
northern and southern parts of the fold belt contain thick
shallow-marine carbonate and clastic deposits of Late Proterozoic and
early Paleozoic age that become finer grained and thicker to the east.

This Kula-Nera passive-continental-margin terrane (KN, figs. 1, 7),
outboard of the Verkhoyansk fold-and-thrust belt (North Asian cratonal
margin; NSV, figs. 1, 3, 7), is juxtaposed against the fold-and-thrust
belt along the Adycha-Taryn Fault, which exhibits older, large-scale
overthrusting and subsequent sinistral strike-slip displacements. The
terrane consists (Parfenov and others, 1989; Bychkov and Kiseleva, 1990)
of a thick assemblage of Permian, Triassic, and Early Jurassic
hemipelagic and pelagic mudstone, siltstone, and minor sandstone and
Permian and Early Jurassic radiolarian chert and tuff. The Kula-Nera
terrane is interpreted as a deep-sea-fan complex interbedded with
continental-rise and marginal-sea pelagic deposits that formed between
the passive margin of the Siberian Continent (North Asian cratonal
margin) and various parts of the Kolyma-Omolon superterrane to the east.
The Kula-Nera terrane is weakly to strongly metamorphosed and deformed,
exhibits lower greenschist- and locally epidote-amphibolite-facies
metamorphic assemblages, and is locally deformed into gently inclined
appressed and superposed folds. The Kula-Nera terrane contains a
Permian, Triassic, and Early Jurassic Boreal fauna (Dagis and others,
1979; Dagis and Dagis, 1984; Zakharov and others, 1984) and is
interpreted as a distal part of the passive continental margin of the
North Asian Craton along which the proximal part is represented by the
Verkhoyansk fold-and-thrust belt. Both parts of the passive continental
margin were overthrust and displaced along the cratonal margin during
late Mesozoic deformation (Parfenov, 1984, 1997; Zonenshain and others,
1990).

The Omulevka passive-continental-margin terrane (OV, figs. 1, 7)
consists chiefly of five units (Bulgakova, 1986; Natapov and Surmilova,
1986; Parfenov, 1991, 1995c; Neustroev and others, 1993): (1) presumed
late Precambrian marble, schist, and metavolcanic rocks; (2) an
unconformably overlying thick (max 1,700 m) unit of boulder conglomerate
that contains pebbles of native and exotic rocks, whereas other units
consist of marble containing Middle and Late Cambrian fossils, schist,
metarhyolite, and quartzite; (3) a thick sequence of Ordovician,
Silurian, Devonian, and Early Carboniferous fossiliferous carbonate
rocks, including limestone, dolomite, marl, and sparse sandstone,
siltstone, mudstone, and (Devonian) volcanic rocks; (4) Carboniferous
and Permian fossiliferous tuff, chert, shale, limestone, siltstone, and
sandstone; and (5) Triassic fossiliferous siltstone, mudstone, marl, and
shaly limestone.

The Prikolyma passive-continental-margin terrane (PR, figs. 1, 7)
consists chiefly of several major units (Tret'yakov, 1989; Beus and
Miledin, 1990; Natapov and Shul'gina, 1991): (1) a basal unit of
high-grade gneiss and schist, metamorphosed to amphibolite facies,
interpreted as either late Precambrian to early Paleozoic, pre-Vendian,
or early Precambrian; (2) Riphean, Vendian, and Cambrian shallow-marine
clastic and carbonate rocks in the central part of the terrane; (3)
Ordovician and Early Silurian shallow-marine carbonate and clastic rocks
in the southwestern part of terrane; (4) Devonian and Early
Carboniferous shallow-water limestone, dolomite, marl, sandstone,
siltstone, and conglomerate; (5) in the central and eastern parts of the
terrane, abundant Late Devonian to late Paleozoic conglomerate and a
thick marine sequence of mainly thin-bedded clastic, volcaniclastic and
subordinate carbonate rocks of Late Devonian to Middle Carboniferous
and, locally, Early Permian age; (6) Late Carboniferous and Early
Permian rift-related alkalic-basalt flows and tuff and alkalic gabbro
sills, stocks, and dikes (Chakhadanskaya Formation); and (7) Late
Triassic and Early Jurassic shallow-marine shale, siltstone, sandstone,
and tuff in the southwestern part of the terrane.

The Viliga passive-continental-margin terrane (VL, figs. 1, 7) consists
chiefly of a thick sequence of Carboniferous, Permian, Triassic, and
Jurassic marine clastic rocks, as much as 10 km thick (Polubotko and
others, 1977; Terekhov, 1979; Bychkov and Kiseleva, 1990). The major
units are (1) Early Carboniferous sandstone and interbedded
conglomerate, mafic tuff, and basalt flows; (2) Late Carboniferous to
Permian sandy argillite, siltstone, sandstone, tuff, chert, basalt, and
shale that gradationally overlie the older units; (3) Triassic shale,
siltstone, intermediate-composition tuff, and limestone; and (4)
Jurassic argillite, siltstone, intermediate-composition tuff, sandstone,
and conglomerate.

Derivation of Passive-Continental-Margin Terranes in West-Central Alaska
from the Verkhoyansk Fold-and-Thrust Belt in the Russian Northeast

A suite of passive-continental-margin terranes in west-central Alaska,
consisting of the Nixon Fork (NX), Dillinger (DL), and Mystic (MY)
terranes (figs. 2, 7), were interpreted as subterranes of the larger
Farewell terrane by Decker and others (1994) and as part of the Central
composite terrane by Plafker and Berg (1994). These terranes occur
within a collage of accreted oceanic and island-arc terranes, a relation
that indicates rifting and migration away from a continental margin.

The Nixon Fork passive-continental-margin terrane (NX, figs. 2, 7;
Palmer and others, 1983; Babcock and Blodgett, 1992; Decker and others,
1994; Patton and others, 1994; Blodgett, 1998; Fryda and Blodgett, 1998)
consists of (1) Late Precambrian basement, mainly pelitic and calcareous
schist with minor marble, quartzite, and felsic metavolcanic rocks; (2)
unmetamorphosed sedimentary rocks of probable Late Proterozoic age that
consist of interbedded sandstone, siltstone, and carbonate rocks and two
dolostone units (Babcock and others, 1993); (3) Middle Cambrian
limestone and chert; (4) Late Cambrian to Early Ordovician platy
limestone (possibly part of the lower part of the Novi Mountain
Formation); (5) Early Ordovician thick platy limestone (Novi Mountain
Formation); (6) Ordovician to Middle Devonian carbonate platform rocks
(Telsitna, Paradise Fork, and Whirlwind Creek Formations and the
Cheeneetnuk Limestone; R.B. Blodgett, written commun., 1993); and (7)
Permian, Triassic, and Cretaceous fossiliferous sedimentary rocks,
mainly calcareous sandstone, siltstone, conglomerate, and sparse chert.
The Late Proterozoic stratified rocks are intruded by Middle Proterozoic
metagranitic rocks that yield a discordant U-Pb zircon age of 1.27 Ga
and are capped by Late Proterozoic metavolcanic rocks that yield a
discordant U-Pb zircon age of 850 Ma. The middle Paleozoic strata grade
laterally into deep-water strata equivalent to the Dillinger terrane
(DL, figs. 2, 7).

The Dillinger passive-continental-margin terrane (DL, figs. 2, 7;
Bundtzen and Gilbert, 1983; Gilbert and Bundtzen, 1984; Blodgett and
Clough, 1985; Decker and others, 1994; Patton and others, 1994; Churkin
and Carter, 1996; Blodgett, 1998; Fryda and Blodgett, 1998) consists of
(1) Cambrian and Ordovician basinal limestone, banded mudstone, and
silty limestone turbidite deposits; (2) Ordovician graptolitic shale and
associated(?) pillow basalt; and (3) unnamed, Late Silurian through
Middle Devonian shallow-marine limestone and dolomite. The terrane is
unconformably overlain by sedimentary rocks of the Cretaceous Kuskokwim
Group. South of the Denali Fault (DE, fig. 4), the terrane consists
chiefly of (1) Cambrian(?) to Ordovician calcareous turbidites, shale,
and minor greenstone; (2) Early Ordovician to Early Silurian graptolitic
black shale and chert; (3) Early to Middle Silurian laminated limestone
and graptolitic black shale; (4) Middle to Late Silurian sandstone
turbidite deposits and shale; and (5) Late Silurian to Early Devonian
limestone, breccia, sandstone, and shale.

The Mystic passive-continental-margin terrane (MY, figs. 2, 7; Gilbert
and Bundtzen, 1984; Blodgett and Gilbert, 1992; Decker and others, 1994;
Patton and others, 1994; Blodgett, 1998; Fryda and Blodgett, 1998)
consists of a complexly deformed, but partly coherent, long-lived
stratigraphic succession of (1) Silurian massive limestone; (2) Late
Devonian sandstone, shale, conglomerate, and limestone that constitute
the informally named Yentna limestone of Fernette and Cleveland (1984);
(3) uppermost Devonian to Pennsylvanian radiolarian chert; (4)
Pennsylvanian siltstone, sandstone, and conglomerate; (5)
Pennsylvanian(?) and Permian flysch, chert, argillite, and conglomerate
(locally plant bearing); and (6) Triassic(?) pillow basalt and gabbro.

Origin of the Nixon Fork, Dillinger, and Mystic Terranes

Debate persists about the origin of the Nixon Fork (NX), Dillinger (DL),
and Mystic (MY) passive-continental-margin terranes that occur within a
collage of accreted oceanic and island-arc terranes, far removed from a
cratonal margin (figs. 2, 7). Two widely different tectonic origins have
been proposed. Studies by T.K. Bundtzen (oral commun., 1994) suggest
derivation from similar strata that occur in the North American cratonal
margin (NAM, figs. 2, 7), in the northern part of the Canadian
Cordillera. This interpretation requires tectonic transport of these
terranes by several hundred kilometers on such dextral-slip faults as
the Denali (DE), Kaltag (KA), Tintina (TI), and related dextral-slip
faults (fig. 4). Alternatively, several recent studies reported early to
middle Paleozoic fauna that are typical of taxa which occur in
similar-age units in the Kolyma region, suggesting that these three
terranes were rifted from the Siberian continent (North Asian cratonal
margin; Blodgett and Brease, 1997; Blodgett, 1998; Dumoulin and others,
1998, 1999; Fryda and Blodgett, 1998; Blodgett and Boucot, 1999). The
terranes also exhibit stratigraphy which is similar to that of the North
Asian cratonal margin (NSV, figs. 1, 3, 7) and are herein interpreted as
being derived from that unit (Nokleberg and others, 1994a). This
interpretation requires rifting of these terranes from the North Asian
cratonal margin during the Late Devonian or Mississippian or earlier,
and tectonic transport by several hundred kilometers to the east
(present-day coordinates).

Derivation of the Kilbuck-Idono Cratonal Terrane from the North Asian
Craton

The Kilbuck-Idono cratonal terrane (KI, figs. 2, 7) occurs in western
Alaska in two fault-bounded fragments, about 330 km apart. The terrane
consists chiefly of metamorphosed diorite, tonalite, trondhjemite, and
granite orthogneiss, subordinate amphibolite, and minor metasedimentary
rocks (Hoare and Coonrad, 1978, 1979; Box and others, 1990, 1993; Miller
and others, 1991). The metasedimentary rocks are mainly quartz-mica
schist, marble, garnet amphibolite, and banded iron-formation of the
informally named Kanektok metamorphic complex of Hoare and Coonrad
(1979). The metaplutonic rocks yield Early Proterozoic (2.06--2.07 Ga)
U-Pb zircon ages of emplacement. Nd-Sm--isotopic analyses indicate a
2.5-Ga (Archean) crustal component. The terrane was metamorphosed to
amphibolite facies, with retrograde greenschist-facies metamorphism,
possibly during the late Mesozoic. A southern fragment constitutes the
Kilbuck terrane of Box and others (1990, 1993), and a northern fragment
constitutes the Idono Complex of Miller and others (1991). The
Kilbuck-Idono terrane is interpreted as a highly displaced cratonal
fragment; no known correlative cratonal rocks occur in Alaska or the
Canadian Cordillera (Miller and others, 1991; Box and others, 1993). The
terrane is herein interpreted as derived from the closest and most
similar craton, the North Asian Craton (NSC, figs. 1, 3, 7). The
stratigraphy of the Kilbuck-Idono terrane also is broadly similar to
that of older parts of the Okhotsk and Omolon cratonal terranes
(described below) in the Russian Northeast, which are interpreted as
derived from the North Asian Craton. In addition, both the Kilbuck-Idono
and Omolon terranes contain similar suites of ironstone (Superior Fe)
deposits (Nokleberg and others, 1996, 1997a).

Derivation of the Okhotsk and Omolon Cratonal Terranes from Devonian and
Older Parts of the North Asian Craton

The Okhotsk (OK, fig. 1, 7) and Omolon (OM, fig. 1) cratonal terranes
occur in the central part of the Russian Northeast, either adjacent to
or as part of the Kolyma-Omolon superterrane. The Okhotsk cratonal
terrane (Avchenko, 1977; Chikov, 1978; Verzkhovskaya and Krichevets,
1987; Pavlov, 1993) consists of (1) large blocks of Archean to Early
Proterozoic gneiss and schist, with a U-Pb age of 3.7 Ga, and Middle and
Late Proterozoic shallow-marine clastic and carbonate rocks; (2) Early
Cambrian limestone, marl, and sandstone; (3) Early Ordovician
conglomerate, limestone, marl, and sandstone with macrofossils; (4)
unconformably overlying Middle Devonian limestone, sandstone, shale, and
conglomerate, and Late Devonian rhyolite, ignimbrite, andesite, dacite,
and tuff that are interlayered with nonmarine sandstone, siltstone, and
conglomerate; and (5) mainly nonmarine clastic rocks of Carboniferous,
Permian, Late Triassic, and Early and Late Jurassic age.

The Omolon cratonal terrane (Bibikova and others, 1981; Terekhov and
others, 1984; Khramov, 1986; Zhulanova, 1990; Natapov and Shul'gina,
1991) consists of (1) a poorly exposed Archean to Early Proterozoic
crystalline basement metamorphosed to granulite and amphibolite facies,
with U-Pb ages of 2.8 to 3.4 Ga and an Rb-Sr age of 3.85 Ga; (2)
unconformably overlying, gently dipping low-grade Proterozoic
conglomerate, sandstone, and siltstone that grade upward into limestone,
quartzite, siltstone, marl, and Vendian dolomite; (3) unconformably
overlying rift-related Cambrian units that consist of nonmarine
sandstone, conglomerate, siltstone, and alkalic basalt, local dolomite,
limestone, sandstone, and siltstone, and widespread sills and stocks of
Middle Cambrian rift-related layered gabbro in several small tectonic
blocks, (4) Early and Middle Ordovician shallow-marine fossiliferous
limestone, dolomite, sandstone, and conglomerate; (5) unconformably
overlying, widespread, gently dipping Middle and Late Devonian and Early
Mississippian calc-alkalic lava, rhyolite tuff, trachyte,
trachyandesite, granitic plutonic rocks, and basalt, interlayered
nonmarine sandstone, conglomerate, and siltstone, and rare
shallow-marine sedimentary rocks; and (6) the unconformably overlying
Korba Formation (Late Mississippian), consisting of coal-bearing
siltstone that includes a basal conglomerate containing clasts and
pebbles of gold-bearing quartz from the Kubaka Au-Au epithermal-vein
deposit (Stepanov and Shishakova, 1994). The volcanic rocks forming the
upper part of unit 5 at the Kubaka Au-Ag epithermal-vein deposit exhibit
an Rb-Sr isochron age of 322 to 344 Ma (Kotlyar, 1997).

Origin of the Okhotsk and Omolon Terranes

The Okhotsk and Omolon terranes are correlated (Nokleberg and others,
1994a) on the basis of (1) similar Early Ordovician brachiopods and
trilobites that also occur in the North Asian (Siberian) Craton (NSC,
figs. 1, 3, 7; Oradovskaya, 1974); (2) similar Boreal faunas of
Carboniferous, Permian, Triassic, and Jurassic age (Korol'kov and
Korol'kova, 1974); and (3) similar suites of Devonian igneous-arc rocks
(Umitbaev, 1976; Lychagin, 1978; Nokleberg and others, 1994a). The
Okhotsk and Omolon terranes are interpreted as derived from the North
Asian Craton because of similar Early Ordovician fauna (Oradovskaya,
1974).

Correlation, Linkage, and Alignment of Late Paleozoic Through
Mid-Cretaceous Island-Arc Terranes of the Wrangellia Superterrane

Sequences of the Wrangellia Superterrane

The Wrangellia island-arc superterrane (WRA, fig. 7), which occurs in
south-central and southeastern Alaska and the Canadian Cordillera,
contains a long succession of four island arcs that are preserved in
combinations of sequences which constitute the superterrane. The four
arcs, which range in age from Devonian through mid-Cretaceous, are the
Devonian Sicker, the late Paleozoic Skolai, the Late Triassic and Early
Jurassic Talkeetna-Bonanza, and the Late Jurassic through mid-Cretaceous
Gravina arcs (Nokleberg and others, 1994a, b). The Devonian Sicker arc,
in the Alexander (AX) and Wrangellia (WR) sequences of the superterrane
(figs. 2, 7), is best defined in the Wrangellia sequence on Vancouver
Island, in the southern part of the Canadian Cordillera. In this region,
the arc consists of the Sicker Group, which contains Late Devonian
arc-related volcanic and sedimentary strata that yield a U-Pb zircon age
of 367 Ma (Sicker Group), and coeval intrusions (Muller, 1980; Parrish
and McNicoll, 1992). Possibly correlative middle Paleozoic arc rocks
also occur in the other sequences of the superterrane (Nokleberg and
others, 1994b). Remnants of the late Paleozoic Skolai arc occur mainly
in the Wrangellia sequence in the eastern part of southern Alaska
(Nokleberg and others, 1994b); correlative units also occur in the
Peninsular sequence on the Alaska Peninsula. Remnants of the Late
Triassic and Early Jurassic Talkeetna-Bonanza arc occur mainly in the
Peninsular sequence (PE) in the western part of southern Alaska, and in
the Wrangellia (WR) sequence in the Canadian Cordillera (figs. 2, 7;
Jones and others, 1977; Muller, 1977; Nokleberg and others, 1994a, b).
Remnants of the Late Jurassic through mid-Cretaceous Gravina arc occur
mainly in the Wrangellia and Alexander sequences in southeastern Alaska.
In addition to the arc sequences, the Wrangellia superterrane also
contains a major sequence of Late Triassic basalt and coeval gabbro
dikes, sills, and small plutons in the Nikolai Greenstone and
correlative units in southern Alaska and in the Karmutsen Formation and
correlative units in the southern part of the Canadian Cordillera that
are interpreted as having formed at a paleolatitude near the Triassic
Equator (Hillhouse, 1977; Hillhouse and Grommé, 1984).

Stratigraphic Succession of Late Paleozoic and Mesozoic Arcs of the
Wrangellia Superterrane

Three distinct sequences, the Alexander, Peninsular, and Wrangellia,
constitute the Wrangellia superterrane and contain various combinations
of Paleozoic and Mesozoic island arcs. Initial analysis of terranes in
southern Alaska interpreted these three sequences as separate terranes
(Jones and others, 1981), whereas a more recent study interpreted that
the three sequences represent various stratigraphic levels within a
large superterrane (Nokleberg and others, 1994b). The reason for the
initial interpretation was that each sequence is dominated by one of the
three arcs. The Alexander sequence, which occurs mostly in southeastern
Alaska, is mainly an early and middle Paleozoic volcanic arc, possibly a
precursor to the Sicker arc, with generally only a local expression of
late Paleozoic and early Mesozoic units of the Wrangellia superterrane.
The Wrangellia sequence, which occurs mainly from the eastern part of
southern Alaska, through southeastern Alaska, into the southern part of
the Canadian Cordillera, consists mainly of a late Paleozoic Skolai arc
sequence and the Nikolai Greenstone, one of the backarc units for the
Late Triassic and Early Jurassic Talkeetna-Bonanza arc. Similarly, the
Peninsular sequence, which occurs principally in the western part of
southern Alaska, consists mainly of the Late Triassic and Early Jurassic
Talkeetna-Bonanza arc. Only locally does a small part of the Peninsular
sequence exhibit either (1) the volcanic and sedimentary rocks of the
late Paleozoic Skolai island arc and the Late Triassic rift or oceanic
flood basalt that form the major part of the Wrangellia sequence, or (2)
possible fragments of metamorphosed Paleozoic or older metasedimentary
and metavolcanic rocks that might be the early and middle Paleozoic part
of the Alexander sequence. Pre-late Paleozoic basement rocks, possibly
of the Alexander sequence, also occur in the Wrangellia sequence in the
eastern part of southern Alaska.

The above relations indicate that, from east to west, the Alexander,
Wrangellia, and Peninsular sequences exhibit successively higher levels
of a structural-stratigraphic succession. The oldest part of the
succession is mainly to the east, in the predominantly early and middle
Paleozoic Alexander sequence; the middle part of the succession, in the
central part of the predominately late Paleozoic and early Mesozoic
Wrangellia sequence; and the youngest part of the succession to the
west, in the predominantly middle and late Mesozoic Peninsular sequence.
Despite these relations, substantial tectonic imbrication has occurred
within the Wrangellia superterrane (Plafker and others, 1989a, b;
Nokleberg and others, 1994a, b). The abrupt structural termination of
the Talkeetna-Bonanza arc and associated plutonic rocks in the eastern
part of the Peninsular sequence against the very minor occurrence of the
arc in the Wrangellia sequence requires extensive post-Middle Jurassic
tectonic displacement of the Wrangellia sequence relative to the
Peninsular sequence. Timing of the suggested strike-slip displacement
between the Peninsular and Wrangellia sequences cannot be constrained
more closely than to the Late Jurassic to Late Cretaceous (Nokleberg and
others, 1994b).

Correlation, Linkage, and Alignment of Triassic Through Mid-Cretaceous
Continental-Margin Arcs, Island Arcs, and Tectonically Paired Subduction
Zones

During the Triassic through mid-Cretaceous, 11 major igneous arcs are
herein recognized around the Circum-North Pacific: (1) the Jurassic
Monakin arc in the Primorski region of the Russian Southeast and the
Jurassic and Cretaceous eastern China-Korean igneous arc in Korea and
China, both part of the Great Hinggan arc; (2) the Jurassic and Early
Cretaceous Umlekan arc in the Russian Southeast; (3) the Early
Cretaceous and mid-Cretaceous Khingan arc in the Russian Southeast; (4)
the Late Jurassic and Early Cretaceous Uda arc in the central part of
the Russian Far East; (5) the Late Triassic to Early Cretaceous
Kony-Murgal Arc in the Russian Northeast; (6) the Late Jurassic through
mid-Cretaceous Mainitskiy arc in the Russian Northeast; (7) the Late
Jurassic and Early Cretaceous Uyandina arc in the Russian Northeast; (8)
the Late Triassic and Early Jurassic Alazeya island arc in the Russian
Northeast; (9) the Late Jurassic through mid-Cretaceous Nutesyn-Koyukuk
arc in the Russian Northeast and western Alaska; (10) the Late Jurassic
through mid-Cretaceous Gravina arc in south-central Alaska, southeastern
Alaska, and the Canadian Cordillera; and (11) the Late Triassic and
Early Jurassic Talkeetna-Bonanza arc in south-central Alaska,
southeastern Alaska, and the Canadian Cordillera.

Middle and Late Jurassic Monakin Arc in the Russian Southeast

The Monakin arc (too small to show in figs. 1 and 3) is defined as a
Middle and Late Jurassic suite of igneous and associated sedimentary
rocks that occur in the Russian Southeast. The arc consists chiefly of
sedimentary and volcanic rocks of the Monakin volcanic-plutonic belt
(mo, fig. 7) and the Umlekan-Ogodzhin volcanic-plutonic belt (uo, fig.
3) that both occur in the Russian Southeast. The Monakin
volcanic-plutonic belt overlies the Sergeevka terrane of the Khanka
superterrane and, in the western part, consists of dacite and rhyolite
flows and tuffs and continental flora-bearing clastic rocks (Oleinikov
and others, 1990; Decisions of the Fourth Interdepartmental Regional
Meeting on Precambrian and Phanerozoic of the Far East and Eastern
Baikal Regions, 1994). In the eastern part, the arc consists of basalt,
andesite, and tuff that are interlayered with shallow-marine deposits
containing a bivalve-mollusk fauna.

Subduction-Zone Terranes in the Russian Southeast and on Hokkaido
Island, Japan, Tectonically Linked to the Jurassic Monakin Arc and
Correlative Igneous Arcs in Korea and China

Tectonically linked to the Jurassic Monakin arc in the Russian Southeast
is a discontinuous collage of accretionary-wedge terranes in northern
Japan and the southern part of the Russian Far East. The
accretionary-wedge terranes, composed mainly of Paleozoic and early
Mesozoic oceanic-crustal and upper-mantle rocks and turbidite deposits,
consist of the Badzhal (BD), Khabarovsk (KB), and Samarka (SMA)
accretionary-wedge terranes (figs. 3, 7). These terranes also are
tectonically linked to the Umlekan arc, as described below. The Badzhal,
Khabarovsk, and Samarka accretionary-wedge terranes (Natal'in, 1993;
Nokleberg and others, 1994a; Khanchuk and others, 1996; Sengör and
Natal'in, 1996a, b) share (1) similar ages of deformation(s) and
melange, formed mainly during Late Triassic through Early Cretaceous
subduction; and (2) a similar tectonic position and occurrence as a
series of narrow, discontinuous, long tectonic lenses outboard of the
Umlekan-Ogodzhin volcanic-plutonic belt (uo, fig. 3) of mainly Late
Jurassic and Early Cretaceous age that intrudes and overlies the Bureya
continental-margin-arc terrane (BU, fig. 1).

Tectonically linked to the Jurassic and Cretaceous eastern China-Korean
igneous arc in Korea and China, coeval units with respect to the Monakin
arc, are the Taukha and Oshima terranes, which are correlated with the
Hern Chichibu terrane in southeastern Japan (Kojima, 1989; Kojima and
others, 1991; Natal'in and Faure, 1991; Faure and Natal'in, 1992;
Mizutani and Kojima, 1992; Golozubov and Khanchuk, 1996).

The Taukha accretionary-wedge terrane (TU, figs. 1, 3, 7) in the
southern part of the Russian Far East consists chiefly of an Early
Cretaceous accretionary complex composed of two main units (Golozubov
and Melnikov, 1986; Mikhailov and others, 1986, 1987, 1989; Khanchuk and
others, 1988; Rudenko and Panasenko, 1990; Natal'in, 1991; Golozubov and
others, 1992; Kemkin and Khanchuk, 1993; Golozubov and Khanchuk, 1996):
(1) a western, structurally lower unit of oceanic basalt overlain by
Callovian to Tithonian radiolarian chert, Berriasian siliceous mudstone,
and Neocomian turbidite deposits, about 3,500 m thick, that contain
ammonites and pelecypods; and (2) an eastern, structurally higher unit
of turbidite and olistostrome deposits containing abundant Valanginian
to Hauterivian radiolarians and a Neocomian flora. The Taukha terrane
also contains tectonic inclusions of oceanic intraplate basalt and chert
with limestone caps (paleoguyots), as much as several thousand meters
wide and 10 km long, containing local Tethyan fauna. Formation of the
Taukha accretionary-wedge terrane is interpreted as ending during the
Hauterivian to Valanginian, with subsequent offset along transpressional
sinistral strike-slip faults (Natal'in, 1991; Natal'in and Faure, 1991;
Golozubov and Khanchuk, 1996).

The Oshima accretionary-wedge terrane (OS, fig. 7), which occurs on
Hokkaido Island in northern Japan, consists chiefly of flysch and
melange (Kato and others, 1986; Minoura, 1990; Natal'in, 1991, 1993;
Natal'in and Faure, 1991). The melange is composed of blocks of basalt,
limestone, chert, siliceous shale, and sandstone in a shale matrix
(Matsumae, Tamdrigawa, and Kamiiso Groups). Middle Carboniferous
fusulinids occur in the limestone blocks, Carboniferous to Permian
radiolarians in the chert blocks, Triassic conodonts and radiolarians in
the limestone and chert blocks, and Late Jurassic to Early Cretaceous
radiolarians in the chert and siliceous-shale blocks. The blocks were
tectonically mixed during the Late Jurassic to Early Cretaceous.

The Taukha and Oshima accretionary-wedge terranes are interpreted as
parts of a Jurassic and Early Cretaceous subduction zone that formed
along the East Asia margin (Taira and Tashiro, 1987; Ichikawa and
others, 1990; Natal'in, 1991, 1993; Natal'in and Faure, 1991; Faure and
Natal'in, 1992; B.A. Natal'in, in Nokleberg and others, 1994a). This
subduction zone was tectonically paired to the Jurassic granitic rocks
in Korea to the southeast (Lee, 1987; Cluzel, 1991; Cluzel and others,
1991) and to the Monakin arc in the Russian Southeast (Khanchuk and
others, 1996). These Jurassic igneous granitic rocks in Korea are
connected by magmatic anomalies with a Jurassic to Cretaceous
volcanic-plutonic belt of southeastern China. During the Cretaceous and
early Cenozoic, dextral slip on numerous Cretaceous strike-slip faults
caused northward tectonic transport of these accretionary-wedge terranes
with respect to the magmatic arc. The eastern China-Korean igneous arc
and tectonically paired accretionary-wedge terranes are the continuation
of the Great Hinggan arc (Natal'in, 1991, 1993; Natal'in and Faure,
1991; Faure and Natal'in, 1992; B.A. Natal'in, in Nokleberg and others,
1994a).

Jurassic and Early Cretaceous Umlekan Arc in the Russian Southeast

The Umlekan arc is defined as a Jurassic and Early Cretaceous
continental-margin igneous arc in the Russian Southeast (Natal'in, 1991,
1993; Natal'in and Faure, 1991; Faure and Natal'in, 1992; Natal'in and
others, 1995; Khanchuk and others, 1996). Remnants of the arc are
preserved in the Umlekan-Ogodzhin volcanic-plutonic belt (uo, fig. 3)
and coeval Late Jurassic and Early Cretaceous granitic plutons that
overlie or intrude various terranes in the Russian Southeast and the
North Asian Craton (NSC, figs. 1, 3, 7). The igneous-rock units of the
arc and tectonically linked subduction units occur inland from, and
parallel to, the coast of the Russian Southeast for about 1,000 km (fig.
3).

Igneous- and Sedimentary-Rock Units of the Umlekan Arc

The Umlekan-Ogodzhin volcanic-plutonic belt (uo, fig. 3; Volsky, 1983;
Kozlovsky, 1988) consists chiefly of (1) Early Cretaceous sandstone,
conglomerate, and mudstone containing sparse flora and freshwater fauna;
(2) Early Cretaceous calc-alkalic andesite, dacite, and tuff that yield
K-Ar ages of 35 to 112 Ma; and (3) Late Cretaceous alkalic basalt and
rhyolite. The belt is intruded by coeval Early Cretaceous granite,
granodiorite, diorite, and monzodiorite. Some granitic plutons are
probably Late Jurassic or older because their detritus was shed into the
Early Cretaceous part of section. The belt is deposited on the Gonzha
terrane and on the Mamyn and Turan terranes of the Bureya superterrane
after collision of these terranes with the Tukuringra-Dzhagdi terrane
(TD, fig. 1, 3).

Subduction-Zone Units Linked to the Umlekan Arc

Tectonically paired to the Umlekan arc was a subduction zone now
preserved in a discontinuous collage of subduction-zone and
accretionary-wedge terranes in the southern part of the Russian Far
East. These terranes, composed mainly of Paleozoic and early Mesozoic
oceanic-crustal and upper-mantle rocks, and turbidite deposits, consist
of the Badzhal (BD), Khabarovsk (KB) (older Jurassic part), and Samarka
(SMA) accretionary-wedge terranes (figs. 1, 3; Natal'in, 1993; Nokleberg
and others, 1994a; Khanchuk and others, 1996; Sengör and Natal'in,
1996a, b).

The Badzhal accretionary-wedge terrane (BD, figs. 1, 3) consists chiefly
of (1) Paleozoic limestone olistoliths in a clastic matrix, (2) Permian
and Triassic chert lenses, (3) Late Triassic through Late Jurassic
turbidite deposits, (4) chert and siliceous shale, and (5) small lenses
of mafic volcanic rocks (Shevelev and Kuzmin, 1990; Zablotsky and
others, 1990; Natal'in, 1991, 1993). The terrane is interpreted as a
Triassic to Middle Jurassic accretionary-wedge complex composed of
tectonically intermixed oceanic and continental-slope deposits.
Limestone units, which contain Carboniferous and Permian Tethyan fauna,
are interpreted as the caps to seamounts.

The Khabarovsk accretionary-wedge terrane (KB, fig. 7) consists chiefly
of a Jurassic and Early Cretaceous melange, with various-size
fault-bounded lenses and slices of Triassic chert, Early to Middle
Jurassic siliceous shale, hemipelagic sedimentary rocks, mafic volcanic
rocks, and gabbro, Late Carboniferous, Permian, and Late Triassic
limestone, and schist and metasandstone of unknown age (Shevelev, 1987;
Natal'in and Alekseenko, 1989; Natal'in and Zyabrev, 1989). The late
Paleozoic limestone, which locally contains volcanic-rock layers and
Tethyan fauna, is interpreted as reef caps on seamounts.

The Samarka accretionary-wedge terrane (SMA, figs. 1, 3) consists
chiefly of a Middle and Late Jurassic accretionary-wedge complex that
contains tectonic sheets and lenses, olistostromes, and melange
inclusions of Carboniferous and Permian reef limestone, Late Triassic
pelagic limestone, interlayered Late Devonian, Carboniferous, Permian,
and Triassic chert, Early Jurassic siliceous shale, and Permian and
Triassic clastic marine rocks (Golozubov and Melnikov, 1986; Khanchuk
and others, 1988; Vrublevsky and others, 1988; Natal'in, 1991).

Origin of the Umlekan Arc

The continental-margin Umlekan arc is interpreted as having formed from
subduction of part of the ancestral Pacific oceanic plate that is now
preserved as tectonically interwoven fragments of the Badzhal (BD, figs.
1, 3), Khabarovsk (KB, fig. 7) (older Jurassic part), and Samarka (SMA,
figs. 1, 3) terranes. This tectonic pairing is based on (1) occurrence
of the accretionary-wedge terranes outboard (oceanward) of the Umlekan
arc (fig. 3); (2) formation of melange structures during the Jurassic
and Early Cretaceous (Nokleberg and others, 1994a; Khanchuk and others,
1996); and (3) where not disrupted by extensive Cretaceous and early
Cenozoic movement along the Central Sihote-Aline strike-slip fault,
dipping of melange structures and bounding faults toward and beneath
igneous-rock units of the arc. Subduction is generally interpreted as
ending in the late Early Cretaceous, when extensive sinistral faulting
occurred along the subduction zone (Khanchuk and others, 1996).

Early and Mid-Cretaceous Khingan Arc in the Russian Southeast

The Khingan arc is defined as an Early Cretaceous and mid-Cretaceous
continental-margin igneous arc in the Russian Southeast (fig. 3;
Natal'in, 1991, 1993; Natal'in and Faure, 1991; Faure and Natal'in,
1992; Natal'in and others, 1995; Khanchuk and others, 1996). The Khingan
arc consists of the Khingan-Okhotsk volcanic-plutonic belt (ko) that
occurs as a chain of Early and mid-Cretaceous volcanic fields with
similar age, lithology, and stratigraphy (fig. 3). The belt consists
(Sukhov, 1975; Scheglov, 1984; Natal'in, 1991, 1993) of mainly Barremian
to Cenomanian (mid-Cretaceous) andesite and minor basalt, with coeval
gabbro, diorite, and granodiorite. The belt overlies and intrudes the
Badzhal (BD), Bureya (BU), and Ulban (UL) terranes (figs. 1, 3).

Tectonically paired with the Khingan continental-margin arc was a
subduction zone, now preserved in a discontinuous collage of
accretionary-wedge terranes in the Russian Southeast. These terranes,
composed mainly of Paleozoic and early Mesozoic oceanic-crustal and
upper-mantle rocks and turbidite deposits, consist of the Amur River
(AM), Khabarovsk (KB) (younger Cretaceous part), and Kiselvka-Manoma
accretionary-wedge terranes (figs. 1, 3; Natal'in and Alexeenko, 1989;
Natal'in and Zyabrev, 1989; Khanchuk and others, 1994).

The Amur River terrane (AM, figs. 1, 3) consists chiefly of abundant
Cretaceous turbidite deposits (Largasinsk, Uktursk, Pionersk, and
Pivansk suites) and subordinate Late Jurassic hemipelagic siliceous
shale that occur in an imbricate stack of southeast-verging thrust
sheets and slices (Natal'in and Aleseenko, 1989, Krasny, 1966). The
Kiselvka-Manoma terrane (too small to show in figs. 1, 3) occurs in a
narrow band along the northeast edge of the Amur River terrane and
contains Jurassic and Early Cretaceous ribbon chert, siliceous shale,
Cretaceous flysch, Jurassic basalt, and Early Jurassic limestone in an
Early Cretaceous olistostrome (Filippov, 1988; Shevlyev, 1987; Natal'in,
1991; Khanchuk and others, 1994). The Khabarovsk terrane (KB) (younger,
Cretaceous part; too small to show in figs. 1, 3) consists of a melange
with various-size fault-bounded lenses and slices of Triassic chert,
Early to Middle Jurassic siliceous shale, hemipelagic sedimentary rocks,
mafic volcanic rocks, and gabbro, Late Carboniferous, Permian, and Late
Triassic limestone, and schist and metasandstone of unknown age
(Shevelev, 1987; Natal'in and Alekseenko, 1989; Natal'in and Zyabrev,
1989). The late Paleozoic limestone, which locally contains
volcanic-rock layers and a Tethyan fauna, is interpreted as reef caps on
seamounts.

Origin of the Khingan Arc

The Khingan continental-margin arc (ko, fig. 3) is interpreted as having
formed from oblique subduction of the ancestral Pacific oceanic plate.
Fragments of this plate are interpreted as occurring in tectonically
interwoven fragments of the Amur River (AM), Khabarovsk (KB) (younger
Early Cretaceous part), and Kiselevka-Manoma accretionary-wedge terranes
(Natal'in, 1991, 1993; Nokleberg and others, 1994a; Sengör and Natal'in,
1996a, b). This tectonic pairing is based on (1) occurrence of
accretionary-wedge terranes outboard (oceanward) of, and parallel to,
the various parts of the Khinghan arc (fig. 3); (2) formation of melange
structures during the Early and mid-Cretaceous (Vrublevsky and others,
1988; Natal'in, 1991; Nokleberg and others, 1994a; Nechaev and others,
1996); and (3) where not disrupted by extensive Cretaceous movement
along the Central Sihote-Aline strike-slip fault, dipping of melange
structures and bounding faults toward and beneath igneous-rock units of
the arc (Natal'in, 1993). Formation of the Khingan arc and associated
subduction is generally interpreted as ending in the late
mid-Cretaceous, when oblique subduction changed into sinistral-slip
faulting along the outboard margin of the arc.

Mid-Cretaceous Kema Island Arc in the Eastern Part of the Russian
Southeast

The Kema arc is defined as a suite of mainly mid-Cretaceous igneous
rocks in the East Sikhote-Alin area in the Russian Southeast and
offshore on Sakhalin Island (Nokleberg and others, 1994a; Khanchuk and
others, 1996). These igneous-arc rocks were originally defined as part
of the mid-Cretaceous and Late Cretaceous East Sikhote-Alin
continental-margin arc (es, fig. 3; Parfenov and Natal'in, 1986) or as
part of the Samaka island arc (SMA, figs. 1, 3; Simanenko, 1986).
However, Late Cretaceous volcanic rocks of the East Sikhote-Alin arc
disconformably overlie igneous rocks of the Kema terrane, thereby
indicating, along with other field relations, that the Kema arc is a
separate terrane (Nazarenko and Bazhanov, 1986; Khanchuk and others,
1996).

Rock Units of the Kema Arc

The Kema island-arc terrane (KE, fig. 3) consists chiefly of a chain of
predominantly volcanic rocks, with a western unit of volcaniclastic
deposits. The volcanic rocks consist of lava, hyaloclastic rocks, and
marine tuff and are composed of basalt, basaltic andesite, and andesite.
These units occur in flows that range in thickness from a few meters to
a few tens of meters. Other rocks are terrigenous volcanic deposits,
flysch composed of fine-grained sandstone and siltstone, and distal
turbidite-type argillite that alternates with beds of volcaniclastic
rocks. Thick layers of basaltic andesite also occur. Sedimentary rocks
contain Aptian to Albian bivalves. In the lower part of the section, the
flysch consists of alternating, medium-grained sandstone and tuffaceous
sandstone, with typical turbidite-graded bedding, and abundant siltstone
fragments. The sandstone is arkosic and medium grained (Nazarenko and
Bazhanov, 1986; Simanenko, 1986; Khanchuk and others, 1996).

Subduction-Zone Units Related to the Kema Arc

Tectonically linked to the Kema arc was an elongate, transpressional
subduction zone that is now preserved in a discontinuous and disrupted
collage of terranes in the Sakhalin and Hokkaido Islands. The terranes
are the older part of the Aniva subduction-zone terrane (ANV) on
Sakhalin Island and the Kamuikotan subduction-zone terrane (KK) on
Hokkaido Island (figs. 1, 3). The older part of the Aniva
subduction-zone terrane consists chiefly of a melange unit with a matrix
of mid-Cretaceous turbidite that encloses bodies of serpentinite
melange, ophiolite, blueschist, and greenschist (Richter, 1986). The
Kamuikotan subduction-zone terrane consists chiefly of high-pressure
metamorphic rocks, serpentinite melange, and ophiolite. K-Ar ages of the
ophiolite range from 100 to 125 Ma (Kato and Nakagawa, 1986; Ichikawa
and others, 1990).

Origin of the Kema Arc

The Kema arc is interpreted as having formed from subduction of part of
the ancestral Pacific oceanic plate that is now preserved as
tectonically interwoven fragments of the Aniva and Kamuikotan
subduction-zone terranes. Volcanic rocks of the Kema arc correlate with
the Early Cretaceous and mid-Cretaceous volcanic rocks that
disconformably overlie the Oshima accretionary-wedge terrane on Hokkaido
Island (too small to show in fig. 1) and volcanic rocks of the
northeastern part of Honshu Island (Kiminami and Kontani, 1983; Ichikawa
and others, 1990). The Early Cretaceous and mid-Cretaceous Kema arc is
similar to the present-day Aleutian-Wrangell arc.

Late Jurassic and Early Cretaceous Uda Arc in the Central Part of the
Russian Far East

The Uda igneous arc is defined as a suite of mainly Late Jurassic and
Early Cretaceous and lesser Late Triassic to Middle Jurassic
igneous-rock units in the central part of the Russian Far East
(Parfenov, 1984; Parfenov and Natal'in, 1985, 1986; Natal'in, 1993; B.A.
Natal'in, in Nokleberg and others, 1994a; Sengör and Natal'in, 1996a,
b). Remnants of the arc are preserved in the Uda volcanic-plutonic belt
(ud, fig. 3), the Uniya-Bom turbidite-basin terrane (UB, fig. 1), the
Umlekan-Ogodzhin volcanic-plutonic belt (uo, fig. 3), and the Upper Amur
sedimentary assemblage (ua, fig. 3). The Uda arc was deposited on,
adjacent to, and intruded into the North Asian Craton (NSC), the
Stanovoy block of the North Asian Craton (NSS), and the Okhotsk terrane
(OK) and was formed as part of the Mongol-Okhotsk active continental
margin (figs. 1, 3, 7). Farther south, magmatic equivalents of the Uda
arc occur in the Great Hinggan Mountains of northeastern China
(Natal'in, 1993; B.A. Natal'in, in Nokleberg and others, 1994a; Sengör
and Natal'in, 1996a, b). The various igneous-arc-related units of the
Uda arc (Uda volcanic-plutonic belt, Uniya-Bom turbidite-basin terrane,
Umlekan-Ogodzhin volcanic-plutonic belt, and Upper Amur sedimentary
assemblage) are grouped into a single arc on the basis of similar age,
similar arc origin, geographic proximity, and simplicity.

Rock Units of the Uda Arc

The Uda volcanic-plutonic belt (ud, fig. 3) consists chiefly of basalt,
andesite-basalt, andesite, and tuff that are interlayered with nonmarine
sandstone, siltstone, conglomerate, and coal containing a Late Jurassic
and Early Cretaceous flora (Filatova, 1979, 1988; Sosunov and others,
1982; Lebedev and others, 1989; Zmievskiy and others, 1990). The belt
also contains Jurassic granitic rocks, including granodiorite, diorite,
and granite, which extend westward along the southern part of the North
Asian cratonal margin (NSC, figs. 1, 3, 7). The granitic rocks of the
belt yield reliable isotopic ages ranging from 130 to 200 Ma.

The Uniya-Bom turbidite-basin terrane (UB, fig. 1) consists chiefly of a
tectonic sheet that is composed of Late Triassic to Early Jurassic
turbidite deposits and interbedded olistostromes (Kirillova and Turbin,
1979; Natal'in and others, 1985). The turbidite deposits contain lenses
of greenstone and chert that are typical of the Tukuringra-Dzhagdi
terrane (TD). Sandstone and conglomerate clasts were derived in part
from the North Asian Craton (NSC, figs. 1, 3, 7). The terrane is
intensively deformed and contains a penetrative stretching lineation
that formed by ductile deformation during strike-slip tectonic
transport.

The Umlekan-Ogodzhin volcanic-plutonic belt (uo, fig. 3) consists
chiefly (Volsky, 1983; Kozlovsky, 1988) of (1) Early Cretaceous
sandstone, conglomerate, mudstone, calc-alkalic andesite, dacite, and
tuff, with K-Ar ages of 112 to 135 Ma; (2) Late Cretaceous alkalic
basalt and rhyolite; and (3) Early Cretaceous granite, granodiorite,
diorite, and monzodiorite.

The Upper Amur sedimentary assemblage (ua, fig. 3) consists chiefly of
Late Jurassic shallow-marine sandstone, siltstone, and shale, and
nonmarine Early Cretaceous clastic rocks containing coal (Kirillova and
Turbin, 1979). The structural thickness of the sedimentary rocks is
about 3,000 m.

Subduction-Zone Units Linked to the Uda Arc

Tectonically paired to the Uda continental-margin arc was a subduction
zone that is now preserved in a discontinuous collage of terranes in the
central part of the Russian Far East. These terranes, composed mainly of
Paleozoic and early Mesozoic oceanic-crustal rocks, upper-mantle rocks,
and turbidite deposits, consist of the Tukuringra-Dzhagdi
subduction-zone (TD), the Galam accretionary-wedge (GL), and the Ulban
accretionary-wedge (UL) terranes (fig. 3; Parfenov, 1984; Parfenov and
Natal'in, 1985, 1986; Natal'in, 1991, 1993; Natal'in and Borukayev,
1991; Natal'in and Faure, 1991, Faure and Natal'in, 1992; B.A. Natal'in,
in Nokleberg and others, 1994a; Khanchuk and others, 1996; Sengör and
Natal'in, 1996). These subduction-zone terranes occur along splays of
the Mongol-Okhotsk Fault, along which substantial middle Mesozoic
through early Tertiary sinistral-slip faulting has occurred.

The Turkuringra-Dzhagdi accretionary-wedge terrane (TD, figs. 1, 3)
consists chiefly of fault-bounded units of tectonic lenses or
olistoliths of Late Proterozoic limestone, Silurian and Devonian mafic
volcanic rocks and chert, Carboniferous and Permian sandstone,
siltstone, shale, and turbidites, flysch, greenstone, chert, and
limestone containing Permian Tethyan fusulinids, and a narrow tectonic
lens of ophiolite (Pikansk complex) along the southern margin of the
terrane that consists of gabbro, amphibolite pyroxenite, serpentinite,
and plagiogranite (Natal'in and others, 1985, Kozlovsky, 1988).

The Galam accretionary-wedge terrane (GL, figs. 1, 3) consists chiefly
of (1) Cambrian and Early Ordovician limestone olistoliths in a flysch
matrix; (2) Silurian to Early Carboniferous and Late Permian turbidite
deposits; and (3) lesser mafic volcanic rocks, chert, siliceous shale,
pelagic shale, and fine-grained graywacke that are included in
widespread olistostrome deposits. Oceanic chert, mafic volcanic rocks,
and clastic rocks of Silurian to Late Permian age also occur in local
tectonic slices (Kirillova and Makhinin, 1983; Roganov and others, 1986;
Natal'in and Popeko, 1991). Along the boundary with the Baladek cratonal
terrane (BL, fig. 1) are fault slices of harzburgite, dunite, and
websterite.

The Ulban accretionary-wedge terrane (UL, fig. 3) consists chiefly of
Early and Middle Jurassic turbidite deposits and unconformably overlying
Callovian turbidite deposits (Natal'in, 1991). The turbidite deposits
contain local tectonic lenses of oceanic-crustal rocks that include
chert, siliceous shale, and mafic volcanic rocks.

Origin of the Uda Arc

The Uda continental-margin arc is interpreted as having formed from
subduction of the Mongol-Okhotsk Ocean that is now preserved as
tectonically interwoven fragments of the Turkuringra-Dzhagdi, Galam, and
Ulban subduction-zone and accretionary-wedge terranes (figs. 7--15;
Natal'in, 1993; B.A. Natal'in, in Nokleberg and others, 1994a; Sengör
and Natal'in, 1996a, b). This tectonic pairing is based on (1)
occurrence of these accretionary-wedge terranes outboard (oceanward),
southward of (in present-day coordinates), and parallel to, the various
parts of the Uda arc (ud, fig. 3); (2) formation of melange structures
during the Jurassic and Early Cretaceous (Nokleberg and others, 1994a);
and (3) where not disrupted by extensive Cretaceous and early Cenozoic
dextral slip along the Mongol-Okhotsk Fault (MU, fig. 3), dipping of
melange structures and bounding faults toward and beneath igneous-rock
units of the arc. Subduction is generally interpreted as ending in the
Early to mid-Cretaceous, during final closure of the Mongol-Okhotsk
Ocean.

Late Triassic to Early Cretaceous Kony-Murgal Arc in the Russian
Northeast

Remnants of the Kony-Murgal continental-margin and island arc are
preserved in the Kony-Murgal island-arc terrane (KM, figs. 1, 3) in the
eastern part of the Russian Northeast. The Kony-Murgal terrane occurs
along the northwestern margin of the Sea of Okhotsk, southeast of the
Kolyma-Omolon superterrane (fig. 1). The Kony-Murgal arc is the eastward
extension of the mostly coeval Uda arc. The Kony-Murgal
continental-margin and island-arc terrane consists chiefly of Late
Triassic to Hauterivian folded, calc-alkaline, continental and
island-arc volcanic and sedimentary rocks (Belyi, 1977; Filatova, 1979,
1988; Parfenov, 1984; Nekrasov and Sumin, 1987). The volcanic-rock units
are mainly basalt, andesite-basalt, andesite, and tuff and local
shallow-marine and nonmarine volcaniclastic rocks. The terrane also
contains Late Jurassic and Early Cretaceous (pre-Albian) granodiorite,
tonalite, plagiogranite, and quartz diorite and, locally, Late Permian
through Middle Jurassic shale, siltstone, sandstone, conglomerate, tuff,
and basalt.

Subduction-Zone Units Linked to the Kony-Murgal Arc

Tectonically linked to the Kony-Murgal arc was a subduction zone now
preserved in the discontinuous collage of the Talovskiy (TL) subduction
zone and Penzhina-Anadyr (PA) accretionary wedge (figs. 1, 3). These
terranes, which occur outboard (oceanward) of, and parallel to, the
Kony-Murgal arc (figs. 1, 2), consist mainly of Paleozoic and early
Mesozoic oceanic-crustal rocks, upper-mantle rocks, and turbidite
deposits (Parfenov and others, 1993a, b; Nokleberg and others, 1994a).

The Talovskiy terrane (TL, figs. 1, 3; Khanchuk and others, 1990;
Sokolov, 1990, 1992; Vishnevskaya and others, 1992; Heiphitz and others,
1994b; Sokolov and Byalobzhesky, 1996; Khudoley and Sokolov, 1998)
consists chiefly of (1) tectonic sheets of Bathonian and Tithonian
ophiolite and serpentinite melange, with blocks of ultramafic rock,
gabbro, plagiogranite, oceanic dike suites, amphibolite, and glaucophane
schist; (2) island-arc and forearc andesite, dacite, tuff, and
sedimentary rocks; and (3) the Kuyul subduction-zone melange, composed
of Late Jurassic and Early Cretaceous turbidite deposits.

The Penzhina-Anadyr terrane (PA, figs. 1, 3; Khanchuk and others, 1992;
Sokolov, 1992; Sokolov and Byalobzhesky, 1996; Khudoley and Sokolov,
1998) consists chiefly of (1) thrust slices of serpentinite melange; (2)
an ophiolite sequence that is depositionally overlain by Devonian and
Carboniferous chert, calcareous sandstone, tuff, and limestone; (3)
younger diabase, plagiogranite, and diorite dikes with K-Ar ages of 180
to 304 Ma; (4) shallow-marine sandstone and siltstone with interlayered
conglomerate; and (5) Late Jurassic to Early Cretaceous sandstone,
siltstone, and mudstone.

Origin of the Kony-Murgal Arc

The Kony-Murgal arc is interpreted as having formed from subduction of
part of the ancestral Pacific oceanic plate (Parfenov and Natal'in,
1985, 1986; Filatova, 1988; Zonenshain and others, 1990; Sokolov, 1992;
Parfenov and others, 1993a, b; Nokleberg and others, 1994a) that is
preserved in the Kony-Murgan (KM) continental-margin and island-arc, the
Talovskiy (TL) subduction-zone, and the Penzhina-Anadyr (PA)
accretionary-wedge and subduction-zone terranes (figs. 7--15). This
tectonic pairing is based on (1) occurrence of these subduction-related
terranes outboard (oceanward or to the east using present-day
coordinates) and parallel to the various parts of the other rock units
of the Kony-Murgal arc (fig. 1); (2) formation of melange structures
during the Jurassic and Early Cretaceous (Nokleberg and others, 1994a);
and (3) where not disrupted by displacement along Cretaceous and early
Cenozoic northwest-striking strike-slip faults, dipping of melange
structures and bounding faults toward and beneath igneous-rock units of
the arc. Subduction is generally interpreted as ending in the Early
Cretaceous to mid-Cretaceous during final closure of the Mongol-Okhotsk
Ocean and the accretion of the Kony-Murgal island arc onto the Northeast
Asian continental margin (Stavsky and others, 1989, 1990; Zonenshain and
others, 1990; Sokolov, 1992).

Late Jurassic Through Mid-Cretaceous Pekul'ney Arc in the Russian
Northeast

Remnants of the Pekul'ney island arc are preserved in the West Pekul'ney
island-arc terrane (WP, figs. 1, 3) in the eastern part of the Russian
Northeast. The West Pekul'ney island-arc terrane (Nekrasov and Sumin,
1987; Zhulanova and Pertsev, 1987) consists of various tectonic sheets
composed of (1) thick, folded sequences of flows and volcaniclastic
rocks of intermediate, mafic, and sparse felsic compositions, argillite,
siltstone, sandstone, grit, and rare limestone containing *Buchia* of
Berriasian and Valanginian age and *Aucelline* of Aptian to Albian age;
(2) Hauterivian to Barremian olistostrome with gabbro, ultramafic rock,
jasper, and basalt fragments; (3) Early Cretaceous plagiogranite, and
gabbro, amphibole-pyroxene schist, and olivine gabbro with
Pb-Pb-isotopic ages of 1,200 to 2,900 Ma; and (4) layered gabbro,
pyroxene-amphibole gabbro, and amphibole microgabbro of unknown age.

Subduction-Zone Units Linked to the Pekul'ney Arc

Tectonically linked to the Pekul'ney arc was a subduction zone now
preserved in the discontinuous collage of the Pekul'ney subduction-zone
terrane (PK) that occurs outboard (oceanward) of, and parallel to the
Pekul'ney terrane (fig. 1; Parfenov and others, 1993a, b; Nokleberg and
others, 1994a). The terrane (Nekrasov and Sumin, 1987; Zhulanova and
Pertsev, 1987) has western and eastern units. The western unit consists
of (1) a basal serpentinite-matrix melange that contains fragments of
metamorphic rocks, including greenschist, glaucophane schist, and
picritic basalt, (2) a metamorphic complex composed of amphibolite and
schist that are derived from dunite, spinel peridotite, and
clinopyroxenite that yields Pb-Pb-isotopic ages of 1.6 to 1.8 Ga, and
eclogite inclusions that yield isotopic ages of 1.9 to 2.4 Ga; and (3)
the Late Jurassic and Early Cretaceous Pekulneyveem suite, which is
composed of basalt, tuff, hyaloclastite, radiolarian chert, siltstone,
and sandstone. The eastern unit of the Pekul'ney terrane consists of the
Televeem unit, which is a thick flysch of Early Cretaceous (Aptian to
Albian) and Late Cretaceous (Cenomanian to Turonian) age.

Origin of the Pekul'ney Arc

The Pekul'ney arc is interpreted as having formed from subduction of
part of the ancestral Pacific oceanic plate (Parfenov and Natal'in,
1985, 1986; Filatova, 1988; Zonenshain and others, 1990; Sokolov, 1992;
Parfenov and others, 1993a, b; Nokleberg and others, 1994a) that is
preserved in the Pekul'ney subduction-zone terrane (PK). This tectonic
pairing is based on (1) occurrence of the subduction-related terranes
outboard or east of (in present-day coordinates), and parallel to, the
West Pekul'ney terrane (fig. 1); (2) formation of melange structures
during the Jurassic and Early Cretaceous (Nokleberg and others, 1994a);
and (3) where not disrupted by displacement along Cretaceous and early
Cenozoic northwest-striking, strike-slip faults, dipping of melange
structures and bounding faults toward and beneath other units of the
arc. Subduction is generally interpreted as ending in the Early to
mid-Cretaceous, during accretion of the island arc onto the Northeast
Asian continental margin (Stavsky and others, 1989; Zonenshain and
others, 1990; Sokolov, 1992).

Late Jurassic Through Middle Cretaceous Mainitskiy Arc in the Russian
Northeast

Remnants of the Mainitskiy arc are preserved in the Mainitskiy
island-arc terrane (MAI, figs. 1, 3) that occurs in the eastern part of
the Russian Northeast (Stavsky and others, 1989; Zonenshain and others,
1990; Bogdanov and Til'man, 1992; Sokolov, 1992; Parfenov and others,
1993a, b; Nokleberg and others, 1994a; Sokolov and Byalobzhesky, 1996).
The Mainitskiy island-arc terrane consists of two sequences (Stavsky and
others, 1989; Shmakin, 1991; Vishnevskaya and others, 1991; Sokolov,
1992; Didenko and others, 1993; Sokolov and Byalobzhesky, 1996). An
older sequence consists of a lower unit of serpentinite and serpentinite
melange that contain fragments of late Paleozoic and early Mesozoic
ophiolite with Middle and Late Jurassic radiolarians, and an upper
Berriasian and Valanginian unit of graywacke, siltstone, tuff, and
bedded chert. Local olistoliths are common and are composed of
ophiolite, limestone containing Permian and Triassic foraminifers,
plagiogranite, andesite, and rhyolite. A younger sequence consists of a
thick assemblage of Late Jurassic and Early Cretaceous island-arc
volcanic and sedimentary rocks composed of tholeiitic basalt, andesitic
basalt, rhyolite, tuff, breccia, chert, siltstone, and sandstone
containing Callovian to Kimmeridgian and Tithonian to Hauterivian
radiolarians. The Mainitskiy terrane also contains a complex series of
large, tectonically imbricated nappes of disrupted ophiolite (Yagel
melange) of Late Jurassic to Early Cretaceous (Callovian to Hauterivian)
age and several tectonic sheets of dunite, harzburgite, gabbro, and
ultramafic rocks that are structurally overlain by island-arc volcanic
rocks. The Mainitskiy terrane is interpreted as a fragment of a Late
Jurassic to mid-Cretaceous island arc that is underlain by a basement of
oceanic crust and primitive-island-arc rocks of Triassic to Early
Jurassic age.

Subduction-Zone Units Linked to the Mainitskiy Arc

Tectonically linked to the Mainitskiy arc was a subduction zone now
preserved in the discontinuous collage of the Alkatvaam
accretionary-wedge terrane (AV, figs. 1, 3; Sokolov, 1992; Didenko and
others, 1993; Parfenov and others, 1993a, b; Nokleberg and others,
1994a; Sokolov and Byalobzhesky, 1996; Khudoley and Sokolov, 1998). The
Alkatvaam accretionary-wedge terrane consists chiefly of an intensely
deformed, thick assemblage of clastic flysch and tuffaceous and clastic
deposits, with local coeval intercalated Late Triassic, Late Jurassic,
Cretaceous, and Paleocene island-arc volcanic and pyroclastic rocks
(Pushcharovskiy and Til'man, 1982; Kazimirov, 1985; Grigor'yev and
others, 1987). A basal unit of serpentinite melange contains fragments
of late Paleozoic and Triassic ophiolite and metamorphic rocks.

Origin of the Mainitskiy Arc

The Mainitskiy arc is interpreted as having formed from subduction of
part of the ancestral Pacific oceanic plate (Stavsky and others, 1989;
Zonenshain and others, 1990; Sokolov, 1992; Parfenov and others, 1993a,
b; Nokleberg and others, 1994a; Sokolov and Byalobzhesky, 1996) that is
partly preserved in the Alkatvaam accretionary-wedge terrane (AV, fig.
3). This tectonic pairing is based on (1) the occurrence of the
Alkatvaam terrane outboard of, and parallel to, the various island-arc
terranes (fig. 3); and (2) coeval, Late Jurassic and Early Cretaceous
accretion of the Mainitskiy and Alkatvaam terranes. Subduction is
generally interpreted as ending in the mid-Cretaceous with the accretion
of the Mainitskiy arc and associated subduction zone and the subsequent
outboard (oceanward) stepping of subduction to form the Okhotsk-Chukotka
igneous arc (Parfenov and others, 1993a, b; Nokleberg and others, 1994a;
Sokolov and Byalobzhesky, 1996).

Late Jurassic and Early Cretaceous Uyandina Arc in the Russian Northeast

The Uyandina arc is defined as the suite of igneous rocks of the
Uyandina-Yasachnaya volcanic belt that forms part of the Indigirka-Oloy
sedimentary-volcanic-plutonic assemblage (io, fig. 3) along the western
and southwestern margins (present-day coordinates) of the Kolyma-Omolon
superterrane in the central part of the Russian Far East (Parfenov,
1984, 1991, 1995a, b; Sosunov, 1985; Nokleberg and others, 1994a). The
Indigirka-Oloy assemblage contains the Uyandina-Yasachnaya volcanic
belt, the Zyryanka sedimentary basin, the small Ainakhkurgen, Umkuveem,
and Upper Penzhina basins, and the North Omolon basin. The
Uyandina-Yasachnaya volcanic belt occurs in the southwestern part of the
Indigirka-Oloy assemblage in the Chersky Range.

Rock Units of the Uyandina Arc

The Indigirka-Oloy sedimentary-volcanic-plutonic assemblage (io, fig. 3)
consists chiefly of shallow-marine and nonmarine late Middle Jurassic to
Neocomian formations overlying Precambrian, Paleozoic, and early
Mesozoic rocks of the Kolyma-Omolon superterrane (Parfenov, 1984, 1991,
1995a, b; Archegov and others, 1987; Gaiduk, 1988; Gaiduk and others,
1989, 1993; Shul'gina and others, 1990). The assemblage consists of
mainly sandstone, siltstone, shale, conglomerate, volcanic rocks of
varying composition, and lesser granitic plutonic rocks. The assemblage
is weakly deformed and is folded into large, doubly plunging anticlines
and synclines. It consists of three distinct volcanic belts and
sedimentary basins. (1) The Zyryanka sedimentary basin is a 60-km-wide
and 550-km-long basin, in the central part of the Indigirka-Oloy
assemblage, that contains Late Jurassic through Late Cretaceous marine
clastic rocks. The Zyryanka basin is interpreted as having formed in the
backarc region of the Uyandina-Yasachnaya arc (Parfenov, 1984, 1991,
1995a, b). (2) The small Ainakhkurgen, Umkuveem, and Upper Penzhina
basins along the southeastern margin of the assemblage contain Late
Jurassic and Neocomian graywacke and shale. (3) The North Omolon basin
in the central part of the Kolyma-Omolon superterrane contains shallow
marine and nonmarine Late Jurassic and Neocomian sandstone, shale,
conglomerate, and alkalic basalt.

The Uyandina-Yasachnaya volcanic belt consists of calc-alkalic basalt,
andesite, and rhyolite, interlayered with shallow-marine and nonmarine
sandstone, siltstone, shale, and conglomerate of Oxfordian,
Kimmeridgian, and Early Volgian age. The belt is intruded by granitic
rocks with Ar-Ar and K-Ar ages of 120 to 144 Ma (Fujita and others,
1997).

Subduction-Zone Units Linked to the Uyandina Arc

The subduction zone tectonically linked to the Uyandina arc is assumed
to have been situated along the southwestern and northwestern margins of
the Kolyma-Omolon superterrane (Parfenov, 1984, 1991, 1995b). Along
these margins are the In'yali-Debin and Polousny synclinoria, which are
composed of highly deformed Late Jurassic flysch. These deposits are
interpreted as representing the forearc basin of the Uyandina arc. Near
the Charky-Indigirka thrust fault, which separates the synclinoria from
the Kula-Nera terrane, is the Chersky Range ophiolite belt that contains
the Garbyn'ya and Debin ophiolite complexes (GB, DB, fig. 1) of unknown
age (Oxman and others, 1995). These ophiolites are herein interpreted as
the subducted remnants of the Oimyakon Ocean that formed between the
North Asian cratonal margin and the Kolyma-Omolon superterrane (Oxman
and others, 1995; Parfenov and others, 1996). The backarc basin of the
Uyandina arc is interpreted northeast of the arc and is represented by
Kimmeridgian and Volgian black shale of the Ilin-Tas anticlinorium and
the Zyryanko basin. An alternative interpretation is that the subduction
zone linked to the Uyandina arc was situated to the northeast of the arc
(Zonenshain and others, 1990). With this interpretation, the black shale
of the Ilin-Tas anticlinorium represent the Uyandina-Yasachnaya forearc,
and the flysch deposits in the In'yali-Debin and Polousny synclinorium
represent the backarc.

Origin of the Uyandina Arc

The Uyandina arc is interpreted as having formed from convergence
between the Kolyma-Omolon superterrane and the North Asian cratonal
margin (Verkhoyansk fold-and-thrust belt; NSV, figs. 1, 3, 7) and
closing of the relatively small Oimyakon Ocean (Parfenov, 1984, 1995b,
1997). This ocean is interpreted as opening during the Late Devonian to
Early Carboniferous as a result of rifting of the Omulevka terrane from
the North Asian Craton. The collision of the Kolyma-Omolon superterrane
and the North Asian Craton (Trunilina and Orlov, 1997) resulted in the
formation of (1) the collisional Main batholith granite belt that
extends along the southwestern margin of the superterrane, and (2) the
subduction-related Northern collisional granite belt (no, fig. 3) that
extends along the northwestern margin of the superterrane. 39Ar/40Ar
data indicate that the Main granite belt formed at 144 to 134 Ma and the
Northern collisional granite belt at 127 to 120 Ma (Fujita and others,
1997). These data and relations indicate that the Uyandina arc and
associated subduction ended in the Early Cretaceous with accretion of
the Kolyma-Omolon superterrane to the North Asian cratonal margin (NSV,
figs. 1, 3, 7; Parfenov, 1991, 1995a, b, 1997; Parfenov and others,
1993a, b; Nokleberg and others, 1994a). Many of the data supporting this
interpretation are derived from the northwest-southeast-trending part of
the Kolyma structural loop of Zonenshain and others (1990).

Late Jurassic and Early Cretaceous Oloy and Svyatov Nos Arcs in the
Russian Northeast

The Oloy and Svyatov Nos continental-margin arcs are defined as suites
of igneous rocks of the Oloy and Svyatov Nos volcanic belts that occur
along the eastern and northeastern margins (present-day coordinates) of
the Kolyma-Omolon superterrane (KLO, fig. 7) in the central part of the
Russian Northeast (Parfenov, 1984, 1991, 1995a, b; Sosunov, 1985;
Nokleberg and others, 1994a). The Late Jurassic-Neocomian Oloy volcanic
belt (included in the Indigirka-Oloy sedimentary-volcanic-plutonic
assemblage; io, fig. 3) occurs along the northeastern margin of the
Kolyma-Omolon superterrane. The belt consists of shallow-marine and
nonmarine mafic, intermediate-composition, and siliceous volcanic rocks
and tuff, associated sedimentary rocks, and small plutons of granite,
granodiorite, and monzogranite (Shul'gina and others, 1990; Natapov and
Shul'gina, 1991). The Late Jurassic Svyatov Nos volcanic belt (also
included in the Indigirka-Oloy sedimentary-volcanic-plutonic assemblage;
io, fig. 3) extends in a north-south direction across the Svyatov Nos
Cape and, according to aeromagnetic data, can be traced northward into
the eastern part of the Laptev Sea. The belt contains mainly andesite,
rhyolite, and tuff, with interlayered shallow-marine sandstone,
conglomerate, and siltstone.

Subduction-Zone Units Linked to the Oloy and Svyatov Nos Arcs

Tectonically linked to the Oloy and Svyatov Nos volcanic belts was a
subduction zone now preserved in the South Anyui terrane (SA, fig. 3;
Parfenov, 1984). The South Anyui subduction-zone terrane (Natal'in,
1984; Savostin and Drachev, 1988a, b; Dudko and Spektor, 1989; Lychagin
and others, 1991; Drachev and Savostin, 1992) consists of thrust slices
of (1) tectonic sheets of serpentinized peridotite and Permian to
Triassic turbidite deposits; (2) highly deformed, Carboniferous (in
part) midoceanic-ridge-type pillow lavas; (3) interlayered
midoceanic-ridge-type pillow basalt and Middle and Late Jurassic
graywacke, slate, and chert; and (4) local glaucophane schist and
Berriasian through Hauterivian turbidites.

Origin of the Oloy and Svyatov Nos Arcs

The Oloy and Svyatov Nos volcanic belts are interpreted as parts of
continental-margin igneous arcs that formed during closure of different
parts of the South Anyui Ocean. This tectonic pairing is based mainly on
the occurrence of the South Anyui terrane outboard of, and parallel to,
the newly formed continental margin of Northeast Asia and parallel to
the Oloy and Svyatov Nos volcanic belts (fig. 3). Subduction is
generally interpreted as occurring during the Late Jurassic and Early
Cretaceous, when the arcs were active (Parfenov, 1984, 1991, 1995b;
Parfenov and others, 1993a, b).

Late Paleozoic to Early Jurassic Alazeya Arc in the Russian Northeast

Remnants of the mainly Late Triassic and Early Jurassic and possibly
middle and late Paleozoic Alazeya island arc are preserved in the
Alazeya (AL) and Khetachan (KH) island-arc terranes (fig. 1) in the
Russian Northeast within the Kolyma-Omolon superterrane (fig. 3;
Parfenov, 1984, 1991, 1995a, b; Sosunov, 1985; Nokleberg and others,
1994a). These terranes consist of an extensive suite of mainly Late
Triassic and Early Jurassic volcanic rocks and granitic plutonic rocks
that extend for a distance of only about 150 km (fig. 1). In addition to
Late Triassic and Early Jurassic igneous-arc rocks, the Alazeya
island-arc terrane also contains middle and late Paleozoic igneous-arc
rocks that may correlate with the Carboniferous Skolai island arc of the
Wrangellia superterrane (Nokleberg and others, 1994a).

Rock Units of the Alazeya Arc

The Alazeya island-arc terrane (AL, figs. 1, 3; Rusakov and others,
1975, 1977; Grinberg and others, 1981) consists chiefly of (1) an
intensely deformed tectonic melange composed of deep-water basalt,
chert, graywacke, glaucophane schist, and greenschist of unknown age;
and (2) a thick sequence of Carboniferous to Early Jurassic
littoral-marine and shallow-marine tuff of intermediate, mafic, and
siliceous composition, graywacke, grit, and conglomerate with rare lava
horizons.

The Khetachan island-arc terrane (KH, figs. 1, 3; Afitsky and Lychagin,
1987; Natapov and Shul'gina, 1991) consists chiefly of (1) strongly
deformed, thick, Late Triassic to Early Jurassic volcanogenic sandstone,
grit, and conglomerate and lesser mafic to intermediate-composition tuff
and calc-alkalic volcanic flows, with interbedded siltstone, argillite
and limestone; and (2) Early Jurassic siltstone, volcaniclastic
sandstone and conglomerate, interbedded basaltic and andesitic tuff and
flows, and Late Triassic syenite and diorite.

Subduction-Zone Units Linked to the Alazeya Arc

Tectonically linked to the Alazeya arc was probably an elongate
subduction zone that is preserved only as a small remnant in the Aluchin
subduction-zone terrane (AC, figs. 1, 3), which occurs at the east end
of this chain of island-arc terranes. The Aluchin subduction-zone
terrane (Lychagin and others, 1989; Byalobzhesky and others, 1990;
Seslavinskiy and Ged'ko, 1990) consists chiefly of (1) dismembered
ophiolites of presumed middle Paleozoic age, including harzburgite,
pyroxenite, dunite, lherzolite, gabbro, plagiogranite, a mafic dike
suite, basalt, and local glaucophane schist; (2) tectonic lenses of
Middle Carboniferous to Early Permian island-arc clastic-tuffaceous
deposits, basalt, and andesitic basalt that are intruded by diorite and
tonalite; and (3) unconformably overlying Late Triassic (Norian)
shallow-marine volcanic and sedimentary rocks, and Early Jurassic
clastic deposits that contain pebbles of the underlying diorite and
tonalite. In the inner part of the Kolyma-Omolon superterrane, the
subduction zone linked to the Alazeya arc can be traced beneath Cenozoic
deposits along a horseshoe-like magnetic high (Parfenov, 1991).

Origin of the Alazeya Arc

The Alazeya arc is interpreted as having formed from subduction of the
Aluchin subduction-zone terrane (Parfenov, 1991, 1995a, b; Parfenov and
others, 1993a, b; Nokleberg and others, 1994a). This tectonic linkage is
based mainly on the occurrence of the Aluchin subduction-zone terrane
parallel to the arc (fig. 1). Subduction ended in the Early to Middle
Jurassic with accretion of the arc and subduction zone to other parts of
the Kolyma-Omolon superterrane, including the Omolon, Prikolyma, and
Omulevka terranes.

Late Jurassic Through Mid-Cretaceous Nutesyn-Koyukuk Arc in the Russian
Northeast and Western Alaska

The Nutesyn-Koyukuk igneous arc is herein defined as a discontinuous
suite of mainly Late Jurassic through mid-Cretaceous igneous-rock units
in the Russian Northeast and western Alaska (Parfenov and others, 1993a,
b; Parfenov, 1995a, b, 1997; Nokleberg and others, 1994a, b; Plafker and
Berg, 1994; Monger and Nokleberg, 1996). The arc consists of an
extensive suite of mainly turbidites, volcaniclastic rocks, volcanic
rocks, and plutonic rocks. From west to east (present-day coordinates),
remnants of the arc are preserved in the Nutesyn (NU), Koyukuk (KY),
Nyac (NY), and Togiak (TG) island-arc terranes (figs. 1-4). The various
units of the Nutesyn-Koyukuk arc occur along an east-west trend for
about 2,000 km (figs. 1, 3) and are grouped as parts of a single arc on
the basis of similar age, similar lithologies, geographic proximity, and
simplicity. The Nutesyn part of the arc is interpreted as a
continental-margin arc (Parfenov and others, 1993a, b; Parfenov, 1995a,
b, 1997), whereas the onstrike Koyukuk arc is interpreted by most
workers as an island arc that formed near the passive continental margin
of North America (Nokleberg and others, 1994a, b; Patton and others,
1994; Plafker and Berg, 1994; Monger and Nokleberg, 1996). In western
Alaska, the original linear arrangement of many terranes has been
extensively disrupted by Late Cretaceous and Cenozoic dextral-slip
faulting along the Kobuck (KO), Kaltag (KA), and Denali (DE) Faults
(fig. 4).

Rock Units of the Nutesyn-Koyukuk Arc

The Nutesyn continental-margin terrane (NU, fig. 1; Sizykh and others,
1977; Natal'in, 1984) consists chiefly of (1) a basal unit of
serpentinite and serpentinized peridotite and metagabbro; and (2) an
upper unit of Late Jurassic and Early Neocomian basalt, andesitic
basalt, and andesite, tuff, hypabyssal dacite, rhyodacite bodies,
volcaniclastic sandstone, conglomerate, and shale. Basalt and limestone
containing Early Carboniferous corals occur at the base of the Late
Jurassic volcanic rocks.

The Koyukuk island-arc terrane (KY, figs. 1--3) consists of northern and
southern sequences (Patton, 1973; Box and Patton, 1989; Patton, 1991;
Patton and others, 1994). The northern sequence, north of the Kobuck
Fault, contains chiefly basalt, voluminous Early Cretaceous (Neocomian)
andesite flows, tuff, breccia, conglomerate, tuffaceous graywacke,
mudstone, and bioclastic limestone with fossil and isotopic ages of Late
Jurassic through Early Cretaceous (Berriasian to Aptian). The southern
sequence, south of the Kobuck Fault, contains (1) Middle and Late
Jurassic tonalite and trondhjemite plutonic rocks that locally intrude
the Angayucham terrane (AG, figs. 1--3), which in this area may form the
stratigraphic basement of the Koyukuk terrane; and (2) a sequence of
Late Jurassic to Early Cretaceous volcanic and related rocks that are
associated with, and unconformably overlie, the tonalite and
trondhjemite. The Koyukuk terrane is generally structurally underlain,
and possibly locally stratigraphically underlain, by the Angayucham
terrane.

The Nyac island-arc terrane (NY, fig. 2) consists chiefly of Middle and
Late Jurassic andesite and basalt flows, breccia, tuff, and interbedded
shallow-marine volcaniclastic rocks; and Early Cretaceous gabbroic and
granitic rocks (Hoare and Coonrad, 1978; Box, 1985b, c; Box and others,
1993).

The Togiak island-arc terrane (TG, fig. 2) consists chiefly of two major
sequences (Hoare and Coonrad, 1978; Box, 1985b, c; Coe and others, 1985;
Box and others, 1993): (1) a lower ophiolite sequence at the southwest
end of the terrane that contains Late Triassic midoceanic-ridge pillow
basalt, diabase, gabbro, and ultramafic rocks; and (2) a coherent upper
sequence of Early Jurassic to Early Cretaceous marine volcaniclastic
sandstone, conglomerate, shale, tuffaceous chert, minor argillaceous
limestone, and marine to nonmarine andesite and basalt flows, flow
breccia, and tuff.

Subduction-Zone Units Linked to the Nutesyn-Koyukuk Arc

Tectonically linked to the Nutesyn-Koyukuk arc was an elongate
subduction zone that is now preserved in a discontinuous and disrupted
collage of terranes in the Russian Northeast and western Alaska. The
terranes are the Velmay (VE), Angayucham (AG), and Goodnews (GD)
subduction-zone terranes (figs. 1, 4; Parfenov and others, 1993a, b;
Nokleberg and others, 1994a, b; Plafker and Berg, 1994; Parfenov, 1995a,
b, 1997; Monger and Nokleberg, 1996). These terranes occur (1) outboard
of and thrust over major, partly coeval, passive continental margin,
including the Chukotka terrane (CH) and the Arctic Alaska superterrane
(AA); (2) outboard of and thrust over metamorphosed continental-margin
terranes, including the Seward (SD), Coldfoot (CO), and Ruby (RB)
terranes (figs. 1, 3); and (3) inboard of island-arc terranes of the
Nutesyn-Koyukuk arc. In western Alaska, the original linear arrangement
of these terranes has been extensively disrupted by Late Cretaceous and
Cenozoic dextral-slip faulting along the Kobuck (KO), Kaltag (KA), and
Denali (DE) Faults (fig. 4).

The Velmay subduction-zone terrane (VE, figs. 1, 3) consists chiefly of
a suite of Triassic silicic volcanogenic rocks that are composed of
metamorphosed Triassic basalt, tuff, chert, siliceous and argillaceous
slate, graywacke, and tectonic blocks of serpentinized harzburgite,
pyroxenite, gabbro, and plagiogranite (Voevodin and others, 1978;
Tynankergav and Bychkov, 1987).

The Angayucham subduction-zone terrane (AG, figs. 1--3) consists of
three thrust panels (Patton and others, 1977, 1992, 1994; Jones and
others, 1988; Pallister and Carlson, 1988; Pallister and others, 1989;
Patton, 1992a, b). The lower thrust panel consists chiefly of
phyllonite, melange, and broken sedimentary formations. The sedimentary
rocks are mainly thin-bedded, quartz- and chert-rich graywacke turbidite
deposits of continental derivation, chert, phyllite, and slate. The
panel contains local tectonic blocks of volcanic rocks, chert, limestone
turbidite, chert-pebble conglomerate, and shallow-marine clastic
deposits. The middle thrust panel consists chiefly of structurally
interleaved diabase, pillow basalt, tuff, chert, graywacke, argillite,
minor limestone, and volcanogenic sandstone, conglomerate, and tuff.
Gabbro and diabase are locally abundant. The chert ranges in age from
Late Devonian to Early Jurassic. The upper thrust panel consists chiefly
of serpentinized pyroxenite, harzburgite, dunite, wehrlite, cumulate
gabbro, noncumulate gabbro, and diabase. The basal contact of ophiolite
is locally marked by amphibolite metamorphosed at the time of structural
emplacement in the Middle Jurassic (Boak and others, 1987). The upper
thrust panel is interpreted as the basal part of an ophiolitic
assemblage that was emplaced during Middle or Late Jurassic onto the
unrelated middle thrust panel and may be the root of the Koyukuk island
arc (Patton and others, 1994). Local blueschist metamorphism occurs in
the Angayucham and structurally subjacent terranes, including the
southern margin of the Arctic Alaska superterrane and the Coldfoot and
Ruby terranes (Moore and others, 1994a, b). The blueschist-facies
minerals in units beneath oceanic rocks of the Angayucham terrane are
generally interpreted as having formed during subduction of a passive
continental margin (Moore and others, 1994a, b; Plafker and Berg, 1994).

The Goodnews subduction-zone terrane (GD, fig. 2) consists chiefly of a
disrupted assemblage of pillow basalt, diabase, gabbro, chert,
argillite, minor limestone, volcanogenic sandstone, and ultramafic rocks
(Hoare and Coonrad, 1978; Box, 1985b, c; Box and others, 1993; Patton
and others, 1994). The sedimentary rocks range in age from Ordovician to
Jurassic. The terrane displays prehnite-pumpellyite, greenschist, and
blueschist metamorphic-mineral assemblages (Dusel-Bacon and others,
1996).

Origin of the Nutesyn-Koyukuk Arc

The Nutesyn-Koyukuk island arc is herein interpreted as having formed in
response to Late Jurassic through mid-Cretaceous subduction of the
Angayucham and Goodnews oceanic plates. Remnants of these oceanic plates
are now preserved in discontinuous fragments of the Velmay, Angayucham,
and Goodnews subduction-zone terranes (Nokleberg and others, 1994a, b).
This tectonic pairing is based on (1) occurrence of these
accretionary-wedge and subduction-zone terranes adjacent and parallel to
island-arc terranes (figs. 1-4), (2) formation of melange structures
during the Jurassic through mid-Cretaceous, (3) formation of
blueschist-facies minerals in the subduction-zone units and in
structurally subjacent terranes, and (4) dipping of melange structures
and bounding faults toward and beneath the Nutesyn-Koyukuk arc (Parfenov
and others, 1993a, b; Nokleberg and others, 1994a, b; Plafker and Berg,
1994; Parfenov, 1995a, b, 1997; Monger and Nokleberg, 1996). Subduction
is interpreted as generally ending by the mid-Cretaceous, depending on
the area, with accretion and obduction of the oceanic and ophiolite
terranes onto adjacent continental-margin terranes. Most of the oceanic
and ophiolite terranes exhibit older periods of Jurassic and locally
older (Permian) blueschist-facies metamorphism that is linked to
subduction. In northern and western Alaska, many of the terranes exhibit
a younger period of generally Cretaceous greenschist-facies metamorphism
that some workers have linked to extension which occurred after
accretion (Miller and Hudson, 1991; Moore and others, 1994b; Patton and
others, 1994).

Late Jurassic Through Mid-Cretaceous Gravina Arc in Southern Alaska and
the Canadian Cordillera

The Gravina igneous arc (Gravina-Chisna and Chitina arcs of Plafker and
Berg, 1994) is defined as a suite of mainly Late Jurassic through
mid-Cretaceous igneous-rock units in south-central and southeastern
Alaska and the Canadian Cordillera (Plafker and others, 1989a, b;
McClelland and others 1991, 1992a, b; Nokleberg and others, 1994a, b;
Plafker and Berg, 1994; Monger and Nokleberg, 1996). The arc consists of
an extensive suite of mainly turbidites, volcaniclastic rocks, volcanic
rocks, and plutonic rocks. Remnants of the arc (fig. 4) are preserved in
(1) the Kahiltna sedimentary and volcanic assemblage (ka) in southern
Alaska; (2) the Gravina-Nutzotin-Gambier volcanic-plutonic-sedimentary
belt (gg) in south-central and southeastern Alaska and the western part
of the Canadian Cordillera; and (3) the Cadwallader (CD) (younger part),
Methow (MT), Izee (IZ), and Wallowa (WA) island-arc and turbidite-basin
terranes, the Spences Bridge volcanic-plutonic belt (sb), and the
Tahtsa-Three Sisters-François Lake magmatic assemblage (tt) in the
southern part of the Canadian Cordillera (figs. 2, 4). The Gravina
igneous-arc-related units (Kahiltna assemblage and
Gravina-Nutzotin-Gambier belt) occur along the entire length of the
Wrangellia superterrane (WRA) for about 2,400 km (fig. 4; McClelland and
others, 1991, 1992a, b). In the southern part of the Canadian
Cordillera, the equivalent part of the arc consists of four small
terranes, the Cadwallader (CD) island-arc (younger part), Izee (IZ)
turbidite-basin, Methow (MT) turbidite-basin, and Wallowa (WA)
island-arc terranes that formed mostly on late Paleozoic and early
Mesozoic oceanic basements, and juxtaposed with one another by the
mid-Cretaceous (Monger and others, 1994; Monger and Nokleberg, 1996).
The various igneous-arc-related units of the Gravina arc are grouped
into a single arc on the basis of similar age, similar lithologies, and
geographic proximity. The Gravina arc is generally interpreted by some
workers as an island arc that formed on the Wrangellia superterrane
during migration toward North America (Plafker and others, 1989a, b;
Nokleberg and others, 1994a, b; Plafker and Berg, 1994a, b; Monger and
Nokleberg, 1996).

Rock Units of the Gravina Arc

The Kahiltna sedimentary and volcanic assemblage (kh, fig. 4) consists
chiefly of structurally disrupted, deep-marine, partly volcaniclastic
graywacke, argillite, and flysch, with minor amounts of chert,
limestone, conglomerate, and ande-site (Bundtzen and others, 1988;
Wallace and others, 1989). The assemblage is mainly Early Cretaceous but
includes rocks ranging in age from Late Jurassic to early Late
Cretaceous. The assemblage is interpreted to have originally
stratigraphically overlain the Peninsular sequence on the Alaska
Peninsula and is thrust over older rocks of the Wrangellia superterrane
in the central part of the Alaska Range.

The Gravina-Nutzotin-Gambier volcanic-plutonic-sedimentary belt (gg,
fig. 4) ranges in age from Middle Jurassic (approx 167 Ma) to Early
Cretaceous (approx 110 Ma) (McClelland and others, 1991, 1992a, b;
Monger, 1991, 1993; Wheeler and McFeely, 1991; Haeussler, 1992a, b;
Woodsworth and others, 1992; Cohen and Lundberg, 1993). The belt
consists mainly of argillite, graywacke, and conglomerate, with lesser
andesitic and basaltic volcanic and volcaniclastic rocks, and an
extensive suite of plutons in the southwestern Canadian Coast Mountains,
southeastern Alaska, and in south-central Alaska. These magmatic units
terminate abruptly on the coast of southwestern British Columbia near
lat 48°50' N. In southeastern and south-central Alaska, these
volcanogenic strata were deposited in the intra-arc and backarc Gravina
and Nutzotin basins and in the Kahiltna basin to the west (Cohen and
Lundberg, 1993; Nokleberg and others, 1994b). No direct evidence exists
that the Gravina-Nutzotin-Gambier belt was deposited on the Yukon-Tanana
(YT) and Stikinia (ST) terranes to the northeast (fig. 2; Monger and
Journeay, 1994; Monger and others, 1994). A major thrust-fault system
separates the Gravina-Nutzotin-Gambier belt from units to the east in
the Canadian Cordillera (fig. 4), and petrologic studies indicate that
detritus in the Gravina basin was derived almost entirely from the arc
(Cohen and Lundberg, 1993). Detrital zircons within the Nutzotin part of
the belt may be derived from units to the east (Gehrels and others,
1991).

The Cadwallader island-arc terrane (CD, fig. 2) consists of Permian
oceanic rocks, Triassic arc rocks, and Jurassic clastic deposits
(Vallier and Brooks, 1995; Rusmore, 1987).

The Izee turbidite-basin terrane (IZ, fig. 2) consists chiefly of thick,
mainly flyschoid clastic sedimentary rocks and subordinate
volcaniclastic rocks of Late Triassic through Middle Jurassic
(Callovian) age (Brooks and Vallier, 1978; Dickinson, 1979; Silberling
and others, 1984; Vallier, 1995). Local unconformities and abundant
facies changes indicate a long-lasting and complex depositional basin.
The Izee terrane is interpreted as a suite of forearc deposits for an
island arc.

The Methow turbidite-basin terrane (MT, fig. 2) (forearc deposits)
consists of Triassic basalt and associated ultramafic rocks, Jurassic
arc-related clastic deposits, and Early Cretaceous forearc-basin strata.

The Wallowa island-arc terrane (WA, fig. 2; Vallier, 1977; Vallier and
others, 1977; Brooks and Vallier, 1978; Dickinson and Thayer, 1978;
Hillhouse and Grommé, 1982; Lund and Snee, 1988; Harbert and others,
1990; Vallier, 1995) consists chiefly of (1) Pennsylvanian tuff and
sandstone; (2) an Early Permian sequence of silicic volcaniclastic
rocks; (3) Permian through Late Triassic (Carnian) volcanic and
volcaniclastic sedimentary rocks; (4) abundant Middle and Late Triassic
(Ladinian and Carnian) island-arc tholeiites and associated rocks; (5)
massive carbonate rocks and flysch of Late Triassic (Norian) and Early
Jurassic age; (6) Middle and Late Jurassic alluvial-fan, braided-stream,
and marine sandstone sequences that compose fault-bounded inliers; and
(7) Permian and Triassic plutonic rocks. At the south end of the
Canadian Cordillera, the Wallowa island-arc terrane and adjacent Baker,
Izee, and Olds Ferry terranes (fig. 2) are intruded by Late Jurassic and
Early Cretaceous granitic plutons that are herein interpreted as parts
of the Gravina arc.

Coeval with the Kahiltna assemblage and the Gravina-Nutzotin-Gambier
belt to the west and north are two coeval overlap arc assemblages in the
southern part of the Canadian Cordillera.

The Spences Bridge volcanic-plutonic belt (sb, fig. 4; Thorkelson and
Smith, 1989; Monger and others, 1994) contains (1) a lower part composed
chiefly of intermediate-composition, locally felsic, calc-alkalic,
continental-margin-arc volcanic and lesser plutonic rocks of
mid-Cretaceous age (105 Ma); and (2) an upper part composed of mafic
andesite that may be rift related.

The Tahtsa-Three Sisters-François Lake magmatic assemblage (tt, fig. 4)
consists chiefly of Middle and Late Jurassic and Cretaceous plutonic
rocks (Wheeler and McFeely, 1991; van der Heyden, 1992; Woodsworth and
others, 1992; Monger and others, 1994). The occurrence of coeval
volcanic and plutonic rocks of the Spences Bridge volcanic-plutonic belt
and the Tahtsa-Three Sisters-François Lake magmatic assemblage in the
southern part of the Canadian Cordillera (fig. 4) in an area of
previously accreted terranes suggests that the Late Jurassic to
mid-Cretaceous Gravina arc associated with the Kahiltna assemblage and
Gravina-Nutzotin-Gambier belt extended onto the North American Continent
in this area.

Subduction-Zone Units Linked to the Gravina Arc

Tectonically linked to the Gravina arc was an elongate subduction zone
that is now preserved in a discontinuous and disrupted collage of
terranes in southern Alaska and the western part of the Canadian
Cordillera. These terranes, mainly of Late Triassic, Jurassic, and Early
Cretaceous age, are the Chugach (CG), Pacific Rim (PR), Bridge River
(BR), and Baker (BA) accretionary-wedge and subduction-zone terranes
(figs. 2, 4). These terranes (Nokleberg and others, 1994a; Plafker and
Berg, 1994; Monger and Nokleberg, 1996) exhibit (1) rare tectonic lenses
of mainly limestone with Tethyan faunas, (2) similar ages of
deformation(s) that are generally interpreted as occurring during mainly
Middle Jurassic to Early Cretaceous subduction (Plafker and others,
1989a, b, 1994; Plafker and Berg, 1994; Monger and Nokleberg, 1996), and
(3) local blueschist-facies metamorphism.

The Chugach accretionary-wedge and subduction-zone terrane (CG, figs. 2,
4) consists of a compound, complexly deformed accretionary-wedge and
subduction-zone complex of Late Triassic to Late Cretaceous melange,
flysch, and oceanic rocks (Nokleberg and others, 1994a; Plafker and
Berg, 1994; Kusky and others, 1997; Kusky and Bradley, 1999). The major
units of the Chugach terrane (Plafker and others, 1989a, b, 1994) are
(1) a northern boundary unit of blueschist dated as mainly Late Triassic
to Early Jurassic; (2) the McHugh Complex, a Late Triassic through
mid-Cretaceous melange composed mainly of argillite, chert, basalt,
graywacke, and melange, with rare limestone blocks containing Permian
Tethyan fusulinids; and (3) the Valdez Group, an accretionary complex
composed mainly of Late Cretaceous graywacke and argillite. The terrane
forms a long, narrow belt that extends for several thousand kilometers
along the south rim of Alaska (figs. 2, 4). The eastern part of the
Chugach terrane in southern Alaska contains a large zone of
upper-amphibolite-facies metamorphic rocks and associated anatectic
granitic rocks of early Tertiary age (Plafker and others, 1989a, b,
1994; Plafker and Berg, 1994). This zone is interpreted as having formed
during underplating of part of the Kula-Farallon oceanic ridge under the
Chugach terrane during the Eocene (Plafker and others, 1989a, b; Sisson
and others, 1989; Harris and others, 1996).

The Pacific Rim accretionary-wedge and subduction-zone terrane (PR,
figs. 2, 4) consists of Late Triassic to Early Jurassic arc-related
volcanic rocks and unconformably overlying disrupted graywacke,
argillite, conglomerate, chert, and tuff of mainly Late Jurassic (late
Kimmeridgian and early Tithonian) to Early Cretaceous (mid-Valanginian)
age (Muller, 1977; Brandon, 1989).

The Bridge River accretionary-wedge and subduction-zone terrane (BR,
figs. 2, 4) consists of disrupted Mississippian to early Late Jurassic
chert, pelite, basalt, ultramafic rocks, and rare Triassic blueschist.
These units are gradationally overlain by a clastic succession whose
upper parts are Early Cretaceous. Rocks in the Northwestern U.S. Cascade
Range that may be correlative with the younger part of the Bridge River
terrane contain Jurassic and Cretaceous blueschist (Garver, 1992;
Journeay and Northcote, 1992; Cordey and Schiarizza, 1993; Mahoney and
Journeay, 1993; F. Cordey, written commun., 1994; Monger and others,
1994).

The Baker accretionary-wedge terrane (BA, fig. 2) consists chiefly of
disrupted late Paleozoic and Triassic oceanic and island-arc volcanic
and plutonic rocks and deep-marine sedimentary rocks (Burnt River
Schist, Mine Ridge Schist, Elkhorn Ridge Argillite, and Nelson Marble)
and melange with serpentinite matrix and tectonic blocks (Vallier, 1977,
1994; Vallier and others, 1977).

Origin of the Gravina Arc

The Gravina island arc is interpreted as having formed during Late
Jurassic through mid-Cretaceous subduction of the Farallon oceanic plate
along the margin of the Wrangellia superterrane and outboard of the
Cadwallader and Methow terranes to the south (fig. 3). This oceanic
plate is now preserved in discontinuous fragments in the younger parts
of the Chugach, Bridge River, and Baker terranes and in the Pacific Rim
terrane (Plafker and others, 1989a, b; Nokleberg and others, 1994a, b;
Plafker and Berg, 1994; Monger and Nokleberg, 1996). This tectonic
pairing is based on (1) occurrence of these accretionary-wedge and
subduction-zone terranes outboard (oceanward), southward (in Alaska) or
westward (in the Canadian Cordillera) (in present-day coordinates), and
parallel to the various parts of the arc (figs. 2, 4); (2) formation of
melange structures during the Jurassic through mid-Cretaceous; and (3)
where not disrupted by Late Cretaceous and Cenozoic dextral slip along
the Denali Fault (DE) and companion faults (fig. 4), dipping of melange
structures and bounding faults toward and beneath igneous-rock units of
the arc. Subduction is generally interpreted as ending in the Late
Jurassic to mid-Cretaceous when the Wrangellia superterrane was accreted
to the North American continental margin.

Late Triassic and Early Jurassic Talkeetna-Bonanza Arc in Southern
Alaska and the Canadian Cordillera

The Talkeetna-Bonanza arc occurs discontinuously in southern Alaska and
the Canadian Cordillera (Plafker and others, 1989a, b; Nokleberg and
others, 1994a, b; Plafker and Berg, 1994; Monger and Nokleberg, 1996).
The arc consists mainly of an extensive suite of volcanic rocks,
volcaniclastic rocks, turbidites, and plutonic rocks. Remnants of the
arc (figs. 2, 4) are preserved in (1) the Peninsular sequence of the
Wrangellia superterrane (WRA) in southwestern Alaska, (2) the Bonanza
Volcanics in the Canadian Cordillera (part of an overlap assemblage on
the Wrangellia superterrane), and (3) older parts of the Cadwallader
island-arc (CD) and Methow turbidite-basin (MT) terranes (fig. 2). The
various igneous-arc-related units of the Talkeetna-Bonanza arc are
grouped into a single arc on the basis of similar age, similar arc
origin, geographic proximity, and simplicity. The Talkeetna-Bonanza arc
is interpreted by most workers as an island arc that formed on the
Wrangellia superterrane during migration toward North America (Plafker
and others, 1989a, b; Nokleberg and others, 1994a, b; Plafker and Berg,
1994; Monger and Nokleberg, 1996).

Rock Units of the Late Triassic and Early Jurassic Talkeetna-Bonanza Arc

In southwestern Alaska, the Peninsular sequence (PE, fig. 2; western
part of the Wrangellia superterrane in Alaska) consists mainly of an
areally extensive Jurassic island-arc volcanic and plutonic sequence,
which constitutes the Talkeetna arc, and younger sedimentary-rock units
(Jones and others, 1981; Pavlis, 1983; Plafker and others, 1989a, b;
Nokleberg and others, 1994a, b; Detterman and others, 1996). The
volcanic part of the Talkeetna arc consists mainly of Late Triassic
(Norian) and Early Jurassic andesitic flows, breccia, and volcaniclastic
siltstone and sandstone of the Talkeetna Formation. The plutonic part of
the Talkeetna arc consists of Jurassic batholithic granitic rocks.
Overlying the volcanic-rock units are Middle Jurassic to Cretaceous
arc-derived clastic rocks (Shelikof and Chinitna Formations, Tuxedni
Group, and Kialagvik, Naknek, Staniukovich, and Herendeen Formations),
and bioclastic limestone with Boreal fauna (Nelchina Limestone).
Unconformably overlying units are Cretaceous to early Tertiary
progradational marine and nonmarine sandstone, shale, and minor
conglomerate (Matanuska, Hoodoo, Chignik, and Kaguyak Formations). The
southern part of the Peninsular sequence, adjacent to the Denali Fault
(DE, fig. 4), consists of the Early Jurassic Border Ranges
ultramafic-mafic assemblage (BRUMA), which is interpreted as the mafic
and ultramafic roots of the Talkeetna arc (Burns, 1985; DeBari and
Coleman, 1989; Plafker and others, 1989a, b).

In the Canadian Cordillera, the Bonanza Formation (southeastern part of
the Wrangellia superterrane) consists of Early Jurassic volcanic-arc
rocks and Middle Jurassic arc rocks composed of volcanic-rock units
ranging in composition from basalt to andesite and interlayered with
mainly fine grained clastic rocks and intruded by the coeval Island
intrusions. These units extend into the Canadian Coast Mountains to the
east and are equivalent to the Bowen Island Group and the Harrison Lake
Volcanics (Monger and Journeay, 1994). In the region are coeval Early
and Middle Jurassic granitic intrusions (Grantz and others, 1991;
Monger, 1991; Parrish and McNicoll, 1992; van der Heyden, 1992).

The Cadwallader island-arc terrane and the Methow turbidite-basin
terrane, also interpreted as part of the Talkeetna-Bonanza arc, are
described in the subsection above on the Gravina arc.

Subduction-Zone Units Linked to the Talkeetna-Bonanza Arc

Tectonically linked to the Talkeetna-Bonanza arc was the older part of
an elongate subduction zone that is now preserved in a discontinuous and
disrupted collage in southern Alaska and the western part of the
Canadian Cordillera. These terranes, mainly of Late Triassic, Jurassic,
and Cretaceous age, consist of the Chugach (CG), Bridge River (BR), and
Baker (BA) accretionary-wedge and subduction-zone terranes (fig. 2).
Descriptions of these terranes and the basis for correlating them are
given in the subsection above on the Gravina arc. The Permian Tethyan
faunas, which occur mainly in shallow-water carbonate rocks locally in
the inner part of the Chugach terrane (McHugh Complex), are obviously
exotic faunas and are generally interpreted as derived from the late
Paleozoic and early Mesozoic Tethys Sea now preserved in various units
in the Mediterranean region, the Middle East, the Himalayas, Southeast
Asia, eastern China, the Russian Southeast, and Japan (Monger and Ross,
1971; Monger and others, 1972; Stevens and others, 1997).

Backarc Sequences Linked to the Talkeetna-Bonanza Arc

Two major sequences of Late Triassic tholeiitic pillow basalt and
associated units form distinctive parts of the Wrangellia superterrane.
In south-central Alaska, the Nikolai Greenstone constitutes a major unit
of Late Triassic (Norian) subaerial and marine tholeiitic pillow basalt
and lesser argillite and associated mafic intrusions that is thousands
of meters thick; and in southeastern Alaska, a similar thick sequence of
Late Triassic basalt and rhyolite, part of a bimodal suite, is present
(Nokleberg and others, 1994b). On Vancouver Island, in the coastal
southern part of the Canadian Cordillera, the Karmutsen Formation (too
small to show in fig. 4) constitutes a coeval and distinctive Middle(?)
to Late Triassic tholeiitic basalt with associated mafic intrusions. The
units are interpreted as major backarc sequences with respect to the
coeval Talkeetna-Bonanza arc (Barker and others, 1989; Nokleberg and
others, 1994b; Plafker and Berg, 1994; Monger and Nokleberg, 1996).
Alternatively, the mafic magmatism may have formed in a short-lived
mantle-plume setting similar to that in Java in the South Pacific
(Richards and others, 1991; Lassiter and others, 1995).

Origin of the Talkeetna-Bonanza Arc

The Talkeetna-Bonanza arc is interpreted as having formed from the Late
Triassic and Early Jurassic subduction of part of the Cache Creek
oceanic plate along the margin of the Wrangellia superterrane, and along
the geographically adjacent Cadwallader and Methow terranes. This plate
is now preserved in discontinuous fragments in the older parts of the
Chugach, Bridge River, and Baker terranes (Plafker and others, 1989a, b;
Nokleberg and others, 1994a, b; Plafker and Berg, 1994; Monger and
Nokleberg, 1996). The younger parts of these terranes are also
tectonically paired to the Gravina arc discussed above. This tectonic
pairing is based on (1) occurrence of these accretionary-wedge and
subduction-zone terranes outboard (oceanward) of, and parallel to,
various parts of the arc (fig. 2); (2) formation of melange structures
during the Late Triassic through Early Jurassic; and (3) where not
disrupted by Late Cretaceous and Cenozoic dextral slip along the Denali
Fault (DE) and companion faults (fig. 4), dipping of melange structures
and bounding faults toward and beneath igneous-rock units of the arc.
Subduction is generally interpreted as ending in the mid-Cretaceous,
when a major change in the direction of sea-floor spreading occurred.

Late Triassic and Early Jurassic Stikinia-Quesnellia Island Arc in
East-Central Alaska and the Canadian Cordillera

Remnants of the Stikinia-Quesnellia island arc are preserved in the
Stikinia (ST) and Quesnellia (QN) terranes in east-central Alaska and in
the Canadian Cordillera (fig. 2; Plafker and Berg, 1994; Mihalynuk and
others, 1994; Monger and others, 1994; Monger and Nokleberg, 1996).
These terranes consist of an extensive suite of mainly Late Triassic and
Early Jurassic volcanic and granitic plutonic rocks, each extending for
a distance of about 1,200 km (fig. 2). They occur on opposite limbs of
an apparent oroclinal warp that also includes, in a complex map pattern,
the Yukon-Tanana (YT) and Cache Creek (CC) terranes (fig. 2). In the
core of the warp is the Cache Creek subduction-zone terrane. In
successive sheaths toward the northwest are (fig. 2) (1) the Stikinia
and Quesnellia island-arc terranes, (2) the Yukon-Tanana metamorphosed
continental-margin terrane, and (3) the Slide Mountain (SM) and
Seventymile (SV) accretionary-wedge and subduction-zone terranes. These
relations were interpreted by Mihalynuk and others (1994) as the result
of counterclockwise rotation during the Late Triassic and Early Jurassic
of the Stikinia and Yukon-Tanana terranes to oroclinally entrap the
Cache Creek terrane.

Rock Units of the Stikinia-Quesnellia Arc

The Stikinia island-arc terrane (ST, fig. 2; Monger and Ross, 1971;
Monger, 1977; Monger and Irving, 1980; Monger and others, 1982; Symons,
1983a, b; Wernicke and Klepacki, 1988; Anderson, 1989; Gehrels and
others, 1990; Vandal and Palmer, 1990; Evenchick, 1991; Gabrielse, 1991;
Nelson and Mihalynuk, 1993) consists chiefly of (1) Early Devonian,
Mississippian, Late Pennsylvanian, and Permian volcanic-arc rocks
(Stikine assemblage) that are interbedded with carbonate and
fine-grained clastic rocks (Brown and others, 1991); (2) unconformably
overlying Late Triassic volcanic-arc rocks and interfingering clastic
rocks (Stuhini Formation and Takla Group) and coeval granitic rocks; and
(3) unconformably overlying Early Jurassic andesitic volcanic rocks and
intercalated sedimentary rocks (Hazelton and Spatzizi Groups and
Takwahoni Formation; Tipper and Richards, 1976; Monger, 1977; Anderson,
1989; Gabrielse, 1991). The basement of the Stikinia terrane is unknown.
Suggestions have been made that it is underlain by metamorphosed
continental-margin strata of the Yukon-Tanana terrane (Gehrels and
others, 1990; McClelland, 1992). The Stikinia terrane is herein
interpreted as occurring most probably stratigraphically, rather than
structurally, above the Yukon-Tanana terrane. With this stratigraphic
interpretation, the Stikinia terrane is interpreted as a fragment of an
extensive early Mesozoic island arc that formed on rifted
continental-margin fragments of the Yukon-Tanana and Kootenay(?)
terranes, similar to the setting of modern-day volcanic arcs of New
Zealand and Japan. Nd-isotopic studies from late Paleozoic through
Jurassic units of the Stikinia terrane suggest a juvenile composition
for the igneous rocks (Sampson and others, 1991).

The Quesnellia island-arc terrane (QN, fig. 2) consists chiefly of
west-facing Late Triassic to Early Jurassic (Carnian to Sinemurian)
volcanic-arc rocks (Nicola Group, Rossland Formation), coeval
calc-alkalic and alkalic plutons, and laterally equivalent clastic
sedimentary rocks (Mortimer, 1987; Monger, 1989; Andrew and others,
1990; Monger and others, 1994). In the southwestern part of the Canadian
Cordillera, the volcanic-arc rocks are unconformably overlain by clastic
rocks of the Pliensbachian to Callovian Ashcroft Formation. The early
Mesozoic volcanic-arc rocks overlie at least two basement complexes
(Monger and Berg, 1987): (1) Devonian through Permian chert, clastic
rock, basalt, and ultramafic rocks of the oceanic Apex Mountain Complex
and, probably, units of the Slide Mountain terrane; and (2) and coeval
volcaniclastic rocks, pelite, and carbonate of the arc-related Harper
Ranch Group. These Paleozoic strata were deformed and juxtaposed with
one another and, possibly, with parts of the Kootenay terrane before the
Late Triassic (Read and Okulitch, 1977; Klepacki, 1983; Orchard and
Danner, 1991).

Subduction-Zone Units Linked to the Stikinia-Quesnellia Arc

Tectonically linked to the Stikinia-Quesnellia arc was a subduction zone
now preserved in the discontinuous collage of the Cache Creek
accretionary-wedge and subduction-zone terrane (CC), the Slide Mountain
accretionary-wedge terrane (SM), and the Seventymile subduction-zone
terrane (SV, fig. 2). These terranes consist mainly of a complex
assemblage of Mississippian through Triassic mafic and ultramafic rocks,
chert, shale, turbidite deposits, and volcanic-arc rocks.

The Cache Creek accretionary-wedge and subduction-zone terrane (CC, fig.
2), which ranges in age from Early Mississippian to Early Jurassic,
consists of disrupted chert, pelite, basalt, ultramafic rocks, and local
volcaniclastic rocks of arc origin, as well as distinctive large bodies
of Late Mississippian to Triassic reefoidal limestone containing exotic
Permian Tethyan fauna (Monger, 1977; Travers, 1978; Monger and Irving,
1980; Ross and Ross, 1983; Monger, 1985; Cordey and others, 1987, 1991;
Mortimer, 1987; Gabrielse, 1991; Nelson and Mihalynuk, 1993; Monger and
others, 1994). The carbonate rocks consist of distinctive large bodies
of upper Paleozoic or Triassic reefoidal rocks that at least locally
overlie volcanic rocks. The Late Triassic volcaniclastic rocks are of
probable arc origin; in one locality, associated pelitic rocks are
possibly as young as Pliensbachian (Early Jurassic); and, to the south,
the unit may be as young as Middle Jurassic (Monger, 1977; Cordey and
others, 1987, 1991). Late Triassic blueschist occurs locally in these
terranes and in similar rocks in northern California to the south
(Nokleberg and others, 1994a; Monger and others, 1996). The occurrence
of Permian Tethyan fauna in the Cache Creek terrane is similar to that
in other parts of the Circum-North Pacific, including the
Turkuringra-Dzgadi, Badzhal, Khabarovsk, and inner Chugach (McHugh
Complex) terranes. This fauna occurs mostly in detached, shallow-water,
tropical-origin limestone blocks in melange. In places, the limestone
blocks cap vol-canic seamounts (guyots).

The Slide Mountain accretionary-wedge terrane (SM, fig. 2) consists
chiefly of Late Devonian to Permian oceanic rocks but also contains
structurally intermixed subordinate volcanic-arc rocks, granitic rocks,
and minor continent-derived clastic rocks (Struik and Orchard, 1985;
Harms and others, 1988; Nelson and Bradford, 1989; Mortensen, 1992a;
Richards and others, 1993; Roback and others, 1994). Substantial
lithologic variation occurs within the terrane. To the south, in central
and northern British Columbia, Canada, the Slide Mountain terrane
consists of numerous fault-bound slices, each composed of one or several
rock types, including chert, pelitic rocks, basalt, diorite, gabbro, and
ultramafic rocks, with minor volcanic-arc and carbonate rocks (Struik
and Orchard, 1985; Harms and others, 1988; Nelson and Bradford, 1989).
Rarely can the stratigraphy be correlated between tectonic slices.
Permian and Devonian to Carboniferous granitic rocks (Mortensen, 1992a)
locally cut bounding faults. To the north, continent-derived clastic
rocks are structurally imbricated within the Slide Mountain terrane and
are possible lateral equivalents to late Paleozoic mafic volcanic rocks
in the Kootenay terrane to the east (Klepacki, 1983; Roback and others,
1994). Permian plutons in the Yukon-Tanana terrane (Mortensen, 1992a, b)
crosscut thrust faults in the Slide Mountain terrane (Harms, 1986;
Nelson, 1993), indicating late Paleozoic juxtaposition of at least parts
of the Yukon-Tanana and Slide Mountain terranes.

The Seventymile subduction-zone terrane (SV, fig. 2) occurs as scattered
remnants of three highly deformed and locally folded thrust sheets and
several smaller klippen that structurally overlie the Yukon-Tanana and
Stikinia(?) terranes in east-central Alaska (Keith and others, 1981;
Foster and others, 1994). The lower thrust sheet, interpreted as a
fragment of an island arc, is composed chiefly of a structural melange
of undated metasandstone, metagraywacke, metaconglomerate, and
meta-andesite. The middle thrust sheet is composed chiefly of a
structural melange of pillow basalt, basalt, mafic tuff, chert,
argillite, and limestone of Mississippian, Permian, and Late Triassic
age; rare glaucophane occurs in pillow basalt. The middle thrust sheet
is interpreted as a subduction-zone melange composed of oceanic crust
and seamounts. The upper thrust sheet is composed chiefly of harzburgite
and peridotite, with minor clinopyroxenite, as well as gabbro and
diabase with a local amphibolite sole. It is interpreted as the possible
root to part of the Jurassic(?) Stikinia island arc.

Origin of the Stikinia-Quesnellia Arc

The Stikinia-Quesnellia arc is interpreted as having formed during the
Pennsylvanian, Permian, Late Triassic, and Early Jurassic subduction of
part of the Cache Creek oceanic plate along one margin of the Stikinia
and Quesnellia terranes, and from the Early Jurassic subduction of the
Slide Mountain and Seventymile oceanic plates along the other margin of
the Stikinia and Quesnellia terranes (Mihalynuk and others, 1994;
Plafker and Berg, 1994; Monger and Nokleberg, 1996). These oceanic
plates are now preserved in discontinuous fragments in the Cache Creek,
Slide Mountain, and Seventymile terranes (Plafker and others, 1989a, b;
Nokleberg and others, 1994a, b; Plafker and Berg, 1994; Monger and
Nokleberg, 1996). This tectonic pairing is based on (1) occurrence of
these accretionary-wedge and subduction-zone terranes adjacent and
parallel to the various parts of the arc, as reconstructed in our
tectonic model; and (2) formation of melange structures during the Late
Triassic through Early Jurassic. Subduction is generally interpreted as
ending in the Middle Jurassic when the Stikinia, Quesnellia, Cache
Creek, Slide Mountain, and Seventymile terranes were obducted onto the
accretionary margin of the Canadian Cordillera and onto the North
American cratonal margin (NAM, figs. 2, 7; Mihalynuk and others, 1994;
Plafker and Berg, 1994; Monger and Nokleberg, 1996).

Correlation, Linkage, and Alignment of Late Cretaceous and Early
Cenozoic Continental-Margin Arcs, Island Arcs, and Tectonically Paired
Subduction Zones

After the mid-Cretaceous, much of the Circum-North Pacific was uplifted,
along with the formation of a series of continental-margin arcs and
tectonically paired subduction zones. These arcs and subduction zones
are the immediate ancestors of the current continental-margin arcs and
subduction zones that ring the Pacific Ocean. Thus, from the Late
Cretaceous onward, the major tectonic units of the region are more
readily recognized and interpreted.

During the Late Jurassic to early Cenozoic, four major igneous arcs
formed that are herein recognized around the Circum-North Pacific: the
East Sikhote-Alin arc in the Russian Southeast, the Okhotsk-Chukotka arc
in the Russian Northeast, the Olyutorka arc in the Russian Far East, and
the Kluane and Coast arcs in southern Alaska and the Canadian Cordillera
(figs. 3, 4).

Cretaceous and Early Tertiary East Sikhote-Alin Arc in the Russian
Southeast

The East Sikhote-Alin arc is defined as a extensive suite of Late
Cretaceous and early Tertiary volcanic and plutonic rocks in the Russian
Southeast along the present-day continental margin. Remnants of the arc
are preserved in the East Sikhote-Alin (es) volcanic-plutonic belt and
in the Sorachi-Yezo (SY) and West Sakhalin (WSA) turbidite-basin
terranes (figs. 1, 3; Natal'in, 1993; B.A. Natal'in and A.I. Khanchuk,
in Nokleberg and others, 1994a; Khanchuk and others, 1996; Sengör and
Natal'in, 1996). These three igneous-arc-related units form a major
continental-margin-arc sequence that occurs along the entire length of
the Russian Southeast for about 1,250 km (fig. 3). The various
igneous-arc-related units of the East Sikhote-Alin arc (East
Sikhote-Alin volcanic-plutonic belt and Sorachi-Yezo and West Sakhalin
turbidite-basin terranes) are grouped into a single arc on the basis of
similar age, similar arc origin, geographic proximity, and simplicity.
Both the Sorachi-Yezo and West Sakhalin turbidite-basin terranes are
interpreted as forearc-basin units for the East Sikhote-Alin arc.

Rock Units of the East Sikhote-Alin Arc

The East Sikhote-Alin volcanic-plutonic belt (es, fig. 3; Nazarenko and
Bazhanov, 1986; Nevolina and Sokarev, 1986) consists chiefly of (1)
Cenomanian rhyolite, dacite, basalt, and andesite; (2) thick Turonian to
Santonian ignimbrite; (3) Maastrichtian to Danian basalt, andesite, and
rhyolite; and (4) coeval, mainly intermediate-composition granitic
plutons.

The Sorachi-Yezo turbidite-basin terrane (SY, fig. 1) in northern Japan
(Kato and others, 1986) consists chiefly of (1) an ocean-floor basement
assemblage of Tithonian to Barremian and Early Cretaceous basalt, chert,
siliceous shale, shale, sandstone, and limestone; (2) an overlying
forearc-basin assemblage of Aptian to Maastrichtian siltstone,
sandstone, conglomerate, and volcaniclastic rocks, with deep-marine
turbidites; (3) shallow-marine siltstone and sandstone; and (4) Aptian
to Maastrichtian shallow-marine sandstone and conglomerate.

The West Sakhalin turbidite-basin terrane (WSA, fig. 1) on Sakhalin
Island and Japan consists chiefly of a basal sequence of Early
Cretaceous volcanic rock, jasper, and pelagic rocks and an upper
sequence of Late Cretaceous clastic and tuffaceous clastic rocks
(Parfenov, 1984; Zyabrev, 1984; Nevolina and Sokarev, 1986;
Rozhdestvensky, 1987).

Subduction-Zone Units Linked to the East Sikhote-Alin Arc

Tectonically linked to the East Sikhote-Alin arc was a subduction zone
now preserved in a discontinuous collage of terranes in the Russian
Southeast and northern Japan. These terranes, composed mainly of
Paleozoic and early Mesozoic oceanic-crustal and upper-mantle rocks and
turbidite deposits, consist of the older part of the Hidaka
accretionary-wedge terrane (HI), the younger part of the Aniva (ANV)
subduction-zone terrane, and the Nabilsky (NAB) and Tokoro (TO)
subduction-zone terranes (figs. 1, 3; Khanchuk and others, 1988;
Khanchuk, 1993; Natal'in, 1993; Nokleberg and others, 1994a; Sengör and
Natal'in, 1996).

The Hidaka accretionary-wedge terrane (HI, figs. 1, 3) consists chiefly
of flysch and melange of the Hidaka Group that includes blocks of
basalt, chert, limestone, siliceous shale, and sandstone within a shale
matrix (Iwata and Tajika, 1986; Kato and others, 1986; Sakai and Kanie,
1986). The basalt occurs both as blocks in melange and as lava flows
within a sedimentary succession. The Hidaka Group contains Permian
fusulinids and corals, Late Triassic sponge spicules in limestone, Late
Jurassic to Early Cretaceous radiolarians in chert, Early Cretaceous
nannofossils in limestone, and Early Cretaceous to Eocene radiolarians
in shale. The southwestern part of the Hidaka terrane includes
high-temperature, low-pressure metamorphic rocks, metamorphosed from
granulite to greenschist facies. The metamorphic rocks include a
metamorphosed ophiolite succession that ranges from basal tectonites to
an upper-level dike complex.

The Aniva subduction-zone terrane (ANV, fig. 3) consists chiefly of (1)
a melange composed of lenses of Middle Triassic, Jurassic, and Early
Cretaceous oceanic Ti-rich tholeiite, alkalic basalt, and chert; (2)
fragments of guyots with late Paleozoic and Late Triassic limestone
caps; (3) local exotic bodies of intensely metamorphosed ultramafic and
mafic rocks; and (4) a matrix of Albian to Cenomanian turbidite and
olistostromes (Dobretsov, 1978; Rikhter, 1986; Khanchuk and others,
1988; Bekhtold and Semenov, 1990). The terrane is complexly folded and
faulted and is metamorphosed to transitional blueschist-greenschist
facies.

The Nabilsky subduction-zone terrane (NAB, figs. 1, 3) consists chiefly
of a melange unit with a matrix of late Campanian to early Paleogene(?)
turbidites and Campanian chert olistostromes that enclose bodies of Late
Jurassic and Early Cretaceous radiolarian chert and basalt, and guyot
fragments (Geology of the U.S.S.R., 1970; Rikhter, 1986; Khanchuk and
others, 1988). The guyots are capped by Late Jurassic to Early
Cretaceous limestone that contains Tethyan reef corals. The melange also
locally contains ophiolitic fragments that include large harzburgite and
lherzolite bodies, sparse cumulate gabbro, sheeted dikes, and
midoceanic-ridge-type seamount basalt.

The Tokoro subduction-zone terrane (TO, figs. 1, 3) consists chiefly of
ultramafic cumulate rocks, diabase, pillow basalt, trachyte, alkali
rhyolite, volcaniclastic rocks, chert, and limestone of Jurassic and
Cretaceous age (Koji Wakita, in Nokleberg and others, 1994a).

Origin of the East Sikhote-Alin Arc

The East Sikhote-Alin continental-margin arc is interpreted as having
formed from subduction of part of the ancestral Pacific Ocean plate that
is now preserved as tectonically interwoven fragments of the Hidaka,
Aniva, and Nabilsky accretionary-wedge and subduction-zone terranes
(fig. 4; Khanchuk and others, 1988, 1996; Zonenshain and others, 1990;
Natal'in, 1993; Rozhdestvensky, 1993; B.A. Natal'in and A.I. Khanchuk,
in Nokleberg and others, 1994a; Sengör and Natal'in, 1996). This
tectonic pairing (Parfenov, 1984, 1991; Khanchuk and others, 1988;
Natal'in, 1991, 1993; Parfenov and others, 1993a, b; Nokleberg and
others, 1994a) is based on (1) occurrence of these accretionary-wedge
terranes outboard from (oceanward of), southward of (in present-day
coordinates), and parallel to the various parts of the East Sikhote-Alin
arc (fig. 3); (2) formation of melange structures and blueschist-facies
metamorphism during the Late Cretaceous and early Tertiary (Nokleberg
and others, 1994a); and (3) where not disrupted by extensive early
Cenozoic slip along the Central Sikhote-Alin and companion faults,
dipping of melange structures and bounding faults toward and beneath
igneous-rock units of the arc. Subduction is generally interpreted as
ending in the early Tertiary with strike-slip dismemberment of the
Russian Southeast and subsequent outboard (oceanward) stepping of
subduction to form the East Japan and Kuril igneous arcs.

Cretaceous and Early Tertiary Okhotsk-Chukotka Arc in the Russian
Northeast

The Okhotsk-Chukotka arc is defined as an extensive suite of partly
coeval Cretaceous and early Tertiary volcanic and plutonic rocks along
the continental margin in the Russian Northeast. Remnants of the arc are
preserved in the Okhotsk-Chukotka volcanic-plutonic belt (oc, figs. 3,
4, 7) and the Penzhina sedimentary basin (pn, fig. 7) and in a series of
Late Cretaceous and early Tertiary granitic plutons in western Alaska
(Belyi, 1977, 1978; Parfenov, 1984, 1991, 1995a, b; Parfenov and
Natal'in, 1985; Sosunov, 1985; Filatova, 1988; Stavsky and others, 1989,
1990; Zonenshain and others, 1990; Bogdanov and Til'man, 1992; Sokolov,
1992; Nokleberg and others, 1994a; Sokolov and Byalobzhesky, 1996).
These three units of igneous-arc-related rocks constitute a major
continental-margin-arc sequence that occurs for about 3,500 km along the
entire length of the Russia Northeast into western Alaska. The
Okhotsk-Chukotka arc was deposited on, or intruded, the North Asian
Craton (NSC), the North Asian cratonal margin (NSV), the Kolyma-Omolon
superterrane (KLO), the Chukotka terrane, the Seward terrane, and many
adjacent, smaller terranes (figs. 1, 3, 7). The various
igneous-arc-related units of the Okhotsk-Chukotka arc (Okhotsk-Chukotka
volcanic-plutonic belt and Penzhina sedimentary basin) are grouped into
a single arc on the basis of similar age, similar arc origin, geographic
proximity, and simplicity. The Penzhina sedimentary basin is interpreted
as a forearc-basin unit for the arc.

Rock Units of the Okhotsk-Chukotka Arc

The Okhotsk-Chukotka volcanic-plutonic belt (oc, figs. 3, 4, 7) consists
of Early Cretaceous and Late Cretaceous, locally Paleocene gently
dipping basalt, andesite-basalt, andesite, dacite, rhyolite, tuff, and
rare beds of nonmarine clastic rocks, with conglomerate, grit, and
sandstone at the base. Silicic volcanic rocks (mainly ignimbrites) are
locally widespread (Bakharev, 1976; Belyi, 1977, 1978; Zagruzina, 1977;
Parfenov, 1984; Filatova, 1988; Lebedev and others, 1989).

The Penzhina sedimentary basin (pn, fig. 7) consists chiefly of Albian
to Late Cretaceous littoral-marine rocks, nonmarine clastic rocks, and
coal in a northeast-striking trough, about 90 km wide by 500 km long
(Parfenov, 1984). The clastic rocks consist chiefly of volcanic and
polymictic sandstone, conglomerate, siltstone, argillite, and local tuff
containing mollusks and plant fossils.

Subduction-Zone Units Linked to the Okhotsk-Chukotka Arc

Tectonically linked to the Okhotsk-Chukotka arc was a subduction zone
now preserved in a discontinuous collage of terranes in the Russian
Northeast. These terranes are the West Kamchatka (WK), Ekonay (EK), and
Yanranay (YN) accretionary-wedge terranes (figs. 1, 3, 7; Khanchuk and
others, 1990; Sokolov, 1990, 1992; Parfenov and others, 1993a, b;
Nokleberg and others, 1994b; Sokolov and Byalobzhesky, 1996; Khudoley
and Sokolov, 1998). The West Kamchatka, Ekonay, and Yanranay terranes
are extensively overlapped by the West Kamchatka sedimentary basin (wk)
and the Central Kamchatka (kc) and the East Kamchatka volcanic belts
(ek) (fig. 7).

The West Kamchatka accretionary-wedge terrane (WK, fig. 7) consists
chiefly of intensely deformed pillow and massive basalt interlayered
with siliceous and carbonate rocks, and tuff of Jurassic and Early
Cretaceous age; turbidite deposits (mainly graywacke, arkose, and lesser
subarkose) of Late Cretaceous (Santonian to Maastrichtian) and early
Paleogene age; and local olistostrome layers (Shantser and others, 1985;
Bondarenko and Sokolkov, 1990; Sokolov, 1990, 1992). The terrane
generally is complexly folded and imbricately thrusted.

The Ekonay accretionary-wedge terrane (EK, fig. 1, 3, 7; Byalobzhesky
and others, 1986; Bychkov and others, 1990; Sokolov, 1990; Didenko and
others, 1993) consists chiefly of (1) serpentinized ultramafic rocks,
layered gabbro, and ultramafic rocks and leucocratic gabbro,
gabbro-diabase, diabase, and plagiogranite; and (2) an upper Paleozoic
to Triassic volcanic-sedimentary assemblage (spilite, basalt, and rare
ande-site and plagiorhyolite; various tuffaceous, cherty biogenic
tuffaceous, and clastic rocks; subordinate carbonate and clastic rocks,
argillite, and volcaniclastic siltstone and sandstone) that includes
tectonic fragments of Carboniferous to Triassic units containing Tethyan
foraminifers, radiolarians, and conodonts.

The Yanranay accretionary-wedge terrane (YN, fig. 7; Byalobzhesky and
others, 1986; Grigor'yev and others, 1987; Sokolov, 1992) consists
chiefly of (1) Late Jurassic and Cretaceous (as young as Campanian)
midoceanic-ridge-type basalt, pelagic sedimentary rocks, chert, rare
carbonate rocks, and a condensed section of radiolarite and jasper
containing Tithonian, Berriasian, and Valanginian radiolarians; and (2)
Early and Late Cretaceous argillite, siltstone, sandstone, and
associated rocks. A local Senonian olistostrome is composed of fragments
of Paleozoic to early Mesozoic and Late Jurassic to Early Cretaceous
sedimentary and volcanic rocks in a siltstone matrix. The terrane is
exposed in tectonic windows beneath the Ekonay terrane and is highly
deformed into folds, thrusts, imbricated fault slices, and duplex
structures.

Origin of the Okhotsk-Chukotka Arc

The continental-margin Okhotsk-Chukotka igneous arc is interpreted as
having formed from subduction of part of the ancestral Pacific oceanic
plate that is now preserved as the West Kamchatka, Ekonay, and Yanranay
accretionary-wedge terranes (fig. 3). This tectonic pairing (Parfenov,
1984, 1991; Parfenov and Natal'in, 1985; Filatova, 1988; Stavsky and
others, 1989; Zonenshain and others, 1990; Parfenov and others, 1993a,
b; Nokleberg and others, 1994a) is based on (1) occurrence of these
accretionary-wedge terranes outboard (oceanward), southward of (in
present-day coordinates), and parallel to the various parts of the
Okhotsk-Chukotka arc (fig. 3); (2) formation of melange structures
during the Late Cretaceous and early Tertiary (Nokleberg and others,
1994a); and (3) where not disrupted by extensive early Cenozoic slip
along northwest-striking faults (fig. 3), dipping of melange structures
and bounding faults toward and beneath igneous-rock units of the arc.
Subduction is generally interpreted as ending in the early Tertiary with
accretion of the Kula oceanic plate and subsequent outboard (oceanward)
stepping of subduction to form the Kuril and Kamchatka igneous arcs
(Scholl and others, 1992, 1994).

The units of the Okhotsk-Chukotka arc, the Okhotsk-Chukotka
volcanic-plutonic belt and Penzhina sedimentary basin and related units,
are interpreted by most workers as various parts of a long
continental-margin arc that was active during the Cretaceous and early
Tertiary along the eastern margin of the Russian Northeast and western
Alaska (Parfenov and others, 1978; Parfenov and Natal'in, 1985; Stavsky
and others, 1990; Zonenshain and others, 1990; Parfenov, 1991, 1994;
Bogdanov and Til'man, 1992; Parfenov and others, 1993a, b; Nokleberg and
others, 1994a). The arc overlaps the previously accreted Kolyma-Omolon
superterrane and adjacent terranes in the Russian Northeast and
previously accreted terranes in western Alaska (figs. 3, 4).

Late Cretaceous and Early Tertiary Olyutorka Arc in the Russian Far East

Remnants of the Late Cretaceous and early Tertiary Olyutorka arc are
preserved, from north to south, in the Olyutorka-Kamchatka (OKA),
Iruneisky (IR), Kronotskiy (KRO), Shmidt (SH), Terpeniya (TR), and
Nemuro (NE) island-arc terranes in the central and southern parts of the
Russian Far East (figs. 3, 7; Rikhter, 1986; Tsukanov, 1991; Sokolov,
1992; Zinkevich and Tsukanov, 1992, 1993; Nokleberg and others, 1994a;
Sokolov and Byalobzhesky, 1996). These terranes constitute an extensive
suite of coeval Late Cretaceous and early Tertiary island-arc volcanic
and related rocks for about 2,700 km on the Kamchatka Peninsula, the
southern Kuril Islands, and Sakhalin Island (figs. 1, 3).

Rock Units of the Olyutorka Arc

The Olyutorka-Kamchatka island-arc terrane (OKA, figs. 3, 7; Zinkevich
and others, 1990, 1993; Tsukanov, 1991; Kovalenko, 1992; Zinkevich and
Tsukanov, 1992, 1993; Heiphitz and others, 1994a; Brandon and others,
1997, 1998; Ramthun and others, 1997; Garver and others, 1998; Solo'ev
and others, 1998; Konstantinovskaya, 1999) consists of (1) a local unit
of serpentinite melange composed of blocks of mid-Cretaceous jasper,
basalt, gabbro, and ultramafic rock; (2) late Campanian to early
Maastrichtian island-arc deposits (Hapitskiy Complex) composed of
basalt, andesite flows and tuff, tuffaceous siltstone, volcaniclastic
sandstone, and tuffaceous jasper; and (3) an upper part of Maastrichtian
to Paleocene volcaniclastic island-arc deposits. The terrane is locally
intruded by zoned intrusive rocks ranging in composition from dunite and
clinopyroxenite to gabbro (Kepezhinskas and others, 1993).

The Iruneisky island-arc terrane (IR, figs. 3, 7) consists chiefly of
several tectonic sheets and overlying Cretaceous clastic deposits
(Shantser and others, 1985; Zinkevich and Tsukanov, 1992, 1993): (1)
pillow basalt, siliceous shale, tuff, and jasper of Albian to Cenomanian
age, with structurally overlying Late Cretaceous tuff and jasper and
coarse-grained mafic and intermediate-composition volcanic breccia; and
(2) fine-grained silicic tuffaceous deposits, coarse-grained clastic
tuffaceous deposits with Late Cretaceous basalt, and overlying tuff
breccia and calc-alkalic volcanic rocks with tuffaceous sedimentary
lenses that grade into Maastrichtian siliceous siltstone.

The Kronotskiy island-arc terrane (KRO, figs. 3, 7) consists chiefly
Coniacian to early Paleocene island-arc basalt, lava and tuff breccia
that contains hyaloclastite fragments of mafic and silicic volcanic
rocks in a coarse-grained tuff, and chert (Mys Kamenistyi Complex and
Kronotskaya Suite; Khubunaya, 1981; Tsukanov, 1991; Bazhenov and others,
1992). Also locally occurring is a serpentinite melange containing
ophiolite fragments.

The Shmidt island-arc terrane (SH, fig. 7; Geology of the U.S.S.R.,
1970; Raznitsin, 1982; Yurkova, 1991) consists chiefly of three units.
(1) A lower unit of serpentinite melange, interpreted as a
subduction-zone complex, is composed of harzburgite, cumulate gabbro,
high-Ti mafic dikes, basalt, and Late Jurassic to Early Cretaceous
radiolarian chert (Tominskia sequence). (2) An intermediate-composition
unit consists of bimodal sheeted dikes and flows, siliceous tuff that
yields mid-Cretaceous (Albian to Cenomanian) radiolarians, and
plagiogranite. The bimodal igneous rocks are geochemically similar to
those of primitive island arcs. (3) An upper unit consists of basalt,
andesite, tuff, argillite, and sandstone that yield Cenomanian to
Santonian *Inoceramus* (Slavyansk sequence).

The Terpeniya island-arc terrane (TR, fig. 7) consists chiefly of a
thick tectonic melange composed of deep-marine and terrestrial Santonian
to Campanian volcanic and sedimentary rocks (Berozovskaya, Rakitinskaya,
and Bogatinskaya sequences; Geology of the U.S.S.R., 1970; Khanchuk and
others, 1988). The volcanic rocks consist of island-arc tholeiitic,
calc-alkalic, and shoshonitic rocks. Abundant
peridotite-pyroxenite-gabbroic and gabbro-plagiogranite intrusions are
interpreted as the magmatic part of the island arc. The terrane is
structurally disrupted and strongly folded.

The Nemuro island-arc terrane (NE, figs. 3, 7) consists chiefly of two
subterranes (Parfenov and others, 1983; Grapes, 1986; Kato and others,
1986; Okada and others, 1989; Golionko, 1992; Bazhenov and Burtman,
1996). (1) A northern subterrane is composed of a monoclinal sequence of
conglomerate, breccia, grit, sandstone, massive calc-alkalic pillow
basalt, andesitic basalt, and basalt agglomerate and tuff. The basaltic
rocks contain Campanian *Inoceramus* and yield a K-Ar age of 88 Ma. The
basaltic rocks are unconformably overlain by tuffaceous flysch with
layers of alkalic pillow basalt, diabase, and shoshonite sills that
yield K-Ar ages of 65 to 89 Ma and that contain Campanian to
Maastrichtian *Inoceramus.* (2) A southern subterrane is composed of
folded continental and shallow-marine lava, breccia, and andesite basalt
tuff, basalt, rare andesite that yields K-Ar ages of 69 to 82 Ma, and
local layers of sandstone, grit, and cherty siltstone containing wood
and plant detritus. The southern subterrane is intruded by local gabbro
and sheeted dikes.

Subduction-Zone Units Linked to the Olyutorka Arc

Tectonically linked to the Olyutorka arc was a subduction zone now
preserved in the discontinuously exposed Vetlov-skiy accretionary-wedge
terrane (VT, figs. 1, 3, 7; Sokolov, 1992; Zinkevich and Tsukanov, 1992,
1993; Nokleberg and others, 1994a; Sokolov and Byalobzhesky, 1996). The
Vetlovskiy terrane occurs in thin thrust sheets that are composed mainly
of volcanic and sedimentary rocks, deep-water chert, mudstone, carbonate
rocks, and midoceanic-ridge basalt (Vetlovskiy Complex; Fedorchuk and
others, 1990; Tsukanov, 1991; Zinkevich and Tsukanov, 1992, 1993). The
volcanic and sedimentary rocks range from Maastrichtian to lower Eocene.

Origin of the Olyutorka Arc

The Olyutorka arc is interpreted as having formed from subduction of
part of the ancestral Pacific oceanic plate (Zonenshain and others,
1990; Sokolov, 1992; Zinkevich and Tsukanov, 1992, 1993; Nokleberg and
others, 1994a; Sokolov and Byalobzhesky, 1996; Khudoley and Sokolov,
1998) and is partly preserved in the Vetlovskiy accretionary-wedge
terrane (VT, figs. 1, 3, 7). This tectonic pairing is based on (1)
occurrence of the Vetlovskiy terrane outboard of, and parallel to, the
various island-arc terranes that constitute the arc (fig. 3); and (2)
coeval, Late Cretaceous and early Tertiary deformation and accretion of
units in the Vetlovskiy terrane. Subduction is generally interpreted as
ending in the early Tertiary with accretion of the Olyutorka arc and
associated subduction zone and subsequent outboard (oceanward) stepping
of subduction to form the Kuril and Kamchatka igneous arcs (Zinkevich
and Tsukanov, 1992, 1993; Nokleberg and others, 1994a; Sokolov and
Byalobzhesky, 1996; Khudoley and Sokolov, 1998).

Late Cretaceous and Early Tertiary Kluane and Coast Arcs in Southern
Alaska and the Canadian Cordillera

The Kluane arc is defined as an extensive suite of coeval Late
Cretaceous and early Tertiary volcanic and plutonic rocks in southern
and eastern Alaska. Remnants of the arc are preserved in the Kuskokwim
Mountains sedimentary, volcanic, and plutonic belt (km, figs. 3, 4, 7),
the Alaska Range-Talkeetna Mountains volcanic-plutonic belt (at, figs.
4, 7), and various coeval granitic plutons too small to show in figure 4
(Plafker and others, 1989a, b; Nokleberg and others, 1994a, b; Plafker
and Berg, 1994; Monger and Nokleberg, 1996). Similarly, remnants of the
Coast arc are preserved in the Coast-North Cascade plutonic belt (cn,
figs. 4, 7) and in the Kamloops magmatic belt (kl, fig. 4) in the
Canadian Cordillera. These volcanic-plutonic belts form a major
continental-margin-arc sequence along the length of southern Alaska and
the Canadian Cordillera, about 3,000 km. The various igneous-arc-related
units of the Kluane and Coast arcs are grouped into a single arc on the
basis of similar age, similar arc origin, geographic proximity, and
simplicity. The Kluane and Coast arcs overlap the Wrangellia
superterrane and adjacent, previously accreted inboard units, including
the Yukon-Tanana, Stikinia, Cache Creek, and Quesnellia terranes (figs.
2, 4). The Kluane and Coast arcs are interpreted as having formed
immediately after accretion of the Wrangellia superterrane in the Late
Jurassic to mid-Cretaceous (Plafker and others, 1989a, b; Nokleberg and
others, 1994a, b; Plafker and Berg, 1994; Monger and Nokleberg, 1996).
Both the Kluane and Coast arcs are extensively disrupted by dextral-slip
movement that occurred from the Late Cretaceous through the present on
the Denali (DE), Tintina (TI), and companion faults (fig. 4).

Rock Units of the Kluane Arc

The Kuskokwim Mountains sedimentary, volcanic, and plutonic belt (km,
figs. 3, 4, 7) consists chiefly of volcanic and minor interlayered
tuffaceous sedimentary rocks (Moll-Stalcup, 1990, 1994; Miller and
Bundtzen, 1993; Moll-Stalcup and others, 1994). The belt also includes
minor conglomerate to coarse-grained sandstone turbidite deposits
deposited in deep-marine conditions, and lesser sandstone and
conglomerate deposited in shallow-marine to nonmarine conditions along
the flanks of the unit. The volcanic rocks consist chiefly of rhyolite
and dacite domes, flows, and tuff and dacite, andesite, and basalt flows
with isotopic ages of 58 to 77 Ma. The unit also contains numerous
related volcanoplutonic complexes, dikes, and plutons that exhibit a
wide compositional range, including gabbro, quartz diorite,
granodiorite, monzonite, and syenite. The Alaska Range-Talkeetna
Mountains volcanic-plutonic belt (at, figs. 4, 7) consists chiefly of
large and small volcanic fields composed of calc-alkalic rhyolite,
dacite, and andesite flows, pyroclastic rocks, and interlayered basalt
and andesite flows (Plafker and others, 1989a, b; Moll-Stalcup, 1990,
1994; Moll-Stalcup and others, 1994). Isotopic ages range mainly from 50
to 75 Ma. The belt also contains numerous related diorite, quartz
diorite, granodiorite, granite, and, locally, monzonite and syenite
plutons.

Rock Units of the Coast Arc

The Coast-North Cascade plutonic belt (cn, figs. 4, 7) forms a major
granitic plutonic belt that extends the length of the Canadian
Cordillera into east-central Alaska. The belt consists chiefly of quartz
diorite, granodiorite, and, locally, more mafic or felsic plutons
(Gehrels and others, 1990; Rubin and others, 1991; Wheeler and McFeeley,
1991; van der Heyden, 1992; Woodsworth and others, 1992; Journeay and
Friedman, 1993). Crystallization ages are generally younger toward the
east. In the central and southern parts of the belt, age zonation
permits division into three subbelts: (1) mid-Cretaceous and Late
Cretaceous plutons (approx 96--70 Ma), (2) plutons that straddle the
Cretaceous-Tertiary boundary (70--60 Ma), and (3) early Tertiary plutons
(60--40 Ma). The early Late Cretaceous through early Tertiary intrusions
were emplaced concurrently with structures formed sequentially during
contraction and local(?) dextral transpression and transtension,
accompanied by regional metamorphism (Rubin and others, 1991; Journeay
and Friedman, 1993). The Kamloops magmatic belt (kl, fig. 4) consists
chiefly of 46- to 55-Ma calc-alkalic to alkalic felsic,
intermediate-composition, and mafic volcanic and sedimentary strata and
comagmatic granodiorite, syenite, and quartz monzonite plutonic rocks
(Ewing, 1980; Parrish and others, 1988; Symons and Wellings, 1989). The
volcanic rocks may be surface equivalents of early Tertiary plutonic
rocks in the eastern Coast belt (youngest part of Coast-North Cascade
belt). In areas of the southern part of the Canadian Cordilleran and to
the south, the belt is typically alkalic, and emplacement was concurrent
with widespread basin-and-range-style extension.

Subduction-Zone Units Linked to the Kluane and Coast Arcs

Tectonically linked to the Kluane continental-margin arc were the
younger parts of the Chugach terrane (Late Cretaceous accretionary-wedge
Valdez Group) and the older part of the Prince William
accretionary-wedge terrane (fig. 4). Both terranes occur in a similar
tectonic position, as a series of narrow, discontinuous, long tectonic
lenses situated outboard of the igneous-arc-related units of the Kluane
arc (fig. 4). Tectonically linked to the Coast continental-margin arc
was the Pacific Rim accretionary-wedge and subduction-zone terrane that
occurs outboard of the igneous-arc-related units of the Coast arc in the
Canadian Cordillera (fig. 4). The Chugach and Pacific Rim terranes,
described above in the subsection on the Gravina arc, were long-lived
accretionary-wedge and subduction-zone complexes that formed from the
Late Triassic through Late Cretaceous for the Chugach terrane (Nokleberg
and others, 1994a; Plafker and Berg, 1994) and from the Late Jurassic
though mid-Cretaceous for the Pacific Rim terrane (Nokleberg and others,
1994a; Monger and Nokleberg, 1996).

The Prince William accretionary-wedge terrane (PW, figs. 1, 2, 4, 7)
consists chiefly of a complexly folded and faulted, thick assemblage of
graywacke, argillite, minor conglomerate, pillow basalt, basaltic tuff,
sills, dikes, and mafic and ultramafic rocks (Orca Group, Sitkalidak
Formation, and Ghost Rocks Formation; Moore and others, 1983; Nelson and
others, 1985; Dumoulin, 1988; Plafker and others, 1989a, b; Bol and
others, 1992; Nelson, 1992; Bol, 1993). The terrane includes the Late
Cretaceous and early Tertiary Ghost Rocks terrane of Jones and others
(1987) and contains rare megafossils and microfossils of Paleocene and
Eocene age. The terrane contains the Resurrection Peninsula ophiolite,
which is interpreted as a remnant of the Kula-Farallon oceanic ridge
that was subducted under the margin of southern Alaska (Lytwyn and
others, 1997; Kusky and Young, in press).

Origin of the Kluane and Coast Arcs

The igneous-rock units that define the Kluane and Coast arcs are
interpreted by most workers as various parts of a long
continental-margin arc that was active during the Late Cretaceous and
early Tertiary (Plafker and others, 1989a, b; Nokleberg and others,
1994a, b; Plafker and Berg, 1994; Monger and Nokleberg, 1996). The arcs
are interpreted as having formed in response to subduction of part of
the Kula oceanic plate. During subduction, substantial accumulations of
igneous-arc-derived flysch (some from erosion of the Kluane arc) were
deposited into a continental-margin trench bordering present-day
southern Alaska. These deposits were underthrust along a major,
north-dipping subduction zone (present-day coordinates) and underplated
into a large accretionary-wedge complex of the Valdez Group of the
southern Chugach terrane (Nokleberg and others, 1989; Plafker and
others, 1989a, b; Plafker and Berg, 1994). Subduction is generally
interpreted as ending in the early Eocene with accretion of the Kula
oceanic plate and Kula Ridge and subsequent outboard (oceanward)
stepping of subduction to form the modern-day Aleutian-Wrangell and
Cascade arcs (Plafker and others, 1989a, b; Scholl and others, 1992,
1994; Plafker and Berg, 1994).

Correlation, Linkage, and Alignment of Middle and Late Cenozoic
Continental-Margin Arcs and Tectonically Paired Subduction Zones

From about the early Eocene or Miocene through the present, three
continental-margin arcs have been active around the Circum-North Pacific
(figs. 3, 4): (1) the Northeast Asia arc, consisting of the East Japan
volcanic-plutonic belt, the Central Kamchatka volcanic belt, the Central
Kamchatka volcanic and sedimentary basin, the East Kamchatka volcanic
belt, the Eastern Sakhalin sedimentary basin (too small to show in fig.
3), and the West Kamchatka sedimentary basin (also too small to show in
fig. 3); (2) the Aleutian-Wrangell arc, consisting of the Aleutian
volcanic belt (al, figs. 3, 4, 7) and the Wrangell volcanic field; and
(3) the Cascade arc, consisting of the Cascade volcanic-plutonic belt.

Northeast Asia Arc

The Northeast Asia arc is a major continental-margin igneous arc that
has been active since its inception in the early Eocene to Miocene. The
arc is being preserved in the East Japan volcanic-plutonic belt (ej,
fig. 3) and the Kamchatka arc, which consists of the Central Kamchatka
volcanic belt (kc), the Central Kamchatka volcanic and sedimentary basin
(ck), the East Kamchatka volcanic belt (ek), the Eastern Sakhalin
sedimentary basin (too small to show in fig. 3), and the West Kamchatka
sedimentary basin (wk, fig. 7; Shahiro and others, 1987; Nokleberg and
others, 1994a). This arc occurs along the entire length of northern
Japan and the southern and central parts of the Russian Far East for
about 2,500 km. The Northeast Asia arc overlaps all previously accreted
inboard terranes in the region (figs. 1, 3).

Rock Units of the Northeast Asia Arc

The East Japan volcanic-plutonic belt (ej, fig. 3) consists chiefly of
Neogene to Holocene large andesite and rhyolite and smaller basalt
volcanoes, dacite to andesite and lesser basalt lava, tuff, breccia,
volcanic avalanche deposits and domes, and minor
intermediate-composition plutons (Koji Wakita, in Nokleberg and others,
1994a). Major modern volcanoes occur at Oshima-oshima, E-san,
Komagatake, Kariba, Raiden, Niseko, Toya, Usu, Yotei, Shikotsu, Tarumae,
Tokachi, Daisetsu, Akan, Kutcharo, Masyu, and Shiretoko. The East Japan
belt is coeval with the volcanic part of the Kuril arc to the northeast.
The belt overlies many terranes of Hokkaido Island, including the Oshima
(too small to show in figs. 1, 3, and 7), Sorachi-Yezo (SY), Kamuikotan
(KK), Hidaka (HI), Tokoro (TO), and Nemuro (NE) terranes (figs. 1, 3,
7).

The Central Kamchatka volcanic belt (too small to show in fig. 3)
consists chiefly of late Tertiary and Quaternary, thick, gently dipping
andesite, dacite, and rhyolite strata, interlayered with sandstone,
siltstone, and conglomerate, and widespread large ignimbrite fields
(Erlikh, 1973; Popolitov and Volynets, 1981; Shapiro and others, 1987).
Shallow-marine deposits are predominant in the lower part, and nonmarine
deposits in the upper part. Formation of the belt culminated with
eruptions of Pliocene to Quaternary plateau basalts that are associated
with stratovolcanoes.

The Central Kamchatka volcanic and sedimentary basin (too small to show
in fig. 3) consists chiefly of late Pliocene and Quaternary volcanic and
sedimentary rocks, as much as 6 km thick; it ranges from 20 to 70 km in
width and is 350 km long (Vlasov, 1964; Shapiro and others, 1987). The
basin contains mainly shallow-marine sedimentary rocks and widespread
tuff, basalt, and basaltic andesite. The basin overlies deformed Late
Cretaceous to early Tertiary sedimentary rocks and is interpreted as a
forearc unit for the Central Kamchatka volcanic belt.

The East Kamchatka volcanic belt (too small to show in fig. 3) consists
chiefly of a major chain of modern volcanoes of Pliocene and younger
age. The main rock types are basalt, andesite basalt, rare dacite, and
tuff (Vlasov, 1964; Erlikh, 1973; Shapiro and others, 1987; Volynets and
others, 1990). The belt is the northward continuation of the modern
Kuril volcanic arc, which started to form during the Neogene.

The Eastern Sakhalin sedimentary basin (too small to show in fig. 3)
consists chiefly of an Oligocene to Quaternary sedimentary basin, as
much as 8,000 m thick (Baboshina and others, 1984, 1985; Kosygin, 1985).
Seismic-reflection data suggest that late Miocene to Quaternary marine
clastic and siliceous sedimentary rocks form most of basin.

The West Kamchatka sedimentary basin (too small to show in fig. 3)
consists chiefly of thick, gently folded littoral-marine and nonmarine
Cenozoic coal-bearing deposits, as much as 6 km thick (Vlasov, 1964,
1977). The basin contains major linear echelon folds that are diagonal
to the general strike of basin. It is interpreted as an oblique-slip
backarc basin for the Central Kamchatka volcanic belt to the east.

Subduction-Zone Units Linked to the Northeast Asia Arc

Tectonically linked to the Northeast Asia continental-margin arc is the
Kuril-Kamchatka accretionary-wedge and subduction-zone terrane (KUK),
which occurs outboard of the arcs in northern Japan and the Russian Far
East (figs. 1, 3, 7). The terrane is forming along the Kuril-Kamchatka
megathrust (Nokleberg and others, 1994a) and consists chiefly of three
major units (Lomtev and Patrikeev, 1965; Gnibidenko and others, 1980;
Seliverstov and others, 1988). (1) A structurally lower unit is composed
of bedded turbidites of Quaternary to Pliocene age and underlying
oceanic crust. The turbidites generally range from about 100 to 500 m in
thickness but are as much as 1,000 m thick near the junction of the
Kuril-Kamchatka and Aleutian Trenches. Seismic-reflection surveys
indicate that the turbidites unconformably overlie oceanic crust. The
turbidites are folded and deformed near the continental slope and can be
traced below the accretionary-wedge unit at an angle of 5--15°. (2) A
structurally emplaced upper unit consists of accretionary-wedge deposits
that occur in a series of overthrusts which enclose fragments of the
deformed bedded turbidites. Rocks dredged from the accretionary deposits
consist of turbidites that contain Pliocene diatoms, Late Cretaceous
oceanic chert that contains radiolarians, and basalt. (3) As determined
from seismic-reflection surveys, an older, structurally higher part of
the accretionary wedge consists of units bounded by numerous thrust
faults. Rocks dredged from that part of the trench slope consist of
turbidites that contain Miocene to Pliocene diatoms, as well as volcanic
rocks that are metamorphosed to greenschist facies. Locally along the
northwestern margin, this older part of the accretionary wedge lies in a
depression as much as 20 km wide and consists of well-stratified
turbidite deposits that range from 1.5 to 2.5 km in thickness.
Transverse canyons along the trench are filled with Miocene to
Quaternary turbidite deposits, as much as 3 km thick.

Backarc Units Linked to the Northeast Asia Arc

Also tectonically linked to the Northeast Asia continental-margin arc
are the Sea of Japan (sj), the Sakhalin-Primorye (sp) volcanic belt, and
the Kuril (kr) backarc units (figs. 3, 7). These three units consist of
mainly alkalic or midoceanic-ridge-type basalt and related rocks, and
all occur inboard (continentward) from the Northeast Asia arc (Uyeda,
1986; Tamaki, 1988; Tatsumi and others, 1989; Bogdanov and Til'man,
1992).

The Sea of Japan backarc unit (sj, figs. 3, 7) consists chiefly of
volcanic rocks ranging in composition from midoceanic-ridge-type basalt
to trachyrhyolite, as dredged from seamounts and ridges (Ingle and
others, 1975; Bersenev and others, 1987). Tholeiitic basalt forms about
80 to 90 percent of the total dredged material; the rest is sparse
clinopyroxene-olivine ferrobasalt. The basalt commonly contains
lehrzolite xenoliths, has a predominant olivine-plagioclase mineral
assemblage, and includes subordinate chromium clinopyroxene and chrome
spinel. The age of the basalt is tentatively estimated at 0 to 15 Ma
from interpretation of the time of opening of the Sea of Japan, as
determined by paleomagnetic data (table 3). The basalt is overlapped by
a sedimentary cover, as much as 2 km thick.

The Sakhalin-Primorye volcanic belt (sp, fig. 7) consists chiefly of
late Cenozoic basalt in relatively small eruptive fields that are
closely associated with grabens and bounding faults (Semenov, 1982;
Nakamura and others, 1990; Martynov and Okamura, 1993; Martynov, 1994).
The basalt ranges in composition from quartz tholeiite to olivine
nephelinite and includes basanite that locally contain xenoliths of
spinel and garnet peridotite, pyroxenite, and harzburgite. Alkali basalt
is predominant in the continental area of eastern China, whereas
tholeiite, with an unusually low K2O content (less than 0.25 weight
percent), occurs in the East Sikhote-Alin region adjacent to the rift
basin of the Sea of Japan. On Sakhalin Island, the belt consists mainly
of (1) Miocene subalkalic andesite-basalt, basalt, and rare rhyolite;
(2) Late Miocene to early Pliocene trachybasalt, trachydiabase, and
subvolcanic intrusions of monzonite, essexite, and other alkalic rocks;
and (3) Pliocene olivine basalt and diabase, and rare andesite and
dacite.

The Kuril backarc unit (kr, fig. 7; Gnibidenko and Svarichevsky, 1984;
Sergeyev and Krasny, 1987; Maeda, 1990; Zonenshain and others, 1990)
consists of (1) a central and northern part that is interpreted as
Oligocene to Miocene oceanic crust, with an average seismic velocity of
6.7 to 7.0 km/s, a thickness of 12 to 13 km, and a thin upper layer of
sedimentary rocks, on the basis of inferred slow sedimentation rates
(Zonenshain and others, 1990) and heat-flow values that are 2 to 2.5
times higher than in modern oceans; and (2) a southern part that is
interpreted as a backarc unit which started to form at about 15 Ma.
Local, partly buried volcanic cones are overlain by sedimentary rocks.
Direct data on the composition and age of this backarc unit are absent.
Dredging from the eastern part of the unit, on the west slope of the
Kuril island arc, yields granitic rocks, which range in age from 94 to
219 Ma, and granitic clasts in conglomerate interlayered with Paleogene
volcanic rocks.

Origin of the Northeast Asia Arc

The igneous-arc-related units that define the Northeast Asia arc are
interpreted by most workers as various parts of a major active volcanic
arc that occurs along the northeastern margin of Asia. The arc is
interpreted as having formed in response to subduction of part of the
Pacific oceanic plate and formation of the Kuril-Kamchatka
accretionary-wedge and subduction-zone terrane (Parfenov and others,
1978; Parfenov, 1984; Parfenov and Natal'in, 1985; Zonenshain and
others, 1990). Subduction is herein interpreted as commencing in about
the Eocene after accretion of the Olyutorka arc and associated
subduction zones to the Northeast Asia margin, and outward stepping of
subduction. Also associated with the Northeast Asia arc are three major
backarc units: the Sea of Japan backarc unit, the Sakhalin-Primorye
volcanic belt, and the Kuril backarc unit, which are all inboard of the
arc (fig. 3). The three backarc units are interpreted as the result of
backarc rifting. The major rift basins that contain these units are
interpreted as the loci of extension and thinning of previously accreted
terranes, and as the loci of migration of the arc oceanward or away from
the Northeast Asia continental margin (Uyeda, 1986).

Aleutian-Wrangell Arc in Southern Alaska

The Aleutian-Wrangell arc is a major intraoceanic (western part) and
continental-margin (eastern part) igneous arc that started forming
during the early Eocene to Miocene and is continuing to form through the
present. The arc is being preserved in the Aleutian (al) volcanic belt
and the Wrangell (wr) volcanic field (figs. 3, 4, 7; Moll-Stalcup, 1990,
1994; Nokleberg and others, 1994a; Plafker and others, 1994; Vallier and
others, 1994). This arc occurs along the entire south edge of the Bering
Sea and southern Alaska for about 4,000 km. The Aleutian-Wrangell arc
overlaps all previously accreted inboard terranes in the region (figs.
2, 4).

Rock Units of the Aleutian-Wrangell Arc

The Aleutian volcanic belt (al, figs. 3, 4, 7) comprises three parts
(Harbert, 1987; Tsvetkov and others, 1990; Moll-Stalcup, 1990, 1994;
Bazhenov and others, 1992; Vallier and others, 1994). (1) The extreme
western part of the arc in the Komandorsky Islands consists of Eocene
and Miocene volcanic, tuffaceous, and sedimentary deposits, including
basalt, andesite basalt, and andesite and interbedded tuff. The
sedimentary rocks include sandstone, conglomerate, clay mudstone, and
diatomite. This part of the arc is unconformably overlain by thin
subalkalic basalt and alkalic basal middle Miocene tuff and tuffaceous
siltstone, crossbedded sandstone and gritstone, and extensive
interlayered Quaternary and Holocene glacial deposits. (2) The western
part of the arc in the Aleutian Islands is subdivided into early (37--55
Ma), middle (5.3--37 Ma), and late series (5.3 Ma--Holocene; Scholl and
others, 1992; Miller and Richter, 1994; Vallier and others, 1994). The
early series forms the base of the arc and consists predominantly of
flows and volcaniclastic rocks. Igneous composition ranges from basalt
to rhyolite but is mainly calc-alkalic basalt and andesite. Local
hypabyssal and plutonic rocks also occur. The middle series is
predominantly volcanic flows, volcaniclastic rocks, conglomerate, and
dolomite. Locally abundant sills, dikes, plugs, and large quartz diorite
and granodiorite plutons also occur. The late series is predominantly
sedimentary and volcanic strata, mainly in offshore basins and along the
flanks of volcanoes. The early Tertiary part of arc, named the "Meshik
arc" on the Alaska Peninsula, consists chiefly of andesite and dacite
flows and volcaniclastic rocks. The younger, middle Tertiary through
Holocene part of the arc consists of about 37 subaerial stratocones
composed predominantly of calc-alkalic andesite to dacite flows, tuffs,
and volcaniclastic rocks. (3) The eastern part of the arc on the Alaska
Peninsula and in the Alaska Range overlaps the Peninsular sequence of
the Wrangellia superterrane and consists of the 50- to 55-Ma Teklanika
Formation, the 37- to 45-Ma Mount Galena, Sheep Creek, and Post River
volcanic complexes, and associated unnamed units that range in
composition from basalt to rhyolite.

The Wrangell volcanic field (wr, figs. 4, 7) consists chiefly of
andesite and lesser basaltic andesite shield volcanoes, satellitic
cones, and andesite and lesser dacite flows, tuff, breccia, volcanic
avalanche deposits, mudflows, and domes of 0- to 20-Ma age (Miller and
Richter, 1994). The volcanic field also includes lesser rhyolite and
rhyodacite flows and domes, basalt and basaltic andesite cinder cones,
and associated flows and dikes. Pyroclastic rocks are mainly lithic and
crystal tuff, with lesser agglomerate and ash. Local associated shallow
andesite plutons, dikes, dike swarms, and plugs also occur. The volcanic
field overlies mainly the Wrangellia superterrane in south-central
Alaska and locally is extensively interlayered with Quaternary and
Holocene glacial deposits.

Subduction-Zone Units Linked to the Aleutian-Wrangell Arc

Tectonically linked to the Aleutian-Wrangell continental-margin arc is
the western (Attu Island) part of the Prince William accretionary-wedge
terrane, which constitutes the younger part of the terrane (Nokleberg
and others, 1994b); the Yakutat accretionary-wedge and subduction-zone
terrane; and the modern-day subduction-zone complex that is forming
inboard of the Aleutian megathrust (Plafker and others, 1994) (fig. 4).

The Attu Island part of the Prince William accretionary-wedge terrane
(western part of PW, figs. 1, 2, 4, 7) consists predominantly of early
Tertiary trench sedimentary rocks accreted to the hanging wall of the
subduction zone (Cooper and others, 1987, 1992; Scholl and others, 1992;
Plafker and others, 1994; Scholl and Hart, 1994). The terrane is exposed
on the lower landward trench slope near the Attu and Kodiak Islands. The
overall Prince William accretionary-wedge terrane is described in the
above subsection on the Kluane arc.

The Yakutat accretionary-wedge terrane (YAK, figs. 2, 7) is a composite
terrane that consists of the Mesozoic Yakutat Group in the eastern part
and Eocene oceanic crust in the western part (Jones and others, 1981;
Plafker and others, 1994). Both the eastern and western parts are
overlain by younger Cenozoic sedimentary and volcanic rocks. The Yakutat
Group is divided into (1) the melange facies, chiefly basalt, chert,
argillite, tuff, and sandstone of Late Jurassic(?) and Early Cretaceous
age, exotic blocks of Permian and Late Triassic carbonate rocks, and
Middle and Late Jurassic tonalite; and (2) the flysch facies, chiefly
Late Cretaceous volcanic sandstone, siltstone, and minor conglomerate,
with structurally interleaved lenses of disrupted chert, argillite, and
volcanic rocks. The Yakutat Group is metamorphosed from zeolite to lower
greenschist facies and is intruded by Eocene granitic plutons. The
Yakutat terrane is interpreted as a fragment of the Chugach terrane
(Yakutat Group) and Eocene oceanic crust that, together with an
overlying pre-Miocene sequence, was displaced at least 600 km northward
along the Fairweather transform fault since the early Miocene. Isotopic
studies by Heller and others (1992) suggest formation of the Cenozoic
sedimentary rocks of the Yakutat terrane in a basin offshore of the U.S.
Pacific Northwest and subsequent northward tectonic migration of about
600 km (Plafker and Berg, 1994).

Origin of the Aleutian-Wrangell Arc

The igneous-rock units that define the Aleutian-Wrangell arc are
interpreted by most workers as various parts of an elongate
continental-margin arc that has been active since its inception in the
late Eocene (Plafker and others, 1989a, b; Scholl and others, 1992;
Nokleberg and others, 1994a, b; Plafker and Berg, 1994; Plafker and
others, 1994; Monger and Nokleberg, 1996). The arc is interpreted as
having formed in response to successive, oblique subduction (combination
of dextral slip and underthrusting) of three major units along the
continentward-dipping Contact Fault (CO), the Aleutian megathrust (AL),
and parallel intervening faults (fig. 4): (1) the younger, Paleocene and
Eocene part of the Prince William accretionary-wedge terrane; (2) the
Yakutat accretionary-wedge terrane, with underthrust sedimentary rocks
as young as Eocene; and (3) part of the Pacific oceanic plate (PAC,
figs. 1, 3, 4). The Aleutian-Wrangell arc is not associated with any
conspicuous backarc unit.

Cascade Arc in the Southern Part of the Canadian Cordillera and the U.S.
Pacific Northwest

The Cascade arc is a major continental-margin igneous arc that continues
to be active since its inception in the early Eocene. The arc is
preserved in the Cascade volcanic-plutonic belt (ca, figs. 4, 7; Wells
and Heller, 1988; England and Wells, 1991; Goldfinger and others, 1996,
1997; Flueh and others, 1997). The Cascade arc overlaps all previously
accreted inboard terranes in the region (figs. 2, 4).

The Cascade volcanic-plutonic belt (ca, figs. 4, 7) has both Canadian
and U.S. parts (Vance and others, 1987; Wells, 1990; Walker and MacLeod,
1991; Smith, 1993). In the Canadian Cordillera, the belt consists of
Pleistocene and Holocene basalt, andesite, and dacite eruptive centers
and late Eocene(?), Oligocene, and Miocene plutons (Chilliwack and Mount
Barr batholiths). The belt includes age-equivalent, possibly unrelated
volcanic rocks (Masset Formation) on the Queen Charlotte Islands. In the
U.S. Pacific Northwest, the belt consists of volcanic rocks of
stratovolcanoes, mostly andesite but ranging in composition from basalt
to rhyolite. The belt includes interbedded fluvial and lacustrine
deposits and minor tonalite to granodiorite plutons. In Washington,
parts of belt are included in the Ohanapecosh, Fifes Peak, and
Northcraft Formations (Vance and others, 1987; Smith, 1993). The parts
of the belt in Oregon are included in many formations and informal
units, as listed by Walker and MacLeod (1991). The youngest active
volcanoes in the belt are Mounts Jefferson, Hood, Adams, St. Helens, and
Rainier.

Subduction-Zone and Backarc Units Linked to the Cascade Arc

Tectonically linked to the Cascade continental-margin arc are, from
inboard to outboard, the Siletzia (SZ) subduction-zone terrane, the
Olympic Core (OC) and Hoh (HO) accretionary-wedge terranes, and an
unnamed, modern-day subduction complex forming along the Cascadia (CC)
megathrust (figs. 2, 4, 7; Nokleberg and others, 1994a, 1997; Goldfinger
and others, 1996, 1997; Flueh and others, 1997).

The Siletzia subduction-zone terrane (SZ, figs. 2, 4, 7) consists
chiefly of basalt and greenstone of the early and middle Eocene Crescent
and Metchosin Formations and the Siletz River Volcanics (Tabor and Cady,
1978; Muller, 1980; Wells and others, 1984; Clowes and others, 1987;
Silberling and others, 1987; Babcock and others, 1992, 1993, 1994). The
greenstone consists of metamorphosed tholeiitic pillow basalt, massive
basalt, diabase, gabbro, tuff, and breccia. Intercalated with the
greenstone are minor clastic rocks, ferruginous coccolithic limestone,
and argillite. Total structural thickness of the terrane is more than 16
km. On the Olympic Peninsula in Washington, the greenstone and basalt
sequence appears to be stratigraphically underlain by continent-derived
graywacke, argillite, and minor conglomerate (Tabor and Cady, 1978).
Deep seismic-reflection studies on Vancouver Island, Canada, suggest
that the Siletzia terrane was partly subducted beneath the Wrangellia
superterrane (Clowes and others, 1987). The Siletzia terrane is
stratigraphically overlain by middle and late Eocene turbiditic
sedimentary rocks of the Northern Olympic forearc basin.

The Olympic Core accretionary-wedge terrane (OC, figs. 2, 4, 7) consists
chiefly of broken formation and melange composed of marine clastic rocks
(Needles-Graywolf, Grand Valley, Western Olympic, and Lithic
assemblages) that form the core of the Olympic Mountains, Washington
(Tabor and Cady, 1978; Clowes and others, 1987; M.T. Brandon, written
commun., 1993). The marine clastic rocks are poorly dated but probably
are mostly late Eocene to Oligocene in age; however, some imbricated
Miocene rocks also occur (M.T. Brandon, written commun., 1993). The
terrane includes the western Olympic assemblage of Tabor and Cady
(1978), part of which may correlate with part of the Yakutat terrane in
southeastern Alaska (Heller and others, 1992). The Olympic Core terrane
is interpreted as having been subducted under the Siletzia terrane along
the Hurricane Ridge Fault. Deep seismic-reflection studies on Vancouver
Island suggest that the Olympic Core terrane forms the lowest of several
northeast-dipping thrust sheets that form the crust of Vancouver Island,
above the presently subducting Juan de Fuca plate (Clowe and others,
1987).

The Hoh accretionary-wedge terrane (HO, figs. 2, 4, 7) consists chiefly
of middle Miocene to late Oligocene melange and broken formation
(Snavely and others, 1980; Clowes and others, 1987; Silberling and
others, 1987). Onshore, the terrane consists of sandstone and siltstone
in a sheared siltstone matrix on the western part of the Olympic
Peninsula (Snavely and others, 1980). Deep seismic-reflection studies on
Vancouver Island suggest that the Hoh terrane forms the lowest of the
northeast-dipping thrust sheets which form the crust of Vancouver Island
above the presently subducting Juan de Fuca plate (Clowes and others,
1987).

Also tectonically linked to the Cascade continental-margin arc is a
major backarc-rift unit represented by the Columbia River Basalt Group
(cr, figs. 4, 7). The group consists chiefly of thick flows of olivine
tholeiite erupted as flood basalt, between middle and late Miocene (16.5
and 6 Ma), with minor interbeds of fluvial and lacustrine sedimentary
rocks. The basalt in the group has an estimated volume of 210 km2
(Hooper, 1982; Bevier, 1988; Mathews, 1988; Hooper and Conrey, 1989;
Wells and others, 1989; Wheeler and McFeely, 1991). The group is an
extensive unit in central Washington and northern Oregon. In the
southern part of the Canadian Cordillera, equivalent rocks of the group
consist of the Chilcotin volcanic field of late Tertiary, mainly
Oligocene(?), Miocene, and Pliocene age (2--16 Ma). The group consists
mainly of subaerial, rarely subaqueous olivine basalt flows,
intercalated pyroclastic rocks, and local gabbroic and basaltic
intrusions. The group also locally contains younger volcanic centers of
intermediate to felsic composition, such as the plume-related(?) Anaheim
volcanic rocks and the rift-related Ediza volcanic rocks (Wheeler and
McFeely, 1991).

Origin of the Cascade Arc

The Cascade arc is a major continental-margin arc that has been active
since the late Eocene (Wells and Heller, 1988; England and Wells, 1991;
Goldfinger and others, 1996, 1997; Flueh and others, 1997). The arc is
interpreted as having formed in response to successive, oblique
subduction (combination of sinistral slip and underthrusting) of four
major units along a series of continentward-dipping faults. From inboard
to outboard, the four successively younger units that have been
subducted and accreted during formation of the arc are (1) the middle
Eocene Siletzia subduction-zone terrane, (2) the late Eocene to
Oligocene Olympic Core accretionary-wedge terrane, (3) the middle
Miocene to late Oligocene Hoh accretionary-wedge terrane, and (4) the
unnamed, modern-day subduction complex forming above the Cascadia
megathrust (CC). The Juan de Fuca oceanic plate is presently being
subducted at the Cascadia megathrust (fig. 4). Also associated with the
Cascade arc is the Columbia River Basalt Group, which is interpreted as
having formed from backarc rifting during the middle and late Miocene.
Associated with backarc rifting is extension and thinning of previously
accreted terranes (Wells and Heller, 1988; England and Wells, 1991).

Linkages Between Belts of Anatectically Related (Collisional) Igneous
Rocks andAccretions of Terranes

Linkage of the Verkhoyansk Plutonic Belt with Accretion of the
Kolyma-Omolon Superterrane to the North Asian Cratonal Margin

Characteristics of the Verkhoyansk Collisional Granite Belt

The Verkhoyansk collisional granite belt, which occurs in the Russian
Northeast, consists chiefly of two major belts: the Main collisional
granite belt of Late Jurassic to early Neocomian age, and the Northern
collisional granite belt of Neocomian age. The Main collisional granite
belt (ma, fig. 3), which extends for about 1,000 km along the southwest
border of the Kolyma-Omolon superterrane, stitches the superterrane to
the North Asian cratonal margin (Verkhoyansk fold-and-thrust belt; NSV,
figs. 1, 3, 7). The Main belt consists of inclined sheetlike plutons, as
much as 200 km long, that are generally conformable with major fold
axes. Ar-Ar ages of granitic rocks range from 134 to 144 Ma (Hackett and
others, 1992; Layer and others, 1995; Fujita and others, 1997). Major
rock types in the Main belt are a two-mica granite containing garnet,
cordierite, and sillimanite, and a biotite and biotite-amphibole granite
(Shkodzinsky and others, 1992; Trunilina and Orlov, 1997). A few initial
87Sr/86Sr ratios for granites in the Main belt are higher than 0.7060
(A.G. Bakha, written commun. to L.M. Parfenov, 1997). The regional
metamorphism of the host Kula-Nera terrane, from lower greenschist to
local epidote-amphibolite facies, is interpreted as having occurred
during the collisional event.

The Northern collisional granite belt (no, fig. 3) extends for about 600
km along the northwestern margin of the Kolyma-Omolon superterrane.
Ar-Ar ages of granitic rocks range from 120 to 127 Ma (Layer and others,
1995; Fujita and others, 1997). The Northern belt consists of inclined
sheetlike plutons, as much as 200 km long, that are generally
conformable with major fold trends. Major rocks types are tonalite,
granodiorite, and, less commonly, two-mica leucogranite (Shkodzinsky and
others, 1992; Bakharev and others, 1988).

Within the Verkhoyansk fold-and-thrust belt (North Asian cratonal
margin; NSV, figs. 1, 3, 7), discrete granite plutons of mid-Cretaceous
age occur in the linear West Verkhoyansk granite belt (wvk, fig. 3),
which extends for more than 1,000 km along a north-south strike
(Parfenov and others, 1996). The plutons consist of granodiorite,
granite, monzonite, and quartz monzonite with initial 87Sr/86Sr isotopic
ratios of more than 0.707. 39Ar/40Ar isotopic ratios indicate ages of 95
to 108 Ma (Fujita and others, 1997). Locally, these plutons are
associated with epidote-amphibolite--facies regional metamorphism. Field
relations suggest that regional metamorphism occurred immediately before
granite intrusion. The age of metamorphism and granite intrusion is
correlated with the intense deformation of the Verkhoyansk
fold-and-thrust belt during the mid-Cretaceous to Late Cretaceous
(Parfenov and others, 1996; Fujita and others, 1997), possibly in the
same tectonic event that resulted in the formation of the Omineca-Selwyn
belt.

Collisional Origin of the Verkhoyansk Granite Belt

The Verkhoyansk collisional granite belt (consisting of Main and
Northern parts) extends for 1,300 km along the southwestern and
northwestern margins of the Kolyma-Omolon superterrane (fig. 3). The
granite plutons in the belt intrude several major faults within the
Verkhoyansk fold-and-thrust belt (North Asian cratonal margin; NSV), the
Kula-Nera terrane (KN), and the Uyandina-Yassachnaya volcanic arc (part
of unit io, fig. 3) that formed on the margin of the Kolyma-Omolon
superterrane (figs. 1, 3, 7; Parfenov and others, 1993a, b; Nokleberg
and others, 1994a, b; Parfenov, 1995a, b). These relations indicate that
the Verkhoyansk granite belt formed during and immediately after the
collision of the Kolyma-Omolon superterrane to the east with the North
Asian cratonal margin.

Linkage of the Omineca-Selwyn Plutonic Belt to Mid-Cretaceous Accretion
of Outboard Terranes Along the North American Continental Margin

Characteristics of the Omineca-Selwyn Plutonic Belt

The Omineca-Selwyn plutonic belt (om, figs. 3, 4) occurs in the Canadian
Cordillera, Alaska, and the northern part of the Russian Northeast for a
strike length of about 4,000 km (Nokleberg and others, 1994a, 1997a--c).
The belt includes the easternmost magmatic rocks in the Canadian
Cordillera and the northernmost plutonic rocks in interior and northern
Alaska and the northern part of the Russian Northeast. In the Canadian
Cordillera, the belt consists chiefly of granodiorite, granite, quartz
syenite, and minor syenite plutons of Early Cretaceous to mid-Cretaceous
age (90--110 Ma) that form an extensive belt of discrete intrusions
(Armstrong, 1988; Miller, 1989, 1994; Woodsworth and others, 1992). Many
of the plutons exhibit S-type characteristics. The belt ranges in age
from 90 to 110 Ma and exhibits high initial 87Sr/86Sr ratios (=0.710)
(Armstrong, 1988; Woodsworth and other, 1992). Extrusive equivalents,
such as the South Fork volcanic rocks of the Yukon Territory and Canada,
are rare.

In the Canadian Cordillera, various western Cordillera terranes (Slide
Mountain \[SM\] and Quesnellia \[QN\], fig.2) were thrust over the
distal Kootenay cratonal-margin terrane during the Early to Middle
Jurassic (approx 185 Ma). The overthrusting was accompanied by
high-grade metamorphism and complex deformation of the Kootenay terrane.
From 185 Ma, granitic rocks of the Omineca-Selwyn plutonic belt (om)
show increasing evidence of crustal contamination. Precambrian zircons
and higher initial 87Sr/86Sr ratios occur in the easternmost granites
(Ghosh, 1995). During the mid-Cretaceous, the western terranes (Kootenay
\[KO\], Quesnellia \[QN\], Slide Mountain \[SM\]) were overthrust
eastward over the North American cratonal margin (NAM) and the North
American Craton (NAC), with formation of the distinctive collisional
granites of the Omineca-Selwyn plutonic belt (figs. 2, 4, 7). The
position of this belt relative to west-dipping structures and isotopic
geochemistry suggest that it formed by partial anatectic melting of
structurally depressed continental crust. Alternatively, Armstrong
(1988) interpreted these rocks as the rear part of a single
Cordillera-wide mid-Cretaceous arc.

In interior and northern Alaska, the Omineca-Selwyn belt consists of
large plutons of mid-Cretaceous granite and lesser syenite and
granodiorite in an elongate trend that extends from east-central to
west-central Alaska, the Seward Peninsula, and St. Lawrence Island. The
belt includes the Ruby geanticline plutons of central Alaska (Miller,
1989, 1994; Foster and others, 1994; Patton and others, 1994) and the
mid-Cretaceous and early Late Cretaceous granitic plutons of the
Yukon-Tanana Upland (Pavlis and others, 1993; Foster and others, 1994).
In interior Alaska, granitic plutons tend to be K rich, are locally
ultrapotassic and Na depleted, are weakly to moderately peraluminous,
are locally part of the ilmenite series, and exhibit S-type
characteristics. Th ese plutons are interpreted as the product of
melting or contamination of continental crust. In the Chukotka terrane
(CH, figs. 1, 7) in the northern part of the Russian Northeast, the
Omineca-Selwyn belt consists of a suite of Early Cretaceous granitic
rocks that are overlain by volcanic rocks of Okhotsk-Chukotka
volcanic-plutonic belt (oc, figs. 4, 7; Sosunov and others, 1982;
Sosunov, 1985).

Collisional Origin of the Omineca-Selwyn Belt

The Omineca-Selwyn plutonic belt (om) occurs in a linerar zone of
intense mid-Cretaceous deformation that occurs along the inboard part of
the North American orogen, about 200 to 300 km continentward from the
accretionary margin of the North American continent. The plutonic rocks
of the belt were intruded during the late stages of a period of intense
contraction that was associated with orthogonal convergence between the
Farallon oceanic plate and the North American Cordillera (Englebretson
and others, 1985, 1992), and subsequent regional extension (Pavlis and
others, 1993). In the Canadian Cordillera, the mid-Cretaceous plutons of
the belt exhibit a strong crustal inheritance that may reflect
Andean-style backarc thrusting and melting of the cratonal margin
beneath the continental margin and accreted terranes during this episode
of strong convergence (Monger and Nokleberg, 1996). The thrusting
involved both cratonal-margin deposits and the overlying Jurassic and
Cretaceous clastic deposits derived from the orogen. Similarly, in
interior Alaska, in both the Ruby geanticline and the Yukon-Tanana
Upland, the plutonic belt intruded sedimentary and volcanic rocks of the
two terranes during the waning stages of a complex period of compression
and thrusting followed by regional extension (Pavlis and others, 1993;
Nokleberg and others, 1995a, b). These geologic relations and the
chemical and isotopic characteristics of the Omineca-Selwyn plutonic
belt indicate genesis during anatexis associated with the late stages
of, and immediately after, major terrane collision and orthogonal
compression along the North America Cordillera in a narrow linear zone
that extended from the southern part of the Canadian Cordillera, across
interior Alaska, into the northern part of the Russian Northeast (figs.
3, 4).

Paleomagnetic Constraints

Paleomagnetic Constraints for Plate Reconstructions of Northeast Asia
and North America

In the reconstructions of major tectonic plates presented in this study,
principally the North American Craton and the North Asian Craton, we
used a hierarchical, two-level approach. The first level was to
reconstruct the relative positions of what became North America and
North Asia for each time interval (stage). The second level was to
position the relatively smaller terranes with respect to the major
plates. The positions of terranes were determined primarily on the basis
of stratigraphic and faunal data and, to a lesser degree, paleomagnetic
data. In cases of data conflict, as discussed below for specific
terranes on specific time-stage diagrams, terranes are positioned
according to stratigraphic and faunal data rather than by paleomagnetic
data.

From the Devonian to the present, the timespan that is modeled in this
study, the relative motion between the North American and North Asian
Cratons consisted of two phases. (1) Before the amalgamation of Pangea
in the Permian, the Asian region consisted of several different plates.
The North Asian Craton, one of the principal plates for this study, was
sutured to Baltica (the Russian Platform) in the Late Carboniferous to
Permian, during the final stage of the formation of Pangea. Baltica and
the North American plate had already been sutured during the Silurian to
Early Devonian Caledonian orogeny. (2) After the amalgamation of Pangea
in the Permian, the second major phase of relative motion between the
North American and North Asian Cratons was controlled by a protracted
series of rifts that culminated in the Jurassic and later sea-floor
spreading which formed the North Atlantic Ocean. These two phases of
plate motion (suturing and subsequent rifting) control our methodology
for defining plate positions in the tectonic model. After the Permian,
the relative positions of North American and North Asian Cratons are
constrained by plate reconstructions of the North Atlantic plate; for
earlier times, paleomagnetic data are used as the principal constraint.

Reconstructions of the North Atlantic (North American relative to North
Asian) region utilized in this study are from two principal sources.
Reconstructions constrained by oceanic-sea-floor-spreading data are
based on the study by Srivastava and Tapscott (1986) that encompasses
the Early Cretaceous to the present. From the Permian to the Late
Jurassic, motion between the North American and North Asian Cratons was
accommodated by rifting primarily in the present-day Rockall and North
Sea areas around the British Isles. This rifting must have been
accompanied by some horizontal motion between the plates, but published
estimates of this motion indicate only a few tens of kilometers of
motion (for example, Barton and Wood, 1984; Latin and White, 1990).

For pre-Permian reconstructions, before the North Asian region was
amalgamated to Pangea, the relative positions of present-day North Asia
and North America are based on paleomagnetic data, using the compilation
by Van der Voo (1990) for North America and Baltica. For Siberia, we
used the data of Khramov (1971, 1979, 1986a, b), Khramov and others
(1985), and Didenko and Pechersky (1993). An additional constraint in
the Paleozoic plate reconstructions is provided by geologic data. As is
well known, paleomagnetic data alone cannot provide a unique plate
reconstruction because of inherent longitudinal uncertainty.

Paleomagnetic Constraints for Terranes and Overlap Assemblages

For utilization of paleomagnetic data to construct the tectonic model,
we compiled (table 3) and evaluated the documented paleomagnetic data
available in the literature according to the selection criteria listed
below. We evaluated and ranked each data set, accordingly assigning a
grade between A (very good) and D (marginal). We rejected all other
paleomagnetic data in the literature until such time as positive
magnetic-stability tests of some type become available for them. The
complete compilation of the paleomagnetic data is available from David
B. Stone (or his Internet/World Wide Web site at URL
http://www.gi.alaska.edu/TSRG/People/Stone/). Paleolatitudes mainly from
data graded A, B, or C were utilized to constrain the latitudes of
terranes for each time interval (stage) of the tectonic model. In some
cases, the interpreted positions of specific terranes, according to
stratigraphic and faunal data, conflict with the positions interpreted
from paleomagnetic data. In such cases, we positioned the terranes
primarily according to stratigraphic and faunal data and secondarily
according to supporting paleomagnetic (paleolatitude) data. We discuss
both supporting and conflicting paleomagnetic data for each time
interval (stage) of the tectonic model. Discussions of apparent
conflicts for terrane position according to stratigraphic and faunal
data, on the one hand, versus paleomagnetic data, on the other hand,
outline important new areas for future studies. Supporting paleomagnetic
data are defined as those higher quality paleolatitude values, as ranked
by criteria given below, that agree within about 5--8° of the positions
determined by other geologic and faunal data; conflicting paleomagnetic
data have paleolatitude values that differ by more than about 8--10°.

The criteria for ranking of paleomagnetic data are as follows.

*Grade A*.---Multiple demagnetization steps were applied to most or all
of the samples, and statistically good fold or reversal tests were
quoted, although in some cases we accepted other evidence of a positive
stability test (for example, a conglomerate test or a baked-contact
test).

*Grade B*.---Multiple demagnetization steps were applied to a
significant number of the samples, and the author claims to have
established positive stability for the magnetization.

*Grade C*.---Single-level, blanket demagnetization techniques were
applied, and the author claims positive stability tests but has no
supporting data, or else normal and reversely magnetized samples were
combined (without any quantitative evidence that the magnetizations are
antipodal). Grade C was also assigned to units where the ancient
horizontal was poorly constrained, for example, in data from intrusive
rocks.

*Grade D*.---The author claims to have data that represent the
paleomagnetic field but gives no supporting evidence. Grade D is also
used for units where the data seem accurate but where normal stability
tests are impossible. All other data in the literature were rejected.

Paleolatitudes were calculated from the latitudinal displacements
between the paleomagnetic poles for the sampled localities with respect
to the North Asian Craton for the Russian Northeast or with respect to
the North American Craton for Alaska and Canada. Many of the data for
the Russian Northeast are derived from the compilations of Khramov
(1971, 1979, 1986a, b), as reported in the global paleomagnetic data
base of Lock and McElhinny (1991). The composite apparent-polar-wander
path (APWP) for the North Asian Craton for the pre-Triassic is from
Khramov (1971, 1979, 1986a, b), who utilized data directly related to
the craton. We used the APWP of Besse and Courtillot (1991) for the
Triassic to the present stages of the tectonic model. This APWP is based
on paleomagnetic pole-position data from many places rotated into the
reference frame of the North Asian Craton by using
paleogeographic-reconstruction poles. We used the North American APWP of
Van der Voo (1993) for the Paleozoic and older models, and that of Besse
and Coutillot (1991) for the Triassic to the present models. Most
displacements are southerly with respect to either the North Asian or
North American Cratons; northerly displacements are listed as negative.

Paleomagnetic-Variation Diagrams

For this paleomagnetic analysis, we present five diagrams that
illustrate paleomagnetic versus time values for terranes and overlap
assemblages in the Circum-North Pacific (fig. 5). Paleolatitudes on
these figures were calculated from paleomagnetic-inclination data from
various combinations of terranes from the Russian Far East, Alaska, and
the Canadian Cordillera. Two other paleomagnetic diagrams illustrate
paleolatitude versus time values for the North Asian and North American
Cratons (fig. 6). These paleomagnetic latitudes are interpreted as
ancient geographic latitudes by using the common assumption that the
time-averaged magnetic pole coincides with the geographic pole. The
geologic age assigned to each of the paleomagnetic data points is based
on information given by the cited authors, but when several points have
the same nominal age, then we arbitrarily inserted separations of about
2 Ma to improve the clarity of the diagrams.

Two diagrams illustrate plots for the North Asian (Siberian) and North
American Cratons, respectively, of paleolatitude versus time (fig.
6*A*). These values were calculated from the separation of the North
Asian and North American sampling localities and from the paleomagnetic
reference poles for the appropriate continental block. The two sets of
reference poles were derived from the data of Besse and Courtillot
(1991) for poles of Mesozoic age, and from the data of Van der Voo
(1981, 1990, 1993) and Didenko and Pechersky (1993), for poles of
Paleozoic age for North America and North Asia, respectively. Quite
large variations exist in the published APWP's for North Asia and, to a
lesser extent, for North America, and so these reference latitudes
should be used only as a guide.

The careful reader may note that the paleolatitudes for the continental
blocks of the North Asian and North American Cratons (fig. 6) do not
correspond exactly with the paleolatitudes shown in figures 7 through
20. The largest discrepancies occur for Siberia in the Late Triassic and
Jurassic. The differences are due to the paleolatitudes shown in figures
7 through 20 being based on the paleomagnetic APWP's derived for each
continental block (May and others, 1989), whereas the paleolatitudes
shown in figure 6 are based on mean paleomagnetic poles from several
continents after reconstructing the continental positions from around
the Atlantic Ocean (Besse and Courtillot, 1991). These two approaches
permit the reader to assess how tightly constrained the major tectonic
framework is for any given time. A tectonically produced error in the
North America paleomagnetic data may not be resolved (Butler and others,
1989).

Kolyma-Omolon Superterrane

The plot of paleomagnetic poles versus time for the Kolyma-Omolon
superterrane (fig. 5*A*) includes values for the Omulevka terrane and
smaller terranes that were accreted to the Kolyma-Omolon superterrane
before collision with the North Asian Craton and adjacent passive
continental margin (Verkhoyansk fold-and-thrust belt; NSV, figs. 1, 3,
7) at about the Middle to Late Jurassic. The paleolatitudes of the
Kolyma-Omolon superterrane, from about the Middle Jurassic, closely
match the latitudes expected for their present geographic positions. A
strong indication exists that farther back in time, the terranes were
displaced to the south by about 20° of latitude. However, by the
Devonian, two grade A data points indicate that the North Asian Craton
and the Kolyma-Omolon superterrane were in close proximity. An exception
is a single locality from the Rassokha terrane (RA) that yields a
considerably lower paleolatitude (table 3), possibly representing a very
rapid southerly excursion during the latest Devonian and Early
Carboniferous, a problem with the interpretation of the geologic
relations between these terranes, or an unresolved magnetic overprint.

Outboard Terranes in the Russian Northeast

The plot of paleomagnetic poles versus time for outboard terranes (fig.
5*B*) is for those terranes that are outboard of the Kolyma-Omolon
superterrane toward the ancestral Pacific Ocean. These terranes formed
in various tectonic settings and yield paleomagnetic data of varying
quality. If the grade A data are given more weight than the other data
sets, then a clear northward trend is evident for paleolatitude values
that accelerates in the mid-Cretaceous and Late Cretaceous, such that
these outboard terranes arrived at present-day latitudes by the Eocene.
As defined above, grade A data pass more than one stability test.
Together, all the data yield a very noisy picture, suggesting that some
of the data sets, although they passed the selection criteria, may still
contain a large component of remagnetization. Some of the grades B and C
data were given relatively high grades on the basis of passing a fold
test. The discrepancies seen may be due to postremagnetization folding,
thereby giving a false impression of an original paleomagnetic record.

Interior and Arctic Alaska

The plot of paleomagnetic poles versus time for interior and Arctic
Alaska (fig. 5*C*) is for all the terranes that occur north of the
Denali Fault System. Only one data point exists north of the Brooks
Range in the Arctic Alaska superterrane (AA). This data point is for a
passive-continental-margin terrane that is interpreted as having formed
originally adjacent to the North American Craton in the Canadian Arctic.
The other data points are for terranes south of the Brooks range and
from the Bering Sea region. For this region, the data hints at greater
than 10° of northward motion between the mid-Cretaceous and latest
Cretaceous.

South-Central Alaska

The plot of paleomagnetic poles versus time for south-central Alaska
(fig. 5*D*) is for all terranes south of the Denali Fault System from
the eastern Gulf of Alaska to the Bering Sea. Paleolatitudes clearly
increase onward from the Late Carboniferous. This trend accelerates
markedly during the mid-Cretaceous.

Southeastern Alaska and the Canadian Cordillera

The plot of paleomagnetic poles versus time for southeastern Alaska and
the Canadian Cordillera (fig. 5*E*) shows data for all the terranes in
this region. This plot shows a very marked northward increase in
paleolatitude from the Late Carboniferous to the late Tertiary. Care
should be taken when analyzing this plot, not only because of the wide
range of present-day latitudes of the sampled sites but also because the
overall motion of the North American Continent is nearly identical to
that for these terranes. Relative to the North American Craton (fig.
6*B*), the motions are dominantly northward, but at a lower rate than
the absolute paleolatitude motions shown in figure 5*E*.

Paleomagnetic Dilemma: Loci of Accretion of the Wrangellia Superterrane

A major paleomagnetic dilemma exists for the loci of accretion of
superterranes to the North American cratonal margin during the
mid-Cretaceous to early Tertiary. The dilemma consists of two
conflicting hypotheses for the loci of accretion of the Wrangellia
superterrane, which constitutes most of the Insular superterrane, and of
the Intermontane superterrane, which consists of the Stikinia,
Quesnellia, and Cache Creek terranes (Cowan, 1994; Cowan and others,
1997). One hypothesis, based on geologic evidence, including magmatic
and stratigraphic ties, interprets the Wrangellia superterrane as
accreting at a northerly paleolatitude, approximately at its present
latitude. The other hypothesis, based on paleomagnetic data for both
stratified and plutonic rocks, interprets the Wrangellia superterrane
and the western part of the Intermontane terrane as accreting at a
paleolatitude approximately 3,000 km farther south. This hypothesis is
informally named the "Baja British Columbia controversy," in reference
to accretion of the Wrangellia superterrane at the approximate latitude
of Baja California (Umhoefer, 1987; Cowan and others, 1997; Dickinson
and Butler, 1998). In our tectonic model, these two hypotheses are
termed the "northern-accretion interpretation" and "southern-accretion
interpretation."

Our tectonic analysis cannot currently discriminate between the two
interpretations. Instead, the applicable parts of the tectonic model
describe both the geologic and paleomagnetic data that support the
northern-accretion interpretation, and the moderately abundant
paleomagnetic data that support the southern-accretion interpretation.
Accepting the northern-accretion interpretation requires radical
reinterpretation of the paleomagnetic studies. Accepting the
southern-accretion interpretation require (1) radical reinterpretation
of the geologic data supporting the northern-accretion interpretation
(Monger and others, 1996); (2) construction of a southerly route of
tectonic migration starting in the Late Triassic, when the Wrangellia
superterrane is interpreted to have formed at about 10° paleolatitude
(as discussed by Irving and others, 1996, and Cowan and others, 1997);
(3) accretion of the Wrangellia (Insular) superterrane and, possibly,
the western part of the Intermontane superterrane at the latitude of
present-day Baja California at about 90 to 95 Ma (Irving and others,
1996; Cowan and others, 1997); and (4) a complex tectonic and rapid
migration of the Wrangellia (Insular) superterrane and the western part
of the Intermontane superterrane along the western part of the North
American cratonal margin for a distance of about 3,000 km from about 83
to 34 Ma (Cowan and others, 1997) along a series of faults (such as the
Fraser Creek-Straight Creek and Ross Lake Fault Systems, fig. 20, and
the Pasayten Fault in the southern part of the Canadian Cordillera) that
do not display this amount of displacement (Monger and others, 1996).
The various facets of this dilemma were discussed by Cowan (1994),
Irving and others (1996), Monger and others (1996), Cowan and others
(1997), Monger (1997), and Dickinson and Butler (1998); proposed tests
of the two hypotheses were discussed by Cowan and others (1997).

Phanerozoic Tectonic Model for the Circum-North Pacific

Introduction

This model for the Phanerozoic tectonic evolution of the major geologic
units of the Circum-North Pacific is based on the geologic and
paleomagnetic constraints outlined above. The model attempts to (1)
integrate stratigraphic, age, structural, and paleomagnetic data and
field relations for units of the Circum-North Pacific as summarized in
tables 2 and 3, in above sections, and in supporting studies (Nokleberg
and others, 1994a, 1997b); and (2) portray the regional tectonic
interactions between the North Asian and North American Continents for
the Devonian through the present (figs. 7--20). The tectonic model
illustrates (1) proportionally sized units compared with those on the
summary maps (figs. 1--4; Nokleberg and others, 1994a, 1997b, c; Monger
and Nokleberg, 1996), and (2) known or interpreted displacements along
major strike-slip and thrust faults. In most cases, however, the
tectonic model does not incorporate internal deformation of terranes.

The tectonic model provides a guide for future research by (1)
integrating geologic, paleontologic, isotopic, and paleomagnetic data
from both the Russian Far East, Alaska, the Canadian Cordillera, the
Pacific Ocean, and the Arctic Ocean; (2) proposing a new, unified
interpretation that spans the area from the northeastern part of the
North Asian Craton to the northwestern part of the North American
Craton; and (3) identifying problems with data and interpretations.
Because of a sparsity of Proterozoic and older rock units, exterior to
the cratonal margins, the model starts with the Devonian (fig. 7). For
various published tectonic reconstructions for the Proterozoic, which
illustrate highly different global interpretations, we recommend the
studies by Daziel (1991), Hoffman (1989, 1991), Moores (1991), Ross and
others (1992), Scotese (1997), Unrug (1997), and Karlstrom and others
(1999).

An important complexity of terrane recognition and analysis is that the
margins of terranes have been tectonically removed, either by
dislocation of terranes from distant locations or by tectonic erosion of
the margins of terranes. In the case of dislocation, detailed analysis
of each terrane with respect to inplace overlap assemblages,
passive-continental-margin assemblages, and cratonal assemblages should
provide the original site of origin. In the case of tectonic erosion, as
in the case of subduction-zone terranes, large parts of the original
unit (such as an oceanic plate) may have been thrust to great depths and
thereby may essentially have disappeared.

In some previous tectonic analyses, terranes have been portrayed as
discrete fault-bounded entities. This type of portrayal, sometimes
termed either "iceberg" or "motorboat tectonics," is partly the result
of terranes being defined as fault-bounded units having distinctive
stratigraphies. Our tectonic analysis, however, attempts to (1)
recognize that each terrane was once part of a larger, more continuous
stratigraphic succession of regional extent that was rarely bounded by
faults originally; (2) correlate and group coeval terranes; and (3)
group coeval igneous-arc terranes and tectonically linked
subduction-zone terranes, where geologic data permit, into collinear,
regional-extent arc/subduction-zone complexes. This type of tectonic
synthesis might be termed "spaghetti tectonics."

An important interpretation in the tectonic model is that a succession
of coeval single arcs and companion subduction zones formed on or near
the margins of the North Asian and North American Continents, rather
than migrating across ocean basins to accrete eventually to the margins
of the continents. One consequence of this interpretation is that many
of the complexities of the collage of accreted terranes in the region
(figs. 1--4) are the results of oblique subduction and resulting
strike-slip displacements within active continental margins.
Substantiation of this interpretation will require (1) determination of
the facing directions of the arcs with respect to cratons; (2)
correlation of coeval arc and tectonically linked (companion) subduction
zones to establish them as different parts of a former, single,
curvilinear arc/subduction-zone system; and (3) determination of the
linkage of arcs to cratons. This interpretation is reasonably well
established for most of the Mesozoic and Cenozoic, but less so for the
Paleozoic.

For each time interval (stage) in the tectonic model, specific
(numbered) tectonic events are described in clockwise order, starting
with the area of the Russian Southeast and ending with the area of the
southern part of the Canadian Cordillera. Following the descriptions of
specific tectonic events are summaries of paleolatitude data that either
support or conflict with the interpreted positions of terranes and
overlap assemblages for each time interval. The face values of
paleolatitudes from table 3 are employed; however, in some cases, the
use of data with 95-percent-confidence limits implies a higher level of
agreement than may be warranted. The time scale for the tectonic model
is that of Palmer (1983).

Mesozoic and Cenozoic Changes in Plate Motions

Two major changes in Mesozoic and Cenozoic plate motions are interpreted
for the Circum-North Pacific and were probably responsible for much of
the tectonic evolution of the region (Plafker and others 1989b, 1994;
Monger and Nokleberg, 1996). Each change was superposed on long-lived
convergent plate margins. One major change in about the mid-Cretaceous
consisted of a reversal of relative offset between continental and
oceanic plates. The other major change in the early Tertiary (fig. 17)
resulted in overriding by the North American continental margin of the
Kula-Farallon oceanic ridge and the Farallon oceanic plate, and
accretion of part of the Kula oceanic plate.

Before about the mid-Cretaceous, the oceanic plates in the Circum-North
Pacific were generally rotating clockwise with respect to the North
Asian and North American Cratons, thereby producing a component of
sinistral slip to major fault systems (Engebretson and others, 1985).
From about the Late Cretaceous through the present, the Pacific plate
has been rotating counterclockwise with respect to the North American
plate, thereby producing a component of dextral slip to major fault
systems (Engebretson and others, 1985). An intense period of orthogonal
convergence between the ancestral Pacific Ocean plate and the North
American Continent is interpreted for the mid-Cretaceous.

This change in absolute plate motions, which was superposed on a
long-lived convergent plate margin, is probably responsible for the rise
of the Canadian Cordillera (Monger and Nokleberg, 1996). In Alaska and
the Canadian Cordillera, beginning with the Middle Jurassic and ending
in the early Tertiary, most igneous-arc/subduction-zone complexes were
accreted to the North American cratonal margin, and new
continental-margin arcs were built on the mobile collage of accreted
terranes. Subsequently, these arcs were fragmented by mainly
dextral-slip faults and overprinted by still-younger arcs. This change
probably resulted from long-continued northwestward, then westward,
movement of the North American plate toward the subduction zone
(Engebretson and others, 1985). The combination of strong plate coupling
with oblique convergence created optimum conditions for orogen-parallel
movements within the margin of the upper plate (Jarrard, 1986). Such
movements probably occurred throughout much of the middle and late
Mesozoic, but they are recorded in the substantial displacement along
Late Cretaceous and early Tertiary dextral-slip faults in Alaska and the
Canadian Cordillera.

The later change in absolute plate motion was subduction or overriding
of the Kula-Farallon oceanic ridge and the Farallon oceanic plate along
the margin of southern Alaska during the early Tertiary (Bradley and
others, 1993) and accretion of a fragment of the Kula oceanic plate that
underlies the modern Aleutian-Bowers sedimentary basin in the southern
part of the Bering Sea (Scholl and others, 1992, 1994). The subduction
of the oceanic ridge in the early Tertiary is interpreted as causing (1)
a regional metamorphic welt and formation of anatectic granites (Plafker
and others, 1989b, 1994), (2) rapid changes in components of strike-slip
movement along subduction zones bordering the early Tertiary margin of
southern Alaska (Bradley and others, 1993), and (3) formation of two
extensive belts of early Tertiary granitic rocks that formed in a
near-trench environment (Bradley and others, 1993).

Middle Through Late Devonian (387--360 Ma)

During the Middle to Late Devonian (387--360 Ma), the major tectonic
events were (1) formation of a discontinuous continental-margin arc
(Kedon arc in the Russian Northeast) and associated subduction zone
along the North Asian and North American cratonal margins; (2) during
the Late Devonian, inception of rifting of the North Asian and North
American Cratons and cratonal margins, resulting in the formation of new
terranes and associated metallogenic belts (table 2); and (3) inception
of the Sicker arc and associated subduction in what would eventually
become the Wrangellia superterrane. Sedimentation continued along the
North Asian and North American cratonal margins.

Specific Tectonic Events for the Middle Through Late Devonian

1\. During the early Paleozoic, on the basis of paleomagnetic data, the
North Asian Craton and cratonal margin (NSC, NSV, KN) migrated to a
position adjacent to the North American Craton and cratonal margin (NAC,
NAM) along a pre-Devonian sinistral-slip suture.

2\. The Kedon continental-margin arc and associated subduc-tion zone
(KN) formed along the North Asian Craton and cratonal margin (NSC, NSV)
and along the North American cratonal margin (NAM). In the North Asian
cratonal margin and outboard terranes, the arc is preserved today in (1)
sporadic occurrences of marine and continental volcanic and associated
rocks and subduction-related granitic rocks in the southern part of the
cratonal margin (NSV); (2) units that overlie parts of the Okhotsk
(OK),Akekova (AK), and Omolon (OM) cratonal terranes; (3) the Oloy (OL)
and Yarakvaam (YA) island-arc terranes; and (4) the Beryozovka
turbidite-basin terrane (BE). Associated with this arc was the
subduction of the older part of the Galam accretionary-wedge terrane
(GL) along the North Asian Craton and cratonal margin (NSC, NSV), and
subduction of the Angayucham and ancestral Pacific Oceans along the
North American cratonal margin (NAM). In the North American cratonal
margin (NAM) and outboard terranes, the arc is preserved today in
sporadic occurrences of marine volcanic and associated rocks and shallow
to deep-level subduction-related granitic rocks in various parts of the
Arctic Alaska (AA), Coldfoot (CO), Ruby (RB), Seward (SD), Yukon-Tanana
(YT), and Kootenay (KO) terranes. The Devonian arc is interpreted as
extending discontinuously from present-day Arctic Alaska to northern
California (Rubin and others, 1991; Smith and Gehrels, 1991; Mortensen,
1992; Nokleberg and others, 1994a; Plafker and Berg, 1994).

3\. During the late Late Devonian, rifting of the North Asian and North
American Cratons and cratonal margins occurred. Derived from the North
Asian Craton (NSC) and cratonal margin (NSV) were the Kotelnyi (KT),
Omulevka (OV), Prikolyma (PR), Nixon Fork-Dillinger-Mystic (NX, DL, MY),
Viliga (VL), and Zolotogorskiy (ZL) passive-continental-margin terranes
and the Avekova (AK), Kilbuck-Idono (KI), Okhotsk (OK), and Omolon (OM)
cratonal terranes. Derived from the Devonian continental-margin arc that
formed along the North Asian cratonal margin were the Beryozovka (BE),
Oloy (OL), and Yarakvaam (YA) terranes. The newly created terranes
migrated into the Angayucham Ocean. Derived from the North American
cratonal margin (NAM) were the Kootenay (KO) and Yukon-Tanana (YT)
passive-continental-margin terranes.

4\. The Sicker island arc was active along most of the length of the
Wrangellia superterrane (WRA), which at this time was composed only of
the Alexander terrane (AX). Asso-ciated with the Sicker arc was an
unknown subduction zone (UNK). In the present-day southern part of the
Canadian Cordillera, the Sicker arc is defined by the Sicker Group,
which consists of Late Devonian arc-related volcanic and sedimentary
strata with a U-Pb zircon age of 367 Ma, and coeval intrusions (Muller,
1980; Parish and McNicoll, 1992). Insufficient data exist to ascertain
the relative positions of the Wrangellia superterrane and associated
subduction zone. On the basis of paleomagnetic, geologic,
geochronologic, and faunal data, the Wrangellia superterrane (Alexander
terrane, AX) may have been derived from the Russian platform (Baltica)
in the Barents Sea region (Bazard and others, 1993, 1994; Butler and
others, 1997) or, possibly, from Australia (Gehrels and Saleeby, 1987;
Butler and others, 1997).

Summary of Paleolatitude Data for the Middle Through Late Devonian

For the Russian Far East, supporting paleolatitude data (table 3) are
36° (grade A) for the Omolon terrane. Conflicting paleolatitude data
(table 3) include 12° (grade B) for the Rassokha terrane.

For Alaska, supporting paleolatitude data (table 3) are (1) 14° (grade
B) for the Karheen Formation in the Alexander sequence of the Wrangellia
superterrane, and (2) 37° (grade A) for the Ordovician Novi Mountain
Formation in the Nixon Fork terrane. Conflicting paleolatitude data
include 23° (grade A) for the Ordovician Telsitna Formation in the Nixon
Fork terrane.

Mississippian (360--320 Ma)

During the Mississippian (360--320 Ma), the major tectonic events were
(1) separation of the North Asian and North American Cratons and
cratonal margins along a series of oblique-sinistral rifts, (2) ending
of rifting of fragments from cratons and cratonal margins to form new
terranes, and (3) continuation of the Sicker arc and associated
subduction in what would eventually become the Wrangellia superterrane.
Sedimentation continued along the North Asian and North American
cratonal margins.

Specific Tectonic Events for the Mississippian

1\. Starting in the late Devonian and ending in the Early Mississippian,
rifting occurred along the eastern part of the North Asian cratonal
margin (NSV, KN). This event formed the Kotelnyi (KT), Omulevka (OV),
Prikolyma (PR), Nixon Fork-Dillinger-Mystic (NX, DL, MY), Viliga (VL),
and Zolotogorskiy (ZL) passive-continen tal-margin terranes, the Avekova
(AK), Kilbuck-Idono (KI), Okhotsk OK), and Omolon (OM) cratonal
terranes, and the Beryozovka (BE), Oloy (OL), and Yarakvaam (YA)
terranes. Before the rifting, these terranes were parts of either the
North Asian Craton (NSC), the North Asian cratonal margin (NSV), or the
Devonian continental-margin arc that formed along the North American and
North Asian cratonal margins. The newly created terranes migrated into
the Angayucham Ocean.

2\. At the same time, rifting also occurred along the margin of the
North American cratonal margin (NAM) to produce the Kootenay (KO) and
Yukon-Tanana (YT) passive-continental-margin terranes.

3\. Movement along a series of oblique-sinistral rifts resulted in the
separation of North Asian and North American Cratons and cratonal
margins.

4\. The Kedon continental-margin arc and associated subduction zone (KN)
continued activity along the North Asian Craton and cratonal margin
(NSC, NSV) until about the late Early Mississippian. Associated with the
arc was subduction of the older part of the Galam (GL)
accretionary-wedge terrane. Remnants of the arc are preserved in (1)
part of the North Asian Craton and cratonal margin; (2) units that
overlie parts of the Okhotsk (OK), Akekova (AK), and Omolon (OM)
cratonal terranes; (3) the Oloy (OL) and Yarakvaam (YA) island-arc
terranes; and (4) the Beryozovka turbidite-basin terrane (BE).

5\. The Sicker island arc, which formed in the Devonian along most of
the length of the Wrangellia superterrane (WRA), ceased activity.
Insufficient data exist to ascertain the relative positions of the
Wrangellia superterrane.

Pennsylvanian (320--286 Ma)

During the Pennsylvanian (320--286 Ma), the major tectonic events were
(1) inception of the older parts of Stikinia-Quesnellia arc (Stikinia
and Quesnellia terranes) (table 2) and associated subduction zone in the
Yukon-Tanana (YT) and Kootenay (KO) terranes within an area offshore of
the North American cratonal margin (NAM), and (2) formation of the
Skolai island arc and associated subduction zone in the Wrangellia
superterrane. Sedimentation continued along the passive continental
margins of North Asia and North America.

Specific Tectonic Events for the Pennsylvanian

1\. Along the North Asian cratonal margin (NSC), dextral-slip occurred
along the Mongol-Okhotsk suture (MO), resulting in displacement of its
southern margin relative to the Mongol-Okhotsk Ocean.

2\. Between the North Asian and North American Cratons, sporadic
sea-floor spreading is interpreted as having enlarged the ancestral
Pacific Ocean and formed the Oimyakon, Angayucham, and Goodnews Oceans.
Fragments of the Oimyakon Ocean are preserved in the Debin and Garbyn'ya
terranes (fig. 1). Fragments of the Angayucham and Goodnews Oceans are
preserved in the Angayucham and Goodnews terranes, respectively (fig.
2). Within the Angayucham Ocean were the Kilbuck-Idono cratonal terrane
(KI), derived from the North Asian Craton (NSC), and the combined Nixon
Fork-Dillinger-Mystic passive-continental-margin terrane (NX, DL, MY),
derived from the North Asian cratonal margin. During this timespan,
before accretion to the present-day North American Continent, the
combined Nixon Fork-Dillinger-Mystic terrane may have undergone several
postrifting events that formed additional units, such as the
siliciclastic rocks of the Sheep Creek Formation and the Mount Dall
Conglomerate.

3\. The intraoceanic Omulevka Ridge, which separated the Oimyakon and
ancestral Pacific Oceans, consisted of the Omulevka (OV), Prikolyma
(PR), and Omolon (OM) terranes. These terranes were previously rifted
from North Asian Craton and cratonal margin during the Early
Mississippian. The Paleozoic Yarakvaam (YA), Oloy (OL), and Alazeya (AL)
island-arc terranes, together with the Beryozovka turbidite-basin
terrane (BE), are interpreted as parts of an active island arc on an
extension of the Omulevka Ridge.

4\. Within the Angayucham Ocean, between the North Asian and North
American Cratons and cratonal margins, was the Taimry Peninsula collage
(TA) (Vernovskiy and others, 1998). This collage is interpreted as a
series of Late Proterozoic ophiolite, island-arc, and
passive-continental-margin terranes that were displaced along
dextral-slip faults along the North Asian cratonal margin (NSC, NSV, KN)
(Zonenshain and others, 1990; Vernikovsky and others, 1998).

5\. Fragments of the North American cratonal margin (NAM), (Anvil Ocean
of Templeman-Kluit, 1979) between the Yukon-Tanana (YT) and Kootenay
(KO) continental-margin terranes and the North American cratonal margin.

6\. At an unknown location, the Skolai island arc was active along the
length of the Wrangellia superterrane (WRA). Associated with the arc was
a presumed (unknown) subduction zone (UNK). The Skolai arc deposits
consist mainly of Early to Middle Pennsylvanian plutons and
Pennsylvanian and Permian marine volcanic and volcaniclastic rocks
(Nokleberg and others, 1994b). The basement for the Skolai arc may in
part be the Alexander sequence, which contains a fragment of an early
and middle Paleozoic continental-margin arc (Nokleberg and others,
1994b). Insufficient data exist to ascertain the relative positions of
the Wrangellia superterrane (and contained Skolai arc), and its
associated subduction zone, with respect to the Stikinia and Quesnellia
island-arc terranes and their associated subduction zones. Fauna in the
Slana Spur and Eagle Creek (former Mankommen) Formations of the eastern
Alaska Range indicate a high-latitude environment (Petocz, 1970).

7\. Subsequently, during the Permian, most of the Stikinia-Quesnellia
arc overlapped part of the Yukon-Tanana terrane after weak initiation of
the arc in the Mississippian. This arc, defined by Permian granitic
plutons in the Yukon-Tanana terrane and by the Stikine assemblage in the
Stikinia terrane, may have been tectonically linked to subduction of
part of the Seventymile Ocean. Evidence in the present-day Yukon
Territory favors the Stikine part of the arc facing toward the North
American cratonal margin (NAM) (Monger and Nokleberg, 1996). Along
strike, the extension of the arc occurs in the Harper Ranch Group of the
Quesnellia island-arc terrane (QN). Part of the arc was probably linked
tectonically to subduction of part of the Cache Creek Ocean (Monger and
Nokleberg, 1996).

8\. Fauna of the Quesnellia and Stikinia terranes (QN, ST) are closest
to those present-day Southwestern United States and northern Andean
regions; the terranes probably formed along the continental margin at
lower latitudes than their present positions. Quantitative estimates
suggest that Stikinian fauna were situated anywhere from near 0 to 8,000
km away from the craton (Belasky and Runnegar, 1994). The paleoposition
of these Early Permian fauna is equivocal for that of the Wrangellia
superterrane. Yole (1969) and Petocz (1970) suggested a high-latitude
Uralian or Canadian Arctic affinity, whereas Belasky and Runnegar (1994)
suggested low-latitude positions southeast of the present position of
the Stikinia terrane. Paleomagnetic constraints on faunal locations are
provided by Late Pennsylvanian-Permian data from the Slide Mountain
terrane (SM), which suggest a post-Permian latitudinal shift of about
20° northward with respect to the craton (table 3; Richards and others,
1993), whereas those from the Stikinia terrane exhibit little or no
shift (table 3; Irving and Monger, 1987).

Summary of Paleolatitude Data for the Mississippian, Pennsylvanian, and
Permian

In the Russian Far East, paleolatitude data (table 3) are 54° (grade A)
for unnamed sedimentary and volcanic rocks overlying the Omolon terrane.

For Alaska and the Canadian Cordillera, supporting paleomagnetic data
(table 3) are (1) 8° (grade A) for the Pennsylvanian Landrones and
Klawak units in the Alexander sequence of the Wrangellia superterrane;
(2) 14° (grade A) for the Mississippian Peratrovich unit in the
Alexander sequence of the Wrangellia superterrane; and (3) 6° and 7°
(grades B, C) for two localities in the Pennsylvanian and Permian
Station Creek and Hasen Creek Formations, respectively, in the
Wrangellia sequence of the Wrangellia superterrane. Conflicting
paleomagnetic data (table 3) are (1) 2° and 9° (grade A) for two
localities (Sylvester allochthon and Sliding Mountain) in the Slide
Mountain terrane, respectively; and (2) 23° (grade A) for the Asitka
Group in the Slide Mountain terrane in the central part of the Canadian
Cordillera.

Carnian Through Norian (230--208 Ma)

During the Carnian to Norian (230--208 Ma), the major tectonic events
were (1) inception of continental-margin arcs and associated subduction
along the North Asian cratonal margin, (2) continued formation of the
Stikinia island arc and inception of the Talkeetna and Bonanza island
arcs and associated subduction zones offshore of the North American
cratonal margin (table 2), and (3) beginning of sinistral-slip
imbrication of the Stikinia-Quesnellia island arc and associated
subduction zones. Sedimentation continued along the passive continental
margins of North Asia and North America.

Specific Tectonic Events for the Carnian Through Norian

1\. The continental-margin Uda arc, defined by the Uda
vol-canic-plutonic belt (ud) and associated units, commenced activity
and was associated with subduction and sinistral transpression of the
Mongol-Okhotsk oceanic plate to form the Turkuringra-Dzhagdi (TD) and
Ulban (UL) terranes and the older part of the Galam (GL) terrane (table
2). Subduction and sinistral transpression occurred along the
Mongol-Okhotsk suture (MO).

2\. The extensive Kony-Murgal island arc (KM) commenced activity as an
offshore extension of the Uda arc. Associated with this arc was
subduction of part of the ancestral Pacific oceanic plate to form the
Talovskiy (TL) and Penzhina-Anadyr (PA) terranes (table 2). Inboard of
the Kony-Murgal arc, the Okhotsk (OK) cratonal terrane was accreted to
the North Asian Craton (NSC) and cratonal margin (NSV), together with
the Viliga (VL) passive-continental-margin terrane and the Omolon (OM)
and Avekova (AK) cratonal terranes. The Kony-Murgal terrane contains
Triassic, Jurassic, and Neocomian Boreal fauna (Dagis and others, 1979;
Dagis and Dagis, 1984; Zakharov and others, 1984); the Viliga terrane
contains Carboniferous, Permian, Triassic, and Jurassic Boreal fauna.

3\. The Alazeya arc, consisting of the Alazeya (AL) and Khetachan (KH)
island-arc terranes, continued activity and moved toward the Omulevka
Ridge. Associated with the Alazeya arc was subduction of part of the
ancestral Pacific Ocean to form the Aluchin (AC) and Argatas (ARG)
accretionary-wedge terranes. These terranes can be traced by magnetic
anomalies under extensive Cenozoic deposits of the present-day Russian
Northeast (Parfenov, 1991). Behind the arc were fragments of previous
Devonian to Pennsylvanian island arcs, including the Beryozovka
turbidite-basin (BE) and the Oloy (OL) and Yarakvaam (YA) island-arc
terranes.

4\. The Kotel'nyi passive-continental-margin terrane (KT) was accreted
and became part of the Taimyr Peninsular collage (TA). Within the
Angayucham, Goodnews, and Seventymile Oceans were previously rifted
terranes, including the Kilbuck-Idono cratonal terrane (KI) and the
combined Nixon Fork-Dillinger-Mystic passive-continental-margin terrane
(NX, DL, MY). During this timespan, before accretion to the North
American Con-tinent, the combined Nixon Fork-Dillinger-Mystic terrane
may have undergone several postrifting events that formed additional
units, such as the Triassic basaltic rocks that occur in the present-day
Tatina River area.

5\. The complex Stikinia-Quesnellia island arc and associated subduction
zones were active (table 2). The Stuhini Group is preserved in the
Stikinia terrane (ST), whereas the Takla and Nicola Groups are preserved
in the Quesnellia terrane (QN). The Stikinia-Quesnellia arc is
interpreted as having formed stratigraphically on the Yukon-Tanana (YT)
and Kootenay (KO) terranes, previously rifted fragments of the North
American cratonal margin (NAM) (Mihalynuk and others, 1994). On the
outboard side of the arcs was subduction of part of the Cache Creek
oceanic plate to form the Cache Creek terrane (CC). The Cache Creek
terrane and similar subduction-zone assemblages, which were tectonically
linked to the Talkeetna and Bonanza arcs, along with the Chugach (CG),
possibly Bridge River (BR), and Baker (BA) terranes, all contain exotic
Permian Tethyan faunas in carbonate blocks in matrices of mainly early
Mesozoic age. The Cache Creek terrane contains detritus probably derived
from the Stikinia-Quesnellia arc (Monger and Nokleberg, 1996).

6\. Parts of the Seventymile (SV) and Slide Mountain (SM) (Anvil Ocean
of Templeman-Kluit, 1979) oceanic plates were obducted onto the
Yukon-Tanana (YT) and Kootenay (KO) terranes and onto the North American
cratonal margin (NAM). Part of the obduction occurred by the Late
Triassic and (or) Early Jurassic, when granitic plutons of the
Stikinia-Quesnellia arc intruded across an intervening fault.

7\. The beginning of dextral-slip imbrication of the Stikinia-Quesnellia
arc occurred along the Tally Ho shear zone (inset, fig. 10*A*; Hansen,
1990; Hart, 1995). Alternatively, the present-day configuration of the
Stikinia-Quesnellia island-arc and associated subduction zone terranes
may have formed by oroclinal warping in response to a combination of
oblique convergence and arc migration toward the companion subduction
zone of the Cache Creek terrane (fig. 10*B*; Mihalynuk and others,
1994). Migration of the Stikinia-Quesnellia arc and associated terranes
toward North America was accomplished by subduction and (or) obduction
of the Seventymile oceanic plate along the continental margin.

8\. The Talkeetna and Bonanza arcs formed along the length of the
Wrangellia superterrane (WRA). The Talkeetna arc is preserved in the
Talkeetna Formation and coeval granitic plutonic rocks of the Peninsular
sequence (PE) of the Wrangellia superterrane, and the Bonanza arc is
preserved in the Cadwallader island-arc terrane (CD). Associated with
the island arcs was subduction of part the Cache Creek oceanic plate to
form the Chugach (CG), possibly Bridge River (BR), and Baker (BA)
terranes (table 2). These terranes locally contain early Mesozoic
blueschist (Plafker and others, 1994).

9\. During subduction of the Cache Creek oceanic plate to form the
Talkeetna, Bonanza, and Stikinia-Quesnellia arcs, limestone blocks
containing mainly Permian Tethyan faunas were accreted, locally in thick
and extensive blocks in the subduction-zone complexes of the Chugach
(CG) and Cache Creek (CC) terranes (Monger and Berg, 1987; Monger and
Nokleberg, 1996). Tethyan faunas are generally interpreted as derived
from the late Paleozoic and early Mesozoic Tethys Ocean of the
present-day Mediterranean region, Middle East, Himalayas, Southeast
Asia, eastern China, Russian Southeast, and Japan (Monger and Ross,
1971; Monger and others, 1972; Stevens and others, 1997).

10\. In the Wrangellia superterrane (WRA), backarc rifting or hotspot
activity formed the widespread basalt fields of the present-day Nikolai
Greenstone and Karmutsen Formation (Barker and others, 1989; Richards
and others, 1991; Lassiter and others, 1995). The mafic magmatism
forming those rocks was first interpreted as having formed in a rift
setting (Barker and others, 1989). Alternatively, the mafic magmatism
may have formed in a short-lived mantle-plume setting similar to that in
Java (Richards and others, 1991; Lassiter and others, 1995).

Summary of Paleolatitude Data for the Carnian Through Norian

Supporting paleolatitude data for the Russian Far East (table 3) are 78°
(grade C) for the North Asian cratonal margin (Verkhoyansk
fold-and-thrust belt; NSV, figs. 1, 3, 7). Conflicting paleolatitude
data (table 3) are (1) 57° (grade C) for the North Asian cratonal margin
(Verkhoyansk fold-and-thrust belt), (2) 27° for the Okhotsk terrane
(grade B), (3) 42°--54° (grade C) for three localities in the Omolon
terrane, and (4) 19° (grade B) for a locality at Penzhino Gulf in the
Talovskiy terrane.

For Alaska and the Canadian Cordillera, supporting paleolatitude data
(table 3) are (1) 4°--18° (grades A, C) for seven localities---the
McCarthy, Healy, Mount Hayes quadrangles, the Clearwater Mountains (two
localities), the Amphitheater Mountains, Rainy Mountain, and the Slana
River (two localities)---in the Nikolai Greenstone in the Wrangellia
sequence of the Wrangellia superterrane in southern Alaska; (2) 18°
(grade A) for the Karmutsen Formation of the Wrangellia sequence in the
Wrangellia superterrane in the southern part of the Canadian Cordillera;
(3) 17° (grade A) for the Hound Island unit in the Alexander terrane in
southeastern Alaska; (4) 28° (grade B) for the Nicola Volcanics in the
Quesnellia terrane in the southern part of the Canadian Cordillera; and
(5) 20° (grade C) for the Guichon batholith in the Quesnellia terrane in
the southern part of the Canadian Cordillera.

Hettangian Through Pleinsbachian (208--193 Ma)

During the Hettangian through Pleinsbachian (208--193 Ma), the major
tectonic events were (1) continuation of continental-margin arcs and
associated subduction near the North Asian Craton in the Russian Far
East; (2) beginning of assembly of previously rifted cratonal,
passive-continental-margin, and island-arc terranes between that craton
and the ancestral Pacific Ocean to form the Kolyma-Omolon superterrane;
(3) continuation of the Talkeetna, Bonanza, and Stikinia-Quesnellia arcs
and formation of companion subduction zones (table 2); (4) continued
sinistral-slip imbrication of the Stikinia-Quesnellia island arc and
associated subduction zones during oblique-sinistral convergence between
the ancestral Pacific oceanic plate and the North American cratonal
margin; and (5) with the beginning of accretion of the
Stikinia-Quesnellia arc at about 185 Ma, the start of mountain building
in the North American Cordillera. Sedimentation continued along the
passive continental margins of the North Asian and North American
Cratons.

Specific Tectonic Events for the Hettangian Through Pleinsbachian

1\. The Monakin continental-margin arc, consisting of the Monakin
volcanic-plutonic belt (mo) and the Umlekan continental-margin arc,
consisting of the Umlekan-Ogodzhin volcanic-plutonic belt (uo) and
associated units, commenced activity. Associated with this arc was
oblique (sinistral) subduction of part of the ancestral Pacific oceanic
plate to form the Samarka (SMA), Khabarovsk (KB), and Badzhal (BD)
terranes (table 2).

2\. The Uda continental-margin arc, consisting of the Uda
volcanic-plutonic belt (ud) and the Uda-Zeya sedimentary basin (uz),
continued to form. Associated with this arc was subduction and sinistral
transpression of part of the Mongol-Okhotsk oceanic plate to form the
Turkuringra-Dzhagdinski (TD), Ulban (UL), and Galam (GL) terranes (table
2). Subduction and sinistral transpression occurred along the
Mongol-Okhotsk suture (MO).

3\. The extensive Kony-Murgal island arc (Kony-Murgal terrane, KM)
continued to form as an offshore extension of the Uda arc. Associated
with the arc was subduction of part of the ancestral Pacific oceanic
plate to form the Talovskiy (TL) and Penzhina-Anadyr (PA) terranes
(table 2). Inboard of the Kony-Murgal island arc (KM) were the Okhotsk
(OK), Avekova (AK), and Omolon (OM) cratonal terranes, which were
previously rifted from the North Asian Craton (NSC), and the Viliga (VL)
passive-continental-margin terranes, which was previously rifted from
the North Asian cratonal margin (NSV). Behind the arc were fragments of
previous Devonian to Pennsylvanian island-arc terranes, including the
Beryozovka turbidite-basin (BE) and the Oloy (OL) and Yarakvaam (YA)
island-arc terranes.

4\. The Angayucham Ocean (Kobuck Sea of Plafker and Berg, 1994), along
with the South Anyui Ocean, continued to receive sparse
continent-derived detritus. Previously rifted terranes, including the
Kilbuck-Idono cratonal terrane (KI) and the combined Nixon
Fork-Dillinger-Mystic passive-continental-margin terrane (NX, DL, MY),
continued to migrate toward the North American cratonal margin.

5\. Dextral-slip imbrication of the Stikinia-Quesnellia arc and
associated subduction-zone terranes continued along the Tally Ho shear
zone (inset, fig. 11*A*; Hansen, 1990; Hart, 1995). Part of this shear
zone may be defined by a string of fault-bounded(?) ultramafic rocks
that occur within the Yukon-Tanana terrane in the northern part of
southeastern Alaska (Himmelberg and others, 1985). Alternatively, the
present-day configuration of the Stikinia-Quesnellia island-arc and
associated subduction-zone terranes may have formed by oroclinal warping
in response to a combination of oblique convergence and arc migration
toward the companion subduction zone of the Cache Creek terrane (fig.
11*B*; Mihalynuk and others, 1994). Oroclinal warping is interpreted as
having formed in response to (1) oblique-sinistral convergence between
the ancestral Pacific oceanic plate and the Stikinia-Quesnellia arc; and
(2) arc migration toward the companion subduction zone (trench
rollback), similar to the tectonics of the present-day Banda arc in
Southeast Asia (McCaffrey and Abers, 1991; Mihalynuk and others, 1994).
Migration of the Stikinia-Quesnellia arc and associated terranes toward
North America was accomplished by subduction and (or) obduction of the
Seventymile oceanic plate along the continental margin.

6\. The subduction-related volcanic and plutonic arc rocks of the
Quesnellia part of the arc, consisting of the Takla and Rossland Groups,
and coeval igneous belts formed in response to continued subduction of
part of the Cache Creek oceanic plate (CC) (Mihalynuk and others, 1994).
The Stikinia part of the arc consisted of the extensive suite of
subduction-related volcanic and plutonic arc rocks of the Hazelton Group
that also formed in response to subduction of the Cache Creek oceanic
plate.

7\. In the central part of the Stikinia-Quesnellia island arc, coeval
subduction-related granitic plutonic rocks also intruded the previously
accreted Yukon-Tanana passive-continental-margin terrane (YT), which may
have been the stratigraphic basement for part of the Stikinia island arc
(Mihalynuk and others, 1994). These plutonic rocks also intruded the
structurally overlying Slide Mountain (SM) and Seventymile (SV)
terranes.

8\. Also occurring was obduction of parts of the Seventymile and Slide
Mountain oceanic plates onto the North American cratonal margin (NAM)
(Mihalynuk and others, 1994). Part of the obduction occurred by the Late
Triassic and (or) Early Jurassic, when granitic plutons of the
Stikinia-Quesnellia island arc intruded across an intervening fault.
During the final stage of obduction of the Slide Mountain terrane (SM)
over the metamorphosed Kootenay continental-margin terrane (KO), these
terranes started to be obducted onto the North American cratonal margin.
Migration of the Stikinia-Quesnellia arc and associated terranes toward
the North American cratonal margin was accomplished by subduction of the
Seventymile oceanic plate along the continental margin and by obduction.

9\. Outboard and, possibly, at a lower paleolatitude (either 25° or
45°), the Talkeetna and Bonanza arcs continued activity in the
Wrangellia superterrane (WRA). This extensive arc formed along most of
the length of the Wrangellia superterrane, with coeval equivalents in
the Cadwallader island-arc terrane (CD) and the Methow turbidite-basin
terrane (MT). Associated with the Talkeetna and Bonanza arcs was
subduction of part of the Cache Creek oceanic plate to form the Chugach
(CG), Bridge River (BR), and, possibly, Baker (BA) terranes (table 2).

Summary of Paleolatitude Data for the Hettangian Through Pleinsbachian

For the Russian Far East, supporting paleolatitude data (table 3) are
72° (grade C) for the Omolon terrane. For the Canadian Cordillera,
paleolatitude data (table 3) supporting the southern-accretion
interpretation for the Wrangellia superterrane are (1) 24° (grade A) for
the Bonanza group overlying the Wrangellia sequence of the Wrangellia
superterrane in the central part of the Canadian Cordillera; (2) 19° and
24° (grade C) for the Copper Mountain and Tulameen units, respectively,
in the Quesnellia terrane in the southern part of the Canadian
Cordillera; and (3) nine values ranging from 28° to 37° (grades A, B, C)
for the Topley intrusive rocks and the Telkwa Formation (eight
localities) in the Stikinia terrane in the southern part of the Canadian
Cordillera.

Toarcian Through Callovian (193--163 Ma)

During the Toarcian through Callovian (193--163 Ma), the major tectonic
events were (1) continuation of continental-margin arcs and associated
subduction near the North Asian Craton in the Russian Far East; (2)
beginning of assembly of previously rifted cratonal,
passive-continental-margin, and island-arc terranes between that craton
and the ancestral Pacific Ocean to form the Kolyma-Omolon superterrane;
(3) continuation of the Talkeetna, Bonanza, and Stikinia-Quesnellia arcs
and formation of companion subduction zones (table 2); (4) continued
sinistral-slip imbrication of the Stikinia-Quesnellia island arc and
associated subduction zones during oblique-sinistral convergence between
the ancestral Pacific oceanic plate and the North American cratonal
margin; and (5) with the beginning of accretion of the
Stikinia-Quesnellia arc at about 185 Ma, the start of mountain building
in the North American Cordillera. Sedimentation continued along the
passive continental margins of the North Asian and North American
Cratons.

Specific Tectonic Events for the Toarcian Through Callovian

1\. The Monakin continental-margin arc, consisting of the Monakin
volcanic-plutonic belt (mo), and the Umlekan continental-margin arc,
consisting of the Umlekan-Ogodzhin volcanic-plutonic belt (uo) and
associated units, commenced activity. Associated with this arc was
oblique (sinistral) subduction of part of the ancestral Pacific oceanic
plate to form the Samarka (SMA), Khabarovsk (KB), and Badzhal (BD)
terranes (table 2).

2\. The Uda continental-margin arc, consisting of the Uda
volcanic-plutonic belt (ud) and the Uda-Zeya sedimentary basin (uz),
continued to form. Associated with this arc was subduction and sinistral
transpression of part of the Mongol-Okhotsk oceanic plate to form the
Turkuringra-Dzhagdinski (TD), Ulban (UL), and Galam (GL) terranes (table
2). Subduction and sinistral transpression occurred along the
Mongol-Okhotsk suture (MO).

3\. The extensive Kony-Murgal island arc (Kony-Murgal terrane, KM)
continued to form as an offshore extension of the Uda arc. Associated
with the arc was subduction of part of the ancestral Pacific oceanic
plate to form the Talovskiy (TL) and Penzhina-Anadyr (PA) terranes
(table 2). Inboard of the Kony-Murgal island arc were the Okhotsk (OK),
Avekova (AK), and Omolon (OM) cratonal terranes, which were previously
rifted from the North Asian Craton (NSC), and the Viliga (VL)
passive-continental-margin terranes, which was previously rifted from
the North Asian cratonal margin (NSV). Behind the arc were fragments of
previous Devonian to Pennsylvanian island-arc terranes, including the
Beryozovka turbidite-basin terrane (BE) and the Oloy (OL) and Yarakvaam
(YA) island-arc terranes.

4\. During the Bathonian, the Alazeya island arc, consisting of the
Alazeya (AL) and Khetachan (KH) island-arc terranes, as a result of flip
of the associated subduction zone, migrated toward the terranes forming
the Kolyma-Omolon superterrane. The southern part of the Kolyma
structural loop was formed during the convergence of the Alazeya arc
toward the terranes forming the Kolyma-Omolon superterrane. The major
terranes in this superterrane are the Alazeya (AL), Aluchin (AC),
Argatas (ARG), Beryozovka (BE), Khetachan (KH), Munilkan (MU), Oloy
(OL), Omolon (OM), Omulevka (OV), Prikolyma (PL), Rassokha (RA),
Uyandina (UY), and Yarakvaam (YM) terranes. During this collision,
fragments of the older part of the Angayucham oceanic plate were
obducted onto the Omulevka terrane to form the Munilkan (MU) ophiolite
terrane and the Uyandina, Kybytygas, and Indigirka ophiolite terranes of
Oxman and others (1995).

5\. The Angayucham Ocean (Kobuck Sea of Plafker and Berg, 1994), along
with the South Anyui Ocean, continued to receive sparse
continental-derived detritus. Previously rifted terranes, including the
Kilbuck-Idono cratonal terrane (KI) and the combined Nixon
Fork-Dillinger-Mystic passive-continental-margin terrane (NX, DL, MY),
continued to migrate toward the North American cratonal margin.

6\. Dextral-slip imbrication of the Stikinia-Quesnellia arc and
associated subduction-zone terranes was completed along the Tally Ho
shear zone (Hansen and others, 1990; Hart, 1995). Alternatively,
oroclinal warping of the Stikinia-Quesnellia island-arc and associated
subduction-zone terranes was completed (not shown in fig. 12; Mihalynuk
and others, 1994). For either interpretation, migration of the
Stikinia-Quesnellia arc and associated terranes toward North America was
accomplished by subduction and (or) obduction of the Seventymile oceanic
plate along the continental margin.

7\. Also completed was obduction of parts of the Seventymile and Slide
Mountain oceanic plates onto the North American cratonal margin (NAM)
(Mihalynuk and others, 1994). Migration of the Stikinia-Quesnellia arc
and associated terranes toward the North American cratonal margin was
accomplished by subduction of the Seventymile oceanic plate along the
continental margin and by obduction.

8\. The subduction-related volcanic and plutonic arc rocks of the
Quesnellia part of the arc, consisting of the Takla Group, and coeval
igneous belts formed in response to continued subduction of part of the
Cache Creek oceanic plate (CC) (Mihalynuk and others, 1994). The
Stikinia part of the arc consisted of the extensive suite of
subduction-related volcanic and plutonic arc rocks of the Hazelton Group
that also formed in response to subduction of part of the Cache Creek
oceanic plate. Remnants of this oceanic plate may be preserved in the
terrane of ultramafic and related rocks that occurs discontinuously
along the Denali strike-slip fault (DE, fig. 20) for several hundred
kilometers (Nokleberg and others, 1994b).

9\. Outboard and, possibly, at a lower paleolatitude (either 25° or
45°), the Talkeetna and Bonanza arcs continued activity in the
Wrangellia superterrane (WRA). This extensive arc formed along most of
the length of the Wrangellia superterrane, with coeval equivalents in
the Cadwallader island-arc terrane (CD) and the Methow turbidite-basin
terrane (MT). Associated with the Talkeetna and Bonanza arcs was
subduction of part of the Cache Creek oceanic plate to form the Chugach
(CG), Bridge River (BR), and, possibly, Baker (BA) terranes (table 2).

Summary of Paleolatitude Data for the Toarcian Through Callovian

For the Russian Far East, supporting paleolatitude data (table 3) are
72° (grade C) for the Omolon terrane. For the Canadian Cordillera,
paleolatitude data (table 3) supporting the southern-accretion
interpretation for the Wrangellia superterrane are (1) 24° (grade A) for
the Bonanza group overlying the Wrangellia sequence of the Wrangellia
superterrane in the central Canadian Cordillera; (2) 19° and 24° (grade
C) for the Copper Mountain and Tulameen units, respectively, in the
Quesnellia terrane in the southern part of the Canadian Cordillera; and
(3) nine values ranging from 28° to 37° (grades A, B, C) for the Topley
intrusive rocks and the Telkwa Formation (eight localities) in the
Stikinia terrane in the southern part of the Canadian Cordillera.

Oxfordian Through Kimmeridgian (163--144 Ma)

During the Oxfordian through Kimmeridgian (163--144 Ma), the major
tectonic events were (1) beginning of accretion of the Bureya
superterrane (BU) against the North Asian Craton along the
Mongol-Okhotsk suture, thereby closing the Mongol-Okhotsk Ocean; (2)
establishment of a series of continental-margin arcs and companion
subduction-zone assemblages around the Circum-North Pacific (table 2);
(3) initiation of rift grabens that subsequently formed the present-day
Amerasia and Canada Basins; and (4) ending of the previous long-lived
period (Late Proterozoic through Early Jurassic) of passive
sedimentation along the North Asian and North American cratonal margins.

Specific Tectonic Events for the Oxfordian Through Kimmeridgian

1\. Far to the south at about 60° paleolatitude, the Mainitskiy island
arc (Mainitskiy terrane, MAI) commenced activity. Tectonically linked to
this arc was the Alkatvaam accretionary-wedge terrane (AV), which formed
from subduction of part of the adjacent oceanic plate. The arc and
companion subduction zone migrated northward toward the Kony-Murgal
island arc (KM).

2\. The Monakin arc (Monakin volcanic-plutonic belt, mo) and the Umlekan
arc (Umlekan-Ogodzhin volcanic-plutonic belt, uo and associated units)
continued activity. Associated with these arcs was oblique (sinistral)
subduction of part of the ancestral Pacific oceanic plate to continue
forming the Samarka (SMA), Khabarovsk (KB), and Badzhal (BD) terranes
(table 2). In the same region, the Bureya superterrane (BU) accreted
against the Ulban accretionary-wedge terrane (UL) along the
Mongol-Okhotsk suture (MO), thereby closing the Mongol-Okhotsk Ocean.

3\. The Uda continental-margin arc (Uda volcanic-plutonic belt \[ud\]
and Uda-Zeya sedimentary basin \[uz\]) continued to form. Associated
with this arc was subduction and sinistral transpression of part of the
Mongol-Okhotsk oceanic plate to form the Turkuringra-Dzhagdinsk (TD) and
Ulban (UL) terranes (table 2). Subduction was associated with sinistral
transpression along the Mongol-Okhotsk suture (MO).

4\. The extensive Kony-Murgal continental-margin and island-arc terrane
(KM) continued to form as an extension of the Uda continental-margin arc
(ud). Associated with this arc was continued subduction of part of the
ancestral Pacific oceanic plate to form the Talovskiy (TL) and
Penzhina-Anadyr (PA) terranes (table 2). The Kony-Murgal island arc
overlapped the Okhotsk (OK) and Avekova (AK) cratonal terranes, which
was previously rifted from the North Asian Craton (NSC), and the Viliga
(VL) passive-continental-margin terrane, which was previously rifted
from the North Asian cratonal margin (NSV). As a transform extension of
the Kony-Murgal terrane, the West Pekul'ney island-arc terrane (WP) was
initiated. Associated with this arc was subduction of part of the
ancestral Pacific plate to form the Pekul'ney terrane (PK).

5\. The Kolyma-Omolon superterrane (KLO) continued to migrate toward the
North Asian cratonal margin (NSV). During migration, the Uyandina arc
(consisting of the Uyandina-Yasachnaya volcanic belt in the western part
of the long Indigirka-Oloy sedimentary-volcanic-plutonic assemblage, io)
started to form along the leading edge of this superterrane. Associated
with the Uyandina arc was subduction of the oceanic-crustal rocks
preserved in the Garbyn'ya (GA) and Debin (DB) ophiolite belt (and
corresponding terranes, fig. 1) of Oxman and others (1995) that are
herein interpreted as remnants of the Oimyakon oceanic plate (table 2).

6\. On the opposite side of the Kolyma-Omolon superterrane (KLO), the
Oloy island arc (ol) formed in response to subduction of part the South
Anyui oceanic plate. Along one part of the North Asian cratonal margin
(NSV), the Svyotov Nos continental-margin arc formed along the margin of
the Taymyr Peninsula collage (TA) in response to subduction of another
part of the South Anyui oceanic plate to form the South Anyui
subduction-zone terrane (SA). The Angayucham Ocean continued to exist
along with the South Anyui Ocean.

7\. Adjacent to the North American cratonal margin (NAM), two extensive
arcs formed. The Nutesyn continental-margin arc formed in response to
subduction of part of the South Anyui oceanic plate to form the Velmay
subduction-zone terrane (VE). The Koyukuk (KY), Togiak (TG), and Nyac
(NY) island-arc terranes formed in response to subduction of an (inner)
Angayucham oceanic plate to extend the Angayucham subduction-zone
terrane (AG) (table 2). Locally substantial terrigenous detritus in
Jurassic turbidite deposits in the lower structural part of the
Angayucham terrane (Slate Creek subterrane of Moore and others, 1994b)
may have been derived from erosion of the North American cratonal margin
(Moore and others, 1994b). The polarity of the island arc was
continentward, toward the North American cratonal margin. Outboard of
the island arc were the (outer) Angayucham and Goodnews Oceans. The
Kilbuck-Idono cratonal terrane (KI) and the combined Nixon
Fork-Dillinger-Mystic passive-continental-margin terrane (NX, DL, MY)
were accreted onto the North American cratonal margin at about the same
time as obduction of the Stikinia-Quesnellia island arc, as described
below.

8\. Rift grabens, depicted as rifting associated with sea-floor
spreading, began to open the present-day Amerasia and Canada Basins
(Grantz and others, 1998). These grabens were an early stage of creation
of new oceanic crust during the Early Cretaceous, as described below.

9\. A subduction zone (UNK) with a component of sinistral slip is
inferred to have formed along and parallel to the continental margin in
order to accomplish migration of the Wrangellia superterrane toward the
North American cratonal margin. Remnants of this subduction zone may be
preserved in the terrane of ultramafic and related rocks that occurs
discontinuously along the Denali strike-slip fault (DE, fig. 20) for
several hundred kilometers (Nokleberg and others, 1994b). The mafic and
ultramafic rocks may in part be derived from the Farallon oceanic plate
(FAR) that separated the Wrangellia superterrane from the North American
cratonal margin.

10\. Regional thrust faulting occurred, with obduction of the Stikinia
(ST), Quesnellia (QN), Cache Creek (CC), Slide Mountain (SM),
Yukon-Tanana (YT), and Kootenay (KO) terranes over the Cassiar (CA)
terrane and the North American cratonal margin (NAM). This compressional
event marked the beginning of a major orogenic event, including regional
metamorphism, deformation, crustal thickening, anatectic magmatism, and
uplift in the core of the present-day Canadian Cordillera (Monger and
Nokleberg, 1996). The Nelson plutonic suite (ns), which intrudes the
Stikinia, Quesnellia, Kootenay, Cache Creek, and Slide Mountain
terranes, formed during this compressional event. The Nelson plutonic
suite consists chiefly of granodiorite, quartz monzonite, and local
monzonite plutons that yield isotopic ages mainly of 155 to 185 Ma, with
local crustal inheritance (Parrish and others, 1988; Woodsworth and
others, 1992). By the Late Jurassic (approx 155 Ma), detritus from this
emergent orogenic welt in the eastern part of the Canadian Cordillera
was shed eastward onto the North American cratonal margin (Cant, 1989).

11\. The extensive Gravina island arc was initiated along the length of
the Wrangellia superterrane. Remnants of this arc are preserved in the
Kahiltna (kh) and Gravina-Nutzotin-Gambier (gg) assemblages, which occur
only in the Wrangellia superterrane. Associated with the arc was
subduction of part of the Farallon oceanic plate (FAR) to form the
Chugach (CG), Bridge River (BR), Easton (EA), and Baker (BA) terranes
(table 2).

Summary of Paleolatitude Data for the Oxfordian Through Kimmeridgian

For the Russian Far East, conflicting paleolatitude data (table 3) are
(1) 39° (grade A) for the Indigirka-Oloy assemblage overlying the Omolon
terrane, (2) 62° and 69° (grade A) for the Omulevka terrane, and (3) 65°
(grade B) for the Viliga terrane. The values for the Omulevka and Viliga
terranes, however, have 95-percent-confidence limits that include 90°.
For Alaska, paleolatitude data (table 3) supporting the
southern-accretion interpretation for the Wrangellia superterrane are
(1) 32° (grade B) for the Naknek/Chitina units in the Peninsular
sequence of the Wrangellia superterrane and (2) 39° (grade C) for the
Westcoast Complex in the Wrangellia sequence of the Wrangellia
superterrane.

Neocomian (144--120 Ma)

During the Neocomian (144--120 Ma), the major tectonic events were (1)
completion of accretion of the Bureya superterrane against the North
Asian Craton along the Mongol-Okhotsk suture and formation of associated
metallogenic belts; (2) continuation of the continental-margin and
island arcs and companion subduction-zone assemblages around the
Circum-North Pacific (table 2); (3) accretion of the major Kolyma-Omolon
superterrane in the Russian Northeast; (4) initiation of obduction of
the Angayucham subduction-zone terrane onto the North American
continental margin; (5) continuation of opening of the Amerasia, Canada,
and Eurasia Basins in response to sea-floor spreading in the Arctic
Ocean; (6) beginning of accretion of the Wrangellia superterrane in the
southern part of the Canadian Cordillera (northern-accretion
interpretation); and (7) around the Circum-North Pacific, continued
sinistral transpression between oceanic plates and continents.

Specific Tectonic Events for the Neocomian

1\. Far to the south at about 32° paleolatitude (table 3), the
Mainitskiy island arc (Mainitskiy terrane, MAI) commenced activity.
Associated with this arc was subduction of part of the adjacent oceanic
plate to form the Alkatvaam accretionary-wedge terrane (AV) (table 2).
This arc and companion subduction zone migrated northward toward the
Kony-Murgal island arc.

2\. The Umlekan arc (Umlekan-Ogodzhin volcanic-plutonic belt \[uo\] and
associated units) continued activity. Associated with this belt was
subduction of part of the ancestral Pacific oceanic plate to form the
Amur (AM) and Badzhal (BD) terranes (table 2).

3\. The Uda continental-margin arc (Uda volcanic-plutonic belt, ud, and
Uda-Zeya sedimentary basin, uz) continued to form. Associated with the
arc was subduction and sinistral transpression of the final remnant of
the Mongol-Okhotsk oceanic plate, thereby forming the Ulban terrane
(UL). Sinistral transpression continued along the Mongol-Okhotsk suture
(MO).

4\. The extensive Kony-Murgal continental-margin and island arc and the
Pekulney island arc continued to form. Associated with these arcs was
subduction of part of the ancestral Pacific oceanic plate to form the
Talovskiy (TL), Penzhina-Anadyr (PA), and Pekulney (PK) terranes (table
2).

5\. Behind the Kony-Murgal arc, the Kolyma-Omolon superterrane (KLO) was
accreted between at about 140 to 100 Ma. During the early stage of
accretion, the Main collisional granite belt (ma) (144--134 Ma) formed
(Layer and others, 1995; Fujita and others, 1997). At about the final
stage of accretion, the subduction-related Northern collisional granite
belt (no) formed at about 127 to 120 Ma (Fujita and others, 1997). In
contrast to the Main granite belt, the coeval Northern collisional
granite belt is interpreted as having formed in response to subduction
related to closure of an inlet of the South Anyui Ocean. As a result,
the northern bend of the Kolyma-Omolon structural loop formed (Sengör
and Natal'in, 1996a). As a continuation of this structural loop, the
extension-related Transverse granite belt (tr) formed (Parfenov, 1991,
1995c).

6\. The Oloy island arc and opposing Nutesyn and Koyukuk island arcs
continued to be active on opposite sides of the South Anyui and
Angayucham Oceans. Parts of these arcs are preserved in the Nutesyn
(NU), Koyukuk (KY), Togiak (TG), and Nyac (NY) terranes. Associated with
these arcs was subduction of parts of the South Anyui and Angayucham
oceanic plate, thereby forming the South Anyui (SA), Velmay (VE), and
(inner) Angayucham (AG) terranes, and subduction of the outboard margin
of the Arctic Alaska terrane. An extensive zone of blueschist-facies
metamorphism occurs in this region in both the Angayucham and Arctic
Alaska terranes. The polarity of the Koyukuk, Togiak, and Nyac island
arcs was oceanward, away from the North American passive continental
margin (Arctic Alaska superterrane, AA). After initial accretion of the
Koyukuk arc to the Arctic Alaska superterrane, beginning in the Late
Jurassic at about 160 to 145 Ma (Moore and others, 1994a, b), subduction
flipped to outboard of the new continental margin in this part of
present-day Alaska.

7\. At about 140 to 135 Ma, sea-floor spreading and associated rifting,
which started with the formation of grabens in the Late Jurassic or
earlier (Grantz and others, 1990, 1991, 1998; Lawver and Scotese, 1990),
formed (1) new oceanic crust and the large proto-Amerasia (ab) and
proto-Canada (cb) basins, and (2) a collage of
passive-continental-margin terranes derived from the North American
cratonal margin (Artis Plateau \[AP\], Chukchi Cap \[CK\], Chukchi Spur
\[CS\], and Northwind Ridge \[NR\] terranes). Sea-floor spreading and
opening of the Amerasia and Canada Basins is herein interpreted as
causing (1) closure of the inner Angayucham Ocean; (2) subduction of the
North American continental margin (Chukotka terrane \[CH\] and Arctic
Alaska superterrane \[AA\]); (3) beginning of closure of the South Anyui
Ocean; (4) intense deformation and metamorphism of the southern margin
of the eastern Chukotka terrane (CH) and southern Arctic Alaska
superterrane (AA) to form the Seward (SD), Coldfoot (CO), and Ruby (RB)
terranes; (5) formation of an extensive blueschist-facies belt in both
the subducted continental margin (Arctic Alaska superterrane \[AA\] and
Seward \[SD\], Coldfoot \[CO\], and Ruby \[RB\] terranes) and the
overthrust Angayucham terrane (AG); and (6) deposition of synorogenic
Early Cretaceous to mid-Cretaceous flysch in the Koyukuk Basin in what
became present-day western Alaska. For additional information on the
details of opening of the Canada Basin, whether by rifting and rotation
or by strike-slip translation, or by a combination of these two
processes, see the analyses by Grantz and others (1990, 1998) and Lane
(1994, 1997).

8\. Underthrusting in a subduction zone along the North American
cratonal margin (NAM) resulted in consumption of the Farallon oceanic
plate (FAR). Small tectonic lenses of terranes of alpine ultramafic and
related rocks along the ancestral Denali Fault (see fig. 17; Nokleberg
and others, 1985, 1994a) may be remnants of the subduction-zone
assemblages that may have been mostly thrust under the margin of
present-day North America.

9\. The Gravina arc continued to form. Associated with the Gravina arc
was subduction of part of the Farallon oceanic plate to form the Chugach
(CG), Bridge River (BR), Easton (EA), and Baker (BA) terranes. Part of
this arc was preserved in the Kahiltna (kh) and Gravina-Nutzotin-Gambier
(gg) assemblages, which occur only in the Wrangellia superterrane.

10\. The Wrangellia superterrane (WRA) started to accrete at about 60°
paleolatitude (northern-accretion interpretation), with the
continentward part of the Wrangellia superterrane impinging onto a
collage of terranes previously accreted to the North American cratonal
margin (NAM). With accretion, the arc extended southward with the
formation of two major overlap assemblages: the coeval Tahtsa-Three
Sisters magmatic assemblage (tt) and the Spences Bridge
volcanic-plutonic belt (sb). Alternatively, the Wrangellia superterrane
was far to the south at about 35° paleolatitude (southern-accretion
interpretation; see inset, fig. 14).

Summary of Paleolatitude Data for the Neocomian

For the Russian Far East, supporting paleolatitude data (table 3) are
(1) 32° (grade A) for the Mainitskiy terrane, (2) 76° (grade C) for the
Khetachan terrane, and (3) 88° (grade C) for the Eropol subterrane of
the Oloy terrane. Conflicting paleolatitudes for the Russian Far East
(table 3) are (1) 62° (grade C) for a locality at Penzhino Gulf in the
Talovskiy terrane and (2) 74° (grade C) for the Alkatvaam terrane.

For Alaska and the Canadian Cordillera, supporting paleolatitude data
(table 3) are (1) 69° and 74° (grade B) for the Nanushuk Group and
Kaparuk River Formation overlying the North Slope subterrane of the
Arctic Alaska terrane, (2) 69° (grade A) for another locality (Melozitna
quadrangle) in the Koyukuk terrane, (3) 62° and 67° (grade A) for two
more localities (Melozitna and Nulato quadrangles, respectively) in the
Koyukuk terrane, and (4) 53° (grade B) for the Axelgold pluton intruding
the northern part of the Cache Creek terrane. The paleolatitude for the
Axelgold pluton supports the northern-accretion interpretation for the
Wrangellia superterrane. Paleolatitude data (table 3) supporting the
southern-accretion interpretation for the Wrangellia superterrane are
36° (grade B) for the Duke Island ultramafic complex that is part of the
Gravina-Nutzotin-Gambier overlap assemblage in southeastern Alaska.

Aptian Through Albian (120--100 Ma)

During the Aptian through Albian (120--100 Ma), the major tectonic
events were: (1) inception of the short-lived Khinghan
continental-margin arc and companion subduction zone in the Russian
Southeast (table 2); (2) accretion of the Mainitskiy island arc and
associated Alkatvaam (AV) accretionary-wedge terranes to the active
continental margin by the beginning of the Albian; (3) completion of
accretion of the major Kolyma-Omolon superterrane in the Russian
Northeast; (4) obduction of Angayucham subduction-zone terrane onto the
Arctic Alaska terrane (rifted fragment of North American Continental
Margin); (5) continued opening of the Amerasia, Canada, and Eurasia
Basins; and (6) continuing accretion of the Wrangellia superterrane.

Specific Tectonic Events for the Aptian Through Albian

1\. At about 50º paleolatitude, the Mainitskiy island arc (Mainitskiy
terrane, MAI) continued activity. Associated with this arc was
subduction of part of the adjacent oceanic plate to form the Alkatvaam
accretionary-wedge terrane (AV) (table 2). This arc and companion
subduction zone continued to migrate northward toward the North Asian
cratonal margin and outboard terranes, and was accreted to the active
continental margin by the beginning of the Albian, when deposition of
the overlying Kuibiveem sedimentary assemblage (kb) commenced. The
Kuibiveem assemblage (included in unit oc, fig. 3) is interpreted as a
forearc unit to the Okhotsk-Chukotka continental-margin arc (oc).
Subduction stepped outboard during this accretion.

2\. At the end of the Neocomian, oblique subduction was replaced by
sinistral-slip faulting parallel to the continental margin. This
faulting resulted in structural interleaving of the previously active
subduction-zone terranes. This structural interleaving is interpreted as
similar to the present-day region of southern California and resulted in
formation of the fault-bounded basin of marine turbidites now preserved
in the Zhuravlesk-Tumnin turbidite-basin terrane (ZT) (Golozubov and
Khanchuk, 1996).

3\. The Khingan continental-margin arc (ko) started to form. Associated
with this arc was oblique subduction of part of the ancestral Pacific
oceanic plate to form the Amur River (AM), Khabarovsk (KB), and
Kiselevka-Manoma (KLM) terranes (table 2).

4\. The Uda continental-margin arc and associated subduction zones
ceased activity with accretion of the Bureya superterrane and closure of
the Mongol-Okhotsk Ocean along the Mongol-Okhotsk suture (MO).

5\. The extensive Kony-Murgal continental-margin and island arc and the
Pekulney island arc continued to form. Associated with these arcs was
subduction of part of the ancestral Pacific oceanic plate to form the
Talovskiy (TL), Penzhina-Anadyr (PA), and Pekulney (PK) terranes (table
2).

6\. The final stages of accretion of the Kolyma-Omolon superterrane is
interpreted as causing a second phase of deformation in the Verkhoyansk
fold-and-thrust belt and formation of the West Verkhoyansk collisional
granite belt (wk) (120--90 Ma) along the Lena Fault (LE).

7\. The Nutesyn and Koyukuk island arcs continued activity on opposite
sides of the South Anyui and Angayucham Oceans. Parts of these arcs are
preserved in the Nutesyn (NU), Koyukuk (KY), Togiak (TG), and Nyac (NY)
terranes. Associated with the arcs were subduction of parts of the South
Anyui and Angayucham oceanic plates to form the Velmay (VE) and (outer)
Angayucham (AG) terranes, and subduction of the outboard margin of the
Arctic Alaska terrane. An extensive zone of blueschist-facies
metamorphism occurs in this region in both the Angayucham and Arctic
Alaska terranes.

8\. In the Arctic, sea-floor spreading and associated rifting continued
with the formation of large sedimentary basins and the creation of a
collage of passive-continental-margin terranes derived from the North
American cratonal margin (NAM) (Grantz and others, 1990, 1991, 1998;
Lawver and Scotese, 1990). Continuing was closure of the Angayucham
Ocean, subduction along the North American continental margin, intense
thrusting in the passive-continental-margin terranes, and deposition of
Early Cretaceous to mid-Cretaceous flysch.

9\. On the edge of the Wrangellia superterrane (WRA), the Gravina arc
continued to form. Associated with this arc was subduction of part of
the Farallon oceanic plate to form the Chugach (CG), Bridge River (BR),
Easton (EA), and Baker (BA) terranes. Part of the arc was preserved in
the Kahiltna (kh) and Gravina-Nutzotin-Gambier (gg) assemblages, which
occur only in the Wrangellia superterrane. The Gravina arc extended into
the southern part of the Canadian Cordillera with the formation of the
Spences Bridge volcanic-plutonic belt (sb).

10\. The central and northern parts of the Wrangellia superterrane (WRA)
accreted to the northern part of the Canadian Cordillera and southern
Alaska (northern-accretion interpretation). Along the accreting edge of
the superterrane, the intervening oceanic plate and the Kahiltna overlap
assemblage were thrust during the active continental margin of southern
Alaska and the northern part of the Canadian Cordillera (Stanley and
others, 1990). The small tectonic lenses of terranes of alpine
ultramafic and related rocks along the ancestral Denali Fault (UM)
(Nokleberg and others, 1985, 1994a) may be remnants of this oceanic
lithosphere. Coeval with accretion of the Wrangellia superterrane was
intrusion of the Omineca-Selwyn anatectic granite belt (om) that occurs
along the length of the Canadian Cordillera and Alaska. Alternatively,
the Wrangellia superterrane was far to the south at about 35°
paleolatitude (southern-accretion interpretation; see inset, fig. 15).

Summary of Paleolatitude Data for the Aptian Through Albian

Paleolatitude data for the Aptian through Albian (late Early Cretaceous)
are summarized with other paleolatitude data in the preceding subsection
for the Neocomian.

Cenomanian Through Santonian (100--84 Ma)

During the Albian though Santonian (100--84 Ma), the major tectonic
events were (1) establishment of a series of continental-margin arcs and
companion subduction-zone assemblages almost continuously around the
Circum-North Pacific (table 2); (2) continued opening of an ocean that
would become the Amerasia, Canada, and Eurasia Basins; (3) completion of
accretion of the Wrangellia superterrane (northern-accretion
interpretation); and (4) in the eastern part of the Circum-North
Pacific, a change to orthogonal compression between the Farallon oceanic
plate and North America.

Specific Tectonic Events for the Cenomanian Through Santonian

1\. At about 32°--60° paleolatitude, the Olyutorka island arc commenced
activity (table 3). Parts of this arc are preserved in the Nemuro (NE),
Kronotskiy (KRO), Olyutorka-Kamchatka (OKA), Iruneisky (IR), Shmidt
(SHT), and Terpeniya (TR) terranes. Associated with the arc was
subduction of part of adjacent oceanic plate to form the Vetlovskiy (VT)
terrane (table 2). This arc and companion subduction zone migrated
northward toward the Okhotsk-Chukotka continental-margin arc.

2\. The East Sikhote-Alin continental-margin arc (es) was initiated.
This major Andean-type arc overlapped previously accreted adjacent
terranes in both the Russian Southeast and to the south. The arc
extended for more than 1,600 km along the active Russian Southeast
continental margin. Forming as part of the arc was the West Sakhalin
(WSA) turbidite-basin terrane. Associated with the arc was oblique
subduction of part of the ancestral Pacific oceanic plate (PAC) to form
the Hidaka (HI), Aniva (ANV), and Nabilsky (NAB) terranes (table 2).

3\. The Khingan continental-margin terrane (ko) continued activity.

4\. Subduction stepped seaward, after the accretion of the Mainitskiy
arc, with the consequent inception of the Okhotsk-Chukotka
continental-margin arc (oc) and related Penzhina (forearc) sedimentary
basin (pn) along the new continental margin. This major Andean-type arc
overlapped the previously accreted Kolyma-Omolon superterrane, part of
the North Asian cratonal margin (NSV), and adjacent terranes in the
present-day Russian Northeast and western Alaska and extended for about
3,500 km along an active continental margin. Associated with the arc was
oblique subduction of part of the ancestral Pacific oceanic plate to
form the West Kamchatka (WK), Ekonay (EK), and Yanranay (YN) terranes.

5\. In the Arctic Ocean, sea-floor spreading and associated rifting
continued (Grantz and others, 1990, 1991, 1998; Lawver and Scotese,
1990) with the formation of new oceanic crust and the combined Alpha and
Mendeleev Ridges (am) that are interpreted as large piles of hotspot
basalt and associated deposits (Grantz and others, 1990, 1991, 1998).
The large Amerasia (ab), Canada (cb) and Eurasia (eb) Basins continued
to form. During the opening of these basins, North American
continental-margin terranes, including the Arctic Alaska superterrane
(AA) and the Chukotka terrane (CH), and outboard oceanic and island
terranes migrated toward the North Asian Craton and the previously
accreted Kolyma-Omolon superterrane (KLO). The opening of the basins is
interpreted as causing oroclinal warping of northern Alaska and the
northern part of the Russian Far East.

6\. Also during the opening of the Amerasia (ab), Canada (cb), and
Eurasia (eb) Basins, the South Anyui and Angayucham Oceans were closed,
and the Chukotka (CH) and Arctic Alaska terranes (AA) accreted to
Northeast Asia. During closure, the major Nutesyn and Koyukuk island
arcs and companion subduction zones were thrust onto the Chukotka
continental-margin terrane (CH) and the Arctic Alaska superterrane (AA)
in thrust sheets that are as much as 150 km wide in northern Alaska. The
overthrust subduction-zone terranes include the South Anyui (SA), Velmay
(VE), Angayucham (AG), and Goodnews (GD) terranes; the overthrust
island-arc terranes include the Nutesyn (NU), Koyukuk (KY), and Togiak
(TG) terranes. A final stage of blueschist-facies metamorphism of
oceanic and continental-margin terranes occurred during thrusting. The
absence of evidence of a huge Himalayan-type mountain range in the
Russian Northeast suggests either that (1) strike-slip translation was
more dominant than rifting in formation of the Canada Basin (Lane, 1994,
1997) or that (2) a major part of the rift migration of the Russian
Northeast away from the Canada Basin was absorbed in the subduction zone
associated with formation of the Okhotsk-Chukotka arc.

7\. During accretion, the southern margin of the eastern Chukotka
terrane (CH), the southern part of the Arctic Alaska superterrane (AA),
and the outboard Seward (SD), Coldfoot (CO), Goodnews (GD), and Ruby
(RB) terranes continued to be intensely deformed and metamorphosed. At
the end of accretion, a period of extensional deformation occurred along
the southern margin of the Arctic Alaska superterrane (AA) (Miller and
Hudson, 1991).

8\. Backarc continental-margin sedimentation in the Kuskokwim Basin (kw)
occurred in a dextral wrench-fault setting (Bundtzen and Miller, 1997).

9\. The final stage of accretion of the Wrangellia superterrane (WRA)
was completed at about 95 Ma (northern-accretionary interpretation).
Several major geologic events are interpreted as having been caused by
accretion of the Wrangellia superterrane. (1) The extensive Gravina
island arc, which formed along the leading edge of the superterrane, and
the Spences Bridge volcanic-plutonic belt (sb) ceased activity after
accretion. (2) The Kahiltna (kh) and Gravina-Nutzotin-Gambier (gg)
assemblages were thrust under the North American continental margin
(Stanley and others, 1990; McClelland and others, 1991, 1992a, b;
Nokleberg and others, 1994a) and were intensely deformed during a major
period of orthogonal convergence that replaced the previous sinistral
convergence. (3) The northeasternmost boundary of the accreted
Wrangellia superterrane became the locus of Late Cretaceous high-grade
metamorphism, plutonism, contractional deformation, crustal thickening,
uplift, and erosion that characterize the present-day Coast Mountains of
the Canadian Cordillera and southeastern and south-central Alaska
(McClelland and others, 1991, 1992a, b; Pavlis and others, 1993; Plafker
and Berg, 1994; Monger and Nokleberg, 1996). (4) A regional core complex
formed in the previously accreted Yukon-Tanana terrane (part of the
collage in present-day Alaska) and developed a subhorizontal fabric,
imbricate thrusting of large subhorizontal nappes, and subsequent
extension and removal of as much as 10 km of crust (Pavlis and others,
1993). (5) The southern part of the Gravina arc and companion subduction
zone was doubled during the latest stage of sinistral-slip faulting
during accretion of the Wrangellia superterrane (McClelland and others,
1991, 1992a, b; Monger and others, 1994; Monger and Nokleberg, 1996).
The Methow turbidite-basin terrane (MT), an Early Cretaceous and
mid-Cretaceous forearc part of the Gravina arc, and the companion Bridge
River (BR) and Easton (EA) subduction-zone terranes were structurally
imbricated behind the southern part of the Gravina-Nutzotin-Gambier
assemblage (gg) (Monger and others, 1994). (6) The mainly orthogonal
convergence and accretion of the Wrangellia superterrane initiated
eastward thrusting of the North American cratonal margin (NAM) over the
North American Craton (NAC). (7) Coeval with thrusting and occurring
along the axis of thrusting was intrusion of the Omineca-Selwyn granitic
belt (om) that occurs along the length of present-day Canadian
Cordillera, Alaska, and the northern part of the Russian Northeast. This
belt was generated during an intense period of anatectic melting, major
regional thrusting, and crustal shortening and thickening, all related
to orthogonal convergence. Alternatively, the Wrangellia superterrane
accreted far to the south at about 35° paleolatitude along the margin of
Baja British Columbia (latitude of present-day Baja California)
(southern-accretion interpretation; see inset, fig. 16).

Summary of Paleolatitude Data for the Cenomanian Through Santonian

For the Russian Far East, supporting paleolatitude data (table 3) are
(1) three values ranging from about 28° to 37° (grades A, B) for the
Nemuro terrane, (2) 42° (grade A) for the Vetlovskiy terrane, (3) 76°
(grade C) for the Omolon terrane, (4) 76° (grade A) for Cretaceous rocks
overlapping the Ekonay terrane, and (5) 88° (grade C) for a locality in
the Okhotsk-Chukotka volcanic-plutonic belt overlying the Viliga
terrane. Other paleolatitudes of 22° and 24° (grade A) for Late Triassic
through Early Cretaceous rocks of the Ekonay terrane probably represent
ages of the oceanic lithosphere that constitutes this accretionary-wedge
complex.

For Alaska and the Canadian Cordillera, paleolatitude data (table 3)
supporting the northern-accretion interpretation for the Wrangellia
superterrane are 60° (grade C) for the Skelly Creek batholith and Summit
stock in the Coast-North Cascade plutonic belt. Paleolatitude data
supporting the southern-accretion interpretation for the Wrangellia
superterrane (table 3) are (1) 25° (grade B) for the Chignik/Hoodoo
units in the Peninsular sequence of the Wrangellia superterrane, (2) 32°
(grade B) for the MacColl Ridge Formation in the Wrangellia sequence of
the Wrangellia superterrane in southern Alaska, (3) 37° (grade A) for
the Methow terrane in the southern part of the Canadian Cordillera, and
(4) 38° (grade B) for the Silverquick and Powell Creek units in the
Tyaughton Basin in the Stikinia terrane of the central part of the
Canadian Cordillera. Paleolatitude data supporting an intermediate locus
for accretion of the Wrangellia superterrane are 46° and 53° (grade A)
for localities in the Spences Bridge volcanic-plutonic belt in the
southern part of the Canadian Cordillera.

Campanian Through Early Eocene (84--52 Ma)

During the Campanian though Early Eocene (84--52 Ma), the major tectonic
events were (1) continuation of a series of continental-margin arcs and
companion subduction-zone assemblages around the Circum-North Pacific
(table 2); (2) completion of opening of the Amerasia, Canada, and
Eurasia Basins; (3) completion of accretion of the Wrangellia
superterrane; (4) a change to dextral transpression in the eastern part
of the Circum-North Pacific between the Kula oceanic plate and the North
American continental margin; (5) oblique subduction of the Kula-Farallon
oceanic ridge under the margins of southern and southeastern Alaska; and
(6) northward migration of previously accreted terranes along the margin
of the North American Cordillera.

Specific Tectonic Events for the Campanian Through Early Eocene

1\. Far to the south, at about 50°--60° paleolatitude (table 3), the
extensive Olyutorka island arc continued to form. Parts of this arc are
preserved in the Nemuro (NE), Kronotskiy (KRO), Olyutorka-Kamchatka
(OKA), and Iruneisky (IR) island-arc terranes. Associated with the arc
was subduction of part of the adjacent oceanic plate to form the
Vetlovskiy terrane (VT). This arc and companion subduction zone migrated
northward toward the Okhotsk-Chukotka continental-margin arc. In the
early Eocene, at about 50 Ma (Heiphitz and others, 1994a; Brandon and
others, 1997), the Olyutorka island arc accreted against the West
Kamchatka accretionary-wedge terrane (WK) along the Vatyn thrust of
Brandon and others (1997, 1998), which is interpreted as a low-angle,
seaward-dipping zone of obduction (Brandon and others, 1997; Ramthun and
others, 1997). Accretion is interpreted as occurring during the Eocene
(Brandon and others, 1998; Garver and others, 1998; Solo'ev and others,
1998; Konstantinovskaya, 1999). Alternatively, Geist and others (1994)
inferred that the Olyutorka arc and its companion subduction zone formed
near the margin of present-day Northeast Asia.

2\. Farther west, the East Sikhote-Alin continental-margin arc (es) and
related deposits continued activity. Forming as part of this arc was the
West Sakhalin (WSA) turbidite-basin terrane. Associated with the arc was
oblique subduction of part of the Pacific oceanic plate (PAC) to form
the Hikada (HI), Aniva (ANV), and Nabilsky (NAB) terranes (table 2).

3\. The Okhotsk-Chukotka continental-margin arc continued activity.
Parts of this arc are preserved in the Okhotsk-Chukotka
volcanic-plutonic belt (oc) and related Penzhina (forearc) sedimentary
basin (pn). Associated with the arc was subduction of part of the
Pacific oceanic plate (PAC) to form the West Kamchatka (WK) and Ekonay
(EK) terranes (table 2). Local plutons in the Okhotsk-Chukotka
volcanic-plutonic belt intruded under extension, probably as the result
of rollback of the subduction slab during the Late Cretaceous (Amato and
Wright, 1997). Also in the same region, the Okhotsk-Chukotka and East
Sikhote-Alin continental-margin arcs were offset in a sinistral sense
along the Mongol-Okhotsk Fault System (MO).

4\. Between the areas of the present-day Russian Far East and Alaska,
continental-margin arcs and companion subduction zones in each region
were connected by a major transform fault. In the area of present-day
western Alaska, tectonic escape (crustal extrusion) of terranes occurred
along major dextral-slip faults, including the Denali (DE), Nixon Fork
(NF), Kaltag (KA), and companion faults (Scholl and others, 1992, 1994).
In association with movement on these major dextral-slip faults,
dextral-wrench sedimentary basins formed, including the Kuskokwim Basin
(kw) (Plafker and Berg, 1994; Bundtzen and Miller, 1997). The crustal
extension and wrench faulting were associated with a major period of
extension in interior Alaska, according to the interpretation of Miller
and Hudson (1991). The mid-Cretaceous and Late Cretaceous extension is
interpreted as having formed warm, thin continental crust that was
favorable for crustal extrusion and dextral-wrench faulting (Scholl and
others, 1992, 1994).

5\. By the early Tertiary, in the region of the Amerasia (ab), Canada
(cb), and Eurasia (eb) Basins, sea-floor spreading and associated
rifting was completed (Grantz and others, 1990, 1991, 1998), and
sedimentation continued in these large basins. The formation of the
Alpha and Mendeleev Ridges (am), which are interpreted as large piles of
hotspot basalt and associated deposits, was completed (Grantz and
others, 1990, 1991, 1998).

6\. During the Paleocene (approx 60--56 Ma), in the area of the
present-day Bering Sea, major counterclockwise rotation (oroclinal
bending) of the Pacific oceanic plate (PAC) occurred (at about 30°--50°
paleolatitude) (Lonsdale, 1988). This rotation resulted from compression
between Eurasia and North America (Plafker and Berg, 1994). At the same
time, the extension of dextral-slip faults from the area of present-day
western Alaska into the Bering Sea resulted in capture and accretion of
a fragment of the Kula oceanic plate (KULA) (Scholl and others, 1992,
1994).

7\. In response to oblique subduction of the Kula oceanic plate (KULA),
the major Kluane continental-margin arc formed (Bradley and others,
1993). Parts of this arc are preserved as the Kuskokwim Mountains
volcanic-plutonic belt (km) and the Alaska Range-Talkeetna Mountains
igneous belt (at). The coeval Coast arc formed along the margin of the
North American Cordillera. Parts of this arc are preserved in the
Coast-North Cascade plutonic belt (cn) and the Kamloops magmatic belt
(kl). These continental-margin arcs overlapped the previously accreted
Wrangellia superterrane and adjacent inboard terranes and extended for a
distance of more than 3,200 km along the active continental margin of
the North American Cordillera. Associated with these continental-margin
arcs was subduction of the laterally extensive Chugach terrane (CG) and
the Pacific Rim terrane (PAR) (table 2).

8\. Along the active margin of the North American Cordillera, rapid
northward migration of the Kula oceanic plate (KULA), which started to
form at about 85 Ma (Englebretson and others, 1985), resulted in the
formation of major dextral-slip faults, including the Denali (DE),
Tintina (TI), Ross Lake (RL), and companion faults (Plafker and Berg,
1994). Oblique subduction of the Kula-Farallon oceanic ridge occurred at
about 60 to 50 Ma along the margin of southern Alaska (Bradley and
others, 1993). Subduction of the oceanic ridge, locally partly preserved
in ophiolites in the Prince William terrane (Lytwyn and others, 1997;
Kusky and Young, in press), during the early Tertiary is interpreted as
causing (1) a regional metamorphic welt and the formation of anatectic
granites (Plafker and others, 1989b, 1994), (2) rapid changes in the
components of strike-slip movement along the subduction zone bordering
the early Tertiary continental margin (Bradley and others, 1993), and
(3) formation of belts of early Tertiary granitic and mafic-ultramafic
plutonic rocks of the Sanak-Baranof plutonic belt (sab) (Hudson, 1979;
Moll-Stalcup and others, 1994) in southern and southeastern Alaska that
are interpreted as having formed in a near-trench environment during
subduction of the Kula-Farallon oceanic ridge (Bradley and others, 1993;
Kusky and others, 1997).

9\. Regional extension occurred in the present-day southern part of the
Canadian Cordillera and northeastern Washington. This extension is
interpreted either as (1) the result of a change from transpression to
transtension at about 55 Ma (Parrish and others, 1988); (2) caused by a
change in the obliquity of convergence of the oceanic plate; or (3)
alternatively, but likely, collapse of overthickened thrust units.

10\. The eastward thrusting of the North American cratonal margin (NAM)
over the North American Craton (NAC) ended at about 60 Ma in the
present-day Canadian Cordillera.

11\. For the southern-accretion interpretation for the Wrangellia
superterrane, rapid northward transport of the superterrane commenced
(not shown in fig. 17; Irving and others, 1996; Cowan and others, 1997)
along unknown dextral-slip faults (Monger and others, 1996). The total
amount of Late Cretaceous and early Tertiary northward translation is
under debate (Monger, 1993; Cowan, 1994). Some paleomagnetic studies
suggest that, for this interval, the inner parts of the present-day
Canadian Cordillera, west of the Tintina (TI) and Northern Rocky
Mountain Trench (NR) Faults (fig. 4), were displaced northward about
1,200 to 1,400 km, whereas early Late Cretaceous plutons and stratified
rocks in the present-day Coast Mountains of Canada were displaced about
3,500 km (Irving and others, 1996). However, displacements based on
offsets of geologic units across faults are much smaller (see discussion
in Monger and Nokleberg, 1996). Resolution of this problem is clearly of
major importance.

Summary of Paleolatitude Data for the Campanian Through Early Eocene

For the Russian Far East, supporting paleolatitudes (table 3) include
49°--60° (grades A--C) for four localities in the Olyutorka-Kamchatka
terrane (Koryakia sedimentary rocks, Machevna Bay, Apuka River,
Olytorskii Ridge, and Koryak Highlands). Conflicting paleolatitudes
(table 3) are (1) 37°--43° (grade C) for three localities in the West
Sakhalin terrane, (2) 32° and 81° (grades B, C) for two localities in
the Olyutorka-Kamchatka terrane (Javevyn Bay and Tavlovka River,
respectively), (3) 25° (grade A) for the Kronotskiy terrane, (4) about
39° (grade A) for the Kamchatskiy Mys terrane that occurs at the west
edge of the incipient Aleutian-Wrangell arc (fig. 18), and (5) about 43°
(grade A) for unnamed sedimentary rocks in the Aleutian volcanic belt in
the Komandorski Islands (Medny Island).

For Alaska and the Canadian Cordillera, supporting paleolatitude data
(table 3) are (1) 57°--78° (grades A, C) for various volcanic-rock units
in the Interior Alaska volcanic belt (Unalakleet quadrangle,
Yukon-Koyukuk Basin, Yukon-Tanana Upland); (2) about 70°--80° (grade A)
for overlap volcanic rocks in southern Alaska, including two localities
in the Talkeetna Volcanics, two localities in the Alaskan
Range-Talkeetna Mountains volcanic-plutonic belt, and two localities in
the Cantwell Formation; and (3) 67° (grade A) for the Masset Formation
overlying the southern part of the Wrangellia superterrane. The values
for the overlap volcanic rocks and the Masset Formation support the
northern-accretion interpretation for the Wrangellia superterrane.

For Alaska and the Canadian Cordillera, paleolatitude data (table 3)
supporting the southern-accretion interpretation for the Wrangellia
superterrane are (1) 54° (grade A) for the Chickaloon Formation
overlying the Peninsular sequence of the northern part of the Wrangellia
superterrane on the Alaska Peninsula; (2) 55° (grade A) for the Arkose
Ridge Formation overlying the Peninsular sequence of the northern part
of the Wrangellia superterrane in southern Alaska; (3) 43° (grade C) for
the Butedale pluton in the Coast-North Cascade plutonic belt; (4) about
53°--57° (grades A, C) for igneous and sedimentary rocks intruding or
overlying various parts of the central and southern parts of the
Wrangellia terrane (AX and WR sequences) (Point Camden gabbro, Flores
Volcanics in the Cascade volcanic-plutonic belt, Carmacks volcanic
field, and Coast-North Cascade plutonic belt \[Kelowna Volcanics\]); (5)
46° (grade C) for the East Sooke gabbro, part of the Cascade
volcanic-plutonic belt overlying the southern part of the Wrangellia
superterrane; and (6) 59° (grade A) for the Kamloops volcanic belt in
the southern part of the Canadian Cordillera.

For Alaska, conflicting paleolatitudes (table 3) are (1) 62° (grade A)
for unnamed flows overlying the Kahiltna sedimentary and volcanic
assemblage in the Lake Clarke quadrangle, southern Alaska; (2) 0° (grade
A) for a locality in the Interior Alaska volcanic belt in the
Yukon-Koyukuk Basin; (3) 64° and 67° (grades A, B) for the Kuskokwim
Mountains belt in the Bering Sea region; and (4) 8° (Grade B) for the
Brothers Volcanics overlying the Gravina-Nutzotin-Gambier overlap
assemblage in southern Alaska.

Middle Eocene Through Early Miocene (42--23 Ma)

During the middle Eocene to early Miocene (42--23 Ma), the major
tectonic events were (1) continuation of a series of continental-margin
arcs and companion subduction-zone assemblages around the Circum-North
Pacific (table 2), (2) continuation of sea-floor spreading in the
present-day Arctic and eastern Pacific Oceans, (3) establishment of a
new continental margin in the northern and eastern parts of the
Circum-North Pacific as the result of disappearance of the Kula oceanic
plate and inception of subduction of the leading edge of the Pacific
oceanic plate, (4) continuation of dextral transpression between the
Pacific oceanic plate (PAC) and the North American continental margin in
the eastern part of the Circum-North Pacific, and (5) a change to
orthogonal transpression between the Pacific oceanic plate and the
southern Alaska continental margin because of counterclockwise rotation
of western Alaska.

At about 50 Ma (Vogt and others, 1979), the Gakkel Ridge (GK) (northward
extension of the Mid-Atlantic Ridge) was initiated, and sea-floor
spreading extended into the Eurasia Basin (eb) in the Arctic Ocean,
thereby resulting in the North American-Eurasia plate boundary in the
Russian Northeast. The exact position of the Euler pole changed
throughout the Cenozoic, thereby resulting in regional changes in the
stress regime (Savostin and others, 1984; Harbert and others, 1990).
Analysis of marine magnetic anomalies in the Eurasia Basin suggests that
the region underwent extension from about 56 to 36 Ma (Savostin and
Drachev, 1988a, b; Harbert and others, 1990; Fujita and others, 1997).

Specific Tectonic Events for the Middle Eocene Through Early Miocene

1\. The younger, bimodal volcanic and plutonic rocks of the youngest
part of the East Sikhote-Alin volcanic-plutonic belt (es), mainly
basalt, rhyolite, and associated granitic plutonic rocks, are herein
interpreted as having formed in a dextral-transpression tectonic regime.

2\. In the present-day central and southern parts of the Russian Far
East, tectonic wedging occurred because of accretion of the India plate
against the Eurasia plate (Worall and others, 1996). This tectonic
wedging resulted in sinistral displacement along the reactivated
Mongol-Okhotsk Fault (MO) and dextral displacement along the
Sakhalin-Hokkaido Fault (SH) parallel to the margin of the present-day
Russian Far East. A complex array of normal faults, echelon folds, and
thrusts is interpreted as having formed within and adjacent to the
tectonic wedge (Worall and others, 1996). The relation between sinistral
movement along the reactivated Mongol-Okhotsk Fault and dextral movement
along the Denali (DE), Tintina (TI), and related faults to the east in
present-day mainland Alaska is unclear.

3\. The bimodal volcanic and plutonic rocks of the Kamchatka-Koryak
volcanic-plutonic belt (kk) are herein interpreted as having formed in a
sinistral tectonic regime.

4\. Rifting commenced at about 50 Ma along the Gakkel Ridge (GK)
(northward extension of the Mid-Atlantic Ridge) and extended into the
present-day Russian Northeast (Fujita and others, 1997). This rifting is
interpreted as causing eruption of basalts in the present-day Chersky
Range at about 37 Ma (Fujita and others, 1997). The Lomonosov Ridge
terrane (LO) is interpreted as having formed during the rifting of
passive-continental-margin units now preserved in the Barents Sea region
(outside area of fig. 18; Zonenshain and others, 1990). Sedimentation
continued in the large Amerasia (ab), Canada (cb), and Eurasia (eb)
Basins.

5\. A short-lived period of marine arc volcanism formed the Bowers (bw)
and Shirshov (sh) Ridges in the Bering Sea. The arc formed on the rear
edge of the previously accreted Aleutia terrane (al), a fragment of the
Kula oceanic plate (Scholl and others, 1992, 1994) The Bowers Ridge
volcanic belt consists chiefly of intermediate-composition volcanic
rocks, mainly altered andesite, breccia, volcaniclastic sedimentary
rocks, and lesser diatomaceous siltstone (Cooper and others, 1992;
Scholl and others, 1992). Analysis of sparse dredge samples and Deep Sea
Drilling Project drill cores suggests a Miocene age for the volcanic
rocks. The presence of a trench filled with as much as 12 km of
sedimentary rocks at the base of the north and east slopes of the Bowers
Ridge suggests that the unit formed in an early Tertiary arc-trench
system that faced northeast. The Shirshov Ridge volcanic belt consists
chiefly of two assemblages; (1) a relatively older oceanic assemblage
composed of amphibolite, gabbro, diabase, basalt, and chert, in which
the chert contains Late Cretaceous (Campanian to Maastrichtian) to early
Paleogene microfauna; and (2) a relatively younger volcanic-arc
assemblage composed of altered andesite, volcaniclastic sedimentary
rocks, and shale of Miocene and younger age (Baranov and others, 1991;
Scholl and others, 1992). Alternatively, the Bowers and Shirshov Ridges
may be the northward extension of the Olyutorka-Kamchatka island arc
(OKA) (Brandon and others, 1997). Also in the Bering Sea, a thick
sedimentary prism started to form in the Aleutian-Bowers sedimentary
basin (atb) that overlies the Aleutia terrane (Scholl and others, 1992,
1994; Plafker and Berg, 1994).

6\. Tectonic escape (crustal extrusion) of terranes continued to occur
along major dextral-slip faults, including the Denali (DE), Nixon Fork
(NF), Kaltag (KA), and companion faults in the area of present-day
western Alaska and the Bering Sea (Scholl and others, 1992, 1994).
Dextral-wrench basins continued to form in association with these major
dextral-slip faults and were rapidly filled with continental sedimentary
materials. Coincident with crustal extrusion was counterclockwise
oroclinal bending of present-day Alaska that may have resulted from
compression between Eurasia and North America (Scholl and others, 1992,
1994; Plafker and Berg, 1994). To the east, in the area of present-day
southern Alaska, displacement continued along major dextral-slip faults,
including the Denali, Nixon Fork, and Kaltag Faults. These and similar
dextral-slip faults probably extended into the area of the present-day
Bering Sea.

7\. The Pacific oceanic plate (PAC) moved toward North America as a
result of sea-floor spreading along the Juan de Fuca oceanic ridge.
Along the Aleutian megathrust (AL), plate convergence continued to range
from oblique-orthogonal in the east to oblique in the west.
Oblique-transpressive displacement occurred between the Pacific oceanic
plate and the southern part of the Canadian Cordillera.

8\. As a result of accretion of part of the Kula oceanic plate
(underlying the Aleutian-Bowers sedimentary basin), and stepout of
subduction, the western part of Aleutian-Wrangell arc (al) was initiated
at about 40 Ma. This major Andean-type arc overlapped the previously
accreted Kula oceanic plate and initially extended for a distance of
about 3,000 km along the Bering Strait and southern Alaska. Associated
with the arc was subduction of part of the Pacific oceanic plate (PAC)
to form the Prince William (PW) and Yakutat (YA) terranes along the
Aleutian megathrust (AL).

9\. At about 30 to 25 Ma, a major tectonic change occurred in the
southern part of the Canadian Cordillera with tectonic overriding of the
northern segment of the Juan de Fuca oceanic ridge (JFR) and resulting
establishment of dextral slip along the Queen Charlotte Fault (QC). This
tectonic change ended subduction of the Farallon oceanic plate (FAR) and
started northward migration and subduction of the Yakutat terrane (YAK),
resulting in the beginning of volcanism in the Wrangellia volcanic field
(wr) in the eastern part of the Aleutian-Wrangell arc. Total movement of
the Yakutat terrane is estimated at about 600 km (Plafker and Berg,
1994; Plafker and others, 1994). Movement ceased along major
dextral-slip faults in the interior part of the Canadian Cordillera,
including the Tintina (TI) and Fraser Creek-Straight Creek (FS) Faults.
Between lat 51° and 60° N., the Queen Charlotte transform fault
separated the Cascade arc and the Aleutian-Wrangell arc. This fault
forms the present-day North American plate margin between Vancouver
Island, Canada, and the northern part of southeastern Alaska.

10\. Offshore of the southern part of the Canadian Cordillera, sea-floor
spreading occurred along the Juan de Fuca oceanic ridge (JFR). To the
east, subduction of the Juan de Fuca plate (JF) resulted in initiation
of the Cascade continental-margin arc (ca). Part of the subducting plate
is preserved in the Siletzia (SZ), Olympic Core (OC), and Hoh (HO)
terranes along branches of the Cascadia megathrust (CC).

11\. For the southern-accretion interpretation for the Wrangellia
superterrane, rapid northward transport of the superterrane (not shown
in fig. 18) was completed (Irving and others, 1996; Cowan and others,
1997) along unknown dextral-slip faults (Monger and others, 1996).

Summary of Paleolatitude Data for the Middle Eocene Through Early
Miocene

For the Russian Far East, supporting paleolatitude data (table 3)
include 65° (grade A) for the Central Kamchatka volcanic belt.
Conflicting paleolatitudes (table 3) are (1) 40°--47° (grades A, D) for
the East Kamchatka volcanic belt; and (2) 51°--54° (grade A) for the
Central Kamchatka volcanic belt, Karaginskii Island, and the Ilpinskii
Peninsula.

For Alaska and the Canadian Cordillera, supporting paleolatitude data
(table 3) are (1) 57° (grade A) for sedimentary rocks on Umnak Island,
near the Aleutian Islands, (2) 74° (grade D) for a locality in the
Interior Alaska volcanic belt in the Yukon-Koyukuk Basin, (3) about 51°
(grade C) for the Hope pluton in the Cascade volcanic-plutonic belt, and
(4) 59° (grade A) for the Resurrection Peninsula ophiolite at the base
of the Prince William terrane in southern Alaska. For Alaska and the
Canadian Cordillera, paleolatitude data (table 3) supporting a southerly
origin for the Prince William terrane (not shown in fig. 18) are
34°--47° (grades A, B) for four localities in the Prince William terrane
in south-central Alaska (Kiluda Bay, Alitak Bay, Knight Island, Glacier
Island). For Alaska and the Canadian Cordillera, conflicting
paleolatitudes (table 3) are (1) 69° (grade A) for unnamed sedimentary
rocks on Amlia Island, part of the Aleutian-Bowers sedimentary basin;
and (2) 65° (grade C) for the Quotton pluton in the Coast-North Cascade
plutonic belt.

Miocene (20--10 Ma)

During the Miocene (20--10 Ma), the major tectonic events were (1)
continuation of a series of continental-margin arcs and companion
subduction-zone assemblages around the Circum-North Pacific (table 2);
(2) backarc spreading behind the major arcs; (3) opening of major
sedimentary basins behind major arcs; (4) in the eastern part of the
Circum-North Pacific, a continuation of dextral transpression between
the Pacific oceanic plate and the Canadian Cordillera margin and a
continuation of orthogonal transpression between the Pacific plate and
the southern Alaska continental margin; and (5) continued sea-floor
spreading in the Arctic and eastern Pacific Oceans.

Specific Tectonic Events for the Miocene

1\. After the accretion of various terranes during the early Eocene, the
Northeast Asia arc commenced activity. Parts of this arc are preserved
in the East Japan volcanic-plutonic belt (ej), the Kuril volcanic arc
(ku), and the various parts of the Kamchatka arc consisting of the
Central Kamchatka volcanic belt (kc), the Central Kamchatka volcanic and
sedimentary basin (ck), and the West Kamchatka sedimentary basin (wk).
To the northeast, the Okhotsk-Chukotka arc completed activity. These two
major Andean-type arcs overlapped previously accreted adjacent terranes
in both the Russian Southeast and to the south and extended for a
distance of about 3,000 km. Associated with these arcs was subduction of
part of the Pacific oceanic plate (PAC) along the Kuril-Kamchatka
megathrust (KK) to form the Kuril-Kamchatka subduction-zone terrane
(KUK) (table 2). Intra-arc faulting resulted in tectonic doubling of the
Kamchatka-Koryak (kk) arc, which started to become extinct as the
Central Kamchatka arc (kc) enlarged.

2\. Regional extension associated with backarc spreading behind the
northern Japan part of the Northeast Asia arc (East Japan
volcanic-plutonic belt, ej) resulted in marine eruption of the Sea of
Japan backarc unit (sj), which consists of mainly tholeiitic basalt and
associated rocks.

3\. In the Sea of Okhotsk, backarc spreading occurred behind the Kuril
Island and Kamchatka Peninsular part of the Northeast Asia arc (B.A.
Natal'in, in Nokleberg and others, 1994a), resulting in marine and
continental eruption of tholeiitic to alkalic basalt and associated
rocks forming the Sakhalin-Primorye volcanic belt (sp). This regional
extension is also interpreted as the result of seaward rotation of the
Kamchatka Peninsula, and as resulting in the formation of major units
within the Sea of Okhotsk (B.A. Natal'in, in Nokleberg and others,
1994a). Backarc spreading may have occurred simultaneously with trench
rollback and migration of the Northeast Asia arc into the Pacific
oceanic plate.

4\. In the Arctic Ocean, rifting continued along the Gakkel Ridge (GK)
along with continued sedimentation in the Amerasia Basin (as). Analysis
of marine magnetic anomalies in the Eurasia Basin suggests that this
region underwent compression from about 36 to 5 Ma (Savostin and
Drachev, 1988a, b; Harbert and others, 1990; Fujita and others, 1997).
Geologic mapping reveals that late Miocene thrust faults and companion
folds, which were associated with regional compression, occurred along
the Myatisk and companion faults in the present-day Mona and Chersky
Ranges, as described by Gaiduk and others (1989, 1993). Fault
displacements are about 15 to 20 km.

5\. A major orthogonal junction formed between the west end of the
Aleutian-Wrangell arc (al) and the Central Kamchatka arc (kc). The west
terminus of the Aleutian-Wrangell arc is interpreted as having been
obducted onto the present-day Kamchatka Peninsula, thereby forming the
Kamchatskiy Mys oceanic terrane (too small to show in fig. 19), which is
interpreted as the oceanic base of the ancestral Aleutian-Wrangell arc,
and the Stolbovskoy island-arc terrane (also too small to show in fig.
19), which is interpreted as the older, western part of the arc (Geist
and others, 1988, 1994).

6\. During the early to middle Miocene, a short episode (approx 22--10
Ma) of sea-floor spreading along the Komandorsky Ridge (KOM) formed a
small pair of oceanic plates that exhibit magnetic anomalies 5 and 6.
This spreading occurred after the marine-arc volcanism in this area that
formed the Bowers (bw) and Shirshov (sh) Ridges during the middle Eocene
and early Miocene.

7\. Intense tectonic disruption occurred in the western part of the
Aleutian-Wrangell arc, along the western Aleutian megathrust (AL), as a
result of transform coupling between the Pacific and North American
plates (Geist and others, 1988). A complex array of strike-slip,
extensional, and rotational structures formed in this area (Scholl and
others, 1992, 1994; Vallier and others, 1994). In the area of the
present-day Bering Sea, a thick sedimentary prism continued to form in
the Aleutian-Bowers Basin (atb) that overlies a fragment of accreted
Kula oceanic plate (Scholl and others, 1992, 1994; Plafker and Berg,
1994).

8\. Tectonic escape (crustal extrusion) of terranes continued to occur
along major dextral-slip faults, including the Denali (DE), Nixon Fork
(NF), Kaltag (KA), and companion faults (Scholl and others, 1992, 1994).
Dextral-wrench basins continued to form in association with the
dextral-slip faults and were rapidly filled with continental sedimentary
materials.

9\. The Pacific oceanic plate (PAC) continued to move northwestward.
Along the Aleutian megathrust (AL), plate convergence continued to range
from oblique-orthogonal in the east to oblique to transform in the west.

10\. Dextral displacement continued farther east along major
dextral-slip faults, such as the Denali (DF), Nixon Fork (NF), and
Kaltag (KA) Faults. Estimates of total Cenozoic displacements along the
Denali and Tintina Faults range from 400 to 500 km each (Nokleberg and
others, 1985; Plafker and Berg, 1994; Monger and Nokleberg, 1996). These
and companion dextral-slip faults probably extended into the area of the
present-day Bering Sea.

11\. The Aleutian-Wrangell continental-margin arc was associated with
mainly oblique subduction of the north edge of the Pacific oceanic plate
(PAC) along the Aleutian megathrust (AL) to form the Prince William
terrane (PW) (table 2). During northward migration, the Yakutat terrane
(YA) started to underthrust the Prince William terrane along the eastern
part of the Aleutian megathrust.

12\. Offshore of the southern part of the Canadian Cordillera, sea-floor
spreading continued along the Juan de Fuca Oceanic ridge (JFF).
Northward movement of the Pacific oceanic plate (PAC) and associated
transform displacement on the Queen Charlotte transform fault (QC)
resulted in continued northward migration and subduction of the Yakutat
terrane (YA) beneath the continental margin of present-day southern
Alaska.

13\. To the south, the Cascade continental-margin arc continued
activity. Associated with this arc was continued subduction of part of
the Juan de Fuca plate (JF) along the ancestral Cascadia megathrust
(CC). Regional extension, associated with backarc spreading behind the
Cascade arc (ca), resulted in continental eruption of the Columbia River
Basalt (cr) (Wells and Heller, 1988; England and Wells, 1991).

Summary of Paleolatitude Data for the Miocene

Supporting paleolatitude data (table 3) are (1) 71° (grade D) for
unnamed volcanic rocks overlying the Porcupine terrane in northeastern
Alaska, and (2) 55°--65° (grades A, C) for three igneous-rock localities
in the Cascade volcanic-plutonic belt (Mount Barr pluton, Caribou Plug,
Caribou Lavas).

Pliocene Through the Present (4--0 Ma)

During the Pliocene through the present (4--0 Ma), the major tectonic
events have been (1) continuation of a series of continental-margin arcs
and companion subduction-zone assemblages around the Circum-North
Pacific (table 2); (2) continuation of the opening of major sedimentary
basins behind major arcs; (3) in the eastern part of the Circum-North
Pacific, continuation of dextral transpression between the Pacific
oceanic plate and the present-day Canadian Cordillera margin; (4)
continuation of oblique-orthogonal transpression between the Pacific
plate and present-day southern Alaska; and (5) continuation of sea-floor
spreading in the Arctic and eastern Pacific Oceans. The modern
geodynamic pattern is defined by interaction of the Eurasian, North
American, and Pacific oceanic plates (Cook and others, 1987; Parfenov
and others, 1989; Fujita and others, 1997). The pole of rotation between
the Eurasian and North American plates is on or near the south coast of
the Laptev Sea in the Russian Northeast (Cook and others, 1987; Larson
and others, 1997).

Specific Tectonic Events for the Pliocene Through the Present

1\. Tectonic activity of the Northeast Asia continental-margin arc is
continuing. Parts of this arc are being preserved in the East Japan
volcanic-plutonic belt (ej), the Kuril arc (ku), the Central Kamchatka
volcanic and sedimentary basin (kc), and the East Kamchatka volcanic
belt (ek). Associated with the arc is subduction of the west edge of the
Pacific oceanic plate (PAC) along the Kuril-Kamchatka megathrust (KK) to
form the Kuril-Kamchatka (KUK) terrane (table 2). A major orthogonal
junction occurs between the west end of the Aleutian-Wrangell arc (al)
and the Kamchatka arc (kc).

2\. Rifting continues along the Gakkel Ridge (GK) (northward extension
of the Mid-Atlantic Ridge) and the extension of this ridge toward the
Eurasian plate. The Gakkel Ridge and its extension define the modern
boundary between the North American and Eurasian plates. Analysis of
sea-floor-spreading anomalies in the Eurasia Basin (eb) suggest that the
Russian Northeast underwent extension from about 5 to 0.5 Ma (Moma rift
episode, as discussed by Fujita and others, 1990a, b, 1997; see Savostin
and Drachev, 1988a, b; Harbert and others, 1990; Fujita and others,
1997). The youngest change, a northward pole shift, occurred at about
0.5 Ma, as indicated by resurgent or continued thrusting (Imaev, 1991).
Focal-mechanism studies indicate that parts of this region are
undergoing compression (Cook and others, 1986; Parfenov and others,
1989; Fujita and others, 1990a, b; Riegel and others, 1993). This
compression is relieved by extrusion of the Okhotsk block to the
southeast (Riegel and others, 1993) and by uplift and thrusting in the
CSB area (Koz'min, 1984; Imaev and others, 1990; Koz'min and others,
1996). Sedimentation continues in the Amerasia Basin (ab).

3\. Present-day seismicity defines several new tectonic blocks,
including the Amur, Okhotsk, and Bering blocks (Riegel and others, 1993;
Fujita and others, 1997; Mackey and others, 1997). Boundaries between
blocks are defined by epicenters located by teleseismic and regional
networks (Fujita and others, 1997).

4\. Marine and continental eruption of sparse, generally small, highly
dispersed flows of Bering Strait alkaline basalt (bs) has occurred
during the Quaternary. This volcanism may be related to dextral wrench
faulting and tectonic escape in the region. Rotation of the Bering block
caused extension on the present-day Seward Peninsula and on Chukotka
(Mackey and others, 1997), or the Bering block may have formed as the
backarc with respect to the Aleutian-Wrangell arc.

5\. Tectonic escape (crustal extrusion) of terranes continues along
major dextral-slip faults, including the Denali (DE), Nixon Fork (NF),
Kaltag (KA), and companion faults (Scholl and others, 1992, 1994), which
may extend into the Bering Sea. Dextral-wrench basins continue to form
in association with the dextral-slip faults and are still filling with
continental sedimentary materials. A thick sedimentary prism continues
to form in the Aleutian-Bowers Basin (atb) (Plafker and Berg, 1994). In
interior and southern Alaska, displacement continues along major
dextral-slip faults, such as the Denali Fault (DE).

6\. The Pacific oceanic plate (PAC) continues to migrate northwestward
relative to the North American plate. Along the Aleutian megathrust
(AL), plate convergence continues to range from orthogonal in the east
to oblique to transform in the west.

7\. Intense tectonic disruption continues in the western part of
Aleutian-Wrangell arc along the western Aleutian megathrust (AL), as a
result of transform coupling between the Pacific oceanic plate (PAC) and
the North American plate (Geist and others, 1988; Scholl and others,
1992, 1994). A thick sedimentary prism continues to form in the
Aleutian-Bowers Basin (atb) that overlies a fragment of accreted Kula
oceanic plate (Plafker and Berg, 1994).

8\. Along the margin of southern Alaska, the eastern part of the
Aleutian-Wrangell arc continues activity. Associated with this arc is
mainly oblique subduction of the north edge of the Pacific oceanic plate
(PAC) along the Aleutian megathrust (AL), and continuing formation of
the younger part of the Prince William terrane (PW). The Yakutat terrane
(YA) continues to migrate northwestward and to underthrust the Prince
William terrane (PW) along the eastern part of the Aleutian megathrust
(AL).

9\. Sea-floor spreading continues along the Juan de Fuca oceanic ridge
(JFR). Northward movement of the Pacific oceanic plate (PAC) continues
with transform displacement on the Queen Charlotte transform fault (QC).

10\. The Cascade continental-margin arc continues to form. Associated
with this arc is subduction of part of the Juan de Fuca oceanic plate
(JF) and formation of a subduction-zone complex along the Cascadia
megathrust (CC) (table 2) (Goldfinger and others, 1996, 1997; Flueh and
others, 1997).

Conclusions

The Cenozoic and Mesozoic, and some of the Paleozoic, evolution of the
Circum-North Pacific can be explained as a succession of arcs and
tectonically paired subduction zones that formed along the margins of
the Northeast Asian and North American plates above the subducting
oceanic lithosphere of mainly the Mongol-Okhotsk, Cache Creek, ancestral
Pacific, and Pacific Oceans. In both Northeast Asia and the North
American Cordillera, most of the arcs formed near continental margins as
island arcs or along the continental margins. With respect to Northeast
Asia and North America, the paleopositions of those arcs, which occur
oceanward of coeval accretionary complexes, are highly suspect in the
Paleozoic but successively less so in the Mesozoic. No compelling
evidence exists to suppose that most of these arcs migrated across ocean
basins. Geologic and faunal data and interpretations suggest formation
mostly along the active margin of the Northeast Asian and North American
plates. Some arcs may have formed at sites far removed from continents
and have been subsequently emplaced by Mesozoic lateral displacements
and rotations. The only truly exotic rocks in the North American
Cordillera tectonic collage may be (1) parts of accretionary complexes
that are composed mainly of oceanic-crustal material containing a
Tethyan fauna that is exotic with respect to North America, (2) those
terranes in western Alaska (Nixon Fork-Dillinger-Mystic) that are
interpreted as fragments of the North Asian Craton and cratonal margin,
and (3) the Late Proterozoic and early Paleozoic part of the Alexander
sequence of the Wrangellia superterrane.

The Phanerozoic tectonic evolution is most simply explained by a model
that consists of six main themes: (1) rifting of the northeastern margin
of the North Asian Craton and the northwestern margin of the North
American Craton; (2) formation of successions of single island arcs and
tectonically paired subduction-zone complexes along or near the North
Asian and North American cratonal margins, above subducting oceanic
plates of the ancestral Pacific and modern Pacific Oceans; (3) formation
of a succession of continental-margin arcs and tectonically paired
subduction zones; (4) oblique accretion of arcs and companion
subduction-zone complexes onto the northeastern margin of the North
Asian Craton and the northwestern margin of the North American Craton,
resulting in substantial growth of both continents; (5) deposition of
overlap assemblages, mainly derived from continental-margin igneous
arcs, onto previously accreted terranes; and (6) strike-slip translation
of previously accreted arc/subduction-zone complexes, overlap
assemblages, and fragments of continental margins along the margins of
the cratons.

References Cited

Afitsky, A.I., 1970, Biostratigraphy of Triassic and Jurassic deposits
in the vicinity of the Bolshoy Anyui River: Moscow, Nauka, 150 p. \[in
Russian\].

Afitsky, A.I., and Lychagin, P.P., 1987, Norian andesitic volcanism of
Oloy zone: Tikhookeanskaya Geologiya, no. 3, p. 77--82 \[in Russian\].

Aleksyutin, M.V., and Shipunov, S.V., 1997, Synfolding magnetization of
rocks of the Kuyul' Nappe System, Penzinha district, northeastern
Russia: Physics of the Earth Izvestiya, v. 33, p. 279--284.

Amato, J.M., and Wright, J.E., 1997, Potassic mafic magmatism in the
Kigluaik gneiss dome, northern Alaska; a geochemical study of arc
magmatism in an extensional tectonic setting: Journal of Geophysical
Research, v. 102, no. 4, p. 8065--8084.

Anderson, R.G., 1989, A stratigraphic, plutonic, and structural
framework for the Iskut River map area, northwestern British Columbia,
in Current research, part E: Geological Survey of Canada Paper 89--1E,
p. 145--154.

---------1993, A Mesozoic stratigraphic and plutonic framework for
northwestern Stikinia (Iskut river area), northwestern British Columbia,
Canada, in Dunne, G., and McDougall, K.A., eds., Mesozoic paleogeography
of the western United States---II: Los Angeles, Society of Economic
Paleontologists and Mineralogists, Pacific Section, v. 71, p. 447--494.

Andrew, K.P.E., Hoy, T., and Drobe, J., 1990, Stratigraphy and tectonic
setting of the Archibald and Elise Formations, Rossland Group, Beaver
Creek area, southeastern British Columbia, in Geological fieldwork:
1989, British Columbia Ministry of Energy, Mines, and Petroleum
Resources, Paper 1990--1, p. 19--27.

Archegov, V.B., Golovin, S.V., Zinchenko, V.N., Kirillov, V.O., and
Chochia, N.G., 1987, Basins of the Priverkhoyansk marginal system;
sedimentary basins of the U.S.S.R. Far East and prospects of their oil-
and gas-bearing capacity: Leningrad, Nedra, p. 60--91 \[in Russian\].

Archibald, D.A., Glover, J.K., Price, R.A., Farrar, E., and Carmichael,
D.M., 1983, Geochronology and tectonic implications of magmatism and
metamorphism, southern Kootenay arc and neighbouring regions; part 1,
Jurassic to mid-Cretaceous: Canadian Journal of Earth Sciences, v. 20,
p. 1891--1913.

Argand, E., 1924, La tectonique de l'Asie: Congrès Géologique
International 13er Comptes Rendus, Belgique, 1922, p. 171--372 \[in
French\].

Armstrong, R.L., 1988, Mesozoic and early Cenozoic magmatic evolution of
the Canadian Cordillera, in Clark, S.P., Burchfiel, B.C., and Suppe, J.,
eds., Processes in continental lithospheric deformation: Geological
Society of America Special Paper 218, p. 55--91.

Armstrong, R.L., and Ward, P.L., 1993, Late Triassic to earliest Eocene
magmatism in the North American Cordillera: implications for the Western
Interior Basin, in Caldwell, W.G.E., and Kauffman, E.G., eds., Evolution
of the western interior basin: Geological Association of Canada Special
Paper 39, p. 49--72.

Atwater, Tanya, 1989, Plate tectonic history of the northeast Pacific
and western North America, in Winterer, E.L., Jussong, D.M., and Decker,
R.W., eds., The eastern Pacific Ocean and Hawaii (The Geology of North
America, v. N): Boulder, Colo., Geological Society of America, p.
21--72.

Atwater, Tanya, and Severinghaus, Jeff, 1989, Tectonic map of the
north-central Pacific Ocean, pls. 3A--3C of Winterer, E.L., Hussong,
D.M., and Decker, R.W., eds., The eastern Pacific Ocean and Hawaii (The
geology of North America, v. N): Boulder, Colo., Geological Society of
America, scale 1:6,442,194.

Avchenko, O.V., 1977, Petrology of Okhotsk metamorphic complex: Moscow,
Nauka, 95 p. \[in Russian\].

Babcock, L.E., and Blodgett, R.B., 1992, Biogeographic and
paleogeographic significance of Middle Cambrian trilobites of Siberian
aspect from southwestern Alaska \[abs.\]: Geological Society of America
Abstracts with Programs, v. 24, no. 5, p. 4.

Babcock, L.E., Blodgett, R.B., and St. John, James, 1993, Proterozoic
and Cambrian stratigraphy and paleontology of the Nixon Fork terrane:
Circum-Pacific and Circum-Atlantic Terrane Conference, Guanajuato,
Mexico, 1993, Proceedings, p. 5--7.

Babcock, R.S., Burmester, R.F., Engebretson, D.C., Warnock, D., 1992, A
rifted-margin origin for the Crescent Basalts and related rocks from the
northern Coast Range volcanic province of Washington and British
Columbia: Journal of Geophysical Research, v. 97, no. B, p. 6799--6821.

Babcock, R.S., Suczek, C.A., and Engebretson, D.C., 1994, The Crescent
terrane, Olympic Peninsula and southern Vancouver Island: Washington
Division of Geology and Earth Sciences Bulletin, v. 80, p. 141--157.

Baboshina, V.A., Tereshchenkov, A.A., and Kharakhinov, V.V., 1984, Deep
structure of the Sea of Okhotsk region from geophysical data. Review of
information: Moscow, VNII Gasprom, v. 3, 41 p. \[in Russian\].

---------1985, Gravitational field of the Sea of Okhotsk region and its
interpretation in concert with bathymetry and seismic data:
Tikhookeanskaya Geologiya, no. 6, p. 49--59 \[in Russian\].

Bakharev, A.G., 1976, Stratigraphy and composition of the Ul'ya basin,
in Volcanic and intrusive formations in Priokhot'e: Novosibirsk, Nauka,
p. 53--75 \[in Russian\].

Bakharev, A.G., Gamyanin, G.N., Goryachev, N.A., and Polovinkin, V.L.,
1988, Magmatism and ore formations of the Ulakhan-Tas Range: Yakutsk,
Soviet Union Academy of Sciences, 200 p. \[in Russian\].

Baranov, B.V., Seliverstov, N.I., Muravov, A.V., and Muzuzov, E.L.,
1991, The Komandorsky Basin as a product of spreading behind a transform
plate boundary: Tectonophysics, v. 199, p. 237--269.

Bardous, M., and Irving, E., 1989, Paleomagnetism of Eocene rocks of the
Kelowna and Castlegar areas, British Columbia: studies in determining
paleohorizontal: Canadian Journal of Earth Sciences, v. 26, p. 829--844.

Barker, Fred, Sutherland-Brown, A., Budahn, J.R., and Plafker, George,
1989, Back-arc with frontal-arc component origin of Triassic Karmutsen
basalt, British Columbia, Canada: Chemical Geology, v. 75, p. 81--102.

Barker, Fred, Miller, T.P., and Gehrels, G.E., 1994, Map showing
occurrences of accreted volcanic rocks and the pre-Cenozoic and some
early Tertiary plutonic rocks of Alaska, pl. 13 of Plafker, George, and
Berg, H.C., eds., The geology of Alaska (The Geology of North America,
v. G--1): Boulder, Colo., Geological Society of America, scale
1:2,500,000.

Barton, P., and Wood, R.,. 1984, Tectonic evolution of the North Sea
Basin; crustal stretching and subsidence: Geophysical Journal of Royal
Astronomical Society, v. 79, p. 987--1922.

Bazard, D.R., Butler, R.F., Gehrels, G.E., 1993, Paleomagnetic and
detrital zircon analysis of the Lower Devonian Karheen Formation,
Alexander Terrane, southeastern Alaska \[abs.\]: Eos (American
Geophysical Union Transactions), v. 74, p. 213.

Bazard, D.R., Butler, R.F., Gehrels, G.E., and Soja, C.M., 1994, New
constraints for Late Silurian-Devonian paleogeography of the Alexander
terrane, southeastern Alaska \[abs.\]: Geological Society of America
Abstracts with Programs, v. 26, p. 384.

Bazhenov, M.L., and Burtman, V.S., 1992, Paleomagnetism of Paleogene
rocks of the Central-East Kamchatka and Komandordky Islands; tectonic
implications: Tectonophysics, v. 201, p. 157--173.

---------1996, Upper Cretaceous paleomagnetism of the Shikotan Island;
implications for plate kinematics: Earth and Planetary Science Letters,
v. 122, p. 19--28.

Bazhenov, M.L., Burtman, V.S., Krezhovskikh, O.A., Shapiro, M.N., 1992,
Paleomagnetism of Paleogene rocks of the central-east Kamchatka and
Komanorsky Islands; tectonic implications: Tectonophysics, v. 201, p.
157--173.

Bekhtold, A.F., and Semenov, D.F., 1990, Metabasites and ultramafic
rocks of the Susunai Ridge (Sakhalin Island): Tikhookeanskaya Geologiya,
no. 1, p. 121--125 \[in Russian\].

Belasky, P., and Runnegar, B., 1994, Permian longitudes of Wrangellia,
Stikinia, and eastern Klamath terranes based on coral biogeography:
Geology, v. 22, p. 1095--1098.

Belyaeva, G.V., 1988, The Cambrian of the U.S.S.R. East; stratigraphy:
Moscow, Nauka, 136 p. \[in Russian\].

Belyi, V.F., 1977, Stratigraphy and structures of the Okhotsk-Chukotka
volcanic belt: Moscow, Nauka, 171 p. \[in Russian\].

---------1978, Formations and tectonics of the Okhotsk-Chukotka volcanic
belt: Moscow, Nauka, 213 p. \[in Russian\].

Berg, H.C., Jones, D.L., and Richter, D.H., 1972, Gravina-Nutzotin Belt:
tectonic significance of an upper Mesozoic sedimentary and volcanic
sequence in southern and southeastern Alaska, in Geological Survey
research, 1972: U.S. Geological Survey Professional Paper 800--D, p.
D1--D4.

Bersenev, I.I., Lelikov, E.P., Bezverkhny, V.L., Vashchenkova, N.G.,
S'edin, V.G., Terekhov, E.P., and Tsoi, I.B., 1987, Geology of the
Philippine Sea Floor: Vladivostok, U.S.S.R. Academy of Sciences, Far
East Branch, 138 p. \[in Russian\].

Besse, J., and Courtillot, V., 1991, Revised and synthetic apparent
polar wander paths of African, Eurasian, North American and Indian
plates, and true polar wander since 200 Ma: Journal of Geophysical
Research, v. 96, no. B, p. 4029--4050.

Beus, V.A., and Miledin, A.K., 1990, New data on the age of the
metamorphic complex of the Prikolyma uplift: Akademii Nauk SSSR Doklady,
v. 311, p. 925--928 \[in Russian\].

Bevier, M.L., 1988, Regional stratigraphy and age of Chilcotin Group
basalts, south-central British Columbia: Canadian Journal of Earth
Sciences, v. 20, p. 515--524.

Bibikova, E.V., Makrov, V.A., Gracheva, T.V., and Kalinkina, O.M., 1981,
Ancient rocks of the Omolon massif, in Ancient granitoids of the
U.S.S.R.: Leningrad, Nauka, p. 137--146 \[in Russian\].

Blodgett, R.B., 1998, Emsian (late Early Devonian) fossils indicate a
Siberian origin for the Farewell terrane, in Clough, J.G., and Larson,
F., eds., Short notes on Alaska geology 1997: Alaska Division of
Geological and Geophysical Surveys Professional Report 118, p. 53--61.

Blodgett, R.B., and Boucot, A.J., 1999, Late Early Devonian (Late
Emsian) eospiriferoid brachiopods from Shallabarger Pass, south-central
Alaska, and their biogeographic importance: Senckenbergiana Lethaea, v.
79, p. 209--221.

Blodgett, R.B., and Brease, P.F., 1997, Emsian (Early Devonian)
brachiopods from Shellabarger Pass, Talkeetna C--6 quadrangle, Denali
National Park, Alaska, indicate Siberian origin for Farewell terrane
\[abs.\]: Geological Society of America Abstracts with Programs, v. 29,
p. 5.

Blodgett, R.B., and Clough, J.G., 1985, The Nixon Fork terrane---part of
an in-situ peninsular extension of the Paleozoic North American
continent \[abs.\]: Geological Society of America Abstracts with
Programs, v. 17, p. 342.

Blodgett, R.B., and Gilbert, W.G., 1992, Upper Devonian shallow-marine
siliciclastic strata and associated fauna and flora, Lime Hills D--4
quadrangle, southwest Alaska, in Bradley, D.C., and Dusel-Bacon,
Cynthia, eds., Geological studies in Alaska by the U.S. Geological
Survey, 1991: U.S. Geological Survey Bulletin 2041, p. 106--113.

Blois, C., and ECORS Scientific Parties, 1991, Post-orogenic evolution
of the European crust studied from ECORS deep seismic profiles, in
Meissner, R., Brown, L, Durbaum, H.J., Franke, W., Fuchs, K., and
Seifert, F., eds., Continental lithosphere; deep seismic reflections:
American Geophysical Union Geodynamics Series, v. 22, p. 59--68.

Boak, J.M., Turner, D.L., Henry, D.J., Moore, T.E., and Wallace, W.K.,
1987, Petrology and K-Ar ages of the Misheguk igneous sequence, an
allochthonous mafic and ultramafic complex, and its metamorphic aureole,
western Brooks Range, Alaska, in Tailleur, I.L., and Weimer, Paul, eds.,
Alaskan North Slope geology: Los Angeles, Society of Economic
Paleontologists and Mineralogists, Pacific Section, and Alaska
Geological Society, v. 50, p. 737--745.

Bogdanov, N.A., and Til'man, S.M., 1992, Tectonic map of Northeastern
Asia: Moscow, Russian Academy of Sciences, Institute of Lithosphere, and
Circum-Pacific Council for Energy and Mineral Resources, scale
1:5,000,000.

Bogue, S.W., Grommé, S., and Hillhouse, J.W., 1995, Paleomagnetism,
magnetic anisotropy, and mid-Cretaceous paleolatitude of Duke Island
(Alaska) ultramafic complex: Tectonics, v. 14, p. 1133--1152.

Bol, A.J., 1993, Overprint magnetization in support of northward
displacement of the Chugach-Prince William Terrane, Alaska: Journal of
Geophysical Research, v. 98, no. B, p. 22389--22400.

Bol, A.J., Coe, R.S., Grommé, C.S., Hillhouse, J.W., 1992,
Paleomagnetism of the Resurrection Peninsula, Alaska; implications for
the tectonics of southern Alaska and the Kula-Farallon Ridge: Journal of
Geophysical Research, v. 97, no. B, p. 17213--17232.

Box, S.E., 1985a, Early Cretaceous orogenic belt in northwestern Alaska;
internal organization, lateral extent, and tectonic interpretation, in
Howell, D.G., ed., Tectonostratigraphic terranes of the Circum-Pacific
region (Earth Science Series, v. 1): Houston, Tex., Circum-Pacific
Council for Energy and Mineral Resources, p. 137--145.

---------1985b, Geologic setting of high-pressure metamorphic rocks,
Cape Newenham area, southwestern Alaska, in Bartsch-Winkler, Susan, ed.,
The United States Geological Survey in Alaska; accomplishments during
1984: U.S. Geological Survey Circular 967, p. 37--42.

---------1985c, Terrane analysis, northern Bristol Bay region,
southwestern Alaska, in Bartsch-Winkler, Susan, ed., The United States
Geological Survey in Alaska; accomplishments during 1984: U.S.
Geological Survey Circular 967, p. 32--36.

Box, S.E., Moll-Stalcup, E.J., Frost, T.P., and Murphy, J.M., 1993,
Preliminary geologic map of the Bethel and southern Russian Mission
quadrangles, southwestern Alaska: U.S. Geological Survey Miscellaneous
Field Studies Map MF--2226--A, 20 p., scale 1:250,000.

Box, S.E., Moll-Stalcup, E.J., and Wooden, J.L., 1990, Kilbuck terrane;
oldest-known rocks in Alaska: Geology, v. 18, p. 1219--1222.

Box, S.E., and Patton, W.W., Jr., 1989, Igneous history of the Koyukuk
terrane, western Alaska; constraints on the origin, evolution, and
ultimate collision of an accreted island arc terrane: Journal of
Geophysical Research, v. 94, no. B, p. 15843--15867.

Bradley, D.C., Haeussler, P., and Kusky, T.M., 1993, Timing of early
Tertiary ridge subduction in southern Alaska, in Dusel-Bacon, Cynthia,
and Till, A.B., eds., Geologic studies in Alaska by the U.S. Geological
Survey, 1992: U.S. Geological Survey Bulletin 2068, p. 163--177.

Brandon, M.T., 1989, Geology of the San Juan-Cascade Nappes,
Northwestern Cascade Range and San Juan Islands, in Joseph, N.L., and
others, eds., Geologic guidebook for Washington and adjacent areas:
Washington Division of Geology and Earth Resources Information Circular
86, p. 137--162.

Brandon, M.T., Garver, J.I., Bullen, M.E., Sokovév, A.V., Ledneva, G.V.,
and Bogdanov, N.A., 1997, Eocene collision and obduction of the
Olutorskiy island arc, Koryak Highlands of northern Kamchatka, Russian
Far East \[abs.\]: Geological Society of America Abstracts with
Programs, v. 29, p. 6.

---------1998, Eocene collision and obduction of the Olutorskiy island
arc, Koryak Highlands of northern Kamchatka, Russian Far East \[abs.\]:
Russian Academy of Sciences' L.P. Zonenshain Conference on Plate
Tectonics, 6th, Moscow, 1998, Abstracts, v. 29, p. 172.

Brooks, H.C., and Vallier, T.L., 1978, Mesozoic rocks and tectonic
evolution of eastern Oregon and western Idaho, in Howell, D.G., and
McDougall, K.A., eds., Mesozoic paleogeography of the western United
States: Los Angeles, Society of Economic Paleontologists and
Mineralogists, Pacific Section, Pacific Coast Paleogeography Symposium
2, p. 133--145.

Brown, D.A., Logan, J.M., Gunning, M.H., Orchard, M.J., and Bamber,
W.E., 1991, Stratigraphic evolution of the Paleozoic Stikine assemblage
in the Stikine and Iskut Rivers area, northwestern British Columbia:
Canadian Journal of Earth Sciences, v. 28, no. 6, p. 958--972.

Bulgakova, M.D., 1986, Lithology of Ordovician deposits in northeastern
U.S.S.R.: Moscow, Nauka, 177 p. \[in Russian\].

Bundtzen, T.K., and Gilbert, W.G., 1983, Outline of the geology and
mineral resources of the upper Kuskokwim region, southwest Alaska, in
Sisson, Alex, ed., Symposium on Energy and Mineral Resources of western
Alaska: Journal of Alaska Geological Society, v. 3, p. 98--119.

Bundtzen, T.K., Kline, J.R., Smith, T.E., and Albanese, M.A., 1988,
Geology of the McGrath A--2 quadrangle, western Alaska: Alaska Division
of Geological and Geophysical Surveys Professional Report 91, 10 p.,
scale 1:63,360.

Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with
Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in
Goldfarb, R.J., and Miller, L.D., eds., Mineral deposits of Alaska:
Economic Geology Monograph 9, p. 242--286.

Burchfiel, B.C., 1992, Tectonostratigraphic map, Cordilleran orogen,
conterminous United States, pl. 1A of Burchfiel, B.C., Lipman, P.W., and
Zoback, M.L., eds., The Cordilleran Orogen; conterminous United States
(The Geology of North America, v. G--3): Boulder, Colo., Geological
Society of America, 2 sheets, scale 1:2,500,000.

Burchfiel, B.C., and Davis, G.A., 1972, Structural framework and
evolution of the southern part of the Cordilleran orogen, western United
States: American Journal of Science, v. 272, p. 97--118.

Butler, R.F., Gehrels, G.E., and Bazard, D.R., 1997, Paleomagnetism of
Paleozoic strata of the Alexander terrane, southeastern Alaska:
Geological Society of America Bulletin, v. 109, p. 1372--1388.

Butler, R.F., Gehrels, G.E., McClelland, W.C., May, S.R., Klepacki, D.,
1989, Discordant paleomagnetic poles from the Canadian Coast plutonic
complex; regional tilt rather than large-scale displacement?: Geology,
v. 17, p. 691--1989.

Butler, R.F., Harms, T.A., and Gabrielse, H., 1988, Cretaceous
remagnetization in the Sylvester Allochthon; limits to post-105 Ma
northward displacement of north-central British Columbia: Canadian
Journal of Earth Sciences, v. 25, p. 1316--1322.

Burns, L.E., 1985, The Border Ranges ultramafic and mafic complex,
south-central Alaska; cumulate fractionates of island-arc volcanics:
Canadian Journal of Earth Sciences, v. 22, p. 1020--1038.

Byalobzhesky, S.G., Kolyasnikov, Y.A., and Schmakin, V.B., 1986,
Tectonics of the active continental margin (Koyrak Upland): Magadan,
U.S.S.R. Academy of Sciences, Northeast Scientific Research Institute,
246 p. \[in Russian\].

Byalobzhesky, S.G., Korago, E.A., Lychagin, P.P., Kolyasnikov, Yu.A.,
and Likman, V.B., 1990, South Anyui zone; long-lived development of
folded structure, in Tectonics and metallogeny of U.S.S.R. Northeast:
Magadan, U.S.S.R. Academy of Sciences, p. 29--31 \[in Russian\].

Bychkov, Yu.M., and Kiseleva, L.S., 1990, Local subdivisions of the
Triassic in the upper Kolyma, Yana, and Tauy Rivers: Magadan, U.S.S.R.
Academy of Sciences, 55 p. \[in Russian\].

Bychkov, Yu.M., Byalobzhesky, S.G., and Petrov, A.N., 1990, First
findings of Early and Middle Jurassic fauna in the eastern Koryak
Highland: Akademii Nauk SSSR Doklady, v. 312, p. 1181--1189 \[in
Russian\].

Cant, D.J., 1989, Zuni sequence; the Foreland Basin, Lower Zuni
sequence; Middle Jurassic to Middle Cretaceous, in Ricketts, B.D., ed.,
Western Canada sedimentary basin; a case history: Calgary, Canadian
Society of Petroleum Geologists, p. 251--267.

Chikov, B.M., 1978, Median massifs and problems of tectonic zoning of
orogenic belts: Novosibirsk, Nauka, 249 p. \[in Russian\].

Churkin, M., Jr., and Carter, Claire, 1996, Stratigraphy, structure, and
graptolites of an Ordovician and Silurian sequence in the Terra Cotta
Mountains, Alaska Range, Alaska: U.S. Geological Survey Professional
Paper 1555, 84 p.

Clowes, R.M., Brandon, M.T., Green, A.G., Yorath, C.J., Sutherland
Brown, A., Kanasewich, E.R., and Spencer, C., 1987, LITHOPROBE-southern
Vancouver Island; Cenozoic subduction complex imaged by deep seismic
reflections: Canadian Journal of Earth Sciences, v. 24, p. 31--51.

Cluzel, D., 1990, Geodynamics of the Ogcheon Belt, South Korea:
Tectonophysics, v, 183, p. 41--56.

---------1991, Late Paleozoic to early Mesozoic geodynamic evolution of
the Circum-Pacific orogenic belt in Korea and southwest Japan: Earth and
Planetary Science Letters, v. 108, p. 289--305.

Cluzel, D., Lee, B.-J., and Cadet, J.-P., 1991, Indonesian
dextral-ductile fault system and synkinematic plutonism in the
southwestern Ogcheon belt, South Korea: Tectonophysics, v. 194, p.
131--151.

Coe, R.S., Globerman, B.R., Plumley, P.W., and Thrupp, G.A., 1985,
Paleomagnetic results from Alaska and their tectonic implications, in
Howell, D.G., ed., Tectonostratigraphic terranes of the Circum Pacific
Region (Earth Science Series, v. 1): Houston, Tex., Circum-Pacific
Council for Energy and Mineral Resources, p. 85--108.

Coe, R.S., Globerman, B.R., and Thrupp, G.A., 1988, Rotation of central
and southern Alaska in the early Tertiary; oroclinal bending by
megakink?, in Kissel, C., and Laj, C., eds., Paleomagnetic rotations and
continental deformation (NATO ser. C): Dordrecht, Holland, Kluwer
Academic Publications, p. 327--342.

Cohen, H.A., and Lundberg, N., 1993, Detrital record of the Gravina arc,
southeastern Alaska; petrology and provenance of Seymour Canal Formation
sandstones: Geological Society of America Bulletin, v. 105, p.
1400--1414.

Coney, P.J., Jones, D.L., and Monger, J.W.H., 1980, Cordilleran suspect
terranes: Nature, v. 288, p. 29--33.

Cook, D.B., Fujita, Kazuya, and McMullen, C.A., 1986, Present-day plate
interactions in northeast Asia; North American, Russian, and Okhotsk
plates: Journal of Geodynamics, v. 6, p. 33--51.

Cook, F.A., 1995, Lithospheric processes and products in the southern
Canadian Cordillera; a lithoprobe perspective: Canadian Journal of Earth
Sciences, v. 32, p. 1803--1824.

Cooper, A.K., Scholl, D.W., and Marlow, M.S., 1987, Structural
framework, sedimentary sequences, and hydrocarbon potential of the
Aleutian and Bowers Basins, Bering Sea, in Scholl, D.W., Grantz, Art,
and Vedder, J.G., eds., Geology and resource potential of the
continental margin of western North America and adjacent ocean
basins---Beaufort Sea to Baja California (Earth Science Series, v. 6):
Houston, Tex., Circum-Pacific Council for Energy and Mineral Resources,
p. 473--502.

---------1992, Evidence for Cenozoic crustal extension in the Bering Sea
region: Tectonics, v. 11, p. 719--731.

Cordey, F., Gordy, S., and Orchard, M.H., 1991, New biostratigraphic
data for the northern Cache Creek terrane, Teslin map area, in Current
research, part E: Geological Survey of Canada Paper 91--1E, p. 67--76.

Cordey, F., Mortimer, N., De Wever, P., and Monger, J.W.H., 1987,
Significance of Jurassic radiolarians from the Cache Creek terrane,
British Columbia: Geology, v. 15, p. 1151--1154

Cordey, F., and Schiarizza, P.F., 1993, Long-lived Panthalassic remnant;
the Bridge River accretionary complex, Canadian Cordillera: Geology, v.
21, p. 263--266.

Cowan, D.S., 1982, Geological evidence for post-40 m.y. B.P. large-scale
northwestward displacement of part of southeastern Alaska: Geology, v.
10, p. 309--313.

---------1994, Alternative hypotheses for the mid-Cretaceous
paleogeography of the western Cordillera: GSA Today, v. 4, no. 7, p.
181--186.

Cowan, D.S., Brandon, M.T., and Garver, J.I., 1997, Geologic tests for
large coastwise displacements---a critique illustrated by the Baja
British Columbia controversy: American Journal of Science, v. 297, p.
117--173.

Dagis, A.C., and Dagis, A.A., 1984, The Triassic system, in The
Phanerozoic of Siberia, the Mesozoic and Cenozoic: Novosibirsk, Nauka,
v. 2, p. 4--15 \[in Russian\].

Dagis, A.S., Arkhipov, Yu.U., and Bychkov, Yu.M., 1979, Stratigraphy of
the Triassic system in northeastern Asia: Moscow, Nauka, 243 p. \[in
Russian\].

Dalziel, I.W.D., 1991, Pacific margins of Laurentia and
East-Antarctica-Australia as a conjugate rift pair; evidence and
implications for an Eocambrian supercontinent: Geology, v. 19, p.
598--601.

Davis, G.A., Monger, J.W.H., and Burchfiel, B.D., 1978, Mesozoic
construction of the Cordilleran "collage," central British Columbia to
central California, in Howell, D.G., and McDougall, K.A., eds., Mesozoic
paleogeography of the western United States: Los Angeles, Society of
Economic Paleontologists and Mineralogists, Pacific Section, Pacific
Coast Paleogeography Symposium 2, p. 1--32.

Debari, S.M., and Coleman, R.G., 1989, Examination of the deep levels of
an island arc; evidence from the Tonsina ultramafic-mafic assemblage,
Tonsina, Alaska: Journal of Geophysical Research, v. 94, no. B, p.
4373--4391.

Decisions of the Fourth Interdepartmental Regional Meeting on
Precambrian and Phanerozoic of the Far East and Eastern Baikal Regions,
1994, Stratigraphic scheme of Jurassic deposits of southwestern
Primorye: Khabarovsk, Khabarovskoye Gosudarstvennoye
Gorno-Geologicheskoye Predpriyatiye, 31 tables \[in Russian\].

Decker, J., Bergman, S.C., Blodgett, R.B., Box, S.E., Bundtzen, T.K.,
Clough, J.G., Coonrad, W.L., Gilbert, W.G., Miller, M.L., Murphy, J.M.,
Robinson, M.S., and Wallace, W.K., 1994, Geology of southwestern Alaska,
in Plafker, George, and Berg, H.C., eds., The geology of Alaska (The
Geology of North America, v. G--1): Boulder, Colo., Geological Society
of America, p. 285--310.

Detterman, R.L., Miller, J.W., Case, J.E., Wilson, F.H., and Yount,
M.E., 1996, Stratigraphic framework of the Alaska Peninsula: U.S.
Geological Survey Bulletin 1969--A, 74 p.

Dickinson, W.R., 1979, Mesozoic fore-arc basin in central Oregon:
Geology, v. 7, p. 166--170.

Dickinson, W.R., and Butler, R.F., 1998, Coastal and Baja California
paleomagnetism reconsidered: Geological Society of America Bulletin, v.
110, p. 1268--1280.

Dickinson, W.R., and Thayer, T.P, 1978, Paleogeographic and
paleotectonic implications of Mesozoic stratigraphy and structure in the
John Day inlier of central Oregon, in Howell, D.G., and McDougall, K.A.,
eds., Mesozoic paleogeography of the western United States: Los Angeles,
Society of Economic Paleontologists and Mineralogists, Pacific Section,
Pacific Coast Paleogeography Symposium 2, p. 147--161.

Didenko, A., Harbert, W., and Stavsky, A., 1993, Paleomagnetism of
Khatyrian and Mayinsky terranes, Koryakian Highlands, northeast CIS:
Tectonophysics, v. 220, p. 141--156.

Didenko, A., and Pechersky, D., 1993, Revised Paleozoic apparent polar
wander paths for Eastern Europe, Siberia, Northern China, and Tarim
plates \[abs.\]: Russian Academy of Sciences L.P. Zonenshain Memorial
Conference on Plate Tectonics, Moscow, 1993, Abstracts with Program, p.
47.

Dobretsov, N.L., 1978, Glaucophane schist and eclogite-glaucophane
schist units of the U.S.S.R.: Novosibirsk, Nauka, 430 p. \[in Russian\].

Drachev, S.S., and Savostin, L.A., 1992, Dismembered ophiolitic
association of the New Siberian Islands; structural setting,
composition, and interpretation \[abs.\]: International Conference on
Arctic Margins, Anchorage, 1992, Program with Abstracts, p. 14.

Dudko, E.A., and Spektor, V.B., 1989, Northwestern continuation of the
South Anyui fold zone in the lower reaches of the Kolyma (according to
gravimetric and magnetometric data): Geologiya i Geofizika, no. 2, p.
21--31 \[in Russian\].

Dumoulin, J.A., 1988, Sandstone petrographic evidence and the
Chugach-Prince William terrane boundary in southern Alaska: Geology, v.
16, p. 456--460.

Dumoulin, J.A., Bradley, D.C., Harris, A.G., and Repetski, J.E., 1999,
Lower Paleozoic deep-water facies of the Medfra area, central Alaska, in
Kelley, K.D., ed., Geologic studies in Alaska by the U.S. Geological
Survey: U.S. Geological Survey Professional Paper 1614, p. 75--103.

---------1988, Sedimentology, conodont biogeography, and subsidence
history of the Nixon Fork terrane, Medfra quadrangle, Alaska \[abs.\]:
International Conference on Arctic Margins, 3d, Abstracts, p. 49.

Dumoulin, J.A., and Harris, A.G., 1987, Lower Paleozoic carbonate rocks
of the Baird Mountains quadrangle, western Brooks Range, Alaska, in
Tailleur, I.L., and Weimer, Paul, eds., Alaskan North Slope geology: Los
Angeles, Society of Economic Paleontologists and Mineralogists, Pacific
Section, and Alaska Geological Society, v. 50, p. 311--336.

Dusel-Bacon, Cynthia, Doyle, E.O., and Box, S.E., 1996, Distribution,
facies, ages, and proposed tectonic associations of regionally
metamorphosed rocks in southwestern Alaska and the Alaska Peninsula:
U.S. Geological Survey Professional Paper 1497--B, p. B1--B30.

Dusel-Bacon, Cynthia, and Hansen, V.L., 1992, High-pressure,
amphibolite-facies metamorphism and deformation within the Yukon-Tanana
and Taylor Mountain terranes, eastern Alaska, in Bradley, D.C., and
Dusel-Bacon, Cynthia, eds., Geological studies in Alaska by the U.S.
Geological Survey, 1991: U.S. Geological Survey Bulletin 2041, p.
140--159.

Engebretson, D.C., Cox, A., and Gordon, R.C., 1985, Relative motions
between oceanic and continental plates in the Pacific Basin: Geological
Society of America Special Paper 106, 59 p.

Engebretson, D.C., Kelley, K.P., Cashman, H.P., and Richards, M.A.,
1992, 180 million years of subduction: GSA Today, v. 2, p. 93--100.

England, P.C., and Wells, R.E., 1991, Neogene rotations and
quasicontinuous deformation of the Pacific Northwest continental margin:
Geology, v. 19, p. 978--981.

Erlikh, E.N., 1973, Modern structure and Quaternary volcanism of the
western Pacific realm: Novosibirsk, Nauka, 242 p. \[in Russian\].

Evenchick, C.A., 1991, Geometry, evolution, and tectonic framework of
the Skeena Fold Belt, north-central British Columbia: Tectonics, v. 10,
p. 527--546.

Ewing, T.E., 1980, Paleogene tectonic evolution of the Pacific
Northwest: Journal of Geology, v. 88, p. 619--638.

Faure, M., 1986, The Late Jurassic oblique collisional orogen of
southwestern Japan; new structural data and synthesis: Tectonics, v. 5,
p. 1089--1114.

Faure, M., and Natal'in, B.A., 1992, The geodynamic evolution of eastern
Eurasian margin in Mesozoic times: Tectonophysics, v. 208, p. 397--411.

Fedorchuk, A.V., Tsukanov, N.V., Efremova, L.B., and Savichev, A.T.,
1990, Oceanic magmatism of the Kumroch Range (eastern Kamchatka):
Geokhimiya, no. 12, p. 1721--1729 \[in Russian\].

Fernette, Gregory, and Cleveland, Gregory, 1984, Geology of the Miss
Molly molybdenum prospect, Toyonek C--6 quadrangle, Alaska: Alaska
Division of Geological and Geophysical Surveys Professional Report 86,
p. 35--41.

Filatova, N.I., 1979, Cretaceous-Paleogene volcanism of the transition
zone between the Verkhoyansk-Chukotka and Koryak-Kamchatka regions:
Geotektonika, no. 5, p. 67--82 \[in Russian\].

---------1988, Circum-oceanic volcanic belts: Moscow, Nedra, 264 p. \[in
Russian\].

Fisher, R.A., 1953, Dispersion on a sphere: Royal Society of London
Proceedings, ser. A, v. 217, p. 295--305.

Fitch, T.J., 1972, Plate convergence, transcurrent faults, and internal
deformation adjacent to southeast Asia and western Pacific: Journal of
Geophysical Research, v. 77, no. B, p. 4432--4460.

Flueh, E., Fisher, M., Scholl, D., Parsons, T., ten Brink, Uri,
Klaeschen, D., Kukowski, N., Trehu, A., Childs, J., Bialas, J., and
Vidal, N., 1997, Scientific teams analyze earthquake hazards of the
Cascadia subduction zone: Eos (American Geophysical Union Transactions),
v. 78, p. 153, 157.

Foster, H.L., Keith, T.E.C., and Menzie, W.D., 1994, Geology of the
Yukon-Tanana area of east-central Alaska, in Plafker, George, and Berg,
H.C., eds., The geology of Alaska (The Geology of North America, v.
G--1): Boulder, Colo., Geological Society of America, p. 205--240.

Fryda, Jiri, and Blodgett, R.B., 1998, Two new Cirroidean genera
(Vetigastropoda, Archaeogastropoda) from the Emsian (late Early
Devonian) of Alaska with notes on the early phylogeny of Cirroidea:
Journal of Paleontology, v. 72, p. 265--273.

Fujita, Kazuya, Cambray, F.W., and Velbel, M.A., 1990a, Tectonics of the
Laptev Sea and Moma rift systems, northeastern U.S.S.R.: Marine Geology,
v. 93, p. 95--118.

Fujita, Kazuya, and Cook, D.B., 1990, The Arctic continental margin of
eastern Siberia, in Grantz, Art, Johnson, L., and Sweeney, J.F., eds.,
The Arctic Ocean region (The Geology of North America, v. L): Boulder,
Colo., Geological Society of America, p. 289--304.

Fujita, Kazuya, Cook, D.B., Hasegawa, H., Forsyth, D., and Wetmiller,
R., 1990b, Seismicity and focal mechanisms of the Arctic region and the
North American plate boundary in Asia, in Grantz, Art, Johnson, L., and
Sweeney, J.F., eds., The Arctic Ocean region (The Geology of North
America, v. L): Boulder, Colo., Geological Society of America, p.
79--100.

Fujita, Kazuya, Stone, D.B., Layer, P.W., Parfenov, L.M., and Koz'min,
B.M., 1997, Cooperative program helps decipher tectonics of northeastern
Russia: Eos (American Geophysical Union Transactions), v. 78, p. 245,
252--253.

Fujiwara, Y., and Ohtake, T., 1975, Paleomagnetism of Late Cretaceous
alkaline rocks in the Nemuro Peninsula: Journal of Geomagnetism and
Electricity, v. 26, p. 549--558.

Gabrielse, H., 1985, Major dextral transcurrent displacements along the
Northern Rocky Mountain Trench and related lineaments in north-central
British Columbia: Geological Society of America Bulletin, v. 96, p.
1--14.

---------1991, Late Paleozoic and Mesozoic terrane interactions in
north-central British Columbia: Canadian Journal of Earth Sciences, v.
28, p. 947--957.

Gabrielse, H., and Yorath, C.J., eds., 1991, Geology of the Cordilleran
Orogen, Canada (Geology of Canada, no. 4): Geological Survey of Canada,
844 p. \[also Boulder, Colo., Geological Society of America, The geology
of North America, v. G--2, 844 p.\].

Gaiduk, V.V., 1988, The middle Paleozoic Vilyui rift system: U.S.S.R.
Academy of Sciences, Yakutian Scientific Center, 127 p. \[in Russian\].

Gaiduk, V.V., Grinenko, O.V., and Syundyukov, I.Sh., 1993, Age of
folding in the Moma Zyryanka basin: Tikhookeanskaya Geologiya, no. 3, p.
99--108 \[in Russian\].

Gaiduk, V.V., Syundyukov, I.Sh., Grinenko, O.V., and Imaev, V.S., 1989,
Structure and oil and gas potential of the Cenozoic Indigirka-Zyryanka
Basin; tectonics and oil and gas prospecting in Yakutia: U.S.S.R.
Academy of Sciences, Yakutian Scientific Center, p. 75--87 \[in
Russian\].

Gardner, M.C., Bergman, S.C., Cushing, G.W., Mackevett, E.M., Jr.,
Plafker, George, Campbell, R.B., Dodds, C.J., McClelland, W.C., and
Mueller, P.A., 1988, Pennsylvanian pluton stitching of Wrangellia and
the Alexander Terrane, Wrangell Mountains, Alaska: Geology, v. 16, p.
967--971.

Garver, J.I., 1992, Provenance of Albian-Cenomanian rocks of the Methow
and Tyaughton Basins, southern British Columbia; a mid-Cretaceous link
between North America and Insular terranes: Canadian Journal of Earth
Sciences, v. 96, p. 1--14.

Garver, J.I., Brandon, M.T., and Soloviev, A.V., 1998, Source of
Ukelayat flysch and collision of the Olutorsky arc, northern Kamchatka,
Russian Far East \[abs.\]: Geological Society of America Abstracts with
Programs, v. 30, p. A269.

Gehrels, G.E., and Berg, H.C., 1992, Geologic map of southeastern
Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map
I--1867, 24 p., scale 1:600,000.

---------1994, Geology of southeastern Alaska, in Plafker, George, and
Berg, H.C., eds., The geology of Alaska (The Geology of North America,
v. G--1): Boulder, Colo., Geological Society of America, p. 451--468.

Gehrels, G.E., McClelland, W.C., Samson, S.D., and Patchett, P.J., 1991,
U-Pb geochronology of detrital zircons from a continental margin
assemblage in the northern Coast Mountains, southeastern Alaska:
Canadian Journal of Earth Sciences, v. 28, p. 1285--1300.

Gehrels, G.E., McClelland, W.C., Samson, S.D., Patchett, P.J., and
Jackson, J.L., 1990, Ancient continental margin assemblage in the
northern Coast Mountains, southeast Alaska and northwest Canada:
Geology, v. 18, p. 208--211.

Gehrels, G.E., and Saleeby, J.B., 1987, Geologic framework, tectonic
evolution, and displacement history of the Alexander terrane: Tectonics,
v. 6, p. 151--173.

Geist, E.L., Childs, J.R., and Scholl, D.W., 1988, The origin of the
summit basins of the Aleutian Ridge; implications for block rotation of
an arc massif: Tectonics, v. 7, p. 327--341.

Geist, E.L., Vallier, T.L., and Scholl, D.W., 1994, Origin, transport,
and emplacement of an exotic island-arc terrane exposed in eastern
Kamchatka, Russia: Geological Society of America Bulletin, v. 106, p.
1182--1194.

Geology of the U.S.S.R., 1970, Sakhalin Island: Moscow, Nedra, v. 33,
430 p. \[in Russian\].

Gilbert, W.G., and Bundtzen, T.K., 1984, Stratigraphic relationships
between Dillinger and Mystic terranes, western Alaska Range, Alaska
\[abs.\]: Geological Society of America Abstracts with Programs, v. 16,
p. 286.

Ghosh, D.K., 1995, Nd-Sr isotopic constraints on the interactions of the
Intermontane superterrane with the western edge of North America in the
southern Canadian Cordillera: Canadian Journal of Earth Sciences, v. 32,
p. 1740--1758.

Globerman, B.R., and Coe, R.S., 1983, Paleomagnetic results from Upper
Cretaceous volcanic rocks in northern Bristol Bay, southwest Alaska, and
tectonic implications, in Howell, D.G., Jones, D.L., Cox, A., and Nur,
A., eds., Proceedings of the Circum-Pacific Terrane Conference:
Stanford, Calif., Stanford University Publications in Geological
Sciences, p. 98--102.

Gnibidenko, G.S., Bykova, T.G., Veselov, O.V., Vorob'ev, V.M., Kim, Chun
Un, and Tarakanov, R.Z., 1980, Tectonics of the Kuril-Kamchatka trench:
Moscow, Nauka, 179 p. \[in Russian\].

Gnibidenko, G.S., and Khnedchuki, I.I., 1982, The tectonics of the
Okhotsk Sea: Marine Geology, v. 50, p. 155--198.

Gnibidenko, G.S., and Svarichevsky, A.S., 1984, Tectonics of the South
Okhotsk deep-sea basin: Tectonophysics, v. 102, p. 225--244.

Goldfinger, C., Kulm, L.D., Yeats, R.S., McNeill, L.C., and Hummon, C.,
1997, Oblique strike-slip faulting of the central Cascadia submarine
forearc: Journal of Geophysical Research, v.102, no. B, p. 8217--8243.

Goldfinger, C., McNeil, L.C., Kulm, L.D., and Yeats, R.S., 1996, Width
of the seismogenic plate boundary in Cascadia; structural indicators of
strong and weak coupling \[abs.\]: Geological Society of America
Abstracts with Programs, v. 28, p. 69.

Golionoko, B.G., 1992, Structural and geological development of the
southern Kuril Island arc from the Late Cretaceous to Miocene in
connection with the subduction of the Pacific plate: Moscow, Russian
Academy of Sciences, Geological Institute, summary of Candidate of
Science thesis, 23 p. \[in Russian\].

Golozubov, V.V., and Khanchuk, A.I., 1996, Taukha and Zhuravlevka
terranes of the South Sikhote Alin---fragments of the Early Cretaceous
margin of Asia: Geology of Pacific Ocean, v. 12, p. 203--220.

Golozubov, V.V., Khanchuk, A.I., Kemkin, I.V., Panchenko, I.V., and
Simanenko, V.P., 1992, Taukha and Zuravlevka terranes of South
Sikhote-Alin: Vladivostok, U.S.S.R. Academy of Sciences, 83 p. \[in
Russian\].

Golozubov, V.V., and Melnikov, N.G., 1986, Tectonics of geosynclinal
complexes of the South Sikhote-Alin: Vladivostok, U.S.S.R. Academy of
Sciences, Far East Branch, 128 p.

Govorov, I.N., Golubeva, E.D., and Pushchin, I.K., 1996, Pacific
petrological provinces: Moscow, Nauka, 444 p.

Grantz, Art, Clark, D.L., Phillips, R.L., and Srivastava, S.P., 1998,
Phanerozoic stratigraphy of Northwind Ridge, magnetic anomalies in the
Canada Basin, and the geometry and timing of rifting in the Amerasia
basin, Arctic Ocean: Geological Society of America Bulletin, v. 110, p.
801--820.

Grantz, Art, Mayh, S.D., and Hart, P.E., 1990, Geology of the Arctic
continental margin of Alaska, in Grantz, Art, Johnson, L., and Sweeney,
J.F., eds., The Arctic Ocean region (The Geology of North America, v.
L): Boulder, Colo., Geological Society of America, p. 257--288.

Grantz, Art, Moore, T.E., and Roeske, S.M., 1991, Transect A--3; Gulf of
Alaska to Arctic Ocean: Geological Society of America, Centennial
Continent/Ocean Transect, no. 15, 3 sheets, scale 1:500,000.

Grapes, R., 1986, Mesozoic arc-trench development and Cenozoic orogeny
of the North-West Pacific rim with special reference to Hokkaido: Osaka,
Association for Geological Collaboration in Japan Monograph 31, p.
419--439.

Greninger, M.L., Klemperer, S.L., and Nokleberg, W.J., 1999, Geographic
information systems (GIS) compilation of geophysical, geologic, and
tectonic data for the Circum-North Pacific: U.S. Geological Survey
Open-File Report 99--422, CD--ROM.

Grigor'yev, V.N., Krylov, K.A., and Sokolov, S.D., 1987,
Jurassic-Cretaceous deposits of the Yanranaysk accretionary complex, in
Essays on geology of northwestern sector of the Pacific tectonic belt:
Moscow, Nauka, p. 110--140 \[in Russian\].

Grinberg, G.A., Gusev, G.S., Bakharev, A.G., 1981, Tectonics, magmatic,
and metamorphic complexes of the Kolyma-Omolon Massif: Moscow, Nauka,
400 p. \[in Russian\].

Grommé, S., and Hillhouse, J.W., 1997, Paleomagnetic results from
Devonian and Permian rocks at Saginaw Bay, Kuiu Island, southeastern
Alaska: U.S. Geological Survey Professional Paper 1574, p. 295--306.

Hackett, D.J., Layer, P.W., Fujita, Kazuya, and Parfenov, L.M., 1992,
Geochronology of granites in the Cherski Range, Yakutia, and
implications for accretion of terranes to the Siberian craton \[abs.\]:
Eos (American Geophysical Union Transactions), v. 73, p. 652.

Haeussler, P.J., 1992, Structural evolution of an arc-basin; the Gravina
belt in central southeastern Alaska: Tectonics, v. 11, p. 1245--1265.

Haeussler, P.J., Coe, R.S., and Onstott, T.C., 1992a, Paleomagnetism of
the Late Triassic Hound Island volcanics revisited: Journal of
Geophysical Research, v. 97, no. B, p. 19617--19640.

Haeussler, P.J., Coe, R.S., and Renne, P., 1992b, Paleomagnetism and
geochronology of 23-Ma gabbroic intrusions in the Keku Strait, Alaska,
and implications for the Alexander terrane: Journal of Geophysical
Research, v. 97, no. B, p. 19641--19651.

Halgedahl, S.L., and Jarrard, R.D., 1987, Paleomagnetism of the Kuparuk
River Formation from oriented drill core; evidence for rotation of the
Arctic Alaska Plate, in Tailleur, I.L., and Weimer, Paul, eds., Alaskan
North Slope geology: Los Angeles, Society of Economic Paleontologists
and Mineralogists, Pacific Section, and Alaska Geological Society, v. 2,
p. 581--620.

Hamilton, William, 1969, Mesozoic California and the underflow of
Pacific mantle: Geological Society of America Bulletin, v. 80, p.
2409--2430.

Hansen, V.L., Goodge, J.W., Keep, M., and Oliver, D.H., 1993, Asymmetric
rift interpretation of the western North American margin; Geology, v.
21, p. 1067--1070.

Hansen, V.L., Radloff, J.K., and Hart, C.J.R., 1990, Tally Ho shear
zone, southern Yukon; kinematic evolution and tectonic implications
\[abs.\]: Geological Association of Canada Annual Meeting Program with
Abstracts, v. 15, p. 53--54.

Harbert, W., 1987, New paleomagnetic data from the Aleutian Islands;
implication for terrane migration and deposition of the Zodiac Fan:
Tectonics, v. 6, p. 585--602.

Harbert, W.P., Cox, A., and McLean, H., 1984, Paleomagnetism of Starr
Point and Driftwood Bay, Umnak Island, Alaska \[abs.\]: Eos (American
Geophysical Union Transactions), v. 65, p. 869.

Harbert, W., Frei, L., Jarrad, R., Halgedahl, S., and Engebretson, D.C.,
1990, Paleomagnetic and plate-tectonic constraints on the evolution of
the Alaska-eastern Siberian Arctic, in Grantz, Art, Johnson, L., and
Sweeney, J.F., eds., The Arctic Ocean region (The Geology of North
America, v. L): Boulder, Colo., Geological Society of America, p.
567--592.

Harms, T.A., 1986; Structural and tectonic analysis of the Sylvester
Allochthon, southwest McDame map-area, northern British Columbia:
implications for paleogeography and accretion: Tucson, University of
Arizona, Ph.D. thesis, 114 p.

Harms, T.A., Nelson, J., and Bradford, J., 1988, Geological transect
across the Sylvester allochthon, north of the Blue River, northern
British Columbia, in Geological fieldwork, 1987: British Columbia
Ministry of Energy, Mines, and Petroleum Resources Paper 1988--1, p.
245--248.

Harris, N.R., Sisson, V.B., Wright, J.E., and Pavlis, T.L., 1996,
Evidence for Eocene mafic underplating during fore-arc intrusive
activity, eastern Chugach Mountains, Alaska: Geology, v. 24, p.
263--266.

Harris, R.A., 1985, Paleomagnetism, geochronology and paleotemperature
of the Yukon-Koyukuk province, Alaska: Fairbanks, University of Alaska,
M.S. thesis, 145 p

Harris, R.A., Stone, D.B. and Turner, D.L., 1986, Tectonic implications
of paleomagnetic and geochronologic data from the Yukon-Koyukuk
province, Alaska: Geological Society of America Bulletin, v. 99, p.
362--375.

Hart, C.J.R., 1995, Sinistral translation of accreted terranes; yo-yo
tectonics in the Canadian Cordillera \[abs.\]: Geological Association of
Canada Annual Meeting Program with Abstracts, v. 20, p. 43.

Heiphitz, A., Harbert, W., and Layer, P., 1994b, Preliminary
reconnaissance paleomagnetism of some late Mesozoic ophiolites, Kuyul
region, Koryak superterrane, Russia, in Thurston, D., and Fujita,
Kazuya, eds., Proceedings of 1994 International Conference on Arctic
Margins: Anchorage, U.S. Minerals Management Service, p. 229--234.

Heiphitz, A., Harbert, W., and Savostin, L.A., 1994a, Reconnaissance
paleomagnetism of the Olyutorsky superterrane, northeast Russia, in
Thurston, D., and Fujita, Kazuya, eds., Proceedings of 1994
International Conference on Arctic Margins: Anchorage, U.S. Minerals
Management Service, p. 223--228.

Heller, P.L., Tabor, R.W., O'Neil, J.R., Pevear, D.R., Shafiqullah, M.,
and Winslow, N., 1992, Isotopic provenance of Paleogene sandstones from
the accretionary core of the Olympic Mountains, Washington: Geological
Society of America Bulletin, v. 104, p. 140--153.

Hicken, A., and Irving, E., 1977, Tectonic rotation in western Canada:
Nature, v. 268, p. 219--220.

Hillhouse, J.W., 1977, Paleomagnetism of the Triassic Nikolai
Greenstone, McCarthy quadrangle, Alaska: Canadian Journal of Earth
Science, v. 14, p. 2578--2592.

Hillhouse, J.W., and Grommé, C.S., 1982, Limits to northward drift of
the Paleocene Cantwell formation, central Alaska: Geology, v. 10, p.
552--566.

---------1984, Northward displacement and accretions of Wrangellia; new
paleomagnetic evidence from Alaska: Journal of Geophysical Research, v.
89, no. B, p. 4461--4477.

---------1988, Early Cretaceous paleolatitude of the Yukon-Koyukuk
province: Journal of Geophysical Research, v. 93, no. D, p.
11735--11752.

Hillhouse, G.W., Grommé, C.S., and Csejtey, Béla, Jr., 1984,
Paleomagnetism of early Tertiary volcanic rocks in the northern
Talkeetna Mountains, in Howell, D.G., Jones, D.L., Cox, A., and Nur, A.,
eds., Proceedings of the Circum-Pacific Terrane Conference: Stanford
University Publications in Geological Sciences, p. 111--114.

---------1985, Tectonic implications of paleomagnetic poles from Lower
Tertiary volcanic rocks, south-central Alaska: Journal of Geophysical
Research, v. 90, no. B, p. 12523--12535.

Himmelberg, G.R., Brew, D.A., and Ford, A.B., 1985, Ultramafic bodies in
the Coast plutonic-metamorphic complex near Skagway, southeastern
Alaska, in Bartsch-Winkler, Susan, ed., The United States Geological
Survey in Alaska; accomplishments during 1984: U.S. Geological Survey
Circular 967, p. 92--93.

Hoare, J.M., and Coonrad, W.L., 1978, Geologic map of the Goodnews and
Hagemeister Island quadrangles region, southwestern Alaska: U.S.
Geological Survey Open-File Report 78--9--B, scale 1:250,000.

---------1979, The Kanektok metamorphic complex, a rootless belt of
Precambrian rocks in southwestern Alaska, in Johnson, K.M., and
Williams, J.R., eds., The United States Geological Survey in Alaska;
accomplishments during 1978: U.S. Geological Survey Circular 804--B, p.
B72--B74.

Hoare, J.M., Conden, W.H., Cox, A., and Dalrymple, G.B., 1968, Geology,
paleomagnetism and K-Ar ages of basalts from Nunivak Island, Alaska:
Geological Society of America Memoir 116, p. 337--413.

Hoffman, P.F., 1989, Precambrian geology and tectonic history of North
America, in Bally, A.W., and Palmer, A.R., eds., The geology of North
America---an overview: Boulder, Colo., Geological Society of America, v.
A, p. 447--512.

---------1991, Did the breakout of Laurentia turn Gondwanaland
inside-out?: Science, v. 252, p. 1409--1412.

Hooper, P.R., 1982, The Columbia River Basalts: Science, v. 215, p.
1463--1468.

Hooper, P.R., and Conrey, R.M., 1989, A model for the tectonic setting
of the Columbia River Basalt eruptions, in Reidel, S.P., and Hooper,
P.R., eds., Volcanism and tectonism in the Columbia River flood-basalt
province: Geological Society of America Special Paper 239, p. 293--306.

Howell, D.G., Jones, D.L., and Schermer, E.R., 1985,
Tectonostratigraphic terranes of the Circum-Pacific region: principles
of terrane analysis, in Howell, D.G., ed., Tectonostratigraphic terranes
of the Circum-Pacific region (Earth Science Series, v. 1): Houston,
Tex., Circum-Pacific Council for Energy and Mineral Resources, p. 3--31.

Hudson, T., 1979, Mesozoic plutonic belts of southern Alaska: Geology,
v. 7, p. 230--234.

Ichikawa, K., Mizutani, S., Hara, I., Hada, S., and Yao, A., eds., 1990,
Pre-Cretaceous terranes of Japan in Pre-Jurassic Evolution of eastern
Asia: Osaka, International Geologic Correlations Project Publication
224, 413 p.

Imaev, V.S., 1991, Late Cenozoic overthrusts, reverse faults, and folded
dislocations of the Chersky seismic belt (eastern Yakutia):
Geotectonics, v. 25, p. 356--361.

Imaev, V.S., Imaeva, L.P., and Koz'min, B.M., 1990, Active faults and
seismotectonics of northeast Yakutia: Yakut Science Center, Yakutsk, 138
p. \[in Russian\].

Ingle, J.C., Karig, D.E., and Bouma, A.N., 1975, Leg 31: Deep Sea
Drilling Project Initial Reports, v. 31, p. 351--439.

Iosifidi, A.G., 1989, Paleomagnetic directions and pole positions; data
for the USSR-Soviet Geophysical Committee: Moscow, World Data Center-B,
Catalog, no. 7, as quoted in Lock and McElhinny (1991).

Irving, E., and Archibald, D.A., 1990, Bathozonal tilt corrections to
paleomagnetic data from mid-Cretaceous plutonic rocks; examples from the
Omineca Belt, British Columbia: Journal of Geophysical Research, v. 95,
no. B, p. 4579--4586.

Irving, E., and Brandon, M.T., 1990, Paleomagnetism of the Flores
volcanics, Vancouver Island, in place by Eocene time: Canadian Journal
of Earth Sciences, v. 27, p. 811--817.

Irving, E., and Irving, G.A., 1982, Apparent polar wander paths,
Carboniferous through Cenozoic, and the assembly of Gondwana:
Geophysical Surveys, v. 5, p. 141--188.

Irving, E., and Monger, J.W.H., 1987, Preliminary results from the
Permian Asitka Group, British Columbia: Canadian Journal of Earth
Sciences, v. 24, p. 1490--1497.

Irving, E., and Thorkelson, D.J., 1990, On determining paleohorizontal
and latitudinal shifts; paleomagnetism of Spences Bridge Group, British
Columbia: Journal of Geophysical Research, v. 95, no. B, p.
19213--19234.

Irving, E., Thorkelson, P.M., Wheadon, P.M., and Enkin, R.J., 1995,
Paleomagnetism of the Spences Bridge Group and northward displacement of
the Intermontane Belt, British Columbia; a second look: Journal of
Geophysical Research, v. 100, no. B, p. 6075--6071.

Irving, E., Woodsworth, G.J., Wynne, P.J., and Morrison, A., 1985,
Paleomagnetic evidence for displacement from the south of the Coast
Plutonic Complex, British Columbia: Canadian Journal of Earth Sciences,
v. 22, p. 584--598.

Irving, E., and Wynne, P.J., 1990, Paleomagnetic evidence bearing on the
evolution of the Canadian Cordillera: Royal Philosophical Society of
London Transactions, v. A331, p. 487--509.

---------1991, Paleomagnetism; review and tectonic implications, chap. 3
of Gabrielse, H., and Yorath, C.J., eds., Geology of the Cordilleran
orogen, Canada (Geology of Canada, no. 4): Geological Survey of Canada,
p. 63--86 \[also Boulder, Colo., Geological Society of America, The
Geology of North America, v. G--2, p. 63--86\].

Irving, E., Wynne, P.J., Thorkelsen, D.J., and Schiarrizza, P., 1996,
Large (1000 to 4000 km) northward movements of tectonic domains in the
Northern Cordillera, 83 to 34 Ma: Journal of Geophysical Research, v.
101, no. B, p. 17901--17916.

Irving, E., and Yole, R.W., 1987, Tectonic rotations and translations in
western Canada: new evidence from Jurassic rocks of Vancouver Island:
Royal Astronomical Society Geophysical Journal, v. 91, p. 1025--1048.

Isacks, B., 1988, Uplift of the central Andean plateau and bending of
the Bolivian orocline: Journal of Geophysical Research, v. 93, no. B, p.
3211--3231.

Ivanov, V.V., Klubev, B.A., Lozhkina, N.V., and Pokhialainen, V.P.,
1977, Stratigraphy and paleomagnetic characteristics of the upper
Jurassic and lower Cretaceous deposits of Stolbovoi Island
(Novosibirskiy Archipelago): Geologiya i Geofizika, v. 18, p. 84--89.

Iwata, K., and Tajika, J., 1986, Late Cretaceous radiolarians of the
Yubetsu Group, Tokoro Belt, northeast Hokkaido, Japan: Hokkaido
University: Journal of the Faculty of Science: ser. 4, v. 21, p.
619--644.

Jarrad, R.D., 1986, Relations among subduction parameters: Reviews of
Geophysics, v. 24, p. 217--284.

Jones, D.L., Coney, P.J., Harms, T.A., and Dillon, J.T., 1988,
Interpretive geologic map and supporting radiolarian data from the
Angayucham terrane, Coldfoot area, southern Brooks Range, Alaska: U.S.
Geological Survey Miscellaneous Field Studies Map MF--1993, scale
1:63,360.

Jones, D.L., Howell, D.G., Coney, P.J., and Monger, J.W.H., 1983,
Recognition, character, and analysis of tectonostratigraphic terranes in
western North America, in Hashimoto, M., and Uyeda, S., eds., Accretion
tectonics in the circum-Pacific region: proceedings of the Oji
International Seminar on Accretion Tectonics, Japan, 1981: Tokyo, Terra
Scientific Publishing Co., Advances in Earth and Planetary Sciences, p.
21--35.

Jones, D.L., Silberling, N.J., Berg, H.C., and Plafker, George, 1981,
Map showing tectonostratigraphic terranes of Alaska, columnar sections,
and summary description of terranes: U.S. Geological Survey Open-File
Report 81--792, 20 p., 2 sheets, scale 1:2,500,000.

Jones, D.L., Silberling, N.J., Coney, P.J., and Plafker, George, 1984,
Lithotectonic terrane map of Alaska, in Silberling, N.J., and Jones,
D.L., eds., Lithotectonic terrane maps of the North American Cordillera:
U.S. Geological Survey Open-File Report 84--523, p. A1--A12, scale
1:2,500,000.

Jones, D.L., Silberling, N.J., Coney, P.J., and Plafker, George, 1987,
Lithotectonic terrane map of Alaska (west of the 141st Meridian): U.S.
Geological Survey Miscellaneous Field Studies Map MF--1874--A, scale
1:2,500,000.

Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1977, Wrangellia---a
displaced terrane in northwestern North America: Canadian Journal of
Earth Sciences, v. 14, p. 2565--2577.

Journeay, J.M., and Friedman, R.M., 1993, The Coast Belt thrust system:
evidence of Late Cretaceous shortening in southwest British Columbia:
Tectonics, v. 12, p. 756--775.

Journeay, J.M., and Northcote, B.R., 1992, Tectonic assemblages of the
eastern Coast Belt, southwest British Columbia, in Current research,
part A: Geological Survey of Canada Paper 92--1A, p. 215--224.

Kanygin, A.V., 1967, Ordovician ostracodes from the Chersky Range:
Moscow, Nauka, 152 p. \[in Russian\].

---------1977, Ordovician ostracodes of Chukotka Peninsula: Stratigraphy
and fauna of the Ordovician and Silurian in Chukotka peninsula:
Novosibirsk, Nauka, p. 73--86 \[in Russian\].

Karl, S., and Hoare, J.M., 1979, Results of a preliminary paleomagnetic
study of volcanic rocks from Nuyakuk Lake, southwestern Alaska, in
Johnson, K.M., and Williams, J.R., The United States Geological Survey
in Alaska; accomplishments in 1978: U.S. Geological Survey Circular
804--B, p. B74--B78.

Karlstrom, K.E., Williams, M.L., McLelland, J., Geissman, J.W., and
Ahall, K., 1999, Refining Rodinia; geologic evidence for the
Australia-Western U.S. connection in the Proterozoic: GSA Today, v. 9,
p. 1--7.

Kashik, D.S., Ganelin, V.G., Karavaeva, N.I., Byakov, A.S.,
Miclukhho-Maclay, O.A., Stukalina, G.A., Lozhkina, N.V., Dorofeeva,
L.A., Burkov, J.K., Guteneva, E.I., and Smirnova, L.N., 1990, A key
Permian section of the Omolon massif: Leningrad, Nauka, p. 198.

Kato, T., and Nakagawa, M., 1986, Tectogenesis of ultramafic rocks in
the Kamuikotan tectonic belt, Hokkaido, Japan: Osaka, Association for
Geological Collaboration in Japan Monograph 31, p. 119--135 \[in
Japanese with English abstract\].

Kazimirov, A.D., 1985, Nappes of the eastern Koryak Highland and their
structural and formational homologues: Moscow, Nauka, 112 p. \[in
Russian\].

Keith, T.E., Foster, H.L., Foster, R.L., Post, E.V., and Lehmbeck, W.L.,
1981, Geology of an alpine-type peridotite in the Mount Sorenson area,
east-central Alaska: U.S. Geological Survey Professional Paper 1170--A,
9 p.

Kepezhinskas, P.K., Reuber, I., Tanaka, H., and Miyashita, S., 1993,
Zoned calc-alkaline plutons in northeastern Kamchatka, Russia;
implications for the crustal growth in magmatic arcs: Mineralogy and
Petrology, v. 49, p. 147--174.

Khanchuk, A.I., 1993, Geologic setting and evolution of the northwest
Pacific continental framework: Moscow, Russian Academy of Sciences,
Geological Institute, summary of Ph.D. thesis, 31 p. \[in Russian\].

Khanchuk, A.I., Golozubov, V.V., Panchenko, I.V., Ignatiev, A.V., and
Chudaev, O.V., 1992, Ganychalan terrane of the Koryak Highland: Pacific
Geology, no. 4, p. 84--93.

Khanchuk, A.I., Grigorev, V.I., Golozubov, V.V., Govorov, G.I., Krylov,
K.A., Kurnosov, V.I., Panchenko, I.V., Prainikova, I.E., and Chudaev,
O.V., 1990, Kuyul Ophiolite terrane: Vladivostok, Russian Academy of
Sciences, Far East Branch, 108 p. \[in Russian\].

Khanchuk, A.I., Ognyanov, A.V., Popova, I.M., and Philippov, A.N., 1994,
New data on Early Cretaceous deposits of the Lower Priamurye: Rossiiskoi
Academii Nauk Doklady, v. 338, no. 5, p. 667--671 \[in Russian\].

Khanchuk, A.I., Panchenko, I.V., and Kemkin, I.V., 1988, Paleozoic and
Mesozoic geodynamic evolution of the Sikhote Alin area and Sakhalin
Island: U.S.S.R. Academy of Sciences, Vladivostok, 56 p. \[in Russian\].

Khanchuk, A.I., Ratkin, V.V., Ryazantseva, M.D., Golozubov, V.V., and
Gonokhova, N.B., 1996, Geology and mineral deposits of Primorsky Krai
(territory): Vladivostok, Russian Academy of Sciences, Geological
Institute, Far East Branch, Dalnauka, 61 p.

Khramov, A.N., 1971, Paleomagnetic directions and pole positions; data
for the USSR: Moscow, Soviet Geophysical Committee, World Data Center-B,
no. 1, as quoted in Lock and McElhinny (1991).

---------1979, Paleomagnetic directions and pole positions; data for the
USSR: Moscow, Soviet Geophysical Committee, World Data Center-B, no. 4,
as quoted in Lock and McElhinny (1991).

---------1984, Paleomagnetic directions and pole positions: data for the
USSR: Moscow, Soviet Geophysical Committee, World Data Center-B, no. 1,
94 p. \[in Russian\].

---------1986a, Paleomagnetic directions and pole positions: data for
the USSR: Soviet Geophysical Committee: Moscow, World Data Center-B, no.
6, as quoted in Lock and McElhinny (1991).

---------ed., 1986b, Paleomagnetic directions and pole positions. data
for the USSR: Moscow, Soviet Geophysical Committee World Data Center-B,
no. 6, 38 p. \[in Russian\].

Khramov, A.N., Gurevich, E.L,. Komissarova, R.A., Osipova, E.P.,
Pisarevsky, S.A., Rodioniv, V.P., and Slautsitais, I.P., 1985,
Paleomagnetism, microplates, and Siberian plate consolidation: Journal
of Geodynamics, v. 2, p. 127--139.

Khubunaya, S.A., 1981, Nature of basalt of the Kronotskiy Peninsula
(eastern Kamchatka): Vulkanologiya i Seismologiya, no. 2, p. 36--48 \[in
Russian\].

Khudoley, A.K., and Sokolov, S.D., 1998, Structural evolution of the
northeast Asian continental margin: an example from the western Koryak
fold and thrust belt (northeast Russia): Geological Magazine, v. 135, p.
311--330.

Kiminami, K., and Kontani, Y., 1983, Mesozoic arc trench system in
Hokkaido, Japan, in Hashimoto, M., and Uyeda, S., eds., Accretion
tectonics in Circum-Pacific regions: Tokyo, Terra Educational Publishing
Co., p. 107--122.

Kimura, G., and Tamaki, K., 1986, Collision, rotation and back-arc
spreading; the case of the Okhotsk and Japan Seas: Tectonics, v. 5, p.
389--401.

Kirillova, G.L., and Makhinin, A.V., 1983, Classification of geologic
objects and organization of matter: Tikhookeanskaya Geologiya, no. 3, p.
73--80 \[in Russian\].

Kirillova, G.L., and Turbin, M.T., 1979, Formations and tectonics of the
Dzhagdinsk Zone of the Mongol-Okhotsk foldbelt: Moscow, Nauka, 114 p.
\[in Russian\].

Klepacki, D.W., 1983, Stratigraphic and structural relations of the
Milford, Kaslo, and Slocan groups, Roseberry Quadrangle, Lardeau
map-area, British Columbia, in Current research, part A: Geological
Survey of Canada Paper 83--1--A, p. 229--233.

Kojima, S., 1989, Mesozoic terrane accretion in northeastern China,
Sikhote Alin, and Japan regions: Palaeogeography, Palaeoclimatology, and
Palaeoecology, v. 69, p. 213--232.

Kojima, S., Wakita, Koji, Okamura, Y., Natal'in, B.A., Zyabrev, S.V.,
Zhang, Q.L., and Shao, J.A., 1991, Mesozoic radiolarians from the
Khabarovsk complex, eastern USSR; their significance in relation to Mino
terrane, central Japan: Journal of Geological Society of Japan, v. 97,
p. 549--551.

Kolosev, E.V., 1981, Paleomagnetic characteristics of Middle Paleozoic
sediments of the Omolon massif: magnetism of rocks and paleomagnetic
stratigraphy in Eastern and Northeastern Asia: Soviet Academy of
Sciences, Northeast Integrated Scientific Research Institute, Magadan,
p. 68--74.

Konstantinovskaya, E.A., Geodynamics of island arc-continent collision
in the western Pacific margin: Geotectonics, v. 33, p. 15--34.

Korol'kov, V.G., and Korol'kova, A.M., 1974, Notes on the stratigraphy
of Permian deposits of the Okhotsk median massif. \[abs.\]: Precambrian
and Paleozoic of northeast USSR, Abstracts of papers submitted to the
Interdepartmental Stratigraphic Meeting, USSR Interdepartmental
Committee on Stratigraphy, Magadan, p. 135--134 \[in Russian\].

Kos'ko, M.K., Sobolevskaya, R.F., Nepomiluev, V.F., and Volnov, D.A.,
1974, Lower to Middle Paleozoic of the New Siberian Islands \[abs.\]:
Precambrian and Paleozoic of northeast USSR, Abstracts of Papers
submitted to the Interdepartmental Stratigraphic Meeting, USSR
Interdepartmental Committee on Stratigraphy, Magadan, p. 163--167 \[in
Russian\].

Kotlyar, I.N., 1997, Petrological modeling at the prognostication and
estimation of gold-silver mineralization in poorly-developed mining
regions, in Byalobzhesky, S.G., ed., Magmatism and ore mineralization of
Northeast Russia: Northeast Integrated Scientific Research Institute
(NEISRI), Russian Academy of Sciences, Magadan, p. 34--56.

Kovalenko, D.V., 1992, Geology and paleomagnetism of the northwest
framework of the Bering Sea region: Geotectonics, v. 29, p. 78--95 \[in
Russian\].

---------1996, Paleomagnetism and kinematics of the central Olyutorsky
Range, Koryak Highland: Geotectonics, v. 30, p. 243--257 \[in Russian\].

Kovalenko, D.V., and Remizova, L.L., 1997, Paleomagnetism of the
northwestern Olyotorskii Zone, southern Koryak Upland: Physics of the
Solid Earth Izvestiya, v. 33, p. 589--598.

Kosygin, Yu.A., ed., 1985, Tectonic map of oil and gas areas of the Far
East and adjacent territories: U.S.S.R. Academy of Sciences, Institute
of Tectonics and Geophysics, Far Eastern Branch, Khabarovsk, 9 sheets,
scale 1:2,500,000 \[in Russian\].

Kozlovsky, E.A., ed., 1988, Geology of the BAM Zone, geological
structure: Nedra, Leningrad, 443 p. \[in Russian\].

Koz'min, B.M., 1984, Seismic belts of Yakutia and the mechanisms of
their earthquakes: Moscow, Nauka, 125 p. \[in Russian\].

Koz'min, B.M., Imaev, V.S., Imaeva, L.P., Fujita, Kazuya, Chung, W.Y.,
and Gao, H., 1996, Seismicity and active faults of the eastern Siberian
platform \[abs.\]: Eos (American Geophysical Union Transactions), v. 15,
p. F521.

Krasny, L.I., ed., 1966, Geological description of the Khabarovsk
Territory and Amur Region (Geology of the U.S.S.R., v. 19): Nedra,
Moscow, 736 p. \[in Russian\].

Kusky, T.M., and Bradley, D.C., 1999, Kinematic analysis of melange
fabrics; examples and applications from the McHugh Complex, Kenai
Peninsula, Alaska: Journal of Structural Geology, v. 21, p. 1773--1796.

Kusky, T.M., Bradley, D.C., and Haeussler, P., 1997, Progressive
deformation of the Chugach accretionary complex, Alaska, during a
Paleogene ridge-trench encounter: Journal of Structural Geology, v. 19,
p. 139--157.

Kusky, T.M., Bradley, D.C., Haeussler, P.J., and Karl, S., 1997,
Controls on accretion of flysch and melange belts at convergent margins;
evidence from the Chugach Bay thrust and Iceworm melange, Chugach
accretionary wedge, Alaska: Tectonics, v. 16, p. 855--878.

Kusky, T.M., and Young, C.P., in press, Emplacement of the Resurrection
Peninsula ophiolite in the southern Alaska forearc during a ridge-trench
encounter: Journal of Geophysical Research.

Lane, L.S., 1994, A new plate kinematic model of Canada Basin evolution,
in Thurston, D., and Fujita, Kazuya, eds., Proceedings of 1994
International Conference on Arctic Margins: Anchorage, U.S. Minerals
Management Service, p. 283--288.

---------1997, Canada Basin, Arctic Ocean; evidence against a rotational
origin: Tectonics, v. 16, p. 363--387.

Larson, K.M., Freymueller, J.T., and Philipsen, S., 1997, Global plate
velocities from the Global Positioning System: Journal of Geophysical
Research, v. 102, no. B, p. 9961--9981.

Lassiter, J.C., DePaolo, D.J., and Mahoney, J.J., 1994, Geochemistry of
the Wrangellia flood basalt province: Implications for the role of
continental and oceanic lithosphere in flood basalt genesis: Journal of
Petrology, v. 36, p. 983--1010.

Latin, D., and White, N., 1990, Generating melt during lithospheric
extension; pure shear vs. simple shear: Geology, v. 18, p. 7--31.

Lawver, L.A., and Scotese, C.R., 1990, A review of tectonic models for
the evolution of the Canada Basin, chap. 31 of Grantz, Art, Johnson, L.,
and Sweeny, J.F., eds., The Arctic Ocean region (The Geology of North
America, v. L): Boulder, Colo., Geological Society of America, p.
593--618.

Layer, P.W., Parfenov, L.M., Trunilina, V.A., and Bakharev, A.G., 1995,
Age and tectonic significance of granitic belts within the Verkhoyansk
fold and thrust belt, Yakutia, Russia \[abs.\]: Geological Society of
America Abstracts with Programs, v. 27, p. 60.

Lebedev, E.L., Gur'yanov, V.A., Rasskazov, Yu.P., and Chepygin, V.E.,
1989, Geologic development and volcanism of the southern part of the
Okhotsk-Chukotka volcanic belt: Tikhookeanskaya Geologiya, no. 8, p.
50--55 \[in Russian\].

Lee, D.S., 1987, Geology of Korea: Seoul, Geological Society of Korea,
Kyohak S.A. Publications, 514 p.

Litvinov, V.E., and Umitbaev, R.B., 1974, Stratigraphy of Upper
Paleozoic deposits of the Okhotsk massif and southern Yana Kolyma
geosyncline system \[abs.\]: Precambrian and Paleozoic of northeast
USSR. Abstracts of papers submitted to the Interdepartmental
stratigraphic Meeting, USSR Interdepartmental Committee on Stratigraphy,
Magadan, p. 136--138 \[in Russian\].

Lock, J., and McElhinny, M.W., 1991, The global paleomagnetic data base:
Dordrecht, Holland, Kluwer Academic Publishers, 491 p.

Lomtev, V.L., and Patrikeev, V.N., 1965, Pressure structures in the
Kuril and Japan trenches: Vladivostok, U.S.S.R. Academy of Sciences, Far
Eastern Branch, 147 p. \[in Russian\].

Lonsdale, P., 1988, Paleogene history of the Kula plate; offshore
evidence and onshore implications: Geological Society of America
Bulletin, v. 100, p. 755--766.

Lund, Karen, and Snee, L.W., 1988, Metamorphism, structural development,
and age of the continent-island-arc juncture in west-central Idaho, in
Ernst, W.G., ed., Metamorphism and crustal evolution, western
conterminous United States (Rubey volume 7): Boulder, Colo., Geological
Society of America, p. 296--337.

Lychagin, P.P., 1978, Middle Paleozoic magmatism of the Omolon massif:
Magadan, U.S.S.R. Academy of Sciences, 195 p. \[in Russian\].

Lychagin, P.P., Byalobzhesky, S.G., Kolyasnikov, Yu.A., Korago, E.A.,
and Likman, V.B., 1991, Geology and petrography of the
Gromandensko-Vuruveemskiy gabbro-norite massif, South Anyui folded zone:
Magadan, U.S.S.R. Academy of Sciences, 45 p. \[in Russian\].

Lychagin, P.P., Dylevsky, E.F., Shpikerman, V.I., and Likman, B.V.,
1989, Magmatism of the central region of the northeastern U.S.S.R.:
U.S.S.R. Academy of Sciences, Vladivostok, 120 p. \[in Russian\].

Lytwyn, J., Casey, J., and Gilbert, S., 1997, Arc-like mid-ocean ridge
basalt formed seaward of a trench-forearc system just prior to ridge
subduction: an example from subaccreted ophiolites in southern Alaska:
Journal of Geophysical Research, v. 102, no. B5, p. 10225--10242.

Mackey, K.G., Fujita, Kazuya, Gunbina, L.V., Kovalev, V.N., Imaev, V.S.,
Koz'min, B.M., and Imaeva, L.P., 1997, Seismicity of the Bering Strait
region; evidence for a Bering block: Geology, v. 25, p. 979--982.

Maeda, J., 1990, Opening of the Kuril Basin deduced from the magmatic
history of central Hokkaido, north Japan: Tectonophysics, v. 174, p.
235--255 \[in Russian\].

Mahoney, J.B., and Journeay, J.M., 1993, The Cayoosh assemblage,
southwestern British Columbia; last vestige of the Bridge River Ocean,
in Current research, part A: Geological Survey of Canada Paper 93--1A,
p. 235--244.

Maiboroda, A.A., and Sharueva, L.I., 1979, Composition of Jurassic
deposits in the western part of the Ulbansk basin, Primorye, in
sedimentary and volcanosedimentary formations of the Far East:
Vladivostok, U.S.S.R. Academy of Science, p. 27--36 \[in Russian\].

Marquis, G., and Globerman, B.R., 1987, Northward motion of the
Whitehorse Trough, paleomagnetic evidence from the Upper Cretaceous
Carmacks Group: Canadian Journal of Earth Sciences, v. 25, p.
2005--2016.

Martynov, Yu.A., 1994, The importance of Al2O3 for systematic chemistry
of basaltic rocks: Tikhookeanskaya Geologiya, no. 2, p. 94--99 \[in
Russian\].

Martynov, Yu.A., and Okamura, S., 1993, Variation of Sr and Nd isotopic
ratios in Paleocene-Pleistocene basalts of the East Sikhote-Alin:
Akademii Nauk SSR Izvestiya, Seriya Geologicheskaya, no. 333, p.
366--369 \[in Russian\].

Maxson, J.A., Kleinspehn, K.L., Wynne, P.J., and Irving, E., 1993,
Paleomagnetic evidence for northward displacement of western British
Columbia from the mid-Cretaceous Silverquick fluvial deposits and Powell
Creek volcanics, northern Tyaughton Basin \[abs.\]: Geological Society
of America Abstracts with Programs, v. 25, p. 116

McCaffrey, R., and Abers, G.A., 1991, Orogeny in arc-continent
collision; the Banda arc and western New Guinea: Geology, v. 19, p.
563--566.

McClelland, W.C., 1992, Permian and older rocks of the southwestern
Iskut River map area, northwestern British Columbia, in Current
research, part A: Geological Survey of Canada Paper 92--1A, p. 303--307.

---------1997, Detrital zircon studies of the Proterozoic Neruokpuk
Formation, Sadlerochit and Franklin Mountains, northeastern Alaska
\[abs.\]: Geological Society of America Abstracts with Programs, v. 29,
p. 28.

McClelland, W.C., Gehrels, G.E., and Saleeby, J.B., 1992a, Upper
Jurassic-Lower Cretaceous basinal strata along the Cordilleran margin;
implications for the accretionary history of the
Alexander-Wrangellia-Peninsular terrane: Tectonics, v. 11, p. 832--835.

McClelland, W.C., Gehrels, G.E., Samson, S.D., and Patchett, P.J., 1991,
Protolith relations of the Gravina belt and Yukon-Tanana terrane in
central southeastern Alaska: Journal of Geology, v. 100, p. 107--123.

---------1992b, Structural and geochronologic relations along the
western flank of the Coast Mountains batholith; Stikine River to Cape
Fanshaw, central southeastern Alaska: Journal of Structural Geology, v.
14, p. 475--489.

May, S.R., Beck, M.E., Jr., and Butler, R.F., 1989, North American
apparent polar wander, plate motion, and left-oblique convergence, Late
Jurassic-Early Cretaceous orogenic consequences: Tectonics, v. 8, p.
433--541.

Mihalynuk, M.G., Nelson, J., and Diakow, L.J., 1994, Cache Creek terrane
entrapment: oroclinal paradox within the Canadian Cordillera: Tectonics,
v. 13, p. 575--595.

Mikhailov, V.A., Vrublevsky, A.A., and Yushmanov, Yu.P., 1987, Structure
and conditions of nappe structure formation in the Pribrezhnaya zone
(Primorie): Tikhookeanskaya Geologiya, no. 1, p. 83--91.

Mikhailov, V.A., Volokhin, Yu.G., Parnyakov, V.P., and Oleinik, L.M.,
1989, Age and nature of the Gorbushinsk series, Pribrezhnaya zone in the
Sikhote-Alin fold belt: Tikhookeanskaya Geologiya, no. 4, p. 70--77 \[in
Russian\].

Mikhailov, V.A., Volokhin, Yu.G., Parnyakov, V.P., Oleinik, L.M., and
Buryi, G.I., 1986, Gorbusha series of Dalnegorsk area, in Zakharov,
Y.D., Belyaeva, G.V., and Nikitina, A.P., eds., New data on the
Paleozoic and Mesozoic biostratigraphy of the southern Russian Far East:
Vladivostok, U.S.S.R. Academy of Sciences, p. 28--36 \[in Russian\].

Miller, E.L., and Hudson, T.L., 1991, Mid-Cretaceous extensional
fragmentation of a Jurassic-Early Cretaceous compressional orogen,
Alaska: Tectonics, v. 10, p. 781--796.

Miller, M.L., Bradshaw, J.Y., Kimbrough, D.L., Stern, T.W., and
Bundtzen, T.K., 1991, Isotopic evidence for early Proterozoic age of the
Idono Complex, west-central Alaska: Journal of Geology, v. 99, p.
209--223.

Miller, M.L., and Bundtzen, T.K., 1993, Geologic map of the Iditarod
quadrangle showing K-Ar, major oxide, trace element, fossil,
paleocurrent, and archeological sample localities: U.S. Geological
Survey Map MF--2219, scale 1:250,000.

Miller, T.P., 1989, Contrasting plutonic rock suites of the
Yukon-Koyukuk basin and the Ruby geanticline, Alaska: Journal of
Geophysical Research, v. 94, no. B, p. 15969--15989.

---------1994, Pre-Cenozoic plutonic rocks in mainland Alaska, in
Plafker, George, and Berg, H.C., eds., The geology of Alaska (The
Geology of North America, v. G--1): Boulder, Colo., Geological Society
of America, p. 535--554.

Miller, T.P., and Richter, D.H., 1994, Quaternary volcanism in the
Alaska Peninsula and Wrangell Mountains, Alaska, in Plafker, George, and
Berg, H.C., eds., The geology of Alaska (The Geology of North America,
v. G--1): Boulder, Colo., Geological Society of America, p. 759--780.

Minoura, K., 1990, The pre-Cretaceous geology and tectonics of northern
Kitakami region, in Pre-Cretaceous terranes of Japan: Osaka,
International Geologic Correlations Project Report 224, p. 267--279.

Mizutani, S., 1987, Mesozoic terranes in the Japanese Islands and
neighboring East Asia, in Leitch, E.C., and Scheibner, E., eds., Terrane
accretion and orogenic belts (Geodynamic Series, v. 19): Washington,
D.C., American Geophysical Union, p. 263--273.

---------1990, Mino terrane, in Pre-Cretaceous terranes of Japan: Osaka,
International Geologic Correlations Project Report 224, p. 121--135.

Mizutani, S., and Kojima, S., 1992, Mesozoic radiolarian biostratigraphy
of Japan and collage tectonics along the eastern continental margin of
Asia: Palaeogeography, Palaeoclimatology, and Palaeoecology, v. 96, p.
3--32.

Moll-Stalcup, E.J., 1990, Latest Cretaceous and Cenozoic magmatism in
mainland Alaska: U.S. Geological Survey Open-File Report 90--84, 80 p.

---------1994, Latest Cretaceous and Cenozoic magmatism in mainland
Alaska, in Plafker, George, and Berg, H.C., eds., The geology of Alaska
(The Geology of North America, v. G--1): Boulder, Colo., Geological
Society of America, p. 589--620.

Moll-Stalcup, E.J., Brew, D.A., and Vallier, T.L., 1994, Map of latest
Cretaceous and Cenozoic igneous rocks of Alaska, pl. 5 of Plafker,
George, and Berg, H.C., eds., The geology of Alaska (The Geology of
North America, v. G--1): Boulder, Colo., Geological Society of America,
scale 1:2,500,000.

Monger, J.W.H., 1977, Upper Paleozoic rocks of the western Canadian
Cordillera and their bearing on Cordilleran evolution: Canadian Journal
of Earth Sciences, v. 14, p. 1832--1859.

---------1985, Structural evolution of the southwestern Intermontane
Belt, Ashcroft and Hope map areas, British Columbia, in Current
research, part A: Geological Survey of Canada Paper 85--1A, p. 349--358.

---------1989, Geology of Hope and Ashcroft map-areas: Geological Survey
of Canada Maps 41--1989, 42--1989, scale 1:250,000.

---------1991, Late Mesozoic to Recent evolution of the Georgia
Strait-Puget Sound region, British Columbia and Washington: Washington
Geology, v. 19, no. 4, p. 3--7.

---------1993, Cretaceous tectonics of the North American Cordillera, in
Caldwell, W.G.E., and Kauffman, E.G., eds., Evolution of the western
interior basin: Geological Association of Canada Special Paper 39, p.
31--47.

---------1997, Plate tectonics and northern Cordilleran geology; an
unfinished revolution: Geoscience Canada, v. 24, p. 189--198.

Monger, J.W.H., and Berg, H.C., 1987, Lithotectonic terrane map of
western Canada and southeastern Alaska: U.S. Geological Survey
Miscellaneous Field Studies Map MF--1874--B, 12 p., scale 1:2,500,000.

Monger, J.W.H., Clowes, R.M., Price, R.A., Simony, P.S., Riddihough,
R.P., and Woodsworth, G.J., 1985, Juan de Fuca to Alberta, Canada:
Geological Society of America Centennial Continent/Ocean Transect 7, 2
sheets, scale 1:500,000.

Monger, J.W.H., and Irving, E., 1980, Northward displacement of
north-central British Columbia: Nature, v. 285, p. 289--294.

Monger, J.W.H., and Journeay, J.M., 1994, Basement geology and tectonic
evolution of the Vancouver region, in Geology and geological hazards of
the Vancouver region, southwestern British Columbia: Geological Survey
of Canada Bulletin 481, p. 3--25.

Monger, J.W.H., and Nokleberg, W.J., 1996, Evolution of the northern
North American Cordillera; generation, fragmentation, displacement, and
accretion of successive North American plate margin arcs, in Coyner,
A.R., and Fahey, P.L., eds., Geology and ore deposits of the American
Cordillera: Geological Society of Nevada Symposium, Reno/Sparks, Nev.,
1995, Proceedings, p. 1133--1152.

Monger, J.W.H., Nokleberg, W.J., Dawson, K.M., Parfenov, L.M., Bundtzen,
T.M., and Shpikerman, V.I., 1996, Tectonic settings of Paleozoic through
Cretaceous mineral deposits of the Canadian Cordillera and Alaska, with
extensions into the Russian Northeast \[abs.\]: 1996 Canadian
Cordilleran Roundup Program with Abstracts, p. 27--28.

Monger, J.W.H., Price, R.A., and Tempelman-Kluit, D.J., 1982, Tectonic
accretion and the origin of the two major metamorphic and plutonic welts
in the Canadian Cordillera: Geology, v. 10, p. 70--75.

Monger, J.W.H., Price, R.A., Wynne, P.J., Thorkelson, D.J., Kleinspehn,
K.L., Maxson, J.A., and Irving, E., 1996, Paleomagnetism of the Upper
Cretaceous strata of Mount Tatlow; evidence for 3000 km of northward
displacement of the eastern Coast Belt, British Columbia, and
Paleomagnetism of the Spences Bridge Group and northward displacement of
the Intermontane Belt, British Columbia; a second look; discussion and
reply: Journal of Geophysical Research, v. 101, no. B, p. 13793--13803.

Monger, J.W.H., and Ross, C.A., 1971, Distribution of fusulinaceans in
the Canadian Cordillera: Canadian Journal of Earth Sciences, v. 8, p.
770--791.

Monger, J.W.H., Souther, J.G., and Gabrielse, H., 1972, Evolution of the
Canadian Cordillera; a plate tectonic model: American Journal of
Science, v. 272, p. 577--602.

Monger, J.W.H., van der Heyden, P., Journeay, J.M., Evenchick, C.A., and
Mahoney, J.B., 1994, Jurassic-Cretaceous basins along the Canadian
Cordillera; their bearing on pre-mid-Cretaceous sinistral displacements:
Geology, v. 22, p. 175--178.

Monger, J.W.H., Wheeler, J.O., Tipper, H.W., Gabrielse, H., Harms, T.,
Struik, L.C., Campbell, R.B., Dodds, C.J., Gehrels, G.E., and O'Brien,
J., 1991, Cordilleran terranes, in Gabrielse, H., and Yorach, C.J.,
eds., Geology of the Cordilleran orogen, Canada: Geological Survey of
Canada, Geology of Canada, no. 4, p. 281--327 \[also Boulder, Colo.,
Geological Society of America, The Geology of North America, v. G--2, p.
281--327\].

Moore, J.C., Byrne, T., Plumley, P.W., Reid, M., Gibbons, H., and Coe,
R.S., 1983, Paleogene evolution of the Kodiak Islands, Alaska;
consequences of ridge-trench interaction in a more southerly latitude:
Tectonics, v. 2, p. 265--293.

Moore, T.E., Grantz, Art, and Roeske, S.M., 1994a, Continent-ocean
transition in Alaska; the tectonic assembly of eastern Denalia, in
Speed, R.C., ed., Phanerozoic evolution of North American
continent-ocean transitions (Continent-Ocean Transect Volume): Boulder,
Colo., Geological Society of America, p. 399--441.

Moore, T.E., Wallace, W.K., Bird, K.J., Karl, S.M., Mull, C.G., and
Dillon, J.T., 1994b, Geology of northern Alaska, in Plafker, George, and
Berg, H.C., eds., The geology of Alaska (The Geology of North America,
v. G--1): Boulder, Colo., Geological Society of America, p. 49--140.

Moores, E.M., 1991, Southwest U.S.-East Antarctic (SWEAT) connection; a
hypothesis: Geology, v. 19, p. 425--428.

Mortensen, J.K., 1992, Pre-mid-Mesozoic tectonic evolution of the
Yukon-Tanana terrane, Yukon and Alaska: Tectonics, v. 11, p. 836--853.

Mortimer, N. 1987, The Nicola Group; Late Triassic and Early Jurassic
subduction-related volcanism in British Columbia: Canadian Journal of
Earth Sciences, v. 24, p. 2521--2536.

Muller, J.E., 1977, Evolution of the Pacific Margin, Vancouver Island
and adjacent regions: Canadian Journal of Earth Sciences, v. 14, p.
2062--2085.

---------1980, The Paleozoic Sicker Group of Vancouver Island, British
Columbia: Geological Survey of Canada Paper 79--30, 24 p.

Nakamura, E., McCulloch, M.T., and Campbell, I.H., 1990, Chemical
geodynamics in the back-arc region of Japan based on the trace-element
and Sr-Nb isotopic compositions: Tectonophysics, v. 174, p. 207--283.

Natal'in, B.A., 1984, Early Mesozoic eugeosynclinal systems in the
northern part of the Circum-Pacific: Moscow, Nauka, 136 p. \[in
Russian\].

---------1991, Mesozoic accretionary and collisional tectonics of the
southern Far East: Tikhookeanskaya Geologiya, no. 5 \[in Russian\].

---------1993, History and mode of Mesozoic accretion in southeastern
Russia: Island Arc, v. 2, p. 32--48.

Natal'in, B.A., and Alexeenko, S.N., 1989, Tectonics of the Sredneamursk
basin basement: Vladivostok, U.S.S.R. Academy of Sciences, Far East
Branch, 57 p.

Natal'in, B.A., and Borukayev, Ch.B., 1991, Mesozoic sutures in the Far
East South: Geotectonics, v. 1, p. 84--96.

Natal'in, B.A., and Faure, M., 1991, Geodynamics of the Asia eastern
margin in the Mesozoic: Tikhookeanskaya Geologiya, v. 6, p. 3--23.

Natal'in, B.A., Parfenov, L.M., Vrublevsky, A.A., Karsakov, L.P., and
Yushmanov, V.V., 1986, Main fault systems of the Soviet Far East:
Philosophical Transactions of the Royal Society of London, v. 317, p.
267--275.

Natal'in, B.A., and Popeko, L.I., 1991, The Paleozoic of the Galamsk
segment of the Mongol-Okhotsk fold belt: Tikhookeanskaya Geologiya, no.
2, p. 81--89 \[in Russian\].

Natal'in, B.A., Popeko, L.I., and Chobotov, S.A., 1985, Tectonics of the
West Dzhagdinsk zone of the Mongol-Okhotsk fold belt: Tikhookeanskaya
Geologiya, no. 2, p. 49--64 \[in Russian\].

Natal'in, B.A., and Zyabrev, S.V., 1989, Structure of Mesozoic rocks of
the Amur river valley: International Symposium on Tectonics, Energy and
Mineral Resources of Northwest Pacific, Khabarovsk, 1989, Field Trip
Guide-Book, 48 p.

Natapov, L.M., ed., 1984, Geologic map of the U.S.S.R: Leningrad,
U.S.S.R. Ministry of Geology, 128 p., scale 1:1,000,000 \[in Russian\].

Natapov, L.M., and Shuligina, W.S., eds., 1991, Geologic map of the
U.S.S.R.: Leningrad, U.S.S.R. Ministry of Geology, 111 p., scale
1:1,000,000 \[in Russian\].

Natapov, L.M., and Surmilova, E.P., eds., 1986, Geological map of the
U.S.S.R.: Leningrad, U.S.S.R. Ministry of Geology, 120 p., scale
1:1,000,000 \[in Russian\].

Nazarenko, L.F., and Bazhanov, V.A., 1986, Geology of the Primorsk
Territory: Vladivostok, U.S.S.R. Academy of Sciences, Far East Branch,
154 p. \[in Russian\].

Nechaev, V.P., Markevich, P.V., Malinovsky, A.I., Philippov, A.N., and
Vysotsky, S.V., 1996, Tectonic setting of the Cretaceous sediments in
the Lower Amur Region, Russian Far East: Sedimentary Society of Japan
Journal, v. 43, p. 69--81.

Nekrasov, G.E., 1976, Tectonics and magmatism of Taigonos and
northwestern Kamchatka: Moscow, Nauka, 158 p. \[in Russian\].

Nekrasov, G.E., and Sumin, L.V., 1987, Melanocratic basement of the
Pekul'ney Range and its Pb/Pb thermoisochron age, in Essays on the
geology of northwestern sector of the Pacific tectonic belt: Moscow,
Nauka, p. 183--199 \[in Russian\].

Nelson, J.L., 1993, The Sylvester allochthon: upper Paleozoic
marginal-basin and island-arc terranes in northern British Columbia:
Canadian Journal of Earth Sciences, v. 30, p. 631--643.

Nelson, J.L., and Bradford, J.A., 1989, Geology and mineral deposits of
the Cassiar and McDame areas, British Columbia, in Geological fieldwork
1988: British Columbia Ministry of Energy, Mines and Petroleum Resources
Paper 1989--1, p. 323--338.

Nelson, J.L., and Mihalynuk, M., 1993, The Cache Creek ocean; closure or
enclosure?: Geology, v. 21, p. 173--176.

Nelson, S.W., 1992, Ophiolitic complexes in the Gulf of Alaska: U.S.
Geological Survey Open-File Report 92--20--C, 10 p.

Nelson, S.W., Dumoulin, J.A., and Miller, M.L., 1985, Geologic map of
the Chugach National Forest, Alaska: U.S. Geological Survey
Miscellaneous Field Studies Map MF--1645--B, 16 p., scale 1:250,000.

Neustroev, A., Parfenov, L.M., and Rodionov, V.P., 1993, Paleomagnetic
data and the nature of the Tas-Khayakhtakh terrane in the
Verkhoyansk-Kolyma region: Geologiya i Geofizika, v. 8, p. 25--37 \[in
Russian\].

Nevolina, S.I., and Sokarev, A.N., 1986, Paleomagnetic directions and
pole positions; data for the USSR-Soviet Geophysical Committee: Moscow,
World Data Center-B, Catalog, no. 6, as quoted in Lock and McElhinny
(1991).

Nikolaev, A.A., Oradovskaya, M.M., Preobrazhensky, B.V., Obut, A.M.,
Sobolevskaya, R.F., and Kabanov, V.Ya., 1974, A reference cross-section
of the Ordovician in northeast USSR, in Reference cross-sections of the
Paleozoic of North USSR: Magadan, USSR Academy of Sciences, Northeast
Complex Scientific-Research Institute, p. 3--136 \[in Russian\].

Nokleberg, W.J., Bundtzen, T.K., Dawson, K.M., Eremin, R.A., Goryachev,
N.A., Koch, R.D., Ratkin, V.V., Rozenblum, I.S., Shpikerman, V.I.,
Diggles, M.F., Frolov, Y.F., Gorodinsky, M.E., Melnikov, V.D., Ognyanov,
N.V., Petrachenko, E.D., Petrachenko, R.I., Pozdeev, A.I., Ross, K.V.,
Wood, D.H., Grybeck, D., Khanchuk, A.I., Kovbas, L.I., Nekrasov, I.Ya.,
and Sidorov, A.A., 1997a, Significant metalliferous and selected
non-metalliferous lode deposits and placer districts for the Russian Far
East, Alaska, and the Canadian Cordillera: U.S. Geological Survey
Open-File Report 96--513--B (CD--ROM format).

Nokleberg, W.J., Bundtzen, T.K., Dawson, K.M., Eremin, R.A., Goryachev,
N.A., Koch, R.D. Ratkin, V.V., Rozenblum, I.S., Shpikerman, V.I.,
Frolov, Y.F., Gorodinsky, M.E., Melnikov, V.D., Ognyanov, N.V.,
Petrachenko, E.D., Petrachenko, R.I., Pozdeev, A.I., Ross, K.V., Wood,
D.H., Grybeck, D., Khanchuk, A.I., Kovbas, L.I., Nekrasov, I.Ya., and
Sidorov, A.A., 1996, Significant metalliferous and selected
non-metalliferous lode deposits placer districts for the Russian Far
East, Alaska, and the Canadian Cordillera: U.S. Geological Survey
Open-File Report 96--513--A (paper format), 385 p.

Nokleberg, W.J., Bundtzen, T.K., Grybeck, D., Koch, R.D., Eremin, R.A.,
Rozenblum, I.S., Sidorov, A.A., Byalobzhesky, S.G., Sosunov, G.M.,
Shpikerman, V.I., and Gorodinsky, M.E., 1993, Metallogenesis of mainland
Alaska and the Russian Northeast: mineral deposit maps, models, and
tables, metallogenic belt maps and interpretation, and references cited:
U.S. Geological Survey Open-File Report 93--339, 222 pages, 6 sheets,
scales 1:4,000,000, 1:10,000,000.

Nokleberg, W.J., Foster, H.L., and Aleinikoff, J.N., 1995a, Tectonic
model for the Yukon-Tanana, Seventymile, Stikinia, and Wrangellia
terranes along the Trans-Alaskan Crustal Transect (TACT), East-Central
Alaska \[abs.\]: Geological Society of America Abstracts with Programs,
v. 27, p. 69.

Nokleberg, W.J., Jones, D.L., and Silberling, N.J., 1985, Origin,
migration, and accretion of Andean-type arc and island arc
tectonostratigraphic terranes in the southern Mount Hayes quadrangle and
adjacent areas of the eastern Alaska Range, Alaska: Geological Society
of America Bulletin, v. 96, p. 1251--1270.

Nokleberg, W.J., Monger, J.W.H., and Parfenov, L.M., 1995b, Mesozoic and
Cenozoic tectonics of the Circum-North Pacific \[abs.\]: Geological
Association of Canada Annual Meeting Program with Abstracts, v. 20, p.
A--76 \[also Geological Society of America Abstracts with Programs, v.
27, p. A--68 to A--69, and American Geophysical Union Fall Meeting,
1995, Program, p. F592\].

Nokleberg, W.J., Parfenov, L.M., Monger, J.W.H., Baranov, B.V.,
Byalobzhesky, S.G., Bundtzen, T.K., Feeney, T.D., Fujita, Kazuya,
Gordey, S.P., Grantz, Art, Khanchuk, A.I., Natal'in, B.A., Natapov,
L.M., Norton, I.O., Patton, W.W., Jr., Plafker, George, Scholl, D.W.,
Sokolov, S.D., Sosunov, G.M., Stone, D.B., Tabor, R.W., Tsukanov, N.V.,
and Vallier, T.L., 1997b, Summary Circum-North Pacific
tectono-stratigraphic terrane map: Geological Survey of Canada Open-File
3428, scale 1:10,000,000.

---------1997c, Summary Circum-North Pacific tectono-stratigraphic
terrane map: U.S. Geological Survey Open-File Report 96--727, scale
1:10,000,000.

Nokleberg, W.J., Parfenov, L.M., Monger, J.W.H., Baranov, B.V.,
Byalobzhesky, S.G., Bundtzen, T.K., Feeney, T.D., Fujita, Kazuya,
Gordey, S.P., Grantz, Art, Khanchuk, A.I., Natal'in, B.A., Natapov,
L.M., Norton, I.O., Patton, W.W., Jr., Plafker, George, Scholl, D.W.,
Sokolov, S.D., Sosunov, G.M., Stone, D.B., Tabor, R.W., Tsukanov, N.V.,
Vallier, T.L. and Wakita, Koji, 1994a, Circum-North Pacific
tectono-stratigraphic terrane map: U.S. Geological Survey Open-File
Report 94--714, 210 p., 4 sheets, scales 1:5,000,000, 1:10,000,000.

Nokleberg, W.J., Plafker, George, Lull, J.S., Wallace, W.K., and
Winkler, G.W., 1989, Structural analysis of the southern Peninsular,
southern Wrangellia, and northern Chugach terranes along the
Trans-Alaskan Crustal Transect (TACT), northern Chugach Mountains,
Alaska: Journal of Geophysical Research, v. 94, p. 4297--5320.

Nokleberg, W.J., Plafker, George, and Wilson, F.H., 1994b, Geology of
south-central Alaska, in Plafker, George, and Berg, H.C., eds., The
geology of Alaska (The Geology of North America, v. G--1): Boulder,
Colo., Geological Society of America, p. 311--366.

Nokleberg, W.J., West, T.D., Dawson, K.M., Shpikerman, V.I., Bundtzen,
T.K., Parfenov, L.M., Monger, J.W.H., Ratkin, V.V., Baranov, B.V.,
Byalobzhesky, S.G., Diggles, M.F., Eremin, R.A., Fujita, Kazuya, Gordey,
S.P., Gorodinskiy, M.E., Goryachev, N.A., Feeney, T.D., Frolov, Y.F.,
Grantz, Art, Khanchuk, A.I., Koch, R.D., Natal'in, B.A., Natapov, L.M.,
Norton, I.O., Patton, W.W. Jr., Plafker, George, Pozdeev, A.I.,
Rozenblum, I.S., Scholl, D.W., Sokolov, S.D., Sosunov, G.M., Stone,
D.V., Tabor, R.W., Tsukanov, N.V., and Vallier, T.L., 1998, Summary
terrane, mineral deposit, and metallogenic belt maps of the Russian Far
East, Alaska, and the Canadian Cordillera: U.S. Geological Survey
Open-File Report 98--136, CD--ROM.

Okada, H., Tarduno, J.A., Nakaseko, K., Nishimura, A., and Sliter, W.V.,
1989, Microfossil assemblages from the Late Jurassic to Early Cretaceous
Nikoro pelagic sediments, Tokoro Belt, Hokkaido, Japan: Kyushyu
University, Faculty of Science Memoirs, ser. D, v. 26, p. 193--214.

Oldow, J.S., Bally, A.W., Avé Lallement, H.G., and Leeman, W.P., 1989,
Phanerozoic evolution of the North American Cordillera, in Bally, A.W.,
and Palmer, A.R., eds., The geology of North America---an overview (The
Geology of North America, v. A): Boulder, Colo., Geological Society of
America, p. 139--232.

Oleinikov, A.V., Kovalenko, S.V., Nevolina, S.I., Volynets, E.B., and
Markevich, S.V., 1990, New data on stratigraphy of upper Mesozoic
deposits of the northern Partizansk coal-bearing basin; continental
Cretaceous of the USSR, in Collection of research papers: Vladivostok,
USSR Academy of Sciences, Far Eastern Branch, p. 114--126 \[in
Russian\].

Oradovskaya, M.M., 1974, Stratigraphy and paleogeography of Ordovician
deposits in the Omolon massif, in Reference cross-sections of the
Paleozoic in northeast USSR: Magadan, USSR Academy of Sciences,
North-East Complex Scientific-Research Institute, p. 137--160 \[in
Russian\].

Orchard, M.J., and Danner, W.R., 1991, Paleontology of Quesnellia, in
Smith, P.L., ed., A field guide to the paleontology of southwestern
Canada: Canadian Paleontology Conference 1, Vancouver, p. 139--159.

Otofuji, Y., Matsuda, T., Itaya, T., Shibata, T., Matsumoto, M.,
Yamamoto, T., Morimoto, C., Kulinich, R.G., Zimin, P.S., Matunin, A.P.,
Sakhno, V.G., and Kimura, K., 1995, Late Cretaceous to early Paleocene
paleomagnetic results from Sikote Alin, Russian Far East; implications
for deformation of East Asia: Earth and Planetary Science Letters, v.
130, p. 95--108.

Oxman, V.S., Parfenov, L.M., Prokopiev, A.V., Timofeev, V.F., Tretyakov,
F.F., Nedosekin, Y.D., Lyer, P.W., and Fujita, Kazuya, 1995, The Chersky
Range ophiolite belt, northeast Russia: Journal of Geology, v. 103, p.
539--556.

Packer, D.R., and Stone, D.B., 1974, Paleomagnetism of Jurassic rocks
from southern Alaska and their tectonic implications: Canadian Journal
of Earth Sciences, v. 7, p. 976--997.

Paek, R.J., Kan, H.G., Jon, G.Pu., Kim, Y.M., Kim, Y.H., eds., 1993,
Geology of Korea: Pyongyang, Foreign Languages Book Publishing House,
620 p.

Pallister, J.S., Budahn, J.R., and Murchey, B.L., 1989, Pillow basalts
of the Angayucham terrane; oceanic plateau and island crust accreted to
the Brooks Range: Journal of Geophysical Research, v. 94, no. B, p.
15901--15924.

Pallister, J.S., and Carlson, Christine, 1988, Bedrock geologic map of
the Angayucham Mountains, Alaska: U.S. Geological Survey Miscellaneous
Field Studies Map MF--2024, scale 1:63,360.

Palmer, A.R., 1983, The Decade of North American Geology, geologic time
scale: Geology, v. 11, p. 503--504.

Palmer, A.R., Egbert, R.M., Sullivan, R., and Knoth, J.S., 1985,
Cambrian trilobites with Siberian affinities, southwestern Alaska
\[abs.\]: American Association of Petroleum Geologists Bulletin, v. 69,
p. 295.

Panuska, B.C., 1980, Stratigraphy and sedimentary petrology of the Kiska
Harbor Formation: Fairbanks, University of Alaska, M.S. thesis, 90 p.

---------1984, Paleomagnetism of the Wrangellia and Alexander terranes
and the tectonic history of southern Alaska: Fairbanks, University of
Alaska, Ph.D. thesis, 197 p.

---------1985, Paleomagnetic evidence for a post-Cretaceous accretion of
Wrangellia: Geology, v. 13, p. 880--883.

Panuska, B.C., Decker, J.E., and Berg, H.C., 1984, A preliminary
paleomagnetic study of the Gravina-Nutzotin belt, southern and
southeastern Alaska, in Coonrad, W.L., and Elliott, R.L. eds., The
United States Geological Survey in Alaska; accomplishments during 1981,
U.S. Geological Survey Circular, 868, p. 117--120.

Panuska, B.C., and Macicak, M.A., 1986, Revised paleolatitude for the
Paleocene Teklanika Volcanics, central Alaska Range, Alaska \[abs.\]:
Eos (American Geophysical Union Transactions), v. 67, p. 921.

Panuska, B.C., and Stone, D.B., 1981, Late Paleozoic paleomagnetic data
for Wrangellia; resolution of the polarity ambiguity: Nature, v. 293, p.
561--563.

---------1985a, Confirmation of the pre-50 m.y. accretion age of the
southern Alaska superterrane \[abs.\]: Eos (American Geophysical Union
Transactions), v. 66, p. 863.

---------1985b, Latitudinal motion of the Wrangellia and Alexander
terranes and southern Alaska superterrane, in Howell, D.B., ed.,
Tectonostratigraphic terranes of the Circum-Pacific region (Earth
Science Series, v. 1): Houston, Tex., Circum-Pacific Council for Energy
and Mineral Resources, p. 109--120.

Panuska, B.C., Stone, D.B., and Turner, D.L., 1990, Paleomagnetism of
Eocene volcanic rocks, Talkeetna Mountains, Alaska: Journal of
Geophysical Research, v. 95, no. B, p. 6737--6750.

Parfenov, L.M., 1984, Continental margins and island arcs of Mesozoides
of northeastern Asia: Novosibirsk, Nauka, 192 p. \[in Russian\].

---------1985, The segmentation and fold dislocations of the Verkhoyansk
foldbelt: Geologiya i Geofizika, no. 7, p. 12--24 \[in Russian\].

---------1987, Thrusts and related melanges in the Kharaulakh Mountains:
Akademii Nauk SSSR Doklady, v. 296, no. 3, p. 685--689 \[in Russian\].

---------1991, Tectonics of the Verkhoyansk-Kolyma Mesozoides in the
context of plate tectonics: Tectonophysics, v. 199, p. 319--342.

---------1994, Accretionary history of northeast Asia, in Thurston, D.,
and Fujita, Kazuya, eds., Proceedings of 1994 International Conference
on Arctic Margins: Anchorage, U.S. Minerals Management Service, p.
183--188.

---------1995a, Terrane analysis of the Mesozoic orogenic belts of the
Russian Northeast \[abs.\]: Geological Society of America Abstracts with
Programs, v. 27, p. 70--71.

---------1995b, Terranes and formation of the Mesozoic orogenic belts of
eastern Yakutia: Tikhookeanskaya Geologiya, v. 14, no.6, p. 32--43 \[in
Russian\].

---------1995c, Tectonics and regional metallogeny of the
Verkhoyansk-Kolyma region, in Bundtzen, T.K., Fonesca, A.L., and Mann,
R., eds., The geology and mineral deposits of the Russian Far East:
Anchorage, Glasier House Publications and Alaska Miners Association, p.
61--84.

---------1997, Geological structure and geological history of Yakutia,
in Parfenov, L.M., and Spektor, V.B., eds., Geological monuments of the
Sakha Republic (Yakutia): Novosibirsk, Studio Design, p. 60--77.

Parfenov, L.M., Layer, P., Stone, D.B., and Fujita, Kazuya, 1996,
Mesozoic orogenic belts of Eastern Yakutia and some problems related to
their study: Nauka i Obrazovanie, no. 1, p. 38--44 \[in Russian\].

Parfenov, L.M., and Natal'in, B.A., 1985, Mesozoic accretion and
collision tectonics of northeastern Asia, in Howell, D.G., ed.,
Tectonostratigraphic terranes of the Circum-Pacific region (Earth
Science Series, v. 1): Houston, Tex., Circum-Pacific Council for Energy
and Mineral Resources, p. 363--374.

---------1986, Mesozoic tectonic evolution of northeastern Asia:
Tectonophysics, v. 127, p. 291--304.

Parfenov, L.M., Natapov, L.M., Sokolov, S.D., and Tsukanov, S.D., 1993a,
Terrane analysis and accretion in northeast Asia: Island Arc, v. 2, p.
35--54.

---------1993b, Terranes and accretionary tectonics of northeastern
Asia: Geotectonics, v. 27, p. 62--72 \[in Russian\].

Parfenov, L.M., Oxman, V.S., Prokopiev, A.V., Rozhin, S.S., Timofeev,
V.F., and Tret'yakov, F.F., 1989, Detailed structural studies in the
Verkhoyansk region, their significance for large-scale geological
mapping, in Tectonic investigations in connection with medium and
large-scale geological mapping: Moscow, Nauka, p. 109--127 \[in
Russian\].

Parfenov, L.M., Popeko, V.A., and Popeko, L.I., 1983, Major
structural-material complexes of Shikotan Island and their geologic
nature (Minor Kuril Islands): Geologiya i Geofizika, no. 10, p. 24--31
\[in Russian\].

Parfenov, L.M., and Prokopiev, A.V., 1993, Frontal thrust structures of
the Verkhoyansk foldbelt: Geologiya i Geofizika, v. 34, no. 7, p. 23--34
\[in Russian\].

Parfenov, L.M., Prokopiev, A.V., and Gaiduk, V.V., 1995, Cretaceous
frontal thrusts of the Verkhoyansk fold belt, eastern Siberia:
Tectonics, v. 4, p. 342--358.

Parfenov, L.M., Voinova, I.P., Natal'in, B.A., and Semonov, 1978,
Geodynamics of northeastern Asia in Mesozoic and Cenozoic time and the
nature of volcanic belts: Journal of Physics of the Earth, v. 26, supp.,
p. 5503--5525.

Parrish, R.R., Carr, S.D., and Parkinson, D.L., 1988, Eocene extensional
tectonics and geochronology of the southern Omineca Belt, British
Columbia and Washington: Tectonics, v.7, p. 181--212.

Parrish, R.R., and McNicoll, V., 1992, U-Pb age determinations from the
southern Vancouver Island area, British Columbia, in Radiogenic age and
isotope studies, report 5: Geological Survey of Canada Paper 91--2, p.
97--108.

Patton, W.W., Jr., 1973, Reconnaissance geology of the northern
Yukon-Koyukuk Province, Alaska: U.S. Geological Survey Professional
Paper 774--A, p. A1--A17.

---------1991, Deep crustal composition of the Yukon-Koyukuk basin,
Alaska \[abs.\]: Geological Society of America Abstracts with Programs,
v. 23, p. 88.

---------1992a, Ophiolitic terrane of western Brooks Range, Alaska: U.S.
Geological Survey Open-File Report 92--90--D, 8 p.

---------1992b, Ophiolitic terrane bordering the Yukon-Koyukuk basin,
Alaska: U.S. Geological Survey Open-File Report 92--90--F, 8 p.

Patton, W.W., Jr., Box, S.E., Moll-Stalcup, E.J., and Miller, T.P.,
1994, Geology of west-central Alaska, in Plafker, George, and Berg,
H.C., eds., The geology of Alaska (The Geology of North America, v.
G--1): Boulder, Colo., Geological Society of America, p. 241--270.

Patton, W.W., Jr., Murphy, J.M., Burns, L.E., Nelson, S.W., and Box,
S.E., 1992, Geologic map of ophiolitic and associated volcanic arc and
metamorphic terranes of Alaska (west of the 141st meridian): U.S.
Geological Survey Open-File Report 92--20--A, 1 sheet, scale
1:2,500,000.

Patton, W.W., Jr., Tailleur, I.L., Brosgé, W.P., and Lanphere, M.A.,
1977, Preliminary report on ophiolites of northern and western Alaska,
in Coleman, R.G., and Irwin, W.P., eds., North American ophiolites:
Oregon Department of Geology and Mineral Industries Bulletin 95, p.
51--57.

Pavlis, T.L., 1983, Pre-Cretaceous crystalline rocks of the western
Chugach Mountains, Alaska; nature of the basement of the Jurassic
Peninsular terrane: Geological Society of America Bulletin, v. 94, p.
1329--1344.

Pavlis, T.L., Sisson, V.B., Foster, H.L., Nokleberg, W.J., and Plafker,
George, 1993, Mid-Cretaceous extensional tectonics of the Yukon-Tanana
terrane, Trans-Alaskan Crustal Transect (TACT), east-central Alaska:
Tectonics, v. 12, p. 103--122.

Pavlov, V.E., 1993, Paleomagnetic directions and paleomagnetic pole
positions; data for the former USSR-Soviet Geophysical Committee:
Moscow, World Data Center-B, Catalog, no. 8, as quoted in Lock and
McElhinny (1991).

Pavlov, V.E., Manukyan, A.M., Sharkovskiy, M.B., and Levashova, N.M.,
1991, First paleomagnetic data on the Riphean of the Okhotsk massif:
Akademii Nauk SSSR Doklady, v. 317. p. 688--892 \[in Russian\].

Pechersky, D.M., 1970, Paleomagnetic studies of Mesozoic deposits of the
USSR northeast: Physics of the Earth Izvestiya, v. 6, p. 69--83.

---------1979, Paleomagnetic directions and paleomagnetic pole
positions: data for the former USSR-Soviet Geophysical Committee:
Moscow, World Data Center-B, Catalog, no. 4, as quoted in Lock and
McElhinny (1991).

Pechersky, D.M., and Shapiro, M.N., 1996, Paleomagnetism of Upper
Cretaceous and Paleogene volcanogenic series of Eastern Kamchatka;
evidence for absolute motions of ancient subduction zones: Physics of
the Earth Izvestiya, v. 32, p. 114--137.

Petocz, R.G., 1970, Biostratigraphy and Lower Permian Fusilinidae of the
upper Delta River area, east-central Alaska Range, Alaska: Geological
Society of America Special Paper 130, 94 p.

Plafker, George, Blome, C.D., and Silberling, N.J., 1989a,
Reinterpretation of lower Mesozoic rocks on the Chilkat Peninsula,
Alaska, as a displaced fragment of Wrangellia: Geology, v. 17, p. 3--6.

Plafker, George, and Berg, H.D., 1994, Overview of the geology and
tectonic evolution of Alaska, in Plafker, George, and Berg, H.C., eds.,
The geology of Alaska (The Geology of North America, v. G--1): Boulder,
Colo., Geological Society of America, p. 989--1021.

Plafker, George, Moore, J.C., and Winkler, G.R., 1994, Geology of the
southern Alaska margin, in Plafker, George, and Berg, H.C., eds., The
Geology of Alaska (The Geology of North America, v. G--1): Boulder,
Colo., Geological Society of America, p. 989--1021.

Plafker, George, Nokleberg, W.J., and Lull, J.S., 1989b, Bedrock geology
and tectonic evolution of the Wrangellia, Peninsular, and Chugach
terranes along the Trans-Alaskan Crustal Transect in the northern
Chugach Mountains and southern Copper River basin, Alaska: Journal of
Geophysical Research, v. 94, p. 4255--4295.

Plumley, P.W., 1984, A paleomagnetic study of the Prince William terrane
and the Nixon Fork terrane, Alaska: Santa Cruz, University of
California, Ph.D. thesis, 190 p.

Plumley, P.W., Coe, R.S., and Byne, T., 1983, Paleomagnetism of the
Paleocene Ghost Rocks formation, Prince William terrane, Alaska:
Tectonics, v. 2, p. 295--311.

Plumley, P.W., and Vance, M., 1988, Porcupine river basalt field, NE
Alaska; age, paleomagnetism and tectonic significance \[abs.\]: Eos
(American Geophysical Union Transactions), v. 69, p. 1458.

Polubotko, I.V., Paraketsov, K.B., and Repin, Yu.S., 1977, Jurassic
structural-stratigraphic areas in the northeastern U.S.S.R.; materials
on the geology and mineral resources of the U.S.S.R. Northeast: Magadan,
U.S.S.R. Academy of Sciences, v. 23, p. 42--51 \[in Russian\].

Pope, M.C., and Sears, J.W., 1997, Cassiar platform, north-central
British Columbia; a miogeoclinal fragment from Idaho: Geology, v. 25, p.
515--518.

Popolitov, E.I., and Volynets, O.V., 1981, Geochemical features of
Quaternary volcanism of the Kuril-Kamchatka island arc and some aspects
of petrogenesis: Novosibirsk, Nauka, 182 p. \[in Russian\].

Prokopiev, A.V., 1989, Kinematics of Mesozoic folding in the western
part of the south Verkhoyan'ye: U.S.S.R. Academy of Sciences, Yakutsk
Science Center, 128 p. \[in Russian\].

Pushcharovskiy, Yu.M., and Til'man, S.M., eds., 1982, Essays on
tectonics of the Koryak Highland: Moscow, Nauka, 219 p. \[in Russian\].

Ramthun, Alexander, Brandon, M.T., and Ring, Ewe, 1997, Preservation of
sedimentary fabrics in the footwall of the large-slip Vatyna thrust,
Kamchatka, Russian Far East \[abs.\]: Geological Society of America
Abstracts with Programs, v. 29, p. 58.

Raznitsi, Yu.N., 1982, Ophiolite allochthons and adjacent deep-water
basins in the western Pacific: Moscow, Nauka, 108 p. \[in Russian\].

Read, P.B., and Okulitch, A.V., 1977, The Triassic unconformity of
south-central British Columbia: Canadian Journal of Earth Science, v.
14, p. 606--638.

Richards, B.C., Bamber, E.W., Henderson, C.M., Higgins, A.C., Johnston,
D.J., Mamer, B., and Meijer Drees, M.J., 1994, Uppermost Devonian
(Famennian) and Lower Carboniferous (Tournasian) at Jura Creek and Mount
Rundle, southwestern Alberta: Geological Survey of Canada Open File
2866, 79 p.

Richards, D.R., Butler, R.F., and Harms, T.A., 1993, Paleomagnetism of
the late Paleozoic Slide Mountain terrane, northern and central British
Columbia: Canadian Journal of Earth Sciences, v. 30, p. 1898--1913.

Richards, M.A., Jones, D.L., Duncan, R.A., and DePaolo, D.J., 1991, A
mantle plume initiation model for the formation of Wrangellia and other
oceanic plateaus: Science, v. 254, p. 263--267.

Ricketts, B.D., Evenchick, C.A., Anderson, R.G., and Murphy, D.C., 1992,
Bowser Basin, northern British Columbia; constraints on the timing of
initial subsidence and Stikinia-North America terrane interactions:
Geology, v. 20, p. 1119--1122.

Riegel, S.A., Fujita, Kazuya, Koz'min, B.M., Imaev, V.S., and Cook,
D.B., 1993, Extrusion tectonics of the Okhotsk plate, northeast Asia:
Geophysical Research Letters, v. 20, p. 607--610.

Rikhter, A.V., 1986, The structure and tectonic evolution of Sakhalin
Island in Mesozoic time: Moscow, Nauka, 90 p. \[in Russian\].

Roback, R.C., Sevigny, J.H., and Walker, N.W., 1994, Tectonic setting of
the Slide Mountain terrane, southern British Columbia: Tectonics, v. 13,
p. 1242--1258.

Roe, J.R., and Stone, D.B., 1993, Paleomagnetism of the Fairbanks
basalts, interior Alaska, in Solie, D.N., and Tannian, F., eds., Short
notes on Alaskan geology: Alaska Division of Geological and Geophysical
Surveys Professional Report 113, p. 61--69.

Roganov, G.V., Sobolev, L.P., and others, 1986, Uda-Shantarsk
phosphorite-bearing basin: Novosibirsk, Nauka, 168 p. \[in Russian\].

Ross, C.A., and Ross, J.R.P. 1983, Late Paleozoic accreted terranes of
western North America, in Stevens, C.H., ed., Pre-Jurassic rocks of
western North American suspect terranes: Los Angeles, Society of
Economic Paleontologists and Mineralogists, Pacific Section, p. 7--22.

Ross, B.M., Parrish, R.R., and Winston, Don, 1992, Provenance and U-Pb
geochronology of the Mesoproterozoic Belt Supergroup (northwestern
United States); implications for age of deposition and pre-Panthalassa
plate reconstructions: Earth and Planetary Science Letters, v. 113, p.
57--76.

Rozhdestvensky, V.S., 1987, Tectonic evolution of the Sakhalin Island:
Tikhookeanskaya Geologia, no. 3, p. 42--51 \[in Russian\].

Rozhdestvensky, V.S., 1993, Geodynamic evolution of the
Hokkaido-Sakhalin fold system: Tikhookeanskaya Geologiya, no. 2, p.
76--88 \[in Russian\].

Rubin, C.M., Miller, M.M., and Smith, G.M., 1991, Tectonic development
of Cordilleran mid-Paleozoic volcano-plutonic complexes; evidence for
convergent margin tectonism, in Harwood, D.S., and Miller, M.M., eds.,
Paleozoic and early Mesozoic paleogeographic relations of the Sierra
Nevada, Klamath Mountains, and related terranes: Geological Society of
America Special Paper 225, p. 1--16.

Rudenko, V.S., and Panasenko, E.S., 1990, Permian radiolaria of the
Pantovy Creek member of the Primorye region, in Zakharov, Y.D.,
Belyaeva, G.V., and Nikitina, A.P., eds., New data on the Paleozoic and
Mesozoic biostratigraphy of the southern Russian Far East: Vladivostok,
U.S.S.R. Academy of Sciences, p. 181--193 \[in Russian\].

Rusakov, I.M., Florova, Z.B., Bondarenko, N.S., and others, 1977,
Stratigraphy of Mesozoic deposits of the Alzaeya Plateau: Geologiya i
Geofizika, no. 8, p. 129--133 \[in Russian\].

Rusakov, I.M., Kats, A.G., Bondarenko, N.S., and others, 1975, New data
on the Paleozoic stratigraphy of the Alazeya Plateau: Akademii Nauk SSSR
Doklady, v. 223, no. 1, p. 178--181 \[in Russian\].

Rusmore, M.E., 1987, Geology of Cadwallader Group and the
Intermontane-Insular superterrane boundary: Canadian Journal of Earth
Sciences, v. 24, p. 2279--2291.

Sakai, A., and Kanie, H., 1986, Geology of the Nishicha district, Japan:
Geological Survey of Japan, 92 p., scale 1:50,000.

Sakhno, V.G., 1984, Volcanic zones on the ancient Pre-Cambrian
consolidated substrate; volcanic belts of Eastern Asia: Moscow, Nauka,
p. 160--177 \[in Russian\].

Saleeby, J.B. 1983, Accretionary tectonics of the North American
Cordillera: Annual Reviews of Earth and Planetary Science, v. 15, p.
45--73.

Sampson, S.D., Patchett, P.J., McClelland, W.C., and Gehrels, G.E.,
1991, Nd isotopic characterization of metamorphic rocks in the Coast
Mountains, Alaska and Canadian Cordillera; ancient crust bounded by
juvenile terranes: Tectonics, v. 10, p. 770--780.

Savostin, L.A., and Drachev, S.S., 1988a, Some features of the geologic
structure and tectonics of southern Bol'shoi Lyakhov Island (New
Siberian Islands): USSR Academy of Sciences Doklady, v. 301, p. 169--172
\[in Russian\].

---------1988b, Cenozoic compression in the vicinity of the
Novosibirskiy Islands and its relationship to the opening of the Eurasia
Basin: Oceanology, v. 28, p. 601--606.

Savostin, L.A., Karasik, A.M., and Zonenshain, L.P., 1984, The history
of the opening of the Eurasia Basin in the Arctic: Academy of Sciences
of the USSR Doklady, Earth Science Section, v. 275, p. 79--83.

Savostin, L.A., and Kheyfets, A.M., 1989, Paleomagnetic directions and
pole positions; data for the USSR-Soviet Geophysical Committee: Moscow,
World Data Center-B, Catalog, no. 7, as quoted in Lock and McElhinny
(1991).

Scammell, R.J., and Brown, R.L., 1990, Cover gneisses of the Monashee
Terrane; a record of synsedimentary rifting in the North American
Cordillera: Canadian Journal of Earth Sciences, v. 27, p. 712--726.

Scheglov, S.B., 1984, Volcanic belts of eastern Asia; geology and
metallogeny: Moscow, Nauka, 504 p. \[in Russian\].

Scholl, D.W., and Hart, P.E., 1994, Velocity and amplitude structures on
seismic reflection profiles---possible massive gas-hydrate deposits and
underlying gas accumulations in the Bering Sea Basin, in Howell, D.G.,
ed., The future of energy gases: U.S. Geological Survey Professional
Paper 1570, p. 331--351.

Scholl, D.W., Stevenson, A.J., Mueller, S., Geist, E.L., Engebretson,
D.C., and Vallier, T.L., 1992, Exploring the notion that
southeast-Asian-type escape tectonics and trench clogging are involved
in regional-scale deformation of Alaska and the formation of the
Aleutian-Bering Sea region, in Flower, M., McCabe, R., and Hilde, T.,
eds., Southeast Asia structure, tectonics, and magmatism: Texas A&M
University, Geodynamics Research Institute Symposium, College Station,
Tex., 1992, Proceedings, p. 57--63.

Scholl, D.W., Stevenson, A.J., Mueller, S., Geist, E.L., Vallier, T.L.,
and Engebretson, D.C., 1994, Regional-scale strain partitioning leading
to escape tectonism and formation of offshore arc-trench systems,
Alaska-Aleutian-Bering Sea region: Geological Society of America
Abstracts with Programs, v. 26, p. 136.

Schwarz, E.J., Muller, J.E., and Clark, K.R., 1980, Paleomagnetism of
the Karmutsen basalts from southeast Vancouver Island: Canadian Journal
of Earth Sciences, v. 17, p. 389--399.

Scotese, C.R., 1997, Continental drift, Phanerozoic plate tectonic
reconstructions: Arlington, University of Texas, Department of Geology,
PALEOMAP Progress Report 36, edition 7 (CD--ROM).

Seliverstov, N.I., Baranov, B.V., Egorov, Yu.O., and Shkira, V.A., 1988,
New data on the structure of the southern Komandorsky Basin obtained by
R/V Vulkanolog (26th Cruise): Volcanology and Sedimentology, no. 4, p.
3--20 \[in Russian\].

Semenov, D.F., 1982. Magmatic formations of the Pacific fold systems (in
the case of Sakhalin Island): Moscow, Nauka, 168 p. \[in Russian\].

Sengör, A.M.C., 1990, Plate tectonics and orogenic research after 25
years; a Tethyan perspective: Earth Science Reviews, Elsevier Science
Publishers, v. 27, p. 1--201.

Sengör, A.M.C., and Natal'in, B.A., 1996a, Paleotectonics of Asia;
fragments of a synthesis, in Yin, An, and Harrison, Mark, eds., The
tectonic evolution of Asia: Cambridge, U.K., Cambridge University Press,
p. 486--640.

---------1996b, Turkic-type orogeny and its role in the making of
continental crust: Annual Reviews Earth and Planetary Sciences, v. 24,
p. 263--337.

Sengör, A.M.C., Natal'in, B.A., and Burtman, V.S., 1993, Evolution of
the Altaid tectonic collage and Paleozoic crustal growth in Eurasia:
Nature, v. 364, p. 299--307.

---------1994, Tectonic evolution of the Altaid: Geology and Geophysics,
v. 78, p. 41--59.

Sergeyev, K.F., and Krasny M.L., eds. 1987, Geologic and geophysical
atlas of the Kuril-Kamchatka Island system: Leningrad, Ministry of
Geology, VSEGEI, 36 sheets \[in Russian and English\].

Seslavinskiy, K.B., and Ged'ko, M.I., 1990, Ophiolitic complexes of
western Chukotka and geodynamic interpretation of their genesis, in
Tectonics and mineralogy of the northeastern U.S.S.R.: Magadan, U.S.S.R.
Academy of Sciences, p. 191--194 \[in Russian\].

Shantser, A.E., Shapiro, M.N., Koloskov, A.V., and others, 1985,
Structural evolution of the Lesnovsk uplift and adjacent areas in the
Cenozoic (northern Kamchatka): Tikhookeanskaya Geologiya, no. 4, p.
66--74 \[in Russian\].

Shapiro, M.N., Ermakov, V.A., Shantser, A.E., Shul'dner, V.I., Khanchuk,
A.I., and Vysotsky, S.V., 1987, Essays on the tectonic development of
Kamchatka: Moscow, Nauka, 247 p. \[in Russian\].

Shevelev, E.K., 1987, Age of the volcanogenic siliceous and terrigenous
deposits of the basement of the Middle Amur basin: Tikhookeanskaya
Geologiya, no. 3, p. 13--16 \[in Russian\].

Shevelev, E.K., and Kuzmin, S.P., 1990, New data on the stratigraphy in
the Badzhal zone, in New data on Paleozoic and Mesozoic biostratigraphy
of the southern Far East: Vladivostok, U.S.S.R. Academy of Sciences, p.
72--80 \[in Russian\].

Shkodzinsky, V.S., Nedosekin, Yu.D., and Surnin, A.A., 1992, Petrology
of late Mesozoic magmatic rocks in eastern Yakutia: Novosibirsk, Nauka,
238 p. \[in Russian\].

Shmakin, V.B., 1991, New data on Upper Jurassic deposits of the
Koiverelan River Basin: USSR Academy of Sciences Izvestiya, Geological
Series, no. 4, p. 31--35 \[in Russian\].\*

Shul'gina, V.S., Tkachenko, V.I., and Kuznetsov, V.M., 1990, Geological
map of the U.S.S.R.: Leningrad, U.S.S.R. Ministry of Geology, scale
1:1,000,000 \[in Russian\].

Silberling, N.J., Jones, D.L., Blake, M.C., Jr., and Howell, D.G., 1984,
Lithotectonic terrane map of the western conterminous United States, pt.
C of Silberling, N.J., and Jones, D.L., eds., Lithotectonic terrane maps
of the North American Cordillera: U.S. Geological Survey Open-File
Report 84--523, 43 p.

---------1987, Lithotectonic terrane map of the western conterminous
United States: U.S. Geological Survey Miscellaneous Field Investigations
Map MF--1874--C, scale 1:2,500,000.

Silberling, N.J., Jones, D.L., Monger, J.W.H., and Coney, P.J., 1992,
Lithotectonic terrane map of the North American Cordillera: U.S.
Geological Survey Miscellaneous Investigations Map I--2176, scale
1:5,000,000.

Simanenko, V.P., 1986, Late Mesozoic volcanic arcs of the East Sikhote
Alin and Sakhalin Island: Tikhookeanskaya Geologiya, no. 1, p. 7--13
\[in Russian\].

Sisson, V.B., Hollister, L.S., and Onstott, T.C., 1989, Petrologic and
age constraints on the origin of a low-pressure/high-temperature
metamorphic complex, southern Alaska: Journal of Geophysical Research,
v. 94, p. 4392--4410.

Sizykh, V.I., Ignat'ev, V.A., and Shkol'nyi, L.D., 1977, New data on the
stratigraphy and tectonics on the left bank of Malyi Anyui River, in
Materials on the geology and mineral deposits of the northeastern
U.S.S.R.: U.S.S.R. Academy of Sciences, Magadan, v. 23, p. 29--34 \[in
Russian\].

Slautsitais, I.P., 1971, Paleomagnetic directions and pole positions:
data for the USSR-Soviet Geophysical Committee: Moscow, World Data
Center-B, Catalog, no. 1, as quoted in Lock and McElhinny (1991).

Smith, J.G., 1993, Geologic map of upper Eocene to Holocene volcanic and
related rocks in the Cascade Range, Washington: U.S. Geological Survey
Miscellaneous Investigations Map I--2005, 19 p., scale 1:500,000, 2
sheets.

Smith, M.T., and Gehrels, G.E., 1992, Detrital zircon geochronology of
Upper Proterozoic to lower Paleozoic continental margin strata of the
Kootenay arc; implications for the early Paleozoic tectonic development
of the eastern Canadian Cordillera: Canadian Journal of Earth Sciences,
v. 28, p. 1271--1284.

Smith, P.L., and Tipper, H.W. 1986. Plate tectonics and
paleobiogeography; Early Jurassic (Pliensbachian) endemism and
diversity: Palaios, v. 1, p. 399--412.

Snavely, P.D., Jr., Niem, A.R., MacLeod, N.S., Pearl, J.E., and Rau,
W.W., 1980, Makah Formation---a deep marginal-basin sedimentary sequence
of late Eocene and Oligocene age in the northwestern Olympic Peninsula,
Washington: U.S. Geological Survey Professional Paper 1162--B, 28 p.

Sokolov, S.D., 1990, Exotic complexes (terranes) in the Koryak Ridge
region: Geologiya i Razvedka, Proceedings of the High Educational
Institutions, no. 1, p. 16--29 \[in Russian\].

---------1992, Accretionary tectonics of the Koryak-Chukotka segment of
the Pacific Belt: Moscow, Nauka, 182 p. \[in Russian\].

Sokolov, S.D., and Byalobzhesky, S.G., 1996, Terranes of the Koryak
Highland: Geotectonics, no. 6, p. 68--80.

Solov'ev, A.V., Brandon, M.T., Garver, Bogdanov, N.A., Shapiro, M.N.,
and Ledneva, G.V., 1998, Collision of the Olyutor island arc with the
Eurasian continental margin; kinematic and age aspects: Earth Sciences
Doklady, v. 361, p. 632--634.

Solov'eva, M.F., 1975, Biostratigraphy of Lower and middle Carboniferous
deposits of Kotel'nyi and Wrangel Island and Chukotka based on
foraminifera, in The Upper Paleozoic of Northeast USSR: Leningrad,
Nauka, p. 42--53 \[in Russian\].

Sontag, L.J., and Panuska, B.C., 1990, Paleomagnetic data from Triassic
intrusives in the Wrangell Mountains, Alaska; implications for the age
of magnetization of Paleozoic rocks: State College, Mississippi State
University, Sigma Gamma Epsilon Compass, v. 67, p. 263--268.

Sosunov, G.M., 1985, Geologic map of Northeast U.S.S.R.: Magadan,
U.S.S.R. Ministry of Geology, Northeastern Production and Geological
Association, scale 1:5,000,000. \[in Russian\].

Sosunov, G.M., Pavlova, O.K., and Gel'man, M.L., 1982, Geologic map of
the northeastern U.S.S.R.: Magadan, U.S.S.R. Ministry of Geology, 39 p.,
scale 1:1,500,000 \[in Russian\].

Srivastava, S.P., and Tapscott, C.R., 1986, Plate kinematics of the
North Atlantic, in Vogt, P., and Tucholke, B.E., eds., The western North
Atlantic region (The Geology of North America, v. M): Boulder, Colo.,
Geological Society of America, p. 379--405.

Stamatakos, J., Kodama, K.P., and Pavlis, T.L., 1986, Paleomagnetic
study of early Tertiary sediments along the Castle Mountain Fault,
Matanuska Valley, Alaska \[abs.\]: Eos (American Geophysical Union
Transactions), v. 67, p. 921.

---------1987, Paleomagnetism of Eocene plutonic rocks, Matanuska
Valley, Alaska, and their tectonic significance \[abs.\]: Eos (American
Geophysical Union Transactions), v. 68, p. 291.

---------1988, Paleomagnetism of Eocene volcanic rocks, Matanuska
Valley, Alaska: Geology, v. 16, p. 618--622.

Stamatakos, J., Kodama, K.P., Vittorio, L.F. and Pavlis, T.L., 1989,
Paleomagnetism of Cretaceous and Paleocene sedimentary rocks across the
Castle Mountain Fault, south-central Alaska, in Hillhouse, J.W., ed.,
Deep structure and past kinematics of accreted terranes: American
Geophysical Union and International Union Geodesy and Geophysics
Geophysical Monograph 50, p. 151--177.

Stanley, W.D., Labson, V.F., Nokleberg, W.J., Csejtey, Béla, Jr., and
Fisher, M.A., 1990, The Denali fault system and Alaska Range of Alaska;
evidence for suturing and thin-skinned tectonics from magnetotellurics:
Geological Society of America Bulletin, v. 102, p. 160--173.

Stavsky, A.P., Berezner, O.S., Safonov, V.G., and Zlobin, S.K., 1989,
Tectonics of the Mainits zone of the Koryak Highland: Tikhookeanskaya
Geologiya, no. 3, p. 72--81 \[in Russian\].

Stavsky, A.P., Chekhovich, V.D., Kononov, M.V., and Zonenshain, L.P.,
1990, Plate tectonics and palinspastic reconstructions of the
Anadyr-Koryak region, northeast USSR: Tectonics, v. 9, p. 81--103.

Stepanov, V.A., and Shishakova, L.N., 1994, Kubaka gold-silver deposit:
Vladivostok, Dalnauka, 196 p.

Stevens, C.H., Davydov, V.I., and Bradley, D.C., 1997, Permian Tethyan
fusilinids from the Kenai Peninsula, Alaska: Journal of Paleontology, v.
71, p. 985--994.

Stone, D.B., 1975, Paleomagnetic studies and tectonics in the Aleutian
Islands, in Forbes, R.B., ed., Geology of the Bering Sea region:
Geological Society of America Special Paper 151, p. 59--75.

Stone, D.B., Harbert, W., Vallier, T.L., and McLean, H., 1983, Eocene
paleolatitudes for the Aleutian Islands \[abs.\]: Eos (American
Geophysical Union Transactions), v. 64, p. 87.

Stone, D.B., and Packer, D.R., 1979, Paleomagnetic data from the Alaska
Peninsula: Geological Society of America Bulletin, v. 90, p. 545--560.

Stone, D.B., Panuska, B.C., and Packer, D.R., 1982, Paleolatitudes
versus time for southern Alaska: Journal of Geophysical Research, v. 87,
p. 3697--3707.

Struik, L.C., and Orchard, M.J., 1985, Late Paleozoic conodonts from
ribbon chert delineate imbricate thrusts within the Antler Formation of
the Slide Mountain terrane, central British Columbia: Geology, v. 13, p.
794--798.

Sugimoto, M., 1974, Stratigraphical study in the outer belt of the
Kitakami Massif, northeastern Japan: Tohoru University, Institute of
Geology and Paleontology Contribution 74, p. 1--48.

Sukhov, S.A., 1975, Volcanic formations of the Far East: Moscow, Nauka,
111 p. \[in Russian\].

Symons, D.T.A., 1969a, Geological implications of paleomagnetic studies
in the Bella Coola and Laredo Sound map-areas, British Columbia:
Geological Survey of Canada Paper 68--72, p. 15.

---------1969b, Paleomagnetism of the Late Miocene plateau basalts in
the Caribou region of British Columbia: Geological Survey of Canada
Paper, 69--43, p. 15.

---------1969c, Paleomagnetism of four late Miocene gabbroic plugs in
south-central British Columbia: Canadian Journal of Earth Sciences, v.
6, p. 653--662.

---------1971, Paleomagnetism of the Triassic Guichon batholith and
rotation of the southern Interior Plateau, British Columbia: Canadian
Journal of Earth Sciences, v. 8, p. 1388--1396.

---------1973a, Paleomagnetic results from the Jurassic Topley
intrusions near Endako, British Columbia: Canadian Journal of Earth
Sciences, v. 10, p. 1099--1108.

---------1973b, Paleomagnetic results from the Tertiary Mt. Barr and
Hope plutonic complexes, British Columbia, Geological Survey of Canada
Paper 73--19, p. 1--10.

---------1973c, Concordant Cretaceous paleolatitudes from felsic plutons
in the Canadian Cordillera: Nature Physical Sciences, v. 241, p. 59--61.

---------1973d, Paleomagnetic zones in the Oligocene East Sooke gabbro,
Vancouver Island, British Columbia: Journal of Geophysical Research, v.
78, no. B, p. 5100--5109.

---------1977a, Geotectonics of Cretaceous and Eocene plutons in British
Columbia; a paleomagnetic fold test: Canadian Journal of Earth Sciences,
v. 14, p. 1245--1262.

---------1977b, Paleomagnetism of Mesozoic plutons in the westernmost
coast complex of British Columbia: Canadian Journal of Earth Sciences,
v. 14, p. 2127--2139.

---------1983a, Further paleomagnetic results from the Jurassic Topley
intrusives in the Stikinia subterrane of British Columbia: Geophysical
Research Letters, v. 10, p. 1065--1068.

---------1983b, New paleomagnetic data for the Triassic Guichon
batholith and their bearing on terrane I tectonics: Canadian Journal of
Earth Sciences, v. 20, p. 1340--1343.

---------1985a, Paleomagnetism of the west coast complex and the
geotectonics of the Vancouver Island segment of the Wrangellian
subterrane: Journal of Geodynamics, v. 2, p. 211--228.

---------1985b, Paleomagnetism of the Triassic Nicola Volcanics and
geotectonics of the Quesnellia subterrane of Terrane I, British
Columbia: Journal of Geodynamics, v. 2, p. 229--244.

Symons, D.T.A., and Litalien, C., 1984, Paleomagnetism of the Lower
Jurassic Copper Mountain Intrusions and the Geotectonics of Terrane I,
British Columbia: Geophysical Research Letters, v. 11, p. 685--688.

Symons, D.T.A., and Wellings, M.R., 1989, Paleomagnetism of the Eocene
Kamloops Group and the cratonization of Terrane I of the Canadian
Cordillera: Canadian Journal of Earth Sciences, v. 26, p. 821--828.

Tabor, R.W., 1994, Late Mesozoic and possible early Tertiary accretion
in western Washington State; the Helena-Haystack melange and the
Darrington-Devils Mountain fault zone: Geological Society of America
Bulletin, v. 106, p. 217--232.

Tabor, R.W., and Cady, W.M., 1978, Geologic map of the Olympic
Peninsula: U.S. Geological Survey Miscellaneous Investigations Map
I--994, scale 1:125,000.

Taira, A. and Tashino, M., 1987, Late Paleozoic and Mesozoic accretion
tectonics in Japan and Eastern Asia; historical biogeography and plate
tectonic evolution of Japan and Eastern Asia: Tokyo, Terra Science
Publications, p. 1--43.

Tamaki, K. 1988, Geological evolution of the Japan Sea and its tectonic
implications: Geological Survey of Japan Bulletin, v. 39, p. 269--365.

Tang, K., Wang, Y., He, G., and Shao, J., 1995, Continental-margin
structure of northeast China and its adjacent area: Acta Geologica
Sinica (English ed.), v. 8, no. 3, p. 241--258.

Tatsumi, Y., Otoruji, Y.I., Matsuda, T., and Nohda, S., 1989, Opening of
the Sea of Japan back-arc basin by asthenospheric injection:
Tectonophysics, v. 166, p. 317--329.

Tempelman-Kluit, D.J., 1979, Transported cataclasite, ophiolite, and
granodiorite in the Yukon; evidence of arc-continent collision:
Geological Survey of Canada Paper 79--14, 27 p.

Teplykh, V.I., and Karavaeva, N.I., 1974, Notes on the stratigraphy of
Upper Paleozoic deposits of the Oloy river basin, in The Precambrian and
Paleozoic of northeast USSR \[abs.\]: USSR Interdepartmental Committee
on Stratigraphy, Interdepartmental Stratigraphic Meeting, Magadan, 1974,
Abstracts, p. 150--153 \[in Russian\].

Terekhov, M.I., 1979, Stratigraphy and tectonics of the southern Omolon
massif: Moscow, Nauka, 114 p. \[in Russian\].

Terekhov, M.I., Lychagin, P.P., and Merzlyakov, V.M., 1984, Geologic map
of the Sugoy, Korkodon, Omolon, Oloy, and Gijiiga interfluves: Magadan,
U.S.S.R. Ministry of Geology, 144 p., scale 1:500,000 \[in Russian\].

Thorkelson, D.J., and Smith, A.D., 1989, Arc and intraplate volcanism in
the Spences Bridge Group; implications for Cretaceous tectonics in the
Canadian Cordillera: Geology, v. 17, p. 1093--1096.

Thrupp, G.A., and Coe, R.S., 1986, Early Tertiary paleomagnetic evidence
and the displacement of southern Alaska: Geology, v. 14, p. 213--217.

Till, A.B., and Dumoulin, J.A., 1994, Geology of Seward Peninsula and
Saint Lawrence Island, in Plafker, George, and Berg, H.C., eds., The
geology of Alaska: Boulder, Colo., Geological Society of America, The
Geology of North America, v. G--1, p. 141--152.

Tipper, H.W., and Richards, T.A., 1976, Jurassic stratigraphy and
history of north-central British Columbia: Geological Survey of Canada
Bulletin 720, 73 p.

Tozer, E.T., 1982, Marine Triassic faunas of North America; their
significance for assessing plate and terrane movements: Geologische
Rundschau, v. 71, p. 1077--1104.

Travers, W.B., 1978, Overturned Nicola and Ashcroft strata and their
relation to the Cache Creek Group, southwestern Intermontane Belt,
British Columbia: Canadian Journal of Earth Sciences, v. 15, p. 99--109.

Tret'yakov, F.F., 1989, Evolution of tectonic structures in the Kolyma
massif: Yakutsk, 140 p. \[in Russian\].

Trunilina, V.A., and Orlov, Yu.S., 1997, Late Mesozoic longitudinal and
transversal granite belts of northeast Yakutia: Nauka i Obrazovanie, no.
1, p. 50--56 \[in Russian\].

Tsukanov, N.V., 1991, Tectonic evolution of Kamchatka perioceanic area
in the late Mesozoic and early Cenozoic: Moscow, Nauka, 104 p. \[in
Russian\].

Tsvetkov, A.A., Fedorchuyk, A.V., and Gladenkov, A.Yu., 1990, Geologic
structure and magmatism of Bering Island: Akademii Nauk SSSR Izvestiya,
Seriya Geologicheskaya, no. 7, p. 40--56 \[in Russian\].

Tynankergav, G.A., and Bychkov, Yu.M., 1987, Siliceous, volcanic, and
terrigenous Upper Triassic deposits of the western Chukotka Peninsula:
Akademii Nauk SSSR Doklady, v. 296, p. 698--700 \[in Russian\].

Umhoefer, P.J., 1987, Northward translation of "Baja British Columbia"
along the Late Cretaceous to Paleocene margin of western North America:
Tectonics, v. 6, p. 377--394.

Umitbaev, R.B., 1976, Geological formations of the Okotsk massif, in
Parfenov, L.M., and Til'man, S.M., eds., Tectonics of the eastern Soviet
Asia: Vladivostok, U.S.S.R. Academy of Sciences, Far East Scientific
Center, p. 73--95 \[in Russian\].

Unrug, Raphael, 1997, Rodinia to Gondwana; the geodynamic map of
Gondwana supercontinent assembly: GSA Today, v. 7, p. 1--6.

Uyeda, S., 1986, Facts, ideas, and open problems on trench-arc-backarc
systems, in Wezel, F.C., ed., The origin of arcs: Amsterdam, Elsevier,
p. 435--460.

Vallier, T.L., 1977, The Permian and Triassic Seven Devils Group,
western Idaho and northeastern Oregon: U.S. Geological Survey Bulletin
1437, 58 p.

---------1995, Petrology of pre-Tertiary igneous rocks of the Blue
Mountains province of Oregon, Idaho, and Washington; implications for
the geologic evolution of a complex island arc, in Vallier, T.L., and
Brooks, H.C., eds., Geology of the Blue Mountains region of Oregon,
Idaho, and Washington: U.S. Geological Survey Professional Paper 1438,
p. 125--209.

Vallier, T.L., and Brooks, H.C., eds., 1995, Geology of the Blue
Mountains region of Oregon, Idaho and Washington; stratigraphy,
physiography, and mineral resources of the Blue Mountains region: U.S.
Geological Survey Professional Paper 1439, 198 p.

Vallier, T.L., Brooks, H.C., and Thayer, T.P., 1977, Paleozoic rocks of
eastern Oregon and western Idaho, in Stewart, J.H., Stevens, C.H., and
Fritsche, A.E., eds., Paleozoic paleogeography of the western United
States: Los Angeles, Society of Economic Paleontologists and
Mineralogists, Pacific Section, Pacific Coast Paleogeography Symposium
1, p. 455--466.

van der Heyden, P., 1992, A Middle Jurassic to early Tertiary
Andean-Sierran arc model for the Coast Belt of British Columbia:
Tectonics, v. 11, p. 82--97.

Van der Voo, R., 1981, Paleomagnetism of North America, brief review, in
McElhinny, M.W., and Valencio, D.A., eds., Paleoreconstruction of the
continents (Geodynamics Series, v. 2): Washington, D.C., American
Geophysical Union, p. 159--176.

---------1990, Phanerozoic paleomagnetic poles from Europe and North
America and comparisons with continental reconstructions: Reviews of
Geophysics, v. 28, p. 167--206.

---------1993, Paleomagnetics of the Atlantic, Tethys, and Iapetus
Oceans: Cambridge, U.K., Cambridge University Press, 411 p.

Van der Voo, R., Jones, D.L., Grommé, C.S., Eberlein, G.D. and Churkin,
M., 1980, Paleozoic paleomagnetism and northward drift of the Alexander
terrane, southeastern Alaska: Journal of Geophysical Research, v. 85,
no. B, p. 5281--5296.

Vance, J.A., Clayton, G.A., Mattinson, J.M., and Naeser, C.W., 1987,
Early and middle Cenozoic stratigraphy of the Mount Rainier-Tieton River
area, southern Washington Cascades, in Schuster, J.E., ed., Selected
papers on the geology of Washington: Washington Division of Geology and
Earth Resources Bulletin 77, p. 269--290.

Vandall, T.C., and Palmer, H.C., 1990, Canadian Cordilleran
displacement: paleomagnetic results from the Early Jurassic Hazelton
Group, Terrane I, British Columbia, Canada: Geophysical Journal
International, v. 103, p. 609--620.

Varsek, J.L., Cook, F.A., Clowes, R.M., Journeay, J.M., Monger, J.W.H.,
Parrish, R.R., Kanasewich, E.R., and Spencer, C.S., 1993, Lithoprobe
crustal reflection structure of the southern Canadian Cordillera II;
Coast Mountains transect: Tectonics, v. 12, p. 334--360.

Vernikovsky, V.V., Vernikovskaya, A.E., and Chernykh, A.I., 1998,
Neoproterozoic Taymyr ophiolitic belts and opening of the Paleo-Pacific
Ocean: International Geology Review, v. 40, p. 528--538.

Verzkhovskaya, V.A., and Krichevets, V.I., 1987, Geologic map of the
U.S.S.R.: Leningrad, U.S.S.R. Ministry of Geology, scale 1:1,000,000
\[in Russian\].

Vishnevskaya, V.S., Filatova, N.I., and Dvoryankin, A.I., 1991, New data
on Jurassic deposits of Semiglavaya Mountain: Akademii Nauk SSR
Izvestiya, Seriya Geologicheskaya, no. 4, p. 21--30.

Vishnevskaya, V.S., Peyve, A.A., and Sokolov, S.D., 1992, Age of the
Kuyul ophiolite terrane of northeastern Russian: Moscow, Akademii Nauk
SSSR Doklady, v. 327, p. 364--367 \[in Russian\].

Vlasov, G.M., ed., 1964, Kamchatka, Kuril, and Komandorsky Islands, in
Geologic descriptions, pt. 1 of Geology of the U.S.S.R., v. 31: Moscow,
Nedra, 733 p. \[in Russian\].

---------ed., 1977, Kamchatka, Kuril, and Komondorsky Islands mineral
deposits, in Geology of the U.S.S.R., v. 31: Moscow, Nedra, 351 p. \[in
Russian\].

Voevodin, V.N., Zhitkov, N.G., and Solov'ev, V.A., 1978, Mesozoic
eugeosynclinal complex of Chukotsk Peninsula: Geotektonika, no. 6, p.
101--109 \[in Russian\].

Vogt, P.R., Taylor, P.T., Kovacs, L.C., and Johnson, G.L., 1979,
Detailed aeromagnetic investigation of the Arctic Basin: Journal of
Geophysical Research, v. 84, no. B, p. 1071--1090.

Volsky, A.S., 1983, Geologic structure and history of the Upper
Primorye: Leningrad, Ministry of Geology, VSEGEI, summary of Ph.D.
thesis, 25 p. \[in Russian\].

Volynets, O.N., Antipin, V.S., Perepelov, A.B., and Anoshin, A.B., 1990,
Geochemistry of the volcanic series of an island-arc system in terms of
geodynamics for Kamchatka: Geologiya i Geofizika, no. 5, p. 3--13 \[in
Russian\].

Vrublevsky, A.A., Mel'nikov, N.G., Golozubov, V.V., Shevelev, E.K.,
Yushmanov, Yu.P., and Isozov, L.A., 1988, Mixtites of the Sikhote-Alin
fold belt: Vladivostok, U.S.S.R. Academy of Sciences, 111 p.

Walker, G.W., and MacLeod, N.S., 1991, Geologic map of Oregon: U.S.
Geological Survey, 2 sheets, scale 1:500,000.

Wallace, W.K., Hanks, C.L., and Rogers, J.F., 1989, The southern
Kahiltna terrane: implications for the tectonic evolution of
southwestern Alaska: Geological Society of America Bulletin, v. 101, p.
1389--1407.

Watson, B.R., and Fujita, Kazuya, 1985, Tectonic evolution of Kamchatka
and the Sea of Okhotsk and implications for the Pacific Basin, in
Howell, D.G., ed., Tectonostratigraphic terranes of the Circum-Pacific
region (Earth Science Series, v. 1): Houston, Tex., Circum-Pacific
Council for Energy and Mineral Resources, p. 333--348.

Wells, R.E., 1990, Paleomagnetic rotations and the Cenozoic tectonics of
the Cascade Arc, Washington, Oregon, and California: Journal of
Geophysical Research v. 95, no. B, p. 19409--19417.

Wells, R.E., Engebretson, D.C., Snavely, P.D., Jr. and Coe, R.S., 1984,
Cenozoic plate motions and the volcano-tectonic evolution of western
Oregon and Washington: Tectonics, v. 3, p. 275--294.

Wells, R.E., and Heller, P.L., 1988, The relative contribution of
accretion, shear, and extension to Cenozoic tectonic rotations in the
Pacific Northwest: Geological Society of America Bulletin, v. 100, p.
325--338.

Wells, R.E., Simpson, R.W., Bentley, R.D., Beeson, M.H., Mangan, M.T.,
and Wright, T.L., 1989, Correlation of Miocene flows of the Columbia
River Basalt Group from the central Columbia River Plateau to the coast
of Oregon and Washington, in Reidel, S.P. and Hooper, P.R., eds.,
Volcanism and tectonism in the Columbia River flood-basalt province:
Geological Society of America Special Paper 239, p. 113--128.

Wernicke, B., and Klepacki, D., 1988, Escape hypothesis for the Stikine
block: Geology, v. 16, p. 461--444.

Westgate, J.A., Stemper, V.A., and Péwé, T.R., 1990, A 3-m.y. record of
Pliocene-Pleistocene loess in interior Alaska: Geology, v. 18, p.
858--861.

Wheeler, J.O., Brookfield, A.J., Monger, J.W.H., Tipper, H.W., and
Woodsworth, J.O., 1991, Terrane map of the Canadian Cordillera:
Geological Survey of Canada Map 1731A, 2 sheets, scale 1:2,000,000.

Wheeler, J.O., and Gabrielse, H., 1972, The Cordilleran structural
province, in Price, R.A., and Douglas, R.J.W., eds., Variations in
tectonic styles in Canada: Geological Association of Canada Special
Paper 2, p. 2--81.

Wheeler, J.O., and McFeely, P., 1991, Tectonic assemblage map of the
Canadian Cordillera and adjacent parts of the United States of America:
Geological Survey of Canada Map 1712A, scale 1:2,000,000.

Wilson, J.T., 1968, Static or mobile earth; the current scientific
revolution: American Philosophical Society Proceedings, v. 112, no. 5,
p. 309--320.

Wittbrodt, P.R., 1985, Paleomagnetism and petrology of St. Matthew
Island, Bering Sea, Alaska: Fairbanks, University of Alaska, M.S.
thesis, 210 p.

Wittbrodt, P.R., Stone, D.B., and Turner, D.L., 1989, Paleomagnetism and
geochronology of St. Matthew Island, Bering Sea: Canadian Journal of
Earth Sciences, v. 26, p. 2116--2129.

Witte, W.K., Jr., 1982, Paleomagnetism and paleogeography of Cretaceous
northern Alaska: Fairbanks, University of Alaska, M.S. thesis, 146 p.

Witte, W.L, Stone, D.B., and Mull, G.C., 1987, Paleomagnetism,
paleobotany, and paleogeography of the Cretaceous arctic slopes, in
Tailleur, I.L., and Weimer, Paul, eds., Alaskan North Slope geology: Los
Angeles, Society of Economic Paleontologists and Mineralogists, Pacific
Section, and Alaska Geological Society, v. 50, p. 771--780.

Woodsworth, G.J., Anderson, R.G., and Armstrong, R.L., 1992, Plutonic
regimes, in Gabrielse, H., and Yorath, C.J., eds., Geology of the
Cordilleran orogen, Canada (The Geology of North America, v. G--2):
Boulder, Colo., Geological Society of America, p. 493--631.

Worall, D.M., Kruglyak, V., Kunst, F., and Kuznetsov, V., 1996, Tertiary
tectonics of the Sea of Okhotsk, Russia; far-field effects of the
India-Eurasia collision: Tectonics, v. 15, no. 4, p. 813--826.

Wynne, P.J., Irving, E., Maxon, J.A., and Kleinspehn, K.L., 1993,
Paleomagnetic results from the middle Cretaceous Silverquick and Powell
Creek Formations and northward displacement of the western Intermontane
Belt, British Columbia \[abs.\]: Geological Association of Canada
Program with Abstracts, p. A--112.

---------1995, Paleomagnetism of the Upper Cretaceous strata of Mount
Tatlow; evidence for 3000 km of northward displacement of the eastern
Coast Belt, British Columbia: Journal of Geophysical Research, v. 100,
no. B, p. 6073--6091.

Yole, R.W., 1969, Upper Paleozoic stratigraphy of Vancouver Island:
Geological Association of Canada Proceedings, v. 20, p. 30--40.

Yole, R.W., and Irving, E., 1980, Displacement of Vancouver Island;
paleomagnetic evidence from the Karmutsen Formation: Canadian Journal of
Earth Sciences, v. 17, p. 1210--1288.

Yurkova, R.M., 1991, Mineral alterations of ophiolitic and hosting
volcano-sedimentary units of the northwestern Pacific margin: Moscow,
Nauka, 164 p. \[in Russian\].

Yushmanov, Yu.P., 1986, Synsedimentary tectonic nappes of the East
Sikhote-Alin Pribrezhnay zone in the Dalnegorsk ore region:
Tikhookeanskaya Geologiya, v. 3, p. 99--107 \[in Russian\].

Zablotsky, E.M., Kalachova, E.D., Okuneva, T.M., Sei, I.I., and
Tikhomirova, L.B., 1990, New data on stratigraphy of Triassic and
Jurassic deposits of the Gorinsk synclinorium \[abs.\], in Precambrian
and Phanerozoic stratigraphy of the Transbaikal region and the southern
Far East: U.S.S.R. Academy of Sciences' Far East Regional
Interdepartment Stratigraphic Meeting, 14th, Khabarovsk, Abstracts, p.
148--151 \[in Russian\].

Zagruzina, I.A., 1977, Geochronology of Mesozoic granitoids in the
northeastern U.S.S.R.: Moscow, Nauka, 279 p. \[in Russian\].

Zakharov, V.A., Il'yna, V.I., Meledina, S.V., Nakhyaeva, T.I., and
Shurygin, B.N., 1984, The Jurassic system; the Phanerozoic of Siberia,
the Mesozoic and Cenozoic: Novosibirsk, Nauka, p. 16--53 \[in Russian\].

Zhizhina, M.S., 1959, Age of Paleozoic deposits on the Kotel'nyi Island
(Geologic Series, no. 4): Academy of Sciences of the USSR Izvestiya, p.
90--91 \[in Russian\].

Zhulanova, I.L., 1990, The Earth's crust of northeastern Asia in the
Precambrian and Phanerozoic: Moscow, Nauka, 304 p. \[in Russian\].

Zhulanova, I.L., and Pertzev, A.N., 1987, Basalt of the northern part of
the Pekul'ney Ridge; geology, petrologic characteristics, and problems
of genesis: Tikhookeanskaya Geologiya, no. 3, p. 65--76 \[in Russian\].

Zinkevich, V.P., 1981, Formations and stages of tectonic development of
the northern Koryak Highland: Moscow, Nauka, 108 p. \[in Russian\].

Zinkevich, V.P., Konstantinovskaya, E.A., Magakyan, R.G., and Tsukanov,
N.V., 1990, Accretionary structure of eastern Kamchatka: U.S.S.R.
Academy of Sciences Doklady, no. 5, p. 1186--1190 \[in Russian\].

Zinkevich, V.P., Konstantinovskaya, E.A., Tsukanov, N.V., and Rikhter,
A.V., 1993, Accretionary tectonics of Eastern Kamchatka: Moscow, Nauka,
272 p. \[in Russian\].

Zinkevich, V.P., and Tsukanov, N.V., 1992, The formation of the
accretional structure of Eastern Kamchatka in the late Mesozoic and
early Cenozoic: Geotectonics, v. 26, p. 332--343.

---------1993, Accretionary tectonics of Kamchatka: International
Geology Review, v. 35, p. 953--973.

Zmievskiy, Yu.P., Petukhov, A.D., and Kir'yanova, V.V., 1990, New data
on the structure and age of the Dzhelon suite, in Stratigraphy of the
Precambrian and Phanerozoic in Transbaikal and the southern Far East:
Khabarovsk, U.S.S.R. Academy of Sciences, p. 179--180 \[in Russian\].

Zonenshain, L.P., Kuz'min, M.I., and Natapov, L.M., 1990, Geology of the
USSR; a plate tectonic synthesis (Geodynamics Series, v. 21):
Washington, D.C., American Geophysical Union, 242 p.

Zyabrev, S.V., 1984, Upper Mesozoic turbidites of the southern West
Sakhalin trough: Tikhookeanskaya Geologiya, no. 5, p. 22--33 \[in
Russian\].