bluuebunny/crossref_metadata_2025_split huggingface dataset:
Irish Dinantian biostratigraphy: practical applications
Authors: Jones G. LL. , Somerville I. D. 
Published: April 2008

Abstract
For the last two decades there have been considerable advances in the dating and correlation of marine Dinantian carbonate sequences in Ireland, as elsewhere in Europe, primarily through the increased precision made possible by the use of microfossils, such as conodonts, foraminifers and miospores, together with macrofossils such as rugose corals. The advance was accelerated by the availability of boreholes up to 2km deep drilled by mineral exploration companies in Ireland who routinely use biostratigraphy. Detailed biostratigraphic biozonations are now established and are used for geological mapping and borehole zonation.
Data are assessed and attempts are made to highlight some of the practical problems encountered in locating Dinantian stage boundaries, recognizing biozones in Ireland, and suggesting correlations with other biozonation schemes in Europe. Although there are many difficulties in recognizing each of the stage boundaries in Ireland, two in particular present major problems — the Courceyan/Chadian and Holkerian/Asbian boundaries. From the work of Conil, Groessens and co-workers in Belgium, conodont and foraminiferal biozonation has been applied to the British and Irish Dinantian stages. Unfortunately, the bases of both the Chadian and Asbian stages rarely contain the zonal taxa. Also, at both stratigraphic levels, there are difficulties in comparing basinal and platform faunas. New biostratigraphic data in Ireland have permitted the recognition of two new intervals within the late Asbian Cf6γ Subzone, referred to informally as Cf6γ1 and Cf6γ2.
Until the Dinantian stages in Britain and Ireland are redefined biostratigraphically in the existing stratotype sections, or new stratotype sections are defined with faunal criteria, it is becoming more expedient and practical to recognize and define biozones in Ireland which can be identified and correlated with other Dinantian sections in continental Europe. This paper presents correlations with Belgian and Russian biostratigraphic schemes.
Fish assemblages in the Tournaisian-Viséan environments of the East European Platform
Authors: Lebedev O. A. 
Published: April 2008

Abstract

New fish material, including microremains from the Tournaisian-Viséan interval of the Moscow Syneclise, Northern Urals and Voronezh Anteclise of the East European Platform, comprises new species of Chondrichthyes:
Lissodus pectinatus
sp. nov., (?)
Diplodoselache antiqua
sp. nov.,
Eunemacanthus krapivnensis
sp. nov. Other fish taxa include
Stethacanthus obtusus
(Trautschold 1874), ‘
Orodus’ tumidus
(Trautschold 1874) and
Taeniolepis trautscholdi
(Chabakov 1927) are revised.

Tournaisian-Viséan deposits on the East European Platform are mostly represented by shallow marine or near-shore hyposaline facies with alternating salinity levels. Four major types of aquatic vertebrate environments are suggested: (1) continental fresh- and brackishwater; (2) lagoonal and estuarine with unstable salinity levels; (3) near-shore intertidal; and (4) off-shore neritic. Osteolepidids and actinopterygians are found in two or even three environmental zones, which suggests that they were eurybiontic and tolerant to changes of salinity, temperatures, hydrodynamics and other parameters of the basin. The most stenobiont forms are:
Diplodoselache, Ageleodus, Pycnoctenion
and dipnoans (1);
Deltodus, Streblodus, Copodus
and
petalodontids
(2);
Lissodus
and actinistians (4). The environmental distribution of the other groups is not as well expressed.
The Early Carboniferous chondrichthyans of the South Urals, Russia
Authors: Ivanov A. 
Published: April 2008

Abstract

Vertebrate remains including chondrichthyans were found in the Devonian/Early Carboniferous carbonate beds on the western and eastern slopes of the South Urals. Some of the Late Devonian forms (species of
Phoebodus
, acanthodians (
Devononchus
), placoderms and onychodontid sarcopterygians) disappear by the middle
Siphonodella praesulcata
conodont Zone. The ichthyoassemblages are considerably replenished by the new chondrichthyan taxa in the
Polygnathus communis carina
and
Gnathodus texanus-Mestognathus beckmanni
conodont Zones. The chondrichthyans were abundant among the vertebrate faunas of deep-water facies. A new species of chondrichthyan
Protacrodus aequalis
from the Late Famennian-early Tournaisian of the south Urals is described.
Volcano instability: a review of contemporary themes
Authors: McGuire W. J. 
Published: April 2008

Abstract
Active volcanoes are revealed to be dynamically evolving structures, the growth and development of which are characteristically punctuated by episodes of instability and subsequent structural failure. Edifice instability typically occurs in response to one or more of a range of agencies, including magma emplacement, the overloading or oversteepening of slopes, and peripheral erosion. Similarly, structural failure of a destabilized volcano may occur in response to a number of triggers of which seismogenic (e.g tectonic or volcanic earthquakes) or magmagenic (e.g. pore-pressure changes due to magma intrusion) are common. Edifice failure and consequent debris avalanche formation appears to occur, on average, at least four times a century, and similar behaviour is now known to have occurred at volcanoes on Mars and Venus. Realization of the potential scale of structural failures and associated eruptive activity has major implications for the development of monitoring and hazard mitigation strategies at susceptible volcanoes, which must now address the possibility of future collapse events which may be ten times greater than that which occurred at Mount St Helens in 1980.
Topographic characterization and monitoring of volcanoes via airborne laser altimetry
Authors: Garvin James B. 
Published: April 2008

Abstract

High spatial and vertical resolution airborne laser altimetry surveys of selected volcanic landforms have been used to investigate the metre-scale topographic characteristics of such features. Geodetic-quality airborne laser altimeter cross-sections of the Mount St. Helens dacite lava dome were acquired during the interval from 1987 to 1993; such data indicate that mass wasting of the flanks of the dome has outpaced episodic construction over the past seven years. Massive slumping of the south inner crater walls of the Mount St. Helens amphitheatre has been documented. Laser altimeter cross-sections of Mount Rainier have been compared with Mount St. Helens, Mount Adams, and with the Icelandic lava shield Skjaldbreidur in terms of local slope distributions, revealing basic similarities between the flanks of Rainier and St. Helens at length scales less than 5 m. When simple edifice shape parameters such as aspect ratio (
H/D
) are compared against total inferred edifice volume (
V
), Cascades stratovolcanoes such as Rainier and St. Helens fall along the extrapolation of the trend displayed for simple Icelandic lava shields. Cylindrical harmonic expansions involving laser altimeter cross-sections of volcanoes can be used mathematically to model the three-dimensional shapes of such features on the basis of only a few tens of coefficients and hence can be utilized to reduce the apparent extreme topographic complexity of major stratocones to terms that permit quantitative comparison with simpler volcanoes. In the future, geodetic airborne laser altimetry may be suitable as one of the many useful remote sensing methods for monitoring active volcanoes. A summary of the basic techniques associated with airborne laser altimetry in the context of volcanoes is provided.
Aseismic creep on faults and flank instability at Mount Etna volcano, Sicily
Authors: Rasà R. , Azzaro R. , Leonardi O. 
Published: April 2008

Abstract

This paper presents new data on the nature and significance of shallow fault creep in the Etna region. Sixteen sites where creep behaviour is obvious, have been identified, both from analysis of historical records, and from field surveys. Creep rates at each site vary considerably, from 0.5 to 2.3 cm a
−1
, and two extreme types of aseismic slip are recognized; (a) near-continuous, long-period movement along the aseismic segments of faults, and (b) spasmodic, short-lived, pre- and post-seismic movement related to seismically active fault segments. At most creep sites active displacements range from purely extensional to dip-slip. In some cases oblique-slip movements prevail, whereas purely strike-slip movements have been detected at only a single site. The overall creep kinematics indicate that surface creep on faults is a mode of discontinuous strain restricted to the faults displacing a sector of the eastern flank of the volcanic edifice bordered by the Pernicana fault, the NE Rift, the SE Rift and the Trecastagni-Mascalucia fault zone. We suggest that this mobile sector of the sea-facing flank of the volcano, including its uppermost clay-rich basement, is slowly sliding southeast under the control of a main deep-seated detachment surface.
Recent uplift of Ischia, southern Italy
Authors: Buchner Giorgio , Italiano Antonino , Vita-Finzi Claudio 
Published: April 2008

Abstract

Radiocarbon dating of fossil bivalves and corals from Ischia, in southern Italy, shows that parts of the island have undergone some 70m of uplift in the last 8500 years. Historical evidence reportedly suggests that during the last two millennia parts of the north coast were submerged by up to 4m whereas the southern coast underwent as much as 25 m of emergence. The
14
C results, which represent an average uplift rate of about 9 mm a
−1
, supplement studies based on potassium-argon dating of volcanic deposits which indicate that the Monte Epomeo horst at the centre of the island has risen by at least 800 m during the last 33 000 years, and micropalaeontological evidence, which points to some 700 m of emergence in the same time period. Eyewitness accounts suggest that some of the movement was coseismic. Prolonged uplift has created a steep topography prone to slope failure.
Calderas on Mars: characteristics, structure, and associated flank deformation
Authors: Crumpler L. S. , Head James W. , Aubele Jayne C. 
Published: April 2008

Abstract
Calderas and flank structures of martian volcanoes yield insight into general questions of volcano structural evolution and the underlying magma chambers in an environment where erosion is minimal. We have documented, through detailed geological mapping, the structures, associated volcanological features, and the stratigraphical relationships between the flank structures and caldera events during the building of each martian edifice. Two fundamentally different types of calderas are identified on Mars (the Olympus type and the Arsia type) that may represent end member variations in the size and depth of magma chambers.
Many of the flank structures adjacent to caldera rims are consistent with the predicted effects of magma chamber inflation as well as deflation that exert significant influences in the structural development of many volcanoes. Large-scale terracing and steepening of the upper flanks of the larger martian volcanoes may originate from magma chamber inflation and radial thrusting. Thus the endogenous component of volcano growth resulting from accumulated magma chamber growth may be significant.
Many of the deepest calderas are associated with evidence for voluminous eruptions elsewhere on the flanks and along through-going fissures and appear to result largely from evacuation and deflation of magma chambers without extensive precursor inflation. Draining of the magma chamber in these cases may be aided by the lateral propagation of magma in the form of shallow dykes up to several hundred kilometres in length and the associated formation of linear fissures. Nested caldera sequences, related flank pits, large-scale slumping, terracing, and sector structure are frequently arranged in linear patterns and are part of through-going eruptive lines or fissures several hundred kilometres in length that characterize several martian shield volcanoes. Fissures this long are interpreted to be dykes propagated outward from shallow magma chambers that have followed a minimum regional stress orientation. Comparison of the observed shape and orientation of caldera structures with orientation and style of flank deformation, and with the predictions from theory, indicate that regional stresses have probably been an important influence on the caldera and flank structures of martian volcanoes. The minimum regional stress orientation may be controlled largely by regional slopes associated with the Tharsis region and Elysium regions, and, in the case of Tyrrhena Patera, pre-existing radial fractures associated with the Hellas basin.
Crustal and mantle reflectors from Palaeoproterozoic orogens and their relation to arc-continent collisions
Authors: Snyder D. B. , Lucas S. B. , McBride J. H. 
Published: April 2008

Abstract

Two prominent geological features characterize the Palaeoproterozoic orogenic belts of Laurentia and Baltica: (1) Archaean cratons form the stable footwall during early stages of convergence and throughout crustal collision; and (2) juvenile, predominantly arc-derived crust was accreted to Archaean cratons through arc-continent collision. Seismic reflection profiling over the Svecofennian (Baltic Shield), Lewisian (British & Irish Isles) and Trans-Hudson (Canadian Shield) segments of an arguably once continuous orogenic belt has provided geometries of reflectors throughout both Palaeoproterozoic and Archaean crustal blocks as well as laterally coherent mantle reflectors. Two BABEL deep seismic reflection profiles within the Baltic Shield revealed structures along an irregularly shaped boundary between the juvenile 2.0–1.8 Ga Svecofennian domain and an Archaean craton (Karelia Province). An important result of the survey is the approximately 100 km horizontal offset between the inferred mantle suture, or palaeo-subduction boundary, and the geochemically-mapped crustal suture between juvenile Proterozoic crust and the Archaean craton. On the other side of the Atlantic, LITHOPROBE reflection profiles across the Trans-Hudson Orogen in central Canada reveal that 1.92–1.83 Ga juvenile arc and oceanic terranes of the Reindeer Zone form an allochthonous carapace about an Archaean basement block. Unexpectedly, the juvenile allochthons dip beneath the bounding Superior and Hearne cratons, defining a crustal-scale culmination in the core of the Orogen. The British and Irish Isles form an important bridge between the Palaeoproterozoic orogens of Laurentia and those of Baltica. Twenty deep reflection profiles on the continental shelf north and west of Scotland have traced a mantle reflector for over 800 km along its reconstructed strike, which is at a high angle to younger structures. This feature dips away from the reconstructed cratonic nucleus of Laurentia and may trace the Palaeoproterozoic (1.7–1.9 Ga) suture between the Archaean Lewisian block and accreted juvenile crust represented by the
c.
1.8 Ga Rhinns complex. A common theme that emerges from the integration of all these geological and seismic results is the role played by the Archaean lithosphere during arc-continent collision. In all cases studied, juvenile 1.9–1.8 Ga lithosphere was delaminated and its crustal flakes overrode the Archaean margins. This consistency reflects the relative strength and durability of Archaean crust/lithosphere, and suggests that large parts of the lithosphere underlying detached and flaked Palaeoproterozoic juvenile terranes, such as the Svecofennian or Reindeer Zone terranes, may be Archaean in age but modified during Proterozoic tectonism.
Rare earth and isotopic (Nd, O) heterogeneity of the Archaean mantle, Baltic Shield
Authors: Vrevsky A. , Krimsky R. , Svetov S. 
Published: April 2008

Abstract
Investigations of major and trace element geochemistry, whole-rock Sm-Nd and O isotopic composition of Archaean komatiites from the Baltic Shield show clear evidence of mantle source heterogeneity.

The komatiites were generated by 50–60% partial melting of the mantle at P
c.
35 kb, without garnet in the residue. Three different geochemical types of mantle source can be defined on the basis of HREE concentration: Type I, II and III sources yield komatiites with HREE abundances between 0.5–2, 2–3 and 3.5–5 Chondritic levels respectively. These types of mantle source can be correlated with three U-Pb zircon age groups of greenstone belts and their Nd and O isotopic composition.
Age and geodynamic aspects of the oldest rocks in the Precambrian Belomorian Belt of the Baltic (Fennoscandian) Shield
Authors: Bibikova E. V. , Skiöld T. , Bogdanova S. V. 
Published: April 2008

Abstract

The Belomorian Belt in the White Sea region was until recently considered the oldest core of the Baltic Shield but is now recognized to be essentially Late Archaean. This study reports U-Pb zircon ages and whole-rock Nd-isotopic results for aluminous metasedimentary gneisses and tonalitic-trondhjemitic-granodioritic intrusions. Metamorphic zircons from the aluminous gneisses date the earliest high-grade metamorphism to about 2.86 Ga. This was a low- to moderate-pressure granulite-facies event. Multigrain fractions of detrital zircons from these gneisses preserve little memory of protolith ages, but the whole-rock Sm-Nd DM-model ages are below 3.0 Ga which excludes dominantly Early to Middle Archaean detritus sources and indicates a short crustal prehistory. For the tonalitic-trondhjemitic intrusive rocks, U-Pb zircon and Sm-Nd model ages define two generations formed
c.
2.8 and 2.74–2.72 Ga ago. The oldest events in the Belomorian Belt can thus be correlated with Late Archaean developments in the adjoining Karelian Province further southwest in the Baltic Shield, but occurred at an active continental margin. This supports a Late Archaean accretional/collisional relationship between these two crustal segments.
Burwell domain of the Palaeoproterozoic Torngat Orogen, northeastern Canada: tilted cross-section of a magmatic are caught between a rock and a hard place
Authors: Van Kranendonk Martin J. , Wardle Richard J. 
Published: April 2008

Abstract

The northern segment of the Palaeoproterozoic Torngat Orogen is unique relative to the southern segment in that it is underlain by a 1910–1885 Ma suite of diorite-tonalite-granite rocks (DTG suite) emplaced into the margin of the Archaean Nain Province. Field and geochemical data indicate that it represents a subduction-generated Andean-type magmatic arc. Slivers of MORB-type, tholeiitic amphibolites and metasedimentary rocks within the DTG suite are interpreted as remnants of a backarc basin. Arc rocks are preserved in a tilted section from homogeneous, foliated tonalites at mid-amphibolite facies in the east, through gneissic tonalites, to massive orthopyroxene-bearing granitoid rocks of the Killinek charnockitic suite in the west. This assemblage is separated from the Archaean Rae Province, with which Nain Province collided, by a wide belt of turbiditic sedimentary rocks, now at granulite facies, known as the Tasiuyak gneiss. A younger suite (
c.
1865 Ma) of mafic tonalites and megacrystic metagranites within the Nain arc suite represents either syn-collisional plutons or late additions to the continental magmatic arc.

The southern segment of the orogen differs from the northern segment because it preserves no evidence of the DTG suite on Nain Province margin, but instead contains a widespread suite of calc-alkaline plutons across the Tasiuyak gneiss/Rae Province margin, dated as 1880 Ma. We develop two testable models to account for these along-strike variations and the presence of arc magmas on both sides of the suture. In
Model A
, a flip in subduction polarity from east-dipping at 1910–1885 Ma to west-dipping at
c.
1885 Ma is invoked, in which the
c.
1865 Ma suite of plutons in the northern segment are interpreted to represent syn-collisional magmas generated during accretion of the Burwell arc onto Nain Province. In
Model B
, the younger plutons in the northern segment may be interpreted as a late phase of the arc built on Nain Province, which we suggest may have been accomplished during a phase of double subduction immediately prior to collisional orogeny.

The Nain-Rae collision at
c.
1870–1860 Ma formed a doubly vergent thrust wedge, burying part of the arc in Burwell domain to depths of 35 km. During subsequent sinistral shear deformation at 1845–1822 Ma, Nain Province was buried obliquely beneath the still hot arc to depths of 40 km. At 1798–1780 Ma, crustal-scale disharmonic folding of the northern segment resulted in the simultaneous exhumation of the deeply-buried granulites of the arc and of the northwestern margin of the Nain Province across the Komaktorvik shear zone (KSZ). The KSZ was the site of significant translation between the Burwell domain and unreworked portions of the Nain Province, but it does not represent a fundamental plate boundary.
Accretion, rifting, rotation and collision in the North Atlantic supercontinent, 1700-950 Ma
Authors: Starmer Ian C. 
Published: April 2008

Abstract

Events in the North Atlantic region, from
c.
1700 to 950 Ma, are unified in a model compatible with palaeomagnetic results and Neoproterozoic supercontinent reconstructions. Following Labradorian-Gothian accretion, largely between 1700 and 1550 Ma, post-collisional effects continued until
c.
1500 Ma. Continental extension from
c.
1500 Ma onwards, related to ocean opening, developed granite-rhyolite provinces: the Central Metasedimentary Belt (Grenville Province) started to form at
c.
1425 Ma, with arcs outboard at
c.
1350–1300 Ma. Baltica started to separate from Laurentia and rotate at
c.
1240 Ma, causing crustal delamination of its leading edge, in South Norway. Here, subduction-related gabbroids intruded at
c.
1230–1225 Ma, as rotation proceeded. The Elzevirian Orogeny occurred at
c.
1190 Ma in the Southwest Grenville Province, marking the start of convergence of Baltica, in which backarc extension was accompanied by granites and bimodal volcanics. Collision at
c.
1080 Ma caused the Ottawan Orogeny which thrust accreted terranes northwestwards and closed the Mid-Continental Rift. In southern Baltica, complex deformation occurred. Post-collisional convergence and sinistral slip of Baltica against Laurentia (possibly related to convergence of Amazonia) caused thrusting, sinistral strike-slip faulting, folding and granitic intrusion until
c.
950 Ma. Post-tectonic granites intruded until
c.
900 Ma.