bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Precambrian rocks of Novaya Zemlya
Authors: Korago Eugene A. , Kovaleva Galina N. , Lopatin Boris G. , Orgo Vladimir V. 
Published: April 2008

Abstract
Neoproterozoic and perhaps older metamorphic and igneous rocks in the Novaya Zemlya Archipelago are exposed in four main localities. On the South Island of Novaya Zemlya (the Southern Domain) largely metasedimentary, low greenschist facies, pelitic and flyschoidal formations, dated by acritarchs as late Riphean-Vendian occur; they are intruded by metagabbro-dolerites and lamprophyres. These rocks are overlain by Ordovician strata with sharp, angular unconformity and are therefore considered to be products of Timanian (Baikalian) tectonogenesis. On the southern part of the North Island (the Central Domain), metamorphic rocks of high greenschist to amphibolite facies are preserved which are partly migmatized and comprise metasedimentary and igneous rocks; their contact with Palaeozoic strata here is tectonic. Isotopic age determinations on metasediments and igneous rocks vary from 1550 to 598 Ma and are not yet conclusive. These relatively highly metamorphosed formations may be older than Neoproterozoic. A Neoproterozoic (late Riphean) age was determined for the Mitushev Kamen‘Granite Massif, which is located within the Main Novozemel’sky thrust zone. On the northern part of North Island, (the Northern Domain) Neoproterozoic strata (mainly turbidites) of low greenschist facies pass conformably up into Cambrian and younger strata.
A major NW-trending fault (the Baidaratsky fault zone) is believed to separate the Southern Domain from Central and Northern Domains. It is concluded that the southern area is a peripheral part of the Neoproterozoic Timanian (Baikalian) fold belt. Further to the NE across the Baidaratsky fault zone, lies a broad area of possibly older basement, including the Central and Northern Domains of Novaya Zemlya and possibly the Franz Josef Land Archipelago.
Early Palaeozoic unconformity across the Timanides, NW Russia
Authors: Bogolepova O. K. , Gee D. G. 
Published: April 2008

Abstract
The Lower Palaeozoic sequences, unconformably overlying the Timanides of Timan, Pechora, Pai-Khoi, Vaigach, Novaya Zemlya and the Polar, Northern, Middle and Southern Urals are described and interpreted with regard to their stratigraphy, sedimentation, structure and biogeography. These mainly shallow marine sedimentary successions, with associated igneous rocks (largely alkaline), are Ordovician in age, reaching back into the Late Cambrian in some areas, particularly in the east, along the front of the Urals. They were deposited during rifting of Baltica’s northeastern margin and subsequent development of a passive continental margin. The underlying, mainly Neoproterozoic basement of turbidites in the west and calc-alkaline volcanites and ophiolites further east are briefly referred to, with particular emphasis on the age of the youngest rocks. Based on these data, a Timanian orogenic belt can be traced along the northeastern and eastern margin of the East European Craton. The timing of orogeny can be constrained to the Vendian, perhaps extending into the Early Cambrian.
Late Cambrian relative age constraints by acritarchs on the post-Timanian deposition on Kolguev Island, Arctic Russia
Authors: Moczydłowska M. , Stockfors M. , Popov L. 
Published: April 2008

Abstract

Platformal sedimentary successions, inferred to overlie folded Neoproterozoic basement complexes and the post-Timanian unconformity, were studied in the Bugrino 1 and North-Western 202 boreholes on Kolguev Island, southern Barents Sea. They yielded diverse, age-diagnostic acritarchs and some shelly fossils. The Upper Cambrian strata, referred to the
Peltura
and
Acerocare
zones, are recognized by means of acritarch taxa known from the East European Platform and other areas in Baltica, Avalonia, and Gondwana. Shelly faunas of brachiopods, phyllocarid crustaceans and problematic molluscs are indicative of the Tremadoc and Arenig stages in the upper part of the succession. The boreholes did not reach the Timanian unconformity and older Cambrian strata may be present. Within the area of the Pechora Basin, Cambrian strata have been identified with certainty only on Kolguev Island. Further east in the Polar Urals, Upper Cambrian strata are present and Lower or Middle Cambrian and Vendian strata have been claimed, though not yet proven. They are reported from several localities, but the fossils are poorly documented. The biostratigraphic evidence and facies development indicate that Upper Cambrian deposits may have been distributed widely along the northeastern margin of Baltica, as they were on the East European Craton and in Baltoscandia.
Spreading-rate parameters in ocean crust: analogue for ophiolite?
Authors: Flower M. F. J. 
Published: April 2008

Summary

Geophysical and petrologic studies of ocean crust generated at different spreading rates reveal specific rate-dependent characteristics, e.g. relative thickness of eruptive and intrusive crustal layers, stability of axial magma reservoirs in time and space, and pressure-temperature regimes for magma fractionation. Petrogenetic interpretation of whole-rock and glass selvedge compositional variation in basalts from different spreading axes reflects these relations. Inverse correlation of plagioclase accumulation (separately from mafic phases) and increasing spreading rate is attributed to the predominance of polybaric fractionation system at slow-spreading ridge axes, in contrast to low pressure, isobaric, systems at fast-spreading axes. Evidence for ‘cryptocumulates’ (aphyric lavas showing mass-balance attributes of cumulates) at axes of intermediate spreading rate, appears to reflect a combination of slow-spreading character (e.g. plagioclase accumulation) with fast-spreading character (e.g. relatively ‘open’ magma supply). It is desirable to monitor these effects on low-
K
D
incompatible-elements variation, and to test the applicability of spreading-rate parameters on ophiolite lava associations of ‘oceanic’ affinity.
The structure of the oceanic upper mantle and lower crust as deduced from the northern section of the Oman ophiolite
Authors: Smewing J. D. , Christensen N. I. , Bartholomew I. D. , Browning P. 
Published: April 2008

Summary

The lowermost 7 km of the Oman ophiolite consist of harzburgite, dunite and minor lherzolite of mantle origin overlain by layered gabbros and peridotites of the lower oceanic crust. Detailed structural measurements along three traverses through the ophiolite, complemented by olivine petrofabric determinations on oriented specimens from these traverses, reveal the following geometrical parameters of the spreading process:

(i)
The ultramafic rocks of the mantle sequence have all suffered deformation by simple shear at temperatures exceeding 950°C beneath a spreading ridge.

(ii)
The tectonite fabric which characterizes the mantle sequence passes upwards with no change in orientation or intensity into the layered gabbros and peridotites at the base of the crust.

(iii)
The sense of shear and type of slip system vary at random with depth, reinforcing petrological arguments that the Oman mantle sequence results from the juxtaposition of various mantle ‘packages’ equilibrated at different depths beneath the ridge.

(iv)
No unique kinematic model for the ophiolite can be formulated from the structural data of the three traverses; each traverse has a distinctive geometrical arrangement of the various structural elements relative to the reconstructed ridge directions. Dispersed mineral-layering planes indicate closing directions of magma chambers strung along the ridge.
Intraoceanic tectonism on the Gorringe Bank: observations by submersible
Authors: Auzende J. M. , Ceuleneer G. , Cornen G. , Juteau T. , Lagabrielle Y. , Lensch G. , Mevel C. , Nicolas A. , Prichard H. , Ribeiro A. , Ruellan E. , Vanney J. R. 
Published: April 2008

Summary
The Gorringe Bank is a 200 km long structure, oriented NE-SW, located at the eastern end of the Azores-Gibraltar line, at the Europe-Africa boundary. It consists of two mounts, Mount Gettysburg at the SW (−25 m) and Mount Ormond at the NE (−100 m). Previous works have shown that it corresponds to a section in oceanic mantle and crust.

A recent expedition of the submersible SP 3000 CYANA (May-June 1981) has allowed us:

(i)

to confirm that Mount Gettysburg essentially consists of largely serpentinized peridotites. The study of two oriented samples collected
in situ
allows some inferences about the kinematics of emplacement for these ultramafics;

(ii)
to show that Mount Ormond is mostly composed of various gabbros corresponding to different stages of differentiation. All the samples are more or less recrystallized and display strong deformation from high-temperature mylonitization to low-temperature brecciation. Such a ubiquitous deformation is not common in ophiolite complexes and may be linked with the location of the bank at the Europe-Africa plate boundary;

(iii)
to observe two generations of undeformed dykes cutting the Ormond gabbros: the first one of dolerites genetically linked with the gabbros, the second of alkaline rocks, feeders of the more recent alkaline volcanics capping the mount.
Oxygen-isotope and geochemical characterization of hydrothermal alteration in ophiolite complexes and modern oceanic crust
Authors: Stakes D. S. , Taylor H. P. , Fisher R. L. 
Published: April 2008

Summary
Stable isotopic, geochemical, and mineralogic variations in plutonic and hypabyssal rocks from oceanic crust (mainly from the Indian Ocean) and ophiolitic terranes (principally the Semail complex, Oman) are very similar. Several stages of seawater-oceanic crust interaction are recognized in these gabbros and diabases. Isotopic and chemical compositions of secondary mineral assemblages reflect changing temperatures and water-rock ratios, and record the effects of (i) pervasive seawater-hydrothermal circulation associated with the main stage of crustal formation at an oceanic spreading centre, (ii) subsequent alteration associated with off-axis volcanism (upper pillow-lava sequences), and (iii) progressively lower-temperature alteration associated with hydrothermal ‘ageing’ of the oceanic crust. Along the contact between the high-level, isotropic gabbro of the ophiolite, and the overlying sheeted dyke complex, repeated stoping of hydrothermally altered roof rocks into the magma chamber appears to be a ubiquitous process. Stoping is a maximum where the roof is intruded by large (off-axis) gabbro-diorite-plagiogranite bodies which may be 60% xenoliths. Abundant quartz-epidote-sulphide veins originate near these silicic intrusions and alter the overlying sheeted dyke complex. Diabase from the sheeted dyke complex in Oman, typically much more altered than dredged oceanic rocks of similar texture, exhibits the integrated effects of both the axis and off-axis hydrothermal systems.
Chemical and isotopic heterogeneities in orogenic and ophiolitic peridotites
Authors: Menzies M. A. 
Published: April 2008

Summary

Rare-earth element (REE) and isotopic analysis of clinopyroxenes from orogenic and ophiolitic peridotites reveal a complex multi-stage origin resulting in chemical and isotopic heterogeneity in the upper mantle. The bulk of the pyroxenes plot within the ‘mantle array’ in a region characterized by mantle depleted in light REE for much of Earth’s history. Interestingly the majority of the pyroxenes separated from orogenic and ophiolitic peridotites have ɛ
Nd
and ɛ
Sr
= MORB. As a consequence of such isotopic (and REE) characteristics the mantle sections of ophiolites are not believed to be related to the overlying plutonic and volcanic rocks by a simple parent-daughter melting relationship.
Emplacement of ophiolitic rocks in forearc areas: Examples from central Japan and Izu-Mariana-Yap island arc system
Authors: Ogawa Y. , Naka J. 
Published: April 2008

Summary
Recent results of ocean dredging of ophiolitic rocks in forearc areas in the west Pacific region are summarized and discussed together with the field data in the ophiolitic belts in the Setogawa and Mineoka forearc belts in central Japan. Metamorphism, deformation and sedimentation of the dismembered ophiolites in these regions indicate that they were emplaced at first in transform-fault areas or oceanic fracture zones, and they became the subsequent zones of initiation of subduction. Sometimes the mass of dismembered ophiolite was tectonically and sedimentarily mixed with island-arc materials and incorporated into the forearc belts during subsequent forearc tectonics.
Ophiolites: Figments of Oceanic Lithosphere?
Authors: Hall R. 
Published: April 2008

Summary

To resolve the problem of what a particular ophiolite represents it is necessary to look both at the ophiolite and at the rocks surrounding it: those immediately adjacent to the ophiolite and those of the region. Detailed geochemical and petrological studies are unlikely, on their own, to contribute to an understanding of the tectonic setting of ophiolite formation, nor of emplacement. Evidence from ophiolite complexes of the Mesozoic Arabian margin is inconsistent with the view that they originated at the spreading centre of a major ocean, or in back-arc basins. Instead, it is argued that these ophiolites represent discontinuous ‘oceanic’ rifts formed
within
the Arabian passive margin. Metamorphism of rocks beneath the ophiolite is considered to mark extension of the margin associated with the formation of these oceanic rifts in the late Cretaceous. These ophiolites do not mark a major suture and the true suture lies to the north of the ophiolite zone.
A review of fine-grained sediment origins, characteristics, transport and deposition
Authors: Gorsline D. S. 
Published: April 2008

SummaryFine-grained sediments and sedimentary rocks make up as much as 75% of the present and past sedimentary records. River discharge is the largest single source of fine-grained material, followed by biological, volcanic and aeolian sources. The composition, texture and bulk properties that characterize different sediment facies are controlled primarily by climate, tectonics, sediment supply, oceanic dispersal systems and biological activity.Fine sediments are transported into deep water by low-concentration nepheloid plumes, turbidity currents of a range of concentrations, flows and mass-movements. Mass-movement may be the major process delivering fine-grained sediment to the deep-sea floor over long time periods. Abyssal plains, the end of the passive margin transport system, are more affected by turbidity currents. Much bottom current reworking of sediments occurs at all depths in the ocean with results that may be very subtle. In shallower waters, balances between supply and dispersal may allow for the accumulation of mud belts on shelves and much fine sediments passes through such systems. Organic matter concentrations in fine sediment may be more a function of accumulation rates of organic versus terrigenous matter than local biological productivity.Fine-grained sediments require the application of methodology and results of a broad range of scientific disciplines. Effective understanding of the fine record will require interaction between several sciences.
Sedimentation in the southern Cape Verde Basin: regional observations by long-range sidescan sonar
Authors: Kidd R. B. , Searle R. C. 
Published: April 2008

Summary
A long-range sidescan sonar survey of the lower continental rise in the Cape Verde Basin has detected a dominant acoustic facies characterized by lineated backscattering patterns. These are interpreted as the sedimentary expression of turbidity current pathways across the area. Primary sediment transport directions can be interpreted from the backscattering patterns. Towards the north and west sediment distribution is increasingly affected by abyssal hill topography, either exposed oceanic basement features or hills draped with pelagic sediment.
Fine-grained turbidites and associated mass-flow deposits in the Ulleung (Tsushima) Back-arc Basin, East Sea (Sea of Japan)
Authors: Chough S. K. 
Published: April 2008

Summary

Acoustically laminated Quaternary deposits (up to 800 m thick) dominated by turbidites overlie transparent hemipelagic sediments (Pliocene and older) in the Ulleung (Tsushima) Basin. The topmost layer in sediment cores is post-glacial hemipelagic sediment, about 2 m thick, underlain largely by a repetitive sequence of fine-grained, thinly- or un-laminated turbidites. Coarse-grained, graded and plane-laminated units rarely occur. Turbidites in the Ulleung Basin were accumulated at a rate of about 12 cm/10
3
years. The turbidites in the centre of the Ulleung Basin correspond to slump, slide and debris-flow deposits on the slope and base-of-slope environments. It suggests that the mass-flow processes occur successively from a broad, linear source on the prograding shelf break. Sediments originated from the adjoining margins of the Korean Peninsula and north western Honshu. Turbidites deposited during the major volcanic eruptions were derived from the Oki Spur and San-in coast, whereas those deposited between the volcanic events were mainly from the stable craton of the eastern margin of the Korean Peninsula.
Late Quaternary calcareous clayey-silty muds in the Obock Trough (Gulf of Aden): hemipelagites or fine-grained turbidites?
Authors: Faugères J.-C. , Cremer M. , Gonthier E. , Noel M. , Poutiers J. 
Published: April 2008

Summary
Three cores have allowed us to survey Holocene deposits in a trough of the Gulf of Aden ridge. Within this particular environment (steep slopes, tectonic and volcanic activity) sediments are fine-grained, apparently homogeneous calcareous muds, rich in clay and planktonic microfossils: these features suggest that they are hemipelagic deposits. However, high sedimentation rates (20 to 50 cm/1000 yrs), lateral variation, and the occurrence of dynamic sedimentary structures (visible on X-radiographs and in thin sections), suggest that they have been emplaced mainly by gravity currents. These reworked hemipelagic materials are deposited on the shelf edge and on the trough slopes. This is confirmed by the sequential arrangement of sedimentary characteristics, as shown by analysis of microstructures, microfacies, carbonates, clay minerals, grain-size and other components.

Two types of sequences have been observed; the first we call the ‘type sequence’. This commonly overlies an erosional surface and comprises three divisions from bottom to the top:
Division I
(equivalent to Piper’s E1 division); mud with 8–10% sand fraction, rich in biogenic tests which occur as well-sorted horizontal laminae.

Division II
(equivalent to Piper’s E2 and E3 divisions); mud with low sand fraction (1%), very poor in biogenic material, no lamination, but horizontal orientation of silt-sized bioclasts.

Division III
(equivalent to Piper’s E2 and E3 divisions); mud with low sand fraction (1%), very poor in biogenic material, no lamination, but horizontal orientation of silt-sized bioclasts.

Division III
(equivalent to Piper’s F division); mud with low sandy fraction, poorly-sorted biogenic material, no dynamic sedimentary structures.

The second type of sequence is less common and comprises two divisions:

Division I’a
; very thin layer (millimetric), rich in terrigenous silt, which scours underlying sediment and shows horizontal, oblique and cross lamination.

Division I’b
; mud with low biogenic sand content, showing horizontal more or less clear and irregularly-distributed lamination.

These two sequences correspond to divisions E and F defined by Bouma (1962) and Piper (1978) in terrigenous turbidite sequences. The ‘type sequence’ is comparable to turbiditic sequences described in pelagic or hemipelagic material, deposited in similar morpho-tectonic environments (e.g. the eastern Mediterranean Sea or Mid Atlantic Ridge fracture zone).
Contourite facies of the Faro Drift, Gulf of Cadiz
Authors: Gonthier E. G. , Faugères J.-C. , Stow D. A. V. 
Published: April 2008

Summary
The Faro Drift is an elongate sediment body (50 km long, 300 m thick) that parallels the northern margin of the Gulf of Cadiz south of Portugal. On the basis of location, morphology and seismic character of the drift together with bottom photographs, sediment distribution and the known regional oceanography, we can be certain that the Faro Drift was constructed by bottom currents related to the deep outflow of Mediterranean water. Detailed study of a closely-spaced suite of cores has therefore allowed characterization of the sediments into three contourite facies: sands and silts, mottled silts and muds, and homogeneous muds. The first is equivalent to the sandy contourites and the two others to the muddy contourites of earlier studies. These three facies are arranged in irregular vertical ‘sequences’ that reflect long-term variations in bottom current velocity. They are distinctly different from typical fine-grained turbidite and hemipelagite facies.
The role of canyons in late Quaternary deposition on the United States mid-Atlantic continental rise
Authors: McGregor B. A. , Nelsen T. A. , Stubblefield W. L. , Merrill G. F. 
Published: April 2008

Summary
The continental margin in the US mid-Atlantic region is dissected by many downslope-trending canyons, extending from near or at the shelf-edge out onto the rise. Sediments from the shelf and slope are transported seaward through the canyon system to the rise. Sand-size material from the shelf is introduced by means of spillover into the canyons and onto the upper slope. A dendritic gully system dissecting the entire slope also provides pathways for slope sediments, mainly silts and clays, to be introduced into the canyons. Distinct grain-size distributions of the shelf sands which are interbedded or mixed with the fine-grained sediments of the slope and rise can be used as tracers for transport pathways on the continental margin. Canyon erosion on the rise also may provide a local source of sediment which must be considered. Sand-size-sediment distribution and DSRV Alvin observations show that erosion and deposition take place periodically in the mid-Atlantic canyons and on the rise seaward of New Jersey and Delaware.
Continental source area contributions to fine-grained sediments on the Oregon and Washington continental slope
Authors: Krissek L. A. 
Published: April 2008

Summary
Chemical and quantitative mineral abundance data for the 2–20 μm fraction of 78 samples from the Oregon-Washington continental slope have been modelled using linear programming to estimate sediment contributions from continental source areas and evaluate the effects of mixing material derived from these sources on the formation of hemipelagic sediments. The mineral data distinguish three source areas, while the chemical data define only two. Results from the two data sets indicate similar patterns and magnitudes of source area influence on the continental margin.
The contributions are used to construct a sediment budget for 2–20 μm-sized sediments on the continental slope. The slope sediments contain approximately 47% Columbia River, 32% Klamath Mountain, and 21% California Coast Range material. Approximately 25–50% of the Columbia River, 29–46% of the Klamath Mountain, and 7–12% of the California Coast Range annual suspended sediment input is retained on the slope, indicating that the slope acts as a more effective trap of 2–20 μm material from proximal than distal source areas. This study also demonstrates the importance of multiple sediment sources and sediment mixing in the formation of hemipelagic sediments on a continental margin.