bluuebunny/crossref_metadata_2025_split huggingface dataset:
The sedimentology of the Swedish Alum Shales
Authors: Thickpenny A. 
Published: April 2008

Summary
The middle and upper Cambrian (and locally lowermost Tremadoc) Alum Shale Formation of Scandinavia and the Baltic Sea area outcrops from Finnmark in north Norway to Bornholm in the south, and from Estonia westwards to the Oslo region. The Formation is generally underlain by shallow water sandstones but is locally unconformable on Precambrian continental basement; it is overlain by shallow marine glauconitic, phosphatic limestones.
Detailed examination of borehole cores and some quarry sections from several of the Swedish Lower Palaeozoic outliers indicates the occurrence of five lithofacies: (1) Black laminated mudstone, rich in organic carbon, suggesting extreme anoxic conditions; (2) organically banded mudstone showing more variable organic input: (3) grey mudstone, laminated or unlaminated and lacking significant organic matter, suggesting more oxic conditions; (4) bituminous, fossiliferous limestone concretions also indicative of more oxic conditions, possibly above wavebase; and (5) glauconitic siltstones and sandstones, graded and transported, and quartz rich siltstones, mostly transported. Pyritic laminae may also occur within any of the above mudstone lithofacies. Sedimentation rates for some of the above facies are estimated and show values comparable with modern pelagic sedimentation, the lowest occurring within the bituminous limestones and progressively increasing to interlaminated black and grey mudstones. The sedimentation rates in combination with the lithological variation suggest less extreme reducing conditions in the middle Cambrian compared with the upper Cambrian, a factor important in the control of Uranium and other trace element anomalies found within the upper Cambrian.
Deep-water fine-grained sediments: facies models
Authors: Stow D. A. V. , Piper D. J. W. 
Published: April 2008

Summary
Based on a large amount of published data and stimulated by the papers and discussion at the International Workshop on Fine-Grained Sediments held in Halifax, Canada in August 1982, we have attempted a synthesis of deep-water fine-grained sediment facies. Three main facies groups related to depositional processes can be identified: turbidites, contourites and pelagites/hemipelagites. There is a continuum between the different processes and hence a continuum between facies. Nevertheless, it is possible to define several distinct facies models within each of these groups on the basis of sedimentary structures, texture and composition, and to provisionally interpret these in terms of depositional hydrodynamics. Patterns of horizontal and vertical facies distribution can be related to depositional subenvironments. There is much variability within and departure from the facies models we propose, and many interesting and problematic areas of research remain in the quest for better understanding of deep-water fine-grained sediments.
A model of volcanogenic sedimentation in marginal basins
Authors: Carey Steven , Sigurdsson Haraldur 
Published: April 2008

Summary
Marginal basins adjacent to oceanic island arcs receive volcaniclastic debris from the bordering volcanic arc, back-arc spreading centre, and, to a lesser degree, the remnant arc. The volcanic arc is volumetrically the most important source, with abundant volcaniclastics being produced by explosive subaerial and/or subaqueous eruptions and secondary erosion of the arc complex. Transport of material to the deeper parts of marginal basins occurs by passive settling through the water column or by a variety of sediment gravity flows generated by primary eruptions and secondary remobilization processes. Deposition of arc-derived material at the base of the arc flank produces thick volcaniclastic aprons and results in a marked asymmetry in the accumulation of volcanogenic sediment within basins. The apron facies are complex and not analogous to typical deep-sea fan systems because of the influence of arc volcanism on the nature and delivery of sediment to the deep sea. Back-arc spreading centres supply a small volume of deep-water hyaloclastites and hydrothermally derived volcanogenic sediments which are incorporated into the basal parts of sedimentary sequences. The dispersal and deposition of volcanogenic sediments are profoundly influenced by geological processes associated with marginal basin evolution such as back-arc spreading, faulting, and island-arc splitting.
Geochemical characteristics of basaltic volcanism within back-arc basins
Authors: Saunders Andrew D. , Tarney John 
Published: April 2008

Summary

Back-arc basins are formed by extensional processes similar to those occurring at mid-ocean ridges. However, whereas the magmas erupted along the major ocean ridges are predominantly LIL element-, Ta- and Nb-depleted N-type MORB, many back-arc basins are floored by basalts transitional between N-type MORB and island arc or even calc-alkaline basalts (viz. enrichment of LIL elements (K, Rb, Ba, Th) relative to HFS elements (Nb, Ta, Zr, Hf, Ti)). On a broad scale, it is possible to relate basalt composition, tectonic setting of the basin, and maturity of the adjacent subduction zone. Thus, the Parece Vela Basin, formed during the earliest stages of the Mariana subduction system, is floored by basalts indistinguishable from N-type MORB, whereas the later Mariana Trough is erupting N-type MORB
and
basalts with calc-alkaline characteristics, commonly in close spatial proximity. The calc-alkaline component is best developed in narrow, ensialic basins such as Bransfield Strait, where the extension is adjacent to mature, continent-based magmatic arcs. This range of compositions, from N-type MORB to calc-alkaline basalt, can be satisfactorily explained only by invoking chemical variations in the composition of the mantle material supplying the back-arc basin crust. Two major processes may be suggested: (i) selective contamination of the mantle wedge by LIL-enriched hydrous fluids, perhaps together with sediments, derived from the descending, dehydrating oceanic lithosphere; and (ii) repeated melt (and incompatible element) extraction during basalt genesis. The former process will enrich the mantle source of back-arc basalts with LIL elements; the latter will deplete the source in all incompatible elements, but the net effect of both processes is to increase the LIL/HFS element ratio of the source regions. Consequently, as the subduction zone matures, the LIL/HFS element ratio of successive back-arc basalts will be expected to increase, from initial N-type MORB ‘background’ values, to ratios more typical of island-arc basalts. The model has implications for mantle dynamics in back-arc regions, because transfer of material from the subducted slab may destabilize the overlying mantle, potentially leading to diapiric uprise when tectonic conditions permit extension.
Characteristics and tectonic significance of supra-subduction zone ophiolites
Authors: Pearce J. A. , Lippard S. J. , Roberts S. 
Published: April 2008

Summary
Supra-subduction zone (SSZ) ophiolites have the geochemical characteristics of island arcs but the structure of oceanic crust and are thought to have formed by sea-floor spreading directly above subducted oceanic lithosphere. They differ from ‘MORB’ ophiolites not only in their geochemistry but also in the more depleted nature of their mantle sequences, the more common presence of podiform chromite deposits, and the crystallization of clinopyroxene before plagioclase which is reflected in the high abundance of wehrlite relative to troctolite in their cumulate sequences. Most of the best-preserved ophiolite complexes in orogenic belts are of this type.

Geological reconstructions suggest that most SSZ ophiolites formed during the initial stages of subduction prior to the development of any volcanic arc. Evidence from these ophiolites suggests that the first magma to form in response to intra-oceanic subduction is boninitic in composition, derived by partial melting of hydrated oceanic lithosphere in the ‘mantle wedge’. As subduction proceeds, the magma composition changes to island-arc tholeiite, probably because the hydrated asthenosphere of the ‘mantle wedge’ eventually becomes the dominant mantle source. Other SSZ ophiolites formed in the early stages of back-arc spreading following splitting of a pre-existing arc. Nonetheless the more common mechanism for formation of SSZ ophiolites appears to have been
pre-arc
rather than back-arc spreading.
The Ordovician marginal basin of Wales
Authors: Kokelaar B. P. , Howells M. F. , Bevins R. E. , Roach R. A. , Dunkley P. N. 
Published: April 2008

Summary

The Lower Palaeozoic Welsh Basin was founded on immature continental crust. During late Precambrian-early Cambrian times, volcanism and sedimentation were influenced by NE-SW-trending faults which defined the NW and SE margins of the basin. During the Cambrian, marine sediments infilled a graben and at the end of the Tremadoc widespread tectonism was associated with an island-arc volcanic episode. In the Ordovician this subduction-related activity was succeeded by mainly tholeiitic volcanism related to back-arc extension, with the locus of arc volcanism sited further N, in the Lake District—Leinster Zone of the Caledonides. In Wales, the Ordovician volcanic activity shifted in time and space. In S Wales volcanism persisted from the middle Arenig through the Llanvirn. In N Wales the volcanism can be broadly divided into dominantly pre-Caradoc activity in southern Snowdonia and an intra-Caradoc episode in central and northern Snowdonia. In eastern Wales, including the Welsh Borderland, and in Llŷn, both episodes are represented. In all areas faults greatly influenced both volcanism and sedimentation. Intrusive activity was dominated by high-level emplacement of sills. Granite (
s.l.
) stocks are restricted to central and northern Snowdonia and Llŷn and many were coeval with extrusive volcanism.

Volcanism in the basin was essentially bimodal with voluminous eruptions of tholeiitic basalts with ocean-floor affinities, and of rhyolites. Minor volumes of andesite to rhyodacite resulted from low-pressure fractional crystallization of the tholeiitic basalts. Available evidence suggests that the rhyolites resulted mainly from crustal fusion, although in some instances evolution by crystal fractionation from intermediate magma has been proposed. Calc-alkaline assemblages are petrographically distinct, of minor occurence and, contrary to previous conclusions, are relatively insignificant in the characterization of the tectonic environment of the basin.
Throughout the basin, volcanism was generally succeeded by deposition of black muds and then turbidite-dominated sequences.
The Late Precambrian and early Palaeozoic marginal basin of South China
Authors: Pan Guoqiang 
Published: April 2008

Summary
An integrated study based on recent geological mapping and encompassing the evolution of sedimentary facies, volcanism, plutonism and metamorphism in the Sinian and early Palaeozoic rocks of SE China has led to a reinterpretation of the area as representing a marginal basin situated at the SE margin of the Yangtze continental plate. The marginal basin comprised an active basin or trough and an inactive or marginal sea. The two parts display different sedimentary facies and tectonic and volcanic histories. It is concluded that in the early stages of evolution magma was derived from the mantle but later magmas were generated mainly in the crust.
Evolution of a Mesozoic passive continental margin: Baër-Bassit (NW Syria)
Authors: Delaune-Mayere M. 
Published: April 2008

Summary
The Baër-Bassit area comprises imbricate sheets of ophiolities and pelagic sedimentary rocks thrust eastward onto the Arabian platform.
Deep-water sediments were deposited from Late Triassic to Mid-Cretaceous time (Cenomanian/Turonian). Triassic sediments consist of marls and Halobia-bearing limestones. From Jurassic to Cenomanian the deposits were siliceous mudstones, siltstones and cherts.
Comparisons with the pelagic sediments of the Mamonia Complex (Cyprus) and the Antalya Complex (Turkey) show that the three areas in the East Mediterranean had a similar evolution from Upper Triassic to Lower Cretaceous time. In the Upper Triassic there was continental rifting and formation of oceanic crust in a rift similar to the Red Sea. The opening was more marked in the west than in the east. This was followed by subsidence and sedimentation of siliceous rocks from Jurassic to Lower Cretaceous. Per-alkaline volcanism took place in the Baër-Bassit area at this time. Sedimentation stopped in Hauterivian time in Cyprus, in the Cenomanian/Turonian in Syria, and during Late Cretaceous in Antalya. Sedimentation related to closure of the oceanic basin still remains to be defined.
The Arabian sub-plate during the Mesozoic
Authors: Hirsch F. 
Published: April 2008

Summary
The Mesozoic facies, distribution, palaeo-zoo-geography and tectonic history of the Levantine and Tauride-Zagride autochthonous and para-autochthonous units, suggest that these areas were part of the Arabian sub-plate and never lay far apart. This would tend to invalidate the hypothesis of an oceanic basin (Mesogea) in the present Eastern Mediterranean during the Mesozoic.
The SW segment of the Antalya Complex, Turkey as a Mesozoic-Tertiary Tethyan continental margin
Authors: Robertson A. H. F. , Woodcock N. H. 
Published: April 2008

Summary
The SW segment of the Antalya Complex is an assemblage of Mesozoic carbonate platform, margin and ophiolitic rocks which record the formation and tectonic emplacement of a small Mesozoic ocean basin.

The pros and cons of three alternative models in the literature are outlined. The original model was of a linear continental margin of a southerly Mesozoic ocean basin (Dumont
et al.
1972), emplaced in latest Cretaceous and Miocene time as three major nappes. Ricou
et al.
(1975) reinterpreted these nappes as being rooted in a unique northerly Tethys. In the light of knowledge of modern ocean basins, Robertson and Woodcock then developed the concept of a palaeogeographically complex small southern ocean basin in which strike-slip faulting played an important role in both formation (Reuber, this volume) and emplacement (Woodcock & Robertson 1977).

We discuss here a number of important and controversial topics, including the timing of volcanism and ocean crust genesis, the origin of mountain-sized shallow water limestone masses in the allochthon, and the role of strike-slip versus nappe tectonics in the Antalya Complex. An updated version of our palaeogeographical model views the Antalya Complex as an early Mesozoic (Triassic-Jurassic) rift expanded in the Cretaceous by formation of a small ocean basin strongly influenced by strike-slip faulting during both the opening and closing stages.
Geodynamic evolution of Turkey and Cyprus based on palaeomagnetic data
Authors: Lauer J. P. 
Published: April 2008

Summary
Using all the available palaeomagnetic results tentative reconstructions are given for the past positions of various parts of Turkey. At least two parts were located near the equator in Triassic times, presumably along the south-eastern boundary of the Arabian plate. This implies large-scale continental drift towards the north-west which must be taken into account in interpretations of the Alpine orogeny and the geology of the Eastern Mediterranean.
Structural evolution of the Pelagonian Zone in Northwestern Macedonia, Greece
Authors: Mountrakis D. 
Published: April 2008

Summary
The pre-Upper Palaeozoic basement of the North Pelagonian zone s.1. consists of two units: the Eastern unit of the Voras Mountains and the Western unit of the Vernon Mountains. These units are two parallel crystalline sequences which have been metamorphosed under similar conditions in the greenschist facies. An Upper Carboniferous granite (302.4 ± 5/15 Ma) intrudes the metamorphic rocks of the Vernon unit. During Upper Palaeozoic time, subsidence of the western Pelagonian margin created a possible slope where a meta-clastic sequence was deposited. The clastic sediments were succeeded by a neritic carbonate cover of Middle Triassic-Jurassic age. In the eastern area of the Pelagonian zone a metamorphic carbonate mass, probably of the Triassic-Jurassic age, has been tectonically emplaced on to the crystalline basement. This carbonate cover has a possible para-autochthonous origin; thrust surfaces, folds and linear structures indicate that it was overthrust from the eastern Pelagonian margin. Two metamorphic events in the North Pelagonian zone are inferred: one pre-Upper Carboniferous which affected the crystalline basement and a second post-Jurassic which affected the Upper Carboniferous granite, the Upper Palaeozoic meta-sediments and the Triassic-Jurassic carbonates.
Pre-Neogene nappe structure and metamorphism of the North Sporades and the southern Pelion peninsula
Authors: Jacobshagen Volker , Wallbrecher Eckard 
Published: April 2008

Summary
On the North Sporades and on the southern Pelion Peninsula, four tectonic units can be distinguished. The lowermost is the Pelagonian Nappe which is a sequence of Permo-Triassic metaclastics and platform carbonates of Middle Triassic to Upper Jurassic age. It is overlain by the Eohellenic Nappe, which consists of a melange with ophiolite bodies and crystalline slices, followed by a series of calc-schists, platy marbles and spilites, and, finally, a flyschoid sequence. Subsequent to the overthrusting of the Eohellenic Nappe in the Early Cretaceous, both nappes were partly eroded and then covered by the meso-autochthonous sediments of Middle Cretaceous to Lower Tertiary age. In the Eohellenic Nappe, as well as in the higher units, blue amphiboles often appear, i.e., magnesio-riebeckite in quartzitic and phyllitic layers and crossite or glaucophane in metabasites. The pelitic layers contain phlogopite and stilpnomelane as well as chlorite and phengite. In meta-radiolarites, spessartine and piemontite have also been found. This association, indicating high pressure during very low-grade metamorphism, contrasts greatly with the albite-biotite-almandine assemblage in the underlying Pelagonian Nappe, which is typical of low-grade metamorphism at more moderate pressures. A geodynamic explanation is proposed.
Neotectonic deformation patterns in the convex-northwards arc of the North Anatolian fault zone
Authors: Barka A. Aykut , Hancock Paul L. 
Published: April 2008

Summary
The convex-northwards arc of the North Anatolian fault zone between Çerkeş and Erbaa contains structures and landforms permitting right-lateral displacements for several time intervals to be estimated. Within the Pontus Formation (Late Miocene-Early Pleistocene) in basins along the fault zone, an unconformity, representing a time interval from the latest Tortonian to the earliest Pliocene, is interpreted as marking the transformation of the structure from a broad shear zone to a narrow fault belt. Although the amount of displacement during the shear zone phase is unknown the offset of a sedimentary facies boundary in the Lower Pontus Formation of the Havza-Ladik basin demonstrates that since the latest Tortonian there has been 25 km of right-lateral slip. The offset of valleys and ridges suggests that there has been 8 km of Quaternary displacement, about 2 km of it in the late Quaternary and at least 500 m during the Holocene.
Structures in the Pontus Formation indicate that the early history of the western Neogene basins was influenced by regional compression and that the later histories of all basins were dominated by strike-slip displacements. The main active trace is discontinuous, the 2 km-wide belt containing subordinate en échelon faults whose geometry is consistent with development during right-lateral shear.
Pliocene lacustrine sediments in the volcanic succession of Almopias, Macedonia, Greece
Authors: Chorianopoulou P. , Galeos A. , Ioakim Ch. 
Published: April 2008

Summary
This paper is a geological and palaeobotanical study of the lacustrine sediments occurring in the Voras mountain range NNW of Aridaea, in Western Macedonia, Greece. The sediments are interstratified with Pliocene volcanics from the Almopias volcanic centres. Alternations of chert, pyroclastics, limestone, tuff and breccia overlie a metamorphic basement or trachyandesitic lavas and tuffs.

Analysis of pollen in the lacustrine sediments indicates an Early Pliocene age. The most important species are
Pinus haplostelle, Pinus diplostelle
type, Taxodiaceae, Cupressaceae (
Taxodium, Sequoia
), cf.
Quercus
(
Scabratricolpites microhenrici, Tricolpopollenites henrici
), cf.
Castanea, Symplocos, Nyssa, Liquidambar
and
Tsuga
. Pollen analysis provides important clues to past climates and relief.
Recent shelf clastic sediments
Authors: McCave I. N. 
Published: April 2008

Summary
Shelf sedimentation in the past 21 years has moved from an essentially descriptive study to one where theory and measurement of sediment transport play an important role in accounting for the distribution of shelf sediments. This paper looks briefly at pre-1960 works then presents a view of the major features of present research on shelf clastics. This is organized under shelf muds, tidal-current-dominated sands and wave-dominated sands. Brief consideration is given to processes of mud and sand transport and deposition prior to a discussion of sediment types and bedforms. Storms are emphasized and their capacity to emplace sand layers on the shelf by wind-driven flows is discussed.
Deep-sea pelagic sediments and palaeo-oceanography: a review of recent progress
Authors: Leggett J. K. 
Published: April 2008

Summary
Understanding of present and past patterns of sedimentation, circulation, fertility, biogeography and chemistry in the oceans has advanced greatly in the last decade. In achieving this a diverse range of geological and geophysical techniques has been drawn on. Egress zones of active hydrothermal systems venting sulphide-laden hot water at spreading centres, long predicted on theoretical and other grounds, were discovered using deep-towed geophysical packages and have been fruitfully studied using submersibles. The chemistry of the venting solutions, and the apparent scale of the hydrothermal processes, have engendered a rethink of the oceanic fluxes of many elements. Continuing deep-sea drilling increasingly refines reconstructions of continental-drift events and the consequent changes in circulation patterns. The Deep-Sea Drilling Project planning has become more problem-specific, and on ‘palaeo-environment’ legs, sediment successions have been cored more continuously than was earlier the case. As a result, palaeo-oceanographers have been provided with a flood of data germane to the reconstruction of past behaviour of the CCD, to appreciation of past states of oxygenation of the oceans and of carbon preservation patterns (the ‘black-shale problem’), to documentation and interpretation of hiatus patterns, to calculation of global sediment budgets through time, and to calibration of the overall cooling of the Cenozoic hydrosphere. Isotopic determinations and organic geochemistry have become key tools in these studies. Global sea-level stands, clearly important as a regulator of conditions in the pelagic realm (though to an arguable extent) have been documented using seismic stratigraphy.
Attempts at synthesis of the complex spectrum of palaeo-oceanographic changes evident through time in the pelagic relam stress the rhythmicity with which the oceans have oscillated between broadly uniformitarian and non-uniformitarian conditions. Syntheses build towards identification of driving forces and responses.