bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sedimentation in the southern Cape Verde Basin: seismic and sediment facies
Authors: Auffret G. A. , Le Suave R. , Kerbrat R. , Sichler B. , Roy S. , Laj C. , Muller C. 
Published: April 2008

Summary
A detailed seismic and sedimentological study of a small area at the lower continental rise to abyssal plain transition off NW Africa has revealed a complex pattern of Plio-Quaternary sedimentation. The area is one of extremely low relief. However, the sediment facies distribution mirrors the slight morphological expression of basement structures and downslope shallow channels. Fine-grained hemipelagic sediments are dominant throughout, although in some cases the influence of low-density turbidity currents and of bottom currents is observed. Sandy turbidites, up to 2 metres thick in the channels, were emplaced during periods of lowered sea-level.
North Atlantic contourites: an overview
Authors: Stow D. A. V. , Holbrook J. A. 
Published: April 2008

Summary
We present a brief overview of known bottom circulation and Tertiary to Recent sediment drifts in the North Atlantic Ocean, and outline the distinctive features of contourite sediments recovered from these drifts. There is a gradation of structural and textural characteristics between the finer-grained clayey and muddy contourites and the coarser-grained silty and fine-sandy contourites. There is also a gradation between the three compositional types identified: biogenic, mixed biogenic/terrigenous, and volcanogenic. Other features such as microfabric, or facies sequences are less well documented but potentially diagnostic.
Facies and sequence analysis of Nova Scotian Slope muds: turbidite vs ‘hemipelagic’ deposition
Authors: Hill P. R. 
Published: April 2008

Summary
Five fine-grained mud facies were identified in piston-cores obtained from the Nova Scotian Slope. The sedimentary structures of the muds indicated deposition under varying bottom-current conditions and rates of sediment supply. Two facies associations were recognized using Markov sequence analysis: (a) turbidite and (b) non-turbidite associations. The problems of recognizing turbidite, contourite and hemipelagic deposits in fine-grained sequences are discussed in the context of low-concentration, low-velocity flows. The dynamics of unconfined flows indicates that turbidity currents become unstable and are deflected by Coriolis to near contour-parallel flow. Dilution and deceleration of the flow may produce a transition to hemipelagic-type deposition. Transitions of this type within individual flows make recognition of discrete turbidite, contourite or hemipelagic processes very difficult in parts of the geological record.
Facies, facies-associations and sediment transport/deposition processes in a late Precambrian upper basin-slope/pro-delta,, Finnmark, N. Norway
Authors: Pickering K. T. 
Published: April 2008

Summary

The lower Naeringselva Member of the 2.5 to 3.5 km thick Båsnaering Formation varies from 60 to 540 m thick, and is part of the 9 km thick late Precambrian Barents Sea Group cropping out on Varanger Peninsula, north-east Finnmark, N. Norway. It is underlain by a minimum 3.2 km of submarine fan deposits and passes up into delta front and fluvio-deltaic deposits of the Båsnaering Formation. Within the lower Naeringselva Member (LNM) four main facies are recognized: parallel-laminated mudstone; current-rippled siltstone; structureless mudstone, and wave-rippled fine-grained sandstone. Soft sediment deformation was abundant as slide, slump and
in situ
disturbed layers up to tens of metres thick. Erosional-depositional discordances are evident between packets of beds. Palaeocurrent data, together with a limited number of slide fold readings, suggest a west to south-westerly source area for the submarine fan, upper basin-slope/pro-delta and delta deposits. The stratigraphic position and sedimentology of the LNM suggests that it forms part of an ancient upper basin-slope/pro-delta, with fan deposits on the lower basin-slope. Apart from sporadic storm events visibly affecting the slope, it was below wave-base. Modern analogues for the LNM are the upper part of continental slopes separating fan from delta deposits, as in the Mississippi Delta-Slope-Fan system.
Models for the deposition of Mesozoic-Cenozoic fine-grained organic-carbon-rich sediment in the deep sea
Authors: Arthur M. A. , Dean W. E. , Stow D. A. V. 
Published: April 2008

Summary
The widespread occurrence of organic-carbon-rich strata (‘black shales’) in certain portions of Jurassic, Cretaceous and Cenozoic sequences has been well-documented from Deep Sea Drilling Project sites in the Atlantic and Pacific Oceans and from sequences, now exposed on land, originally deposited in the Tethyan ocean. These ancient black shales usually have been explained by analogy with examples of modern deep-sea sediments in which organic matter locally is preserved by (1) increasing the supply of organic matter, (2) increasing the rate of sedimentation, and/or (3) decreasing the oxygen content of the bottom water. However, detailed examination of many black shales reveals characteristics that cannot be explained by simple local models, including: their approximate coincidence in time globally; their occurrence in a variety of different environments, including open oxygenated oceans, restricted basins, deep and shallow water; their interbedding with organic-carbonpoor strata which often dominate a so-called black shale sequence; their deposition by pelagic, hemipelagic, turbiditic and other processes; and the variations in type and amount of organic matter that occur even within the same sequence.
A more complex model for the origin of black shales therefore appears most appropriate, in which the cyclic preservation of organic matter depends on the interplay of the three main variables, namely supply of organic matter, sedimentation rate, and deep-water oxygenation, each of which varies independently to some extent. The variation and relative importance of these parameters in individual basins and widespread black shale deposition in general are linked globally and temporally by changes in global sea-level, climate and related changes in oceanic circulation. An important and often overlooked factor for the supply of organic matter to deep-basin sediments is the frequency and magnitude of redepositional processes. The interplay of these variables is discussed in relation to the middle Cretaceous and Cenozoic organic-carbon-rich strata, in particular, which show marked differences in the relative importance of the different variables.
Plasticity and compaction characteristics of the Quaternary sediments penetrated on the Guatemalan Transect—DSDP Leg 67
Authors: Faas R. W. 
Published: April 2008

Summary
The plasticity characteristics of the Quaternary sediments of the Guatemalan continental margin were determined from five sites drilled on Leg 67 of the Deep Sea Drilling Project. Sixty-four samples were analysed from various marine environments, including the Cocos oceanic plate, Middle America Trench, and the trench lower slope to mid-slope of the Guatemalan continental slope.
Quaternary sediments on the Guatemalan continental slope are generally mixed siliceous and calcareous hemipelagic silty-clays and clayey-silts, frequently interbedded with volcanic ash. In the Middle America Trench, similar sediments alternate with sandy turbidites. Siliceous hemipelagic silty-clays and clayey-silts form the uppermost 170 metres of the Cocos Plate.
The sediments are generally classified as ‘organic clays of medium to high plasticity, containing micaceous sands and silts,’ with 14% classed as ‘inorganic clays of medium to high plasticity.’

Plasticity (measured by the Plasticity Index,

I
P

) decreases downslope to the trench, then increases sharply in the Cocos Plate sediments. Organic matter is greatest highest on the slope (Site 496) and decreases seaward, averaging 1.14% at Site 495 on the Cocos Plate.

Sediment compaction varies, according to position along the traverse and to the dominant sediment type. Greatest compaction (44.5%) occurs at Site 494 at the base of the lower trench slope. Least compaction (18.6%) is found at Site 495 on the Cocos Plate. Compaction of the trench and mid-slope sediments ranges between 31–38.5%.
High sedimentation rates in Quaternary sediments are due, in part, to sediment gravity-flows which depend upon rheological properties, i.e. sediment plasticity. Mudflows and cohesive debris-flows appear to be significant downslope transport mechanisms in these highly plastic sediments.
Subaqueous pyroclastic flows: their development and their deposits
Authors: Yamada Eizo 
Published: April 2008

Summary
Subaqueous pyroclastic flows are generated by eruptions in shallow water or close to a shore. Their flow mechanism is similar to that of their subaerial counterparts, except that they incorporate steam and not air. Near the source area, their deposits are non-sorted and resemble subaerial flow deposits. In some cases evidence of high temperature is recognized. Within a short distance (less than a few km) they are sorted and five subdivisions can be determined. In upward succession these are: (i) massive graded pumice tuff; (ii) parallel-laminated pumice tuff; (iii) parallel-laminated sandy tuff; (iv) parallel-laminated fine tuff; and (v) massive very fine tuff. With increasing distance from the source, and laterally from the main direction of the flow, the lower divisions gradually die out. Deposition of the upper three divisions is greatly influenced by sedimentary processes. The thickness and constitution of each division vary according to the volume and nature of the associated eruption.
Taupo-Rotorua Depression: an ensialic marginal basin of North Island, New Zealand
Authors: Cole J. W. 
Published: April 2008

Summary
New Zealand lies on the boundary between the Pacific and Indian plates. In the vicinity of North Island, oceanic crust of the Pacific plate is subducted obliquely beneath continental crust of the Indian plate to form the Taupo-Hikurangi arc-trench system.

The volcanic component of this system is the Taupo Volcanic Zone which comprises a young (<50,000 yr) andesite-dacite arc, to the west of which is the Taupo-Rotorua Depression, a basin filled with approximately 2 km of low-density volcanics. Most of these volcanics are rhyolitic (total volume > 10,000 km
3
) and have been erupted in the last 0.6 Ma from the Rotorua, Okataina, Maroa and Taupo Volcanic Centres. Approximately 2 km
3
of high-alumina basalt has also been erupted from the Depression.

Normal faults are common in the Taupo-Rotorua Depression and some have been active in historic time when open fissures formed. No strike-slip movement has been recorded. This evidence, together with the presence of basalt dykes, suggests the area is an extensional ensialic marginal basin. A change in orientation of the faults, from 040° at Taupo to 090° at the N end of the Okataina Volcanic Centre, is considered to be a result of dextral strike-slip movement within the North Island Shear Belt superimposed on the extensional tectonics of the marginal basin. The resultant oblique extension would also account for the
en échelon
basalt dykes in the 1886 Tarawera rift.

Crustal thickness in the marginal basin is estimated to be 15 km compared to 30–35 km outside the basin. This may account for the high heat flow recorded (average may be up to 1575 mW m
−2
) and for partial melting of the base of the crust to produce the voluminous rhyolitic volcanics. The high-alumina basalts are considered to be derived from the upper mantle. They form dykes in the crust which in places reach the surface to form a series of vents aligned parallel to the regional fault pattern. The basalts are considered to be intruded and extruded mainly as a response to the extensional tectonics.
Late Cenozoic volcanism and extension in Eastern Papua
Authors: Smith I. E. , Milsom J. S. 
Published: April 2008

Summary
The sea floor around eastern New Guinea is divided into a number of deep basins, separated by submarine ridges which are capped in places by islands of metamorphic, volcanic or coralline rock. The area has been subject to phases of extension since at least the Palaeocene, when the Coral Sea basin was formed. There have also been major compressive events, including the thrust emplacement of an ophiolite, the Papuan Ultramafic Belt, on to the Papuan Peninsula in the Oligocene. This peninsula, on the E of New Guinea, has been volcanically active from the Middle Miocene to the present day, and there have been eruptions on many of the surrounding islands and in the marine basins. Extension-related volcanic rocks include low-K tholeiites dredged from the floor of the Woodlark Basin and a peralkaline rhyolite association on islands near the E end of the peninsula. Volcanic rock types usually regarded as indicators of subduction, including andesites and high-K trachybasalts (shoshonites), are common.
During the Neogene, two phases of extension with associated igneous activity can be interpreted; the first in the Middle and Late Miocene, and the second from the Middle Pliocene to the present day. Only in the first phase was the formation of marginal basins related to subduction. The later phase is seen as part of the response of the complexly fragmented Melanesian area to changes in relative motions of the surrounding major plates. Sea-floor spreading is currently occurring in the Woodlark Basin, and the post-Miocene calc-alkaline and shoshonitic rocks of the Papuan Peninsula and offshore islands reflect reactivation of subduction-modified mantle under this tensional regime, and not renewed subduction.
Heat flow and magmatism in the NW Pacific back-arc basins
Authors: Sychev P. M. , Sharaskin A. Y. 
Published: April 2008

Summary
High heat flow is a characteristic feature of a number of back-arc basins of the NW Pacific Ocean. Temperature calculations related to the geological and geophysical data reveal that the sources of the high heat flow are located at shallow depths in the upper mantle and probably are zones of partial melting. From the location of these zones, the character and composition of magmas, and the evolution of the basins, it is proposed that injection of magmas, by a magmafracting (magmarupture) mechanism, is the main deep process within the back-arc basins. It is assumed that ‘primitive’ ultrabasic magma rises from great depths in the mantle along vertical or sub-vertical channels and is then distributed nearly horizontally close to the lower boundary of the crust, under the back-arc basins. The initial cause of the magmatic process is apparently a stepped gravity differentiation, beginning perhaps on the core-mantle boundary, and not the supposed subduction of oceanic lithosphere.
Crustal extension in the Southern Andes (45–46°S)
Authors: Bartholomew D. S. , Tarney J. 
Published: April 2008

Summary
As a result of back-arc extension along the Andean margin of southern Chile, marginal basins formed during both Mesozoic and Tertiary times. Crustal extension was limited but was accompanied by tholeiitic basalt or bimodal (acid-basic) volcanism rather than the calc-alkaline magmatism normally characteristic of the Andean margin.
The basement in southern Chile is composed of highly deformed metasediments, part of a major accretionary wedge built out from the Pacific margin in late Palaeozoic to early Mesozoic times in front of the late Palaeozoic magmatic arc now situated in Argentina. In the mid-Jurassic the locus of calc-alkaline magmatism moved W to near the present continental margin, and a narrow marine basin developed behind the magmatic arc from the late Jurassic to the early Cretaceous. The formation of the basin was marked by extensive silicic volcanism, probably a product of melting of the metasedimentary basement, followed by bimodal acid-basic volcanism in the early to mid-Cretaceous and the emplacement of a major batholith. Extension was less than in the contemporaneous ‘rocas verdes’ back-arc basin in southernmost Chile in which new mafic crust was formed. The basin was closed and uplifted during compression in the mid-Cretaceous. However, in the late Cretaceous a new basin, floored by mafic crust, opened within the calc-alkaline arc. Toleiitic volcanism and plutonism continued in this basin during the Tertiary while alkaline volcanism occurred in the back-arc regions. Compression in the Miocene, accompanied by further calc-alkaline plutonism, closed the basin and resulted in deep levels of the Patagonian batholith being juxtaposed with the volcanic sequences of the basin.
Processes of formation and filling of a Mesozoic back-arc basin on the island of South Georgia
Authors: Storey B. C. , Macdonald D. I. M. 
Published: April 2008

Summary
South Georgia contains a diverse suite of rocks representing different stages in the development of a back-arc basin on the Gondwana margin during the Mesozoic. Basin formation initially involved intrusion of large gabbroic plutons into deformed paragneisses and calc-alkaline rocks of a magmatic arc, and then extension of this crust by dyke emplacement. Partial melting of the metasediments formed a migmatitic aureole around the basic rocks. Rifting of this thinned continental crust led to the emplacement of mafic crust composed of lavas, dykes and plutonic gabbros with oceanic crustal characteristics. On an upper slope marginal to the arc, the mafic crust is overlain by a thinly bedded sequence of tuffs and mudstones deposited by turbidity currents. Overlying andesitic volcaniclastic rudites, deposited by debris flows, represent a major channel-fill sequence. The basin was filled by thick sequences of both arc-derived volcaniclastic sandstones and silicic detritus with a continental provenance. The volcaniclastic sediments form a fault-controlled aggrading system, deposited by high- and low-density turbidity currents in an elongate basin.
Ordovician marginal basin development in the central Norwegian Caledonides
Authors: Roberts D. , Grenne T. , Ryan P. D. 
Published: April 2008

Summary
In the Caledonides of central Norway, volcano-sedimentary successions, of the Lower and Upper Hovin and Horg Groups (Ordovician to ?Lower Silurian), unconformably overlie a variable substrate which includes fragmented oceanic crust and ensimatic immature arc assemblages initially deformed and metamorphosed in earliest Ordovician times. In western areas, remnants of a mid-Ordovician, evolved island-arc complex comprise a volcanic-plutonic suite of clear calc-alkaline affinity. To the E, in the Trondheim district, continental margin-type basic to andesitic volcanics, and sediments of comparable age, denote accumulation in a fault-dissected, back-arc marginal basin characterized by marked facies variations and bipolar sediment dispersal patterns. Sediment composition reflects the nature of the contemporaneous volcanism, although an input of metamorphic detritus from a continental margin source can also be determined. Thick, massive to pillowed tholeiitic greenstones, mainly of OFB chemistry, occur in several areas and some contain thick sheeted-dyke units, gabbro complexes and subordinate plagiogranites. These ophiolitic assemblages appear to occur at two stratigraphic levels within the Lower Hovin Group, reflecting separate phases of crustal thinning and oceanic lithosphere accretion. Mega-breccias and an olistostrome may relate to abortive ophiolite displacement or intra-basinal movements in late Arenig times. During the Caradoc and Ashgill, and possibly in earliest Silurian times, continental margin-type acidic volcanism developed widely, particularly in the S, while in central and northern parts of the basin, turbidites and resedimented conglomerates, derived from the basin margins, show SW transport in the deeper-water axial trough. Although there is strong evidence that the marginal basin and arc lay at the edge of the continental plate (Baltoscandia) on the SE side of the Iapetus, with SE subduction, this is not supported by the faunas in the lowest parts of the Ordovician successions, which are largely of North American affinity. A compromise model involving an elongate microcontinental plate within the Iapetus is invoked.
Lower Palaeozoic volcanism of northern Qilianshan, NW China
Authors: Zhang Zhijin 
Published: April 2008

Summary
Thick volcanic sequences of mid-Cambrian-mid-Silurian age crop out in northern Qilianshan in NW China. Volcanism was concentrated in a marine basin almost 1000 km long situated at the SW margin of the N China-Korea paraplatform. The basin was subsequently deformed during Caledonian folding. Calc-alkaline, mildly alkaline and alkaline volcanic rock suites have been identified and a variety of ore deposits, genetically related to the volcanism, have been discovered.
Evidence for a Late Triassic-Early Jurassic orogenic event in the Taurides
Authors: Monod Olivier , Akay Ergün 
Published: April 2008

Summary
A simple view of the Tethys during most of the Mesozoic emphasizes the contrast between the active northern European margin and the passive Southern Gondwanan margin which is considered to remain undeformed until the end of the Cretaceous. However, evidence from various places in the Taurus chain demonstrates the existence of a pre-Jurassic unconformity and a thrusting event. Indirect evidence is also provided by coarse, red oligomict clastic sediments (Çayır Formation) of Late Triassic to Lower Liassic age which are widespread on the older Tauride carbonate platform. A review of the data reveals a wide distribution of these sediments in southern Turkey, and their possible extension into the Hellenides (Chios). Finally, the evidence of Late Triassic to Early Jurassic deformation is considered in the light of recent syntheses of the evolution of the ‘Palaeotethys’.
Permian-early Mesozoic tectonism and continental margin formation in Israel and its implications for the history of the Eastern Mediterranean
Authors: Garfunkel Z. , Derin B. 
Published: April 2008

Summary
The Early Mesozoic tectonic reorganization of the Tethys region also affected the Levant area. Here two processes were superimposed: (a) The pattern of long-wavelength vertical motions of the Arabo-Nubian platform changed in the Late Permian when Israel and nearby areas began to subside. (b) Rifting occurred in this subsiding area, probably in several phases: Late Anisian (and Ladinian?), Carnian-Norian, and Liassic. Differential movements reached 2–3 km and magmatism occurred in the Liassic and perhaps also in the Triassic. The tectonism was strongly felt up to 50 km landward of the present coast. The crust was thinned and modified under the present continental margin and in the main rifts. Passive margin conditions were established in Late Liassic times over the previously faulted area. Later in the Jurassic a carbonate shelf was constructed along this subsiding margin; its basinward edge was 1–1.5 km high, which shows that the adjacent SE Mediterranean was already a deep sea. Hence this basin and its passive margin are considered to have been shaped by the Early Mesozoic rifting which is recognized in Israel. The rifting process probably signifies oblique separation of the Tauride block from the Levant part of Gondwana.