bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hemipelagic deposits in a Miocene basin, California: toward a model of lithologic variation and sequence
Authors: Isaacs C. M. 
Published: April 2008

Summary

Deep marine basins began to form along the continental margin of central California in late Oligocene time as a result of the initiation of a translational plate boundary. Deposition of transgressive shallow-marine sand (Vaqueros Formation) was followed by deposition of a thick (> 500 m) massive clay unit (Rincon Shale). Rapid subsidence (> 2000 m) coincident with rising sea-level created sediment-starved basins by late early Miocene time (
c.
18 Ma).

Typical of many of these borderland basins was the Santa Barbara basin, located at least 50 km from the Miocene strandline. In this basin, between late early and latest Miocene time (18–5.5 Ma), was deposited a heterogeneous sequence of highly biogenous sediment (Monterey Formation) consisting of mixed diatomaceous, foraminiferal-coccolithic, and terrigenous debris generally rich in organic matter (mean 8%). Overlying latest Miocene and Pliocene sediments (Sisquoc Formation) contain increasingly abundant clay debris.

The Miocene biogenous sequence reflects hemipelagic sedimentation from highly productive coastal waters during an extended period of generally low terrigenous influx. Accumulation of terrigenous debris decreased markedly in the early Miocene (from 11 to 1 g/cm
2
·10
3
yr) and was low throughout the middle Miocene, increasing somewhat at about 8 Ma and markedly after 5.5 Ma; this pattern is partly related to global sea-level changes but also resulted from high rates of subsidence and tectonic events. Biogenous silica accumulation peaked (mean 2.5 g/cm
2
·10
3
yr) in the late early Miocene (18–15 Ma) and again in the late Miocene and early Pliocene (8–3.5 Ma) and was 5 to 25 times slower in the interval 15–11 Ma; these variations are thought to reflect primarily variations in the intensity of upwelling and associated production of diatoms. Accumulation rates of biogenous calcite gradually declined from a late early Miocene peak through the early late Miocene and virtually ceased in latest Miocene (8–5.5 Ma), probably due to dissolution.

Massive stratification indicates that bottom waters were oxygenated until latest early Miocene time (
c.
16 Ma), when expansion of the oxygen-minimum zone or tectonic formation of a sill within the oxygen-minimum zone produced marked lowering of oxygen levels resulting in the dominance of laminated stratification between 16 and 5.5 Ma. Abundance of organic matter is closely associated with the abundance of clay and of calcite but is inversely correlated with silica content. Organic matter is also about twice as abundant in massive or discontinuously laminated beds (indicating good to moderate oxygenation) than in associated beds with varve-like lamination (indicating minimal oxygenation). These relations indicate that grain-size outweighed the influence of low-oxygen bottom waters in preserving organic matter.
Fabric of muds and shales: an overview
Authors: Moon C. F. , Hurst C. W. 
Published: April 2008

Summary
This contribution essentially constitutes an attempt to update a previous review of clay sediment microstructure written over a decade ago. Recent developments in this field are considered and a scheme has been developed in which the fabric of argillaceous sediments is traced from its inception during sedimentation and its subsequent modification at and below the depositional interface. It is held throughout that the primary control in the determination of clay fabric is the chemical environment that prevails during and after the deposition of the sediment. Consideration of the evidence from a variety of sources suggests that fissility in mudrocks is the result of an anisotropic microfabric in which clay aggregates are preferentially aligned. This microstructure is thought to result from the dispersing action of organic compounds common in certain sedimentary environments; a brief discussion of these compounds is included. Other factors are also taken into account which have been offered as the cause of differing mudrock fabrics.
Marginal basins of the SW Pacific and the preservation and recognition of their ancient analogues: a review
Authors: Leitch E. C. 
Published: April 2008

Summary
Marginal basins of the SW Pacific floored by oceanic lithosphere comprise those formed by sea-floor spreading immediately behind active magmatic arcs (back-arc basins) and those created by the rifting of continental crust without obvious connection to an arc system (small ocean basins). The basins opened rapidly, range greatly in shape and size, and show diverse relations to sediment sources. Thick sediment piles mainly accumulated adjacent to emergent continental margins or active arcs, with thin sequences of pelagic sediments, ash, and fine grained turbidites on basin floors. Facies are commonly asymmetrically distributed. Basaltic magmatic activity, mild deformation and submarine erosion affect both types of basins. Ancient back-arc basins should be identifiable on the basis of their temporal relations to magmatic arcs and the volcanic influence in their sedimentary sequence, but distinguishing between small and major ocean basins is often difficult. Narrow marginal basins may collapse following accumulation of a thick sediment pile, but most basins close by subduction. Similarities are recognized between the present-day SW Pacific and the formative stage of the North American Cordillera. The Late Mesozoic palaeogeography of the Western Alps resembles the complex of small ocean basins and continental fragments west of the Norfolk Ridge, and the Ordovician palaeogeography of central Newfoundland bears close resemblance to the assemblage of back-arc basins, remnant arcs and active arc east from the Norfolk Basin.
Hydrothermal and volcaniclastic sedimentation on the Tonga-Kermadec Ridge and in its adjacent marginal basins
Authors: Cronan D. S. , Hodkinson R. , Moorby S. A. , Glasby G. P. , Knedler K. , Thomson J. 
Published: April 2008

Summary
Analyses of over 180 sediment samples from the Tonga-Kermadec Ridge and adjacent marginal basins demonstrate volcaniclastic, biogenic, lithogenous and hydrothermal influences on them. The volcaniclastic component decreases westwards from the Tonga-Kermadec Ridge where volcanism is presently active. Biogenic components are predominant in sediment throughout most of the region, but a significant lithogenous component becomes apparent in the S, in the vicinity of New Zealand. Hydrothermal influences have been detected in two areas: (i) on the Tonga-Kermadec Ridge where Mn oxide crusts represent the end member of a hydrothermal fractionation sequence, earlier members of which may occur beneath the sea-floor; and (ii) in the Lau Basin where Fe and Mn are widely dispersed in the sediments and where sulphide deposits may occur in the immediate vicinity of hydrothermal vents.
Volcano-tectonic evolution of Fiji and adjoining marginal basins
Authors: Colley H. , Hindle W. H. 
Published: April 2008

Summary
From the Eocene to the Middle Miocene, Fiji was part of a N-facing Outer Melanesia arc system, stretching from Papua New Guinea to Tonga, and was dominated by tholeiitic arc volcanism. Oligocene back-arc spreading to the S of Fiji led to the formation of the Minerva Plain (South Fiji Basin). Reorganization of the plate boundaries in Outer Melanesia during the Middle Miocene fractured the simple arc system and caused polarity reversal in arc segments W of Fiji. Fiji, the major yield point in the break-up, experienced a compressive event followed by progressive isolation from a subduction regime as arc segments were rotated away from the region. This led to asthenospheric melting with a decreasing subduction component, and a consequent change in Fiji volcanism from arc andesites and tholeiites to alkalic ocean island basalts. During the Upper Miocene to Lower Pliocene, rotation of the Vanuatu arc segment caused opening of the Fiji Plateau marginal basin. This was accompanied by widespread, chemically diverse volcanism in Fiji, in which contamination of rising magma by pre-existing crust may have been an important process. The most recent phase of arc rotation resulted in opening of the Lau Basin between Fiji and Tonga, and effected the final divorce of Fiji from a subduction influence with commencement of ocean island basalt volcanism in the Middle Pliocene.
Spreading-subsidence and generation of ensialic marginal basins: an example from the early Cretaceous of central Chile
Authors: Åberg G. , Aguirre L. , Levi B. , Nyström J. O. , Aguirre L. 
Published: April 2008

Summary

During the early Cretaceous, intracontinental rifting, spreading and subsidence led to the formation of an ensialic trough in central Chile. This trough is interpreted as an aborted marginal basin since no oceanic crust was generated. However, mantle-derived material, represented by flood basalts with low initial
87
Sr/
86
Sr ratio and evolved geochemical characteristics, was deposited in the basin. Rb-Sr dating shows that the lavas suffered burial metamorphism shortly after their extrusion. The flood basalts were extruded during an episode of slow oceanic spreading in the Pacific, and subsequent folding, granitoid intrusion and uplift are correlated with an episode of fast oceanic spreading and plate subduction. The intracontinental events related to these two episodes constitute a cycle, repetition of which might account for the geological evolution of central Chile during the Mesozoic and the Palaeogene.

The western margin of South America, during the Cretaceous, was characterized by basin formation with eruption of mantle-derived basalts. Some basins developed into marginal basins proper, with generation of oceanic crust, others were aborted. The type of basin was determined by the rate and volume of upwelling mantle material, and continental crust thickness. Rapid upwelling gave rise to back-arc spreading and marginal basins with primitive basalts and ocean-floor metamorphism or burial metamorphism reflecting steep thermal gradients. Slow upwelling produced ensialic basins with evolved basalts affected by burial metamorphism with less steep thermal gradients, as in central Chile during the early Cretaceous.
Proximal volcaniclastic sedimentation in a Cretaceous back-arc basin, northern Antarctic Peninsula
Authors: Farquharson G. W. , Hamer R. D. , Ineson J. R. 
Published: April 2008

Summary
During Cretaceous times, the northern Antarctic Peninsula was the site of an active ensialic magmatic arc. Volcanism was dominated by pyroclastic eruptions with rare lava flows. Marine conglomerates and sandstones formed a volcaniclastic apron along the eastern margin of the arc and represent the proximal deposits of an extensive back-arc basin. Volcanogenic material, redeposited by turbidity currents and other sediment gravity flows, forms an important part of the proximal basin fill. Air-fall tuffs and eruption-induced sediment flows form a small but significant part of the succession and large exotic slideblocks of Jurassic sediment are a distinctive feature of the Lower Cretaceous strata on James Ross Island. Aeromagnetic data and regional geology indicate that the arc-back-arc basin boundarv was fault-controlled. Sedimentation within the basin was strongly influenced by both the steep, unstable nature of the faulted arc flanks and the coeval volcanism.
Mud-magma interactions in the Dunnage Mélange, Newfoundland
Authors: Lorenz B. E. 
Published: April 2008

Summary
The Dunnage Mélange, part of back-arc basinal assemblages in north central Newfoundland, is host to a suite of dacitic to rhyolitic intrusions. Intrusion occurred during the late stages of mélange formation. Lobate, pillowed, corrugated and pahoehoe-like igneous contact surfaces, complex interlayering of host mudstone and dacite, and the occurrence of peperite, indicate that the magma intruded unconsolidated mud and the adjacent sediment was fluidized. This evidence for shallow emplacement of the magma is inconsistent with the existence of a tectonic overburden during mélange formation, and supports an olistostromal origin for the Dunnage Mélange.
Introduction: aspects of the geological evolution of the Eastern Mediterranean
Authors: Robertson A. H. F. , Dixon J. E. 
Published: April 2008

Summary
We review extensively the evidence and arguments bearing on the nature of Palaeotethys in relation to the age of formation, location and multiplicity of Neotethyan strands and their fate. We conclude that Palaeotethys did not die early but was only finally subducted northwards in the Tertiary along the Vardar-Intra Pontide-East Anatolian suture. Neotethyan strands must have opened into it at all times. The Adriatic promontory remained attached to Africa but rotated anti-clockwise in the mid-Tertiary. The Pontides are considered to be Eurasian and the Cimmerides are viewed as a ‘collage terrain’ formed along an oblique-convergence margin. The south Aegean, Greek and Turkish microcontinental blocks were rifted-off Gondwana in the Triassic but formation of braided Neotethyan oceanic crustal strands was essentially confined to mid-Jurassic in the Hellenides and to the Cretaceous in Turkey.
We propose a new model of ophiolite genesis by asymmetrical spreading-ridge collapse in an attempt to explain both arc-like ophiolite chemistry prior to major volcanic arc edifice construction, and the synchroneity of sub-ophiolite metamorphic sole formation with Atlantic opening phases.
Jurassic dispersal of Hellenide blocks had little effect in the unexpanded Turkish mosaic, but northwards Cretaceous opening of Tauride Neotethyan strands caused oblique collision deformation in the Pelagonian zone and unresolvable complexity in the Aegean. Late Cretaceous and Tertiary arc-volcanism was related in part to continuing Palaeotethyan subduction, and in part to Neotethyan destruction initiated after ridge-collapse. Diachronous collisions ensued from the Late Cretaceous onwards but significant oceanic tracts must have persisted at least to Mid-Tertiary to satisfy Africa-Eurasia separation constraints determined from Atlantic anomaly fitting. Our favoured plate evolutionary model is presented in 7 sketch-maps.
Facies and tectonic setting of the Upper Carboniferous rocks of Northwestern Turkey
Authors: Kerey I. E. 
Published: April 2008

Summary
In various outcrops along the Black Sea coast, a thick Dinantian shallow water carbonate succession is overlain by four formations of highest Visean to highest Westphalian age. The succession changes upwards from generally shallow marine, to non-marine giving way in the upper levels of flood-plain, lacustrine and fluviatile deposits. All the present outcrops are believed to have belonged to a single large basin in which material was derived from a former Black Sea continent to the north. In contrast to some recent suggestions, the basin was located near the southern edge of the Laurasian plate.
A model is discussed in which uplift of the area north of the modern North Anatolian Fault is attributed to dextral strike-slip faulting in approximately E-W and NNE-SSW directions. Although evidence of strike-slip faulting has been obscured by later tectonic events, in general the North Turkish Upper Carboniferous sedimentary rocks were deformed during a late Hercynian phase of large-scale wrench-faulting caused by oblique collision of the Gondwana and Laurasian plates after Carboniferous time, which may have also displayed the former Black Sea continent eastwards.
Stratigraphic evidence of Variscan and early Alpine tectonics in Southern Turkey
Authors: Demirtaşh E. 
Published: April 2008

Summary
The area between Silifke and Anamur forms the central Taurus belt, in which four geotectonic zones are recognized: the Southern, Intermediate and Northern zones and the Hadim nappe. Stratigraphic successions in each zone show considerable differences from the early Palaeozoic onwards. For example, a Late Triassic non-marine clastic basin dominated the Intermediate and Northern zones, while a marine carbonate basin existed to the south.
The contrasting stratigraphic development of each of the three main tectonic zones studied, particularly reflects Early Permian (Variscan) and Late Triassic (‘Eocimmerian’) orogenic events. Overthrusting of the Northern zones over the Intermediate zone took place before a Late Permian transgression. Later overthrusting of the Intermediate zone over the Southern zone occurred during Middle to Upper Triassic times producing large-scale nappes. The Variscan and early Alpine structures were then unconformably overlain by platform carbonates of Early Jurassic to Late Cretaceous age. Middle and late Alpine movements are also observed in the Intermediate and Northern zones. Ophiolitic melange was thrust over Late Cretaceous-Palaeocene flysch and olistostrome while platformal carbonate deposition continued in the Southern zone, confirming that an ocean basin existed to the north. Orogenic movements ended before the Early Miocene, followed by block-faulting to produce graben (e.g. Çavuşlar basin). Formations of Middle and Late Miocene age unconformably overlying all other units are post-tectonic.
Tectonic and sedimentary history of the NE African margin (Egypt—Libya)
Authors: Sestini G. 
Published: April 2008

Summary
The present structure and thickness variations of the Mesozoic-Cenozoic sediments of the Mediterranean coastal belt of Egypt (west of Sinai) and of North Cyrenaica, indicate that the African Plate at this latitude was part of an unstable zone characterized by a number of fault-controlled marginal depocentres. Triassic to Middle Cretaceous facies are almost everywhere shallow marine, nearshore, deltaic and continental, with no indication of a paleobasin margin. Deeper-water sedimentation occurred in parts, from Senonian onwards. During the Campanian-Eocene phase of plate collision, overthrusting and folding, the African margin was raised in the north and depressed southwards, and mild folding was superimposed on the block structures. Widespread Oligo-Miocene faulting and differential vertical movements shifted the focus of deposition to the Nile Delta region and the Gulf of Suez, while transcurrent movements to NNE (Aqaba-Dead Sea faults) created local compression that magnified and skewed Eocene folds. It is concluded that the onshore coastal belt of NE Egypt-Cyrenaica belongs to a relatively southerly part of the African plate margin.
Emergence of Wadi Mujib (Central Jordan) during Lower Cenomanian time and its regional tectonic implications
Authors: Abed Abdulkader M. 
Published: April 2008

Summary
Detailed sedimentological investigations of Wadi Mujib (Central Jordan), east of the Dead Sea, show that the regional contact of Lower Cretaceous fluviatile deposits on Upper Cretaceous carbonates ushered in a shallow marine environment all over Jordan. Later, an emergent area, in Wadi Mujib only, passes upwards and laterally eastwards into a supratidal environment, followed again by shallow marine conditions. The emergence is marked by a major eroisional unconformity with wadi deposits, caliche and karstification. Wadi Mujib is believed to have been an island during Lower Cenomanian time and is thought to be an example of vertical tectonics in the area prior to Tertiary rifting of the Dead Sea to the west.
Ophiolites and volcanic activity near the western edge of the Arabian plate
Authors: Delaloye Michel , Wagner Jean-Jacques 
Published: April 2008

Summary
The geology of the Eastern Mediterranean is governed partly by the collision of the Arabian plate with the Anatolian block and partly by the Dead Sea Rift.
The oceanic elements which have been formed between these two blocks are still visible as obducted fragments represented amongst others by the two ophiolitic massifs of Hatay and Baër-Bassit.
The opening of the Atlantic ocean give rise, in the Eastern Mediterranean, to complex relative movements which can partly be resolved into a west to east shear and a south to north compression. The shear pre-dates the compression and took place between the Triassic and middle Cretaceous. It is responsible for the rifting and the volcanism in Syria, as well as the formation of a basin capable of producing ophiolites such as Hatay and Baër-Bassit.
The compressive phase began in the middle Cretaceous and resulted in the detachment and the emplacement of the ophiolites on the Arabian continental margin. The timing of this phase can be determined from the age of the Baër-Bassit amphibolitic sole. Traces of this compressive episode are seen as late as the Neogene.
The extension of the Ionian trough into southwestern Turkey
Authors: Poisson A. 
Published: April 2008

Summary
During Mesozoic time the Ionian trough in Greece shows a relatively complex and distinctive geodynamic evolution compared to the adjacent platforms. A similar evolution is found in several series of the Western Taurides in Turkey. The existence of a Mesozoic intra-Tauric trough (previously named ‘Kizilca-Çorak göl trough’), is established and interpreted as an homologue of the Ionian trough.
This situation, external with respect to the Helleno-Tauric belt, is used as a basis for a reconstruction of the general evolution of the eastern part of the Aegean ‘curvature’ that seems to have been initiated during the mid-Miocene (after Langhian but prior to Tortonian). The recent (neotectonic) evolution of the arc started after the Tortonian, possibly as late as the Lower Pliocene.
Miocene clastic sedimentation related to the emplacement of the Lycian Nappes and the Antalya Complex, S.W. Turkey
Authors: Hayward A. B. 
Published: April 2008

Summary
The western Tauride Mountains of S.W. Turkey comprise a central relatively autochthonous carbonate platform unit, the Tauride autochthon bordered by two allochthonous units, the Lycian Nappes to the west and the Antalya Complex to the east. Sequences of Miocene clastic sediments up to 1000 m thick that were derived from both the allochthons document the timing and direction of their emplacement onto the carbonate platform.
Along the western margin of the Miocene basin intial emplacement of the Lycian Nappes, from the northwest, in the Lower Miocene, was coupled with rapid subsidence of the previously stable carbonate platform. The resulting basin was ca 170 km across. Fan-deltas were derived from the leading edge of the nappes and passed basinwards into a series of small submarine fans. At the same time rapid uplift of the central parts of the carbonate-platform, along the margin of the basin opposite the nappe pile, led to a thick wedge of carbonate-derived clastics being shed northwestwards into the basin. Varying sedimentation rates and migrating facies belts in the overlying Middle and Upper Miocene basin-fill document the progressive emplacement of the Lycian Nappes ca 100 km from the northwest over the basin margin.
Along the eastern margin of the basin, palaeocurrent analysis and downslope facies-transitions in the Miocene sediments show that the Antalya Complex was emplaced from the east but only advanced a short distance beyond the eastern margin of the basin.
The Lycian Nappes and the Antalya Complex approached the basin from opposite directions and so their respective ophiolite units must have originated in separate ocean basins on either side of the Bey Daḡlari and the Susuz Daḡ carbonate platform.