bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mesozoic and Cenozoic plutonic evolution of SE Asia: evidence from Sumatra, Indonesia
Authors: McCourt W. J. , Crow M. J. , Cobbing E. J. , Amin T. C. 
Published: April 2008

Abstract
New K/Ar mineral ages from the Barisan Mountains of southern Sumatra suggest four main periods of plutonic activity: Miocene-Pliocene (20–5 Ma), Early Eocene (60–50 Ma), Mid-Late Cretaceous (117–80 Ma) and Jurassic-Early Cretaceous (203–130 Ma). These and all other published ages from exposed plutons in western Sumatra indicate a further period of plutonic activity in the Permian (287–256 Ma). They also suggest either that Early Mesozoic activity began in the Late Triassic, or that there were two distinct magmatic cycles, one in the Late Triassic to Early Jurassic (220–190 Ma) and one extending from the Mid-Jurassic to Early Cretaceous (170–130 Ma). In addition, poorly controlled ages from eastern Sumatra indicate that the important Triassic to Early Jurassic (240–195 Ma) tin-belt magmatism of the peninsular Malaysia Main Range Province extends into that area.
Preliminary geochemical studies on the Mesozoic granitoids of the Barisan Range of southern Sumatra confirm that they are calc-alkaline, I-type, metaluminous, subduction-related volcanic arc granites (VAG). They broadly correspond to the southerly extension of a combination of the Central Valley and Western Granite Provinces of Thailand and Burma, and underline the fact that there has been a history of subduction-related magmatism along the southwestern edge of Sundaland since earliest Mesozoic times. The plutonic suites are crudely arranged in subparallel, locally overlapping, NW-SE trending belts, focused along deep-seated faults that have acted as magmatic conduits. It is proposed as a preliminary model that breaks in plutonic activity broadly correspond to changes in approach angle and/or rate of subduction, and that in some instances at least they relate to periods of collision and accretion of allochthonous material (terranes, slivers or blocks) of both oceanic and continental character. At least two such events seem to have occurred during the Mesozoic-Cenozoic tectono-plutonic evolution of Sumatra. One in the early Middle Cretaceous reflects collision and accretion of the oceanic Woyla terranes, and one in the latest Cretaceous is possibly related to collision of a continental sliver/block, the West Sumatra terrane, to the Sundaland margin.
The Mentawai fault zone and deformation of the Sumatran Forearc in the Nias area
Authors: Samuel M. A. , Harbury N. A. 
Published: April 2008

Abstract
The Sumatran Forearc is the site of oblique plate convergence between the Indo-Australian and SE Asian-Eurasian Plates. It is generally accepted that the forearc sliver is not behaving as a rigid plate and that the rate of slip increases along the right-lateral Sumatran Fault System from southeast to northwest. Two contrasting hypotheses have been invoked to explain this pattern of decoupling: by using slip vectors to suggest arc-parallel stretching; and a second major right-lateral strike slip zone, parallel to the Sumatran Fault System, to accommodate the oblique subduction. This zone, termed the Mentawai fault zone, lies just to the east of the outer-arc ridge and is indicated as intersecting with other faults on Nias Island. In this paper data are presented from Nias where a thick forearc succession is excellently exposed in three subbasins with half-graben geometries and broadly comparable Palaeogene-Recent histories. Mud diapirism has generated melanges which cut the Oligocene to Recent strata. Outcrop data, LANDSAT, Synthetic Aperture Radar and aerial photographs were used to determine fault offset patterns, and marked extension of the island along north-striking right lateral faults and ESE striking left-lateral faults is revealed. Extension was further accommodated along a set of ENE striking normal faults. In the region where the proposed Mentawai fault zone comes onto Nias there is an important, long-lived, basin-bounding fault. This structure had in excess of 5 km normal throw during the Oligocene-Miocene whilst minor contractional reactivation of the fault occurred during the Pliocene phase of uplift and deformation which affected all of Nias. Data from onshore and offshore the Nias region suggest that all the features visible from seismic sections collected over the Mentawai fault zone to the south of Nias can be explained in terms of inversion of originally extensional structures and mud diapirism. It is suggested that strike-slip motion is of limited importance along the 600 km long Mentawai fault zone. Rather this highly structured zone represents a deformation front whose origin can be explained by Pliocene to Recent subduction-driven inversion at the outer margin of the forearc.
Pb and Nd isotope constraints on the provenance of tectonically dispersed continental fragments in east Indonesia
Authors: Vroon P Z. , Van Bergen M. J. , Forde E. J. 
Published: April 2008

Abstract
Microcontinental fragments, tectonically dispersed at the triple junction of the converging SE Asian, Indo-Australian and Pacific plates, are a widespread phenomenon in the east Indonesian region. This paper investigates the potential of Pb-Nd isotope characteristics of igneous and (meta) sedimentary rocks from these fragments as indicators of their provenance. From the correspondence of isotopic signatures, it appears possible to identify provenance areas of four selected microcontinents, which were emplaced in different settings and regions of east Indonesia since late Mesozoic times. According to their isotopic affinities, the blocks of Ambon-Seram, Bacan, the Banda Ridges and Sumba originally formed part of southern New Guinea, north Australia, ‘Pacific’ New Guinea and Sundaland respectively. These conclusions are in line with geological constraints on the palaeopositions of the fragments. The results thus indicate that isotopic signatures are potentially a powerful tool in reconstructions of the tectonic history of east Indonesia.
Dating of Neogene igneous rocks in the Halmahera region: arc initiation and development
Authors: Baker Simon , Malaihollo Jeffrey 
Published: April 2008

Abstract

Potassium-argon ages of Neogene to Recent igneous rocks from the Halmahera region record a history of intra-oceanic arc development since the late Middle Miocene following an earlier phase of collisional plutonism. Arc formation from the Middle Miocene onwards was due to the east-directed subduction of the Molucca Sea plate beneath the Philippine Sea plate as it arrived at the Eurasian margin. The distribution of ages within the Neogene arc indicates a northward migration of volcanic activity during the Late Miocene to Pliocene. Results of the dating work show that after collision with the Australian margin at
c.
22 Ma there was a period of volcanic quiescence and limestone deposition before a new arc formed. This arc began erupting at around 11 Ma on Obi as a result of subduction of the Molucca Sea plate. Initiation of subduction is thought to have occurred around 15–17 Ma and may have been responsible for disturbing potassium-argon ages of pre-Neogene rocks. Dates from fresh rocks show that the volcanic front migrated northwards through Bacan and Halmahera throughout the Late Miocene to Early Pliocene. Limestone deposition was curtailed as arc activity migrated north while volcanism died out from the south. No Neogene volcanism younger than 8 Ma is observed in the Obi area while on Bacan subduction-related volcanism ceased at
c.
2 Ma. Late Pliocene crustal deformation caused a 30–40 km westward shift of the volcanic front. Quaternary volcanic rocks exposed in Bacan and the extreme south of Halmahera are not direct products of subduction but, rather, display geochemical characteristics of both subduction and fault-related magmatism. These volcanic rocks are distributed along splays of the Sorong fault system. The formation and propagation of the Halmahera arc is a consequence of the clockwise rotation of the Philippine Sea plate as the southern edge moved across the northern Australian margin and impinged on the east Eurasian margin. The ages of initiation of volcanism and subduction track the developing plate boundary as subduction propagated northwards.
Thermochronological and geochemical constraints on the tectonic evolution of northern Papua New Guinea
Authors: Crowhurst P. V. , Hill K. C. , Foster D. A. , Bennett A. P. 
Published: April 2008

Abstract

The Bewani-Torricelli-Prince Alexander Mountains, along the northern margin of Papua New Guinea, probably formed as a tholeiitic island arc in the Late Eocene-Early Oligocene. The arc is interpreted to have accreted to the margin by the Late Oligocene, but may have formed on a ribbon of extended continental crust along the New Guinea margin. Inferred roll-back of the subducting slab beneath New Guinea in the Early Miocene placed the margin into extension, creating starved graben in northern New Guinea and causing regional subsidence. Near the graben, metamorphic core complexes resulted as the upper crust was pulled off the lower crust along low angle detachments such that lower crustal rocks cooled rapidly from temperatures >500°C. The two inferred core complexes that have been dated show rapid cooling from 27-23 Ma and 20-18 Ma. Continued subduction beneath New Guinea resulted in formation of the Maramuni arc in the Middle Miocene and the end of extension. In the Late Miocene, collision of the Melanesian arc caused regional uplift of all basement of northern Papua New Guinea, mainly from 8-5 Ma, causing at least 3–4 km of denudation. The compressional deformation propagated south causing uplift, denudation and cooling in the Papuan Fold Belt at
c.
4 Ma, but is continuing at the present.
Geological controls on mineralization and dolomitization of the Lisheen Zn-Pb-Ag deposit, Co. Tipperary, Ireland
Authors: Shearley E. , Redmond P. , King M. , Goodman R. 
Published: April 2008

Abstract
The Lisheen deposit is a stratabound Zn-Pb-Ag deposit hosted in dolomitized Waulsortian limestone of Courceyan age. The deposit was discovered in April 1990 and the current resource is estimated to be 22 million tonnes at 11.5% Zn, 2% Pb and 16% Fe, with 26 g/t Ag. Lisheen is located along the Rathdowney Trend, a NE-SW trending, structurally controlled belt of carbonate rocks. Sulphides are present in the hanging wall of two major E to NE-trending normal faults, the Killoran and Derryville faults. These structures are large, northerly-dipping normal faults with displacements of approximately 200 m. The Killoran and Derryville structures form short fault segments of a major relay fault system that extends along the Rathdowney Trend. Faults are observed to have influenced sedimentation, and exercized a major control on the distribution of mineralization, hydrothermal alteration and dolomitization. Several phases of dolomitization, which affect Chadian rocks and temporally overlapped mineralization, help to constrain the timing of this mineralization to no earlier than the late Chadian.
The use of burial diagenetic calcite cements to determine the controls upon hydrocarbon emplacement and mineralization on a carbonate platform, Derbyshire, England
Authors: Hollis Cathy , Walkden Gordon , Hollis Cathy 
Published: April 2008

Abstract
Late diagenetic calcite cements in the Upper Dinantian limestones of the Derbyshire Platform are contemporaneous with both hydrocarbon emplacement and Mississippi Valley-type (MVT) mineralization. Calcite cementation began during the progressive burial of the Derbyshire Platform and the surrounding basins, principally within fractures generated during the waning effects of Upper Carboniferous extension. Six burial calcite cements can be recognized in dilational vein systems. Successive veins contain progressively more mature hydrocarbon inclusions, and calcite cements are intergrown with fluorite, baryte, galena and sphalerite in increasing quantities. Compacting Dinantian-Namurian shales in basins adjacent to the platform offer the most likely sources of fluids, trace elements and hydrocarbons. Fluids entered the platform along major fault systems, and circulated using smaller fracture systems, precipitating calcite. The final phases of calcite cementation and the main phase of MVT mineralization coincided with the onset of the Variscan Orogeny. A model is now established relating fluid flow to Variscan tectonic events in northern Britain.
Development of coral reef-facies during the Viséan at Los Santos de Maimona, SW Spain
Authors: Rodríguez Sergio 
Published: April 2008

Abstract

The
Siphonodendron
Limestone at Los Santos de Maimona Basin is regarded as a reef structure built mainly by rugose corals. This unit is composed of biogenic marls and biostromal limestones containing abundant rugose corals and brachiopods, and frequent calcareous algae, tabulate corals, foraminiferans, bryozoans, echinoderms, ostracodes and molluscs. It is present throughout the basin, which is 12 km long and 3 km wide, but the thickness, development of the framework and distribution of organic components varies from SE (seaward) to NW (landward). It is 40 m thick in the SE, but its thickness reaches only 6 m in the NW. The unit shows a vertical evolution of lithological facies, from biogenic marls at the bottom up to biostromal limestones at the top. The main environmental factors controlling the development of the organic framework are the tidal regime, minor subsidence pulses and periodic storms.

Arguments in favour of the reefal origin are structural (distribution, development and relationships between different facies of the
Siphonodendron
Limestone) and ecological (distribution and relationships of building organisms, environmental indicators, etc.). Objections to the reefal hypothesis (absence of reef crest and talus, low diversity, problematical wave resistance, biostromal nature of the upper beds, storm layers) are discussed. Building structures by corals, brachiopods and calcareous algae are briefly described.
Dinantian river systems and coastal zone sedimentation in northwest Ireland
Authors: Graham John R. 
Published: April 2008

Abstract

Northwest Ireland either formed or lay close to the coastal zone and represented the northernmost extent of marine sedimentation for large parts of the late Dinantian. The succession deposited during the initial early Viséan transgression in Donegal starts with northerly-derived fluvial gravels which pass upwards into coarse-grained fluvial sandstones and associated siltstones. Channel cross-sections are relatively small, suggesting stream widths of a few tens of metres and depths of up to 4 m. These data suggest small rivers with limited drainage basins and are inconsistent with a single drainage basin >95 000 km
2
, which had been proposed previously. Depositional style in the coastal zone was dominated by laterally migrating tidal creeks, initially containing siliciclastic detrita but with the proportion of carbonate increasing upwards. The succession in North Mayo is similar to that in Donegal but generally lacks the fluvial gravel unit.

Widespread deposition of limestones and shales was interrupted in late Arundian times by a southerly progradation of first-cycle feldspathic sandstones, the Mullaghmore Sandstone Formation and its correlatives. In the more proximal environments this is represented by fluvial sediments cutting down into the pre-existing carbonate shelf. This has the basic character of a Type I sequence boundary and represents a major lowering of sea level in northwest Ireland. During this clastic influx, large tidally-influenced fluvial channels developed, with channel widths up to 200 m and depths >5 m. This indicates an increase in river size in this area during the Dinantian which may have been due to river capture during the evolution of a relatively low-relief landscape. The regression that led to the southerly progradation of clastics is of similar age to fault movements documented elsewhere in Ireland, and may have a regional tectonic cause.
Initiation, growth and decline of a tectonically controlled Asbian carbonate ramp: Cuilcagh Mountain area, NW Ireland
Authors: Kelly John G. 
Published: April 2008

Abstract
The Lough MacNean Valley and the surrounding Cuilcagh and Belmore Mountains expose carbonates and subordinate shales of late Arundian to Asbian age. The Benbulben Shale, of late Arundian to Asbian age, is composed of fossiliferous shales with limestone bands. This is succeeded by the Glencar Limestone, composed predominantly of argillaceous micritic wackestones and packstones, and fossiliferous shales. This is overlain by the Asbian Dartry Limestone, which exhibits extreme lateral and vertical facies variations; it is quite different on east, north and west Cuilcagh, which are described in turn.
Lateral variations in facies and thickness in the Dartry Limestone are attributed to carbonate ramp development on a differentially subsiding block, initiated by sinistral strikeslip movement on the Castle Archdale-Belhavel and Curlew-Clogher Valley fault systems. The sediments exposed on east Cuilcagh represent the proximal portion of the the ramp, whilst the Knockmore and Cloghan Hill Members represent the mid and distal ramp. The chertyfacies limestones mark widespread open shelf conditions at the end of subsidence. Inversion is marked by the shallow-water Cloghany Limestone, the Carn Limestone and the top-Dartry disconformity prior to deposition of the Meenymore Formation.
The influence of climatic change on exposure surface development: a case study from the Late Dinantian of England and Wales
Authors: Vanstone Simon 
Published: April 2008

Abstract
Exposure surfaces represent an integral part of Asbian-Brigantian cyclothemic platform carbonates in England and Wales. These are characterized by the association of clay palaeosols, calcrete and palaeokarst and in most instances would appear to have been polygenetic. Alternating calcrete-karst stratigraphies associated with individual exposure surfaces indicate that the climate changed from semi-arid to humid to semi-arid conditions during each sea-level fall/rise cycle. Lowstand intervals were humid and resulted in karstification of the cyclothem-top sediments and the formation of a mineral soil. In contrast, regressive/transgressive phases were semi-arid and resulted in calcretization of the emergent platform carbonates.
The influence that climatic cyclicity had upon exposure surface development was modulated by variations in platform bathymetry, subsidence and spatial climatic variation, and platforms exhibit their own individual record of what was essentially an idealized sequence of events. As with the sea-level oscillations responsible for cyclothemic sedimentation, the climatic cyclicity is thought to be the product of orbital forcing and probably reflects either eccentricity-driven shifts in the locus of monsoonal precipitation, or precession-driven variations in monsoonal intensity. If precessional in origin, exposure surface development represents a single minimum to minimum excursion, some 20 ka in duration, whereas if eccentricity-driven this may have been appreciably longer. Nevertheless, the immature nature of the exposure surfaces suggests that emergence was probably only of the order of a few tens of thousands of years.
Contemporaneous erosion and reworking within the Dinantian of the South Munster Basin
Authors: Naylor D. , Sevastopulo G. D. , Sleeman A. G. 
Published: April 2008

Abstract
Contemporaneous erosion and reworking of sediment is now known from a wide scattering of locations within the Dinantian rocks of the South Munster Basin. The phenomenon is most marked close to the northern margin of the basin, which lay within the Cloyne Syncline from Cork Harbour westwards to Ballygarvan. Exploration drilling further west in this syncline, near Inishannon, has found Dinantian/Namurian basinal sequences containing thicknesses of breccias with shelf carbonate clasts. The northern basin margin continues obliquely across strike westwards to cross the extension of the Cork Syncline near Crookstown, where recent drilling has located the basin margin. There is no evidence of reworking in the basin during the latest Devonian-early Tournaisian. A widespread sequence boundary is recognized in the middle Tournaisian (base of Courtmacsherry-Reenydonagan Formations). Within the Kinsale sub-basin, Member 2 Courtmacsherry Formation is a silt-sand unit within a mudstone-carbonate sequence; sourcing of the sand demands considerable intrabasinal or basin margin erosion. In the Bantry sub-basin, reworked conodonts occur at different levels within Member 3, Reenydonagan Formation (late Tournaisian to Arundian). There is indirect evidence for a carbonate shelf or intrabasinal high of Tournaisian to Asbian age in this western region.
The Apedale tuffs, North Staffordshire: probable remnants of a late Asbian/Brigantian (P1a) volcanic centre
Authors: Rees J. G. , Cornwell J. D. , Dabek Z. K. , Merriman R. J. 
Published: April 2008

Abstract
A borehole sunk in 1920–21 at Apedale, North Staffordshire, unexpectedly proved a tuff-dominated sequence, at least 840m thick, below a thin cover of Silesian sedimentary rocks. The tuffs were initially interpreted as Dinantian in age. However, there are similarities of form and lineament between an aeromagnetic anomaly centred upon Apedale and anomalies in the Welsh Marches associated with Neoproterozoic (Uriconian) rocks, suggesting that Neoproterozoic rocks occur at Apedale and that the tuffs in Apedale Borehole might also be of this age. Recent modelling of geophysical data shows that Apedale is underlain by two (magnetic) volcanic bodies — a deeper ridge of probable Uriconian rock, and a shallower, broadly stratiform body which includes the tuffs in the Apedale Borehole. Comparison of the tuffs at Apedale with others in the region suggests that they are of P1a (late Asbian to early Brigantian) age. Although our knowledge of the extent of the Apedale tuffs is poor, their thickness shows that they erupted from one of the largest centres of Dinantian volcanism in central England. The trace element geochemistry is very similar to that of Dinantian volcanic rocks in southwest England.