bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sandstone diapirism and clastic intrusion in the Tertiary submarine fans of the Bruce-Beryl Embayment, Quadrant 9, UKCS
Authors: Dixon R. J. , Schofield K. , Anderton R. , Reynolds A. D. , Alexander R. W. S. , Williams M. C. , Davies K. G. 
Published: April 2008

Abstract
Submarine fans of Late Palaeocene and Early Eocene age form important hydrocarbon reservoirs in the Bruce-Beryl Embayment, northern North Sea. The Early Eocene fans are the main reservoirs in the Forth-Gryphon oilfields and in the giant Frigg gasfield. Significant oil discoveries have also been made in Late Palaeocene fans. Forth and Gryphon lie on the flanks of the Crawford Anticline, a drape structure that developed during the Palaeocene above the crest of a Mesozoic tilted fault block. The Early Eocene fans pinchout against the flanks of the anticline implying continued growth of the structure throughout the Eocene. Growth was accompanied by the development of major gravity slides that detached in a sequence of altered, basaltic tephras at the base of the Eocene sequence. Seismic-scale, post-depositional deformation (sandstone diapirism and the intrusion of clastic sills and dykes) connected with this sliding dramatically modified the original depositional geometries of the fans. A detailed account of the deformation features, illustrated with core, wireline log and three-dimensional seismic data is presented together with a discussion of their exploration/appraisal significance.
The sedimentological record of a late Jurassic transgression: Rona Member (Kimmeridge Clay Formation equivalent), West Shetland Basin, UKCS
Authors: Verstralen Ivo , Hartley Adrian , Hurst Andrew 
Published: April 2008

Abstract
Late Jurassic sandstones form important potential reservoirs within the West Shetland Basin. These strata are thin (4–84 m) and broadly equivalent in age to the Kimmeridge Clay Formation. They were deposited predominantly in deep marine environments although subaerial and shallow marine facies are also present. The Rona Sandstone forms the lowermost of three sandstone units within the Upper Jurassic succession. Data from 23 exploration wells show, however, that it is a heterogeneous unit ranging from coarse-grained pebbly sandstones to mudstones and, because of this wide lithological variation, the Rona Member is considered a more appropriate name. The facies identified (cohesionless debris flow, high and low density turbidites, upper and lower shoreface) and their vertical transitions are considered typical of fan delta deposition, initially in a subaerial environment and later under progressively more marine conditions. Coarse-grained sediments (debris flow and high density turbidites) of the Rona Member are restricted to isolated topographic lows within Lewisianoid basement whereas finergrained sediments (low density turbidites) have a wide distribution across the basin and cover much of the Rona Ridge. Previous models have suggested that the coarse-grained sediments were derived from active fault scarps. However, to explain the facies distribution it is suggested that footwall uplift on the Rona and Judd Faults (Rona Ridge and associated basement highs) was responsible for the supply of coarse-grained material to isolated fan deltas. Transgression eventually resulted in: flooding of the basement highs, cut off of sediment supply and deposition of finer-grained sediments. Deposition of the Rona Member is interpreted to have been controlled by the gradual transgression of residual islands of Lewisianoid basement.
Soft lithosphere during periods of Archaean crustal growth or crustal reworking
Authors: Choukroune P. , Bouhallier H. , Arndt N. T. 
Published: April 2008

AbstractField observations, and an analysis of the strain field, have been carried out in Archaean terranes of the Hebei province in the Dharwar craton of India, the Sino-Korean craton in China, and the Man shield in the Ivory Coast.Two broadly different situations can be recognized. In the Dharwar and Man Shields the deformation shows a range of characteristic features. The foliation trajectories outline dome-and-basin structures in which supracrustal rocks of greenstone belts invariably occupy the basins. The foliation trajectories are perturbed only by bands of transcurrent shearing. Variations in deformation directions depend essentially on the geometry of plutonic or migmatitic bodies within which the foliation invariably has a domal form. Changes in the intensity of deformation are essentially limited to boundaries between granitoids and supracrustal series. These changes are largely horizontal. Characteristics of the finite strain ellipsoid (the parameterk) vary extremely rapidly.The second situation is manifested in the Hebei province where the Archaean crust has deformed without the preservation of domes and basins. Here the deformation is characterized by the presence of a foliation and a very strong vertical flattening which extends into catazonal domains. This deformation is homogeneous. To explain these observations it is proposed that this homogeneous deformation was superimposed on pre-existing dome-and-basin structure, obliterating the original geometry. The Hebei example represents a stage of deformation greater than that of the Ivory Coast, which in turn is greater than that in the India craton.It is apparent that the Archaean crust has specific characteristics that controlled the manner in which it deformed. During accretion, or reworking, it was dominated by body forces related to differences in the densities of the two major Archaean lithological units: granitoid and greenstones. Deformation resulting from boundary forces then led to a second type of behaviour controlled by a vertical planar anisotropy induced during the first stage.These characteristics are never reported in modern orogenic belts, which generally are marked by a uniform structural trend and vergence. It is proposed that Archean cratons completely lacked a rigid element during the accretion events responsible for their formation, that the thermal regime in these periods was quite unlike that of today, and that the continental crust formed or was reworked during episodes of enhanced mantle plume activity.
The past of a future syntaxis across the Zagros
Authors: Talbot C. J. , Alavi M. 
Published: April 2008

AbstractLongitudinal components of the Zagros mountain chain change in character and width across N-S trending zones of strike-slip transfer faults lying between 51° and 54°E. To the northwest, a fold-thrust belt with consistent SW vergence has a width ofc.220 km in front of an imbricate beltc.160 km wide. To the southeast, an imbricate zonec.80 km wide is fronted by a gently tapering festoon of upright periclines that isc.350 km wide and punctured by over a hundred emergent salt diapirs.Pre-Zagros stages of the transfer zones in the Zagros are preserved on the Arabian platform and the two most obvious bound what we call the incipient Qatar syntaxis. This is at an early stage of one of the many syntaxes that compartmentalize the Alpine-Himalayan mountain chain. We use structures in the Hormuz salt to map and gauge the tectonic pulse of basement blocks that jostled as ocean basins opened and closed diachronously like zip fasteners along the Tethyan margin of Gondwana. This incipient syntaxis was a lithospheric key that went up while others went down during the rifting and riffling, but not drifting, of the still-born Hormuz basin we call Proto-Tethys.
Development of salt-related structures in the Central North Sea: results from section balancing
Authors: Buchanan Peter G. , Bishop Daniel J. , Hood David N. 
Published: April 2008

Abstract
The geometric and kinematic evolution of salt-related structures in the Central North Sea has been studied using structural restoration and balancing techniques. Strain associated with fault displacements, compaction and isostasy has been systematically removed, thus producing a graphical representation of the temporal and spatial distribution of salt structures through time. The results clearly demonstrate that the Central North Sea can be sub-divided into three structural provinces based on the type of salt structure present: (1) the Central Graben which is characterized by large offset extensional faults with broad salt swells and tall salt diapirs, (2) the Eastern platform comprising the Norwegian-Danish Basin which is dominated by symmetrical salt swells that are typically welded in intervening lows and deeply buried, and (3) the Western platform which is characterized by salt swells and gravity-driven, thin-skinned extension. By restoring the deformation at both a local and a regional scale, it becomes apparent that the Permian salt has controlled the development of structures throughout the Mesozoic and Tertiary in the Central Graben region and the Western Platform, whereas on the Eastern Platform the salt was primarily active during the Triassic only. This has led to a variation in the evolution of structural styles across the Central North Sea. The restorations also suggest that salt dissolution has not been a significant feature during the development of diapirs in this area.
Turonian correlation and sequence stratigraphy of the Chalk in southern England
Authors: Gale Andrew S. 
Published: April 2008

Abstract

A stratigraphical framework for the Turonian Chalk of southern England is described using lithostratigraphy, marker beds, cyclostratigraphy and biostratigraphy. For the Early and Mid-Turonian succession a basin-wide resolution of correlation of about a metre can be achieved. Sequences are identified from various criteria, which include bed-by-bed correlation along transects from platform to basin to provide a precise picture of sediment geometry in Turonian Chalk. Hardgrounds develop towards the platform margins and it is possible to identify some as lithified and commonly glauconitized sequence boundaries. For example, the Ogbourne Hardground, which represents a major Mid-Turonian sea-level fall, rests erosively on highstand chalks. Transgressive surfaces are also represented by hardgrounds; these onlap onto the basin margins and commonly show complex sedimentary histories and phosphatization. Transgressive events are marked by brief positive excursions in δ
13
C, detectable in basinal chalks. During the major Mid-Turonian sea-level lowstand, a thick ‘shelf margin wedge’ developed in the basin. A total of three complete and two partial sequences are identified in the Turonian of southern England. These compare well in number and biostratigraphical position with sequences described from a Turonian succession in Tunisia, which is an order of magnitude thicker.
Spectral gamma ray characterization of high resolution sequence stratigraphy: examples from Upper Carboniferous fluvio-deltaic systems, County Clare, Ireland
Authors: Davies S. J. , Elliott T. 
Published: April 2008

Abstract
The application of high resolution sequence stratigraphy requires the ability to recognize key surfaces which record fluctuations in relative sea-level. In sub-surface studies, gamma ray logs have been used to identify maximum flooding surfaces, but their full potential has not been realized. Gamma ray profiles produced using a portable spectrometer on exposed Upper Carboniferous fluvio-deltaic deposits in western Ireland reveal that key surfaces and systems tracts can be characterized more comprehensively and recognized with greater confidence if spectral gamma ray data (K, U, Th and their respective ratios) are used in conjunction with traditional total count data. Maximum flooding surfaces can be distinguished from lesser flooding surfaces by a distinctive U peak (> 5 ppm) and low Th/U ratio (< 2.5). Erosional unconformities and their associated incised valley fills are characterized by consistently low total counts (40–50 cps) and high Th/K ratios (> 6). Laterally correlative interfluves are represented by distinctive palaeosols that can be clearly identified in spectral gamma ray data by their anomalously low K content (<0.4%) and exceptionally high Th/K ratio (> 17). Finally, the stacking pattern of parasequence sets can be identified using the trends of Th/K ratios from sandstones in successive parasequences. These results have widespread implications for the recognition of high resolution sequence stratigraphic signatures in the stratigraphic record, with particular reference to the subsurface analysis of fluvio-deltaic deposits.
Slip partitioning at convergent plate boundaries of SE Asia
Authors: McCaffrey Robert 
Published: April 2008

Abstract
The active tectonics of SE Asia can be characterized by the interactions of large, rigid plates separated by broad zones of deformation. The relative motion of these plates across their boundaries is often partitioned in the sense that the normal and shear components occur on different structures. Earthquake slip vectors and geological and geodetic measurements are used to infer the degree to which oblique convergence, which is ubiquitous in SE Asia, is partitioned. The active tectonics of Sumatra, the Himalayan thrust, the Philippines, the New Guinea fold-and-thrust belt, the Huon-Finisterre collision, and the San Cristobal trench can be understood in terms of upper plate deformation associated with oblique convergence. Western Java may also exhibit partitioning of oblique subduction. Structures accommodating normal and shear components of the motion are often very close. Arc-parallel strain rates are estimated for forearcs of the region. The arc-parallel deformation of forearcs of the SE Asia region demonstrates that plate convergence, whether normal to structure or not, is a three-dimensional process.
Geophysical evidence for local indentor tectonics in the Banda arc east of Timor
Authors: Snyder David B. , Milsom John , Prasetyo Hardi 
Published: April 2008

Abstract
Two deep seismic reflection profiles and gravity measurements collected across the Banda arc east of Timor help to characterize crustal and uppermost mantle structures in the region where arc-continent collision is thought to be furthest advanced. Reflectors beneath the Sahul Platform of the Australian shelf indicate geometries consistent with older extensional rift structures overprinted by more recent horizontal shortening. To the north, the negative Bouguer gravity feature associated with the southern parts of the accretionary complex is unusually broad and deep. Post-collisional sediments are thin where this feature is crossed by the seismic lines, implying that older sediments or the crust are anomalously thick. Still further north, the forearc basin is notably narrow near eastern Timor and contains few sediments, most undeformed. The backarc region to the north is remarkable for the presence of a N-S trending line of seamounts culminating in an active volcano, Gunung Api, which is situated 400 km above the Wadati-Benioff zone. Reflection profiles across and along the seamount chain indicate underplating at Moho depths and a fault which appears to have acted as a conduit for basalt eruptions at the surface. Collectively, these observations imply anomalously thick and bouyant crust beneath the Banda arc east of Timor, and suggest two possible causes. Either a local promontory in the irregular boundary of the Australian craton was underthrust beneath the volcanic arc and forearc to 50–70 km depths or a Palaeozoic basin similar to the nearby Bonaparte Basin was underthrust and its former crustal structure inverted and thickened to form the buoyant crust. The new seismic reflection data help to locate the anomalously thick crust implied by gravity anomalies by defining the leaky fracture zone containing Gunung Api. It is inferred that the fracture propagates ahead of the indenting wedge of underthrust, thickened Australian crust.
Role of pre-Tertiary fractures in formation and development of the Malay and Penyu basins
Authors: Ngah Khalid , Madon Mazlan , Tjia H. D. 
Published: April 2008

Abstract
Major faults in Sundaland trend NNW to NW, WNW, N and E. Some of the NNW to NW and N-striking faults across Mesozoic areas of the Malay Peninsula were active until mid-Eocene time. Small, fault-bounded Tertiary basins onshore may be pull-apart basins associated with such faults. Mainly from seismic data, NNW to NW, N and E-striking faults have been recognized in the pre-Tertiary basement of the Malay and Penyu basins off the east coast of the peninsula. These faults were reactivated before the Late Oligocene and during the Middle to Late Miocene. N-striking faults in pre-Tertiary areas are common throughout Sundaland. In the field, these faults are found to be the oldest (possibly Jurassic) regional fractures. The regional NNW-NW and WNW fractures are believed to have originated as strike-slip faults when the peninsula was subjected to late Mesozoic deformation. The onshore E-W faults were probably extensional fractures that developed as secondary structures associated with sinistral slip motions along NNW-NW faults. Upper Cretaceous dolerite dykes fill some of the E-W fractures. NW-striking basement faults of the Malay basin continue onshore SE Asia as the Three Pagodas fault zone. Initially these were sinistral basement wrench faults creating secondary E-W extensional fractures. In the Middle to Late Miocene the regional stress field changed, resulting in reversal of slip movement along major wrench faults and structural inversion of the sedimentary basins. This inversion is manifested as E-W anticlines located over half-graben. In the Penyu basin similarly striking half-graben probably developed in the same fashion. There, the NW-striking Rumbia fault divides the basin into two parts. Half-graben in the western part remained orientated E-W, but those in the eastern part became rotated clockwise by continued left-lateral slip along the Rumbia fault. After the Miocene the two basins continued to subside, developing an almost undisturbed blanket of post-Miocene sediments. Locally, residual stress caused some of the structures to grow.
Tectonic evolution of the Bantimala Complex, South Sulawesi, Indonesia
Authors: Wakita Koji , Sopaheluwakan Jan , Miyazaki Kazuhiro , Zulkarnain Iskandar , Munasri  
Published: April 2008

Abstract
The Bantimala Complex of South Sulawesi, Indonesia is an assemblage of northeast-dipping tectonically stacked slices. The slices consist mainly of high pressure metamorphic rocks, radiolarian chert, breccia, sandstone and shale, and melange. In order to understand the tectonic evolution of the Bantimala Complex, we have investigated the lithology, age, stratigraphy, structure and relationships of the components. The K-Ar ages of high P-low T metamorphic rocks suggest that an oceanic plate subducted beneath the Sundaland continent during the Late Jurassic or earliest Cretaceous. The subduction ceased during the Albian, and the high pressure schists were exhumed and eroded at the surface before and during the deposition of middle Cretaceous radiolarian chert. The exhumation of the schists was related to the collision of microcontinents derived from Gondwanaland. The Jurassic shallow marine sedimentary rocks in the Bantimala Complex are possibly remnant fragments of the collided microcontinent. Tectonic stacking of the Bantimala Complex was caused by Neogene subduction and collision of another continental fragment further to the east.
Recent seismicity of Mount Etna: implications for flank instability
Authors: Montalto A. , Vinciguerra S. , Menza S. , Patanè G. 
Published: April 2008

Abstract

This study considers seismic activity recorded beneath the low eastern flank of Etna during the period between April 1989 and December 1991 with the aim of placing some seismological constraints on the investigation of slope instability related to the gravitational sliding of this unsupported side of the volcano. The seismicity essentially consists of rather superficial (
z
< 10 km for more than 90% of cases), low-magnitude (usually
M
< 3) earthquakes. Foci of earthquakes are clustered on the main fault systems crossing the region, such as the Santa Tecla fault and the San Leonardello fault system, that have in recent times produced earthquakes of unusually high intensity covering the whole of the Etnean area. The broad picture of seismicity may be partially attributed to the accumulation of stress related to the seaward displacement of moving blocks in the vicinity of the Valle del Bove and adjacent regions in response to the storage and release of elastic energy associated with frequent episodes of magma intrusion. We propose that eastward sliding probably involves a complicated ensemble of moving blocks, resting on shallow independent décollements rather than on a single, widespread decoupling surface.
The Makkovik Province: extension of the Ketilidian Mobile Belt in mainland North America
Authors: Kerr Andrew , Ryan Bruce , Gower Charles F. , Wardle Richard J. , Kerr Andrew 
Published: April 2008

Abstract

The Makkovik Province of Labrador represents the extension of the Ketilidian Mobile Belt of south Greenland into mainland North America; it exhibits a threefold division into a foreland region, a fold-and-thrust belt, and an interior magmatic zone. The
Kaipokok Domain
is dominated by Archaean basement rocks that form an extension of the North Atlantic Craton, but Proterozoic reworking is recorded by the reorientation of a
c
. 2230 Ma dyke swarm. Supracrustal rocks, consisting of shallow-marine sedimentary rocks overlain by greywackes and mafic volcanic rocks, rest unconformably upon Archaean basement, but towards the interior of the belt the basal unconformity is eradicated by northwest-directed thrusting. In the
Aillik Domain
, highgrade supracrustal rocks of similar aspect to those of the Kaipokok Domain are separated from the basement by mylonite zones, in a thick-skinned fold-and-thrust belt (
Kaipokok Bay Structural Zone
), believed to record significant northwest-directed translation. The Aillik Domain also contains abundant felsic volcanic rocks that lack typical arc-like geochemical signatures. The
Cape Harrison Domain
is dominated by plutonic rocks, including suites of 1840 Ma, 1800 Ma, 1720 Ma and 1650 Ma age, but gneissic inliers apparently represent ‘juvenile’ Proterozoic crust. The dominant 1800-1720 Ma plutonic suites are late-orogenic to post-orogenic, siliceous, potassic granitoid rocks, which resemble Phanerozoic post-collisional suites, rather than subduction-related arc batholiths. Nd isotopic variations position the eastern edge of the North Atlantic Craton close to the boundary between the Aillik and Cape Harrison Domains. The structural evolution of the Makkovik Province records a shift from pre- 1800 Ma northwest-directed thrusting to post-1800 Ma tight upright folding, also northwest-verging. However, there is also evidence for earlier (pre- 1890 Ma) events in the Kaipokok Domain. Major unresolved problems include the timing of early sub-horizontal deformation (perhaps related to collisional events), the age relations and setting of supracrustal sequences, the location of suture zones, the absence of clear arc-like magmatic assemblages, and the nature and antiquity of the eastern juvenile crustal block.