bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deformation around basin-margin faults in the North Sea/mid-Norway rift
Authors: Roberts Alan M. , Yielding Graham 
Published: April 2008

Abstract
It has been demonstrated previously that the rigid-domino model of extensional faulting can account well for the uplift/subsidence patterns observed within particular areas of the North Sea rift. This model, however, provides an unsatisfactory solution to deformation occurring at the basin margins.
It is suggested here that the domino model is an elegant, geometric simplification of the more complete flexural-isostatic solution to fault displacements. Application of a flexural model allows a unified treatment of the basin and its margins.
The basin-margins to the North Sea/Mid-Norway rift are all shown to have responded to extensional faulting by experiencing isostatic uplift in the footwalls to the marginal faults. Uplift magnitude varies from a few hundred metres adjacent to small faults to perhaps 5 km adjacent to the largest faults. Uplift patterns can be modelled or predicted by use of the flexural-cantilever basin model.
Recognition of marginal uplift throughout the rift means that geometric section balancing techniques, all of which require the footwall to be rigid during extension, are inapplicable as a method for analysis of large, basement faults within the North Sea.
Marginal, fault-related uplift is considered to have been a primary source of syn-rift clastic detritus. The precise locus of deposition for material eroded from emergent basin margins will depend on local drainage patterns, but deposition in the hangingwall basin and on the footwall platform may both be anticipated.
Seismic reflections from normal faults in the northern North Sea
Authors: Yielding G. , Badley M. E. , Freeman B. 
Published: April 2008

Abstract
Fault-plane reflections from gravity-driven, listric faults in thick sedimentary sequences are well known. However, reflections from normal faults associated with crustal extension are much rarer and less well studied. We discuss a number of examples of such reflections, present on commercial seismic reflection data from the northern North Sea. Some of these examples have previously been described as reflected refractions, but we show that this requires unrealistic velocities within the sedimentary column. Instead, we consider it more likely that these events are true fault-plane reflections. Depth migration and image-ray migration are used to determine the probable geometry of the faults in both cross section and map view. Estimates of the true geological dip remain sensitive to the velocity structure used, particularly that applied to the Triassic half-graben fill. Despite this uncertainty, the depth-migrations show that these faults are composed of two near-linear segments in cross section. The upper parts (in the Jurassic and Upper Triassic section) dip at 40–50°, but the deeper parts (Triassic hangingwall against basement in the footwall) typically dip at 30–35°. Occasionally, reflections indicate that faults continue into the basement with a 30–35° dip. We interpret this fault geometry as originating from two phases of fault movement. Triassic extension caused rotation of sets of initially steep planar faults. Following Late-Triassic-to-Middle-Jurassic thermal subsidence, renewed extension in the Late Jurassic caused the faults to cut up through the overburden at a steeper angle. Without recognition of a two-phase extension history, such faults might be mistakenly interpreted as forming with a listric geometry.
Geochemical studies of detrital heavy minerals and their application to provenance research
Authors: Morton Andrew C. 
Published: April 2008

Abstract
Although heavy mineral analysis is a sensitive and well-proven technique for determining the provenance of clastic sediments, the interpretation of the data is considerably enhanced by determining the composition of individual detrital grains. Many heavy mineral species, including pyroxene, amphibole, epidote, staurolite, garnet, tourmaline, monazite, chloritoid and spinel, show significant variations in composition that are related to the conditions under which their parent rocks were formed. Thus, as well as giving greater confidence in identification, geochemical analysis of detrital minerals adds precision to the evaluation of the relative contributions of potential source lithologies. Furthermore, by concentrating on stable minerals, geochemical studies avoid, or at least minimize, the problems caused by diagenetic and hydraulic processes.
Palaeoenvironments of the Nordenskjöld Formation: an Antarctic Late Jurassic—Early Cretaceous black shale-tuff sequence
Authors: Doyle Peter , Whitham Andrew G. 
Published: April 2008

Abstract
This study documents the palaeoenvironments of a Jurassic-Cretaceous boundary black shale-tuff sequence exposed on the east coast of the Antarctic Peninsula. Sedimentological and palaeontological indices show that, during the deposition of the lower part of the succession, bottom waters were predominantly anaerobic with brief spells of exaerobic or ‘episodically dysaerobic’ conditions. During the deposition of the upper part of the succession, dysaerobic conditions prevailed with mean levels of dissolved oxygen increasing through time. The upward changes seen in the Nordenskjöld Formation are thought to be related to tectonic uplift of the sea floor, through a pycnocline.
Are numerical models useful in reconstructing the migration of hydrocarbons? A discussion based on the Northern Viking Graben
Authors: Burrus J. , Kuhfuss A. , Doligez B. , Ungerer P. 
Published: April 2008

Abstract

The 2D-finite-difference code TEMISPACK is used to discuss the history of hydrocarbon (HC) generation, expulsion and migration along a 160 km long transect across the Northern Viking Graben. In the first section, HC generation is discussed based on hypotheses on the crustal heat flow; a kinetic model is used to calculate the maturity. Observations are shown to be consistent with a 67 mW m
−2
heat flow, possibly 60 mW m
−2
in the graben axis. The precision of the calibrated heat flow is not more than 10%, which results in an uncertainty of the timing of HC generation of 5–10 Ma. The development of overpressures, observed today in the deep Jurassic reservoirs is shown to be essentially controlled by compaction, with a minor contribution due to gas generation; the model also shows that faults related to the Jurassic rifting are most certainly impermeable. In the second section, the previous overpressures and maturity reconstructions form the framework in which expulsion and migration of HC are modelled, based on the two-phase (water, hydrocarbon) Darcy law. The computation explains the filling of the tilted blocks located in the Tampen Spur zone as well as the presence of gas at Troll. A sensitivity analysis shows the importance of poorly constrained parameters such as the relative permeability curves, capillary pressures, or the properties of the petroleum fluids.
Geochromatography in petroleum migration: a review
Authors: Krooss B. M. , Brothers L. , Engel M. H. 
Published: April 2008

Abstract
Numerous works have been published during recent years discussing the occurrence and effects of chromatographic processes with respect to petroleum migration. ‘Geochromatography’ has been, and still remains, a controversial topic. Based on the principles and conventions of separation science a definition of geochromatography is proposed, followed by a discussion of the relevance and potential occurrence of chromatographic type fractionation effects during primary and secondary petroleum migration. The evaluation of the relevant literature suggests that chromatographic processes in natural systems involving liquid mobile phase can result only in compound class fractionation (saturates, aromatics, polars) whereas molecular fractionation may be expected to occur with gaseous mobile phases. Problems associated with the recognition, experimental verification and quantification of geochromatography are discussed in detail.
Jurassic and Early Cretaceous platform margin configuration and evolution, central Oman Mountains
Authors: Pratt Brian R. , Smewing John D. 
Published: April 2008

Abstract
The Hajar Supergroup is a Middle Permian to middle Cretaceous sequence dominantly composed of shallow-water carbonate rocks which veneer the eastern edge of the Arabian Platform in the Oman Mountains. The Jurassic and Early Cretaceous components of this package were deposited on the passive margin of Neo-Tethys which developed after initial rifting in the Late Permian and Triassic. Strata studied in Jebel Akhdar, Saih Hatat and neighbouring uplifts document low- and high-energy, shallow-water depositional environments punctuated by two drowning events when deeper water, slope conditions migrated onto the shelf margin. The mid-Jurassic event may have been precipitated by synsedimentary down-faulting of the Saih Hatat area as rifting continued. The latest Jurassic, earliest Cretaceous event, depositing the Rayda Formation, is ascribed to a regional decrease in carbonate production because of widespread evaporitic conditions in the Arabian Platform interior.
The configuration of the Mesozoic platform margin in northern Oman conforms to a series of rift and transform segments inherited from the underlying crust when it separated in the Early Jurassic. The transform segments became the focus of major structural lineaments during subsequent thrusting and obduction. This provides an especially clearcut example of the structural control of passive margin geometry, as well as its effect on collision-related deformation. A new Jurassic lithostratigraphic unit, the Saih Hatat Formation, is formally described.
The Alpine deformation of the Central Oman Mountains
Authors: Hanna Samir S. 
Published: April 2008

Abstract

The Saih Hatat, Jebel Nakhl, Jebel Akhdar and the Hawasina Window structures of the Oman Mountains developed as culminations above a major sole thrust associated with late stage emplacement of the ophiolite from the northeast onto the Arabian margin. The outcrop of a pre-Permian sequence in the cores of Jebel Akhdar, Jebel Nakhl and Saih Hatat implies that the major sole thrust is located within the pre-Permian succession. This thrust is emergent in the southern foothills of the mountains south of the Jebel Salakh Range. In the Hawasina Window, however, the thrust is at a higher level and is located within the slope and oceanic sediments. An extensional regime due to the gravity sliding of the Semail ophiolite is recognized from the occurrence of surge zones, extensional duplexes, extensional cleavage and gravity folds. The development of the extensional faults, which occur in the frontal, dorsal, lateral and oblique walls of the above culminations, may account for the absence and locally thinning of the Tethyan thrust sheets around the flanks of these structures. The extensional tectonic regime is also believed to be responsible for the final extensional nature of the ‘Semail Thrust’. The Oman Mountains foreland fold and thrust belt mostly consists of a series of thrust sheets of oceanic sediments (Hawasina) together with widespread exposures of syntectonic (Aruma) deposits. The belt is dominated by imbricate stacks of both Hawasina and Aruma units. These imbricate stacks have been folded around major culminations arranged in a characteristic
en echelon
pattern. Late Alpine (Tertiary) deformation is largely attributed to an extensional regime of culmination collapse. Folds and thrusts were developed at the leading edge of the extensional faults (surge zones). Tertiary folding and thrusting may reactivate the pre-existing Early Alpine (Late Cretaceous) structures.
The post-Campanian tectonic evolution of the Central Oman Mountains: Tertiary extension of the Eastern Arabian Margin
Authors: Mann A. , Hanna S. S. , Nolan S. C. , Mann A. , Hanna S. S. 
Published: April 2008

Abstract
This paper documents the structural history of the central Oman Mountains after the obduction of the Semail ophiolite onto the eastern margin of the Arabian continent during the Late Cretaceous (Santonian/Campanian). The post-obduction history is recorded by a Late Campanian/Maastrichian-Tertiary sedimentary cover to the mountain belt. These sediments have been deformed within an extensional tectonic regime which is continuous northeastwards into the Gulf of Oman hinterland basin and southwestwards away from the SW foothills.
Large-scale down-to-the-basin normal faults have been recognized on the Batinah Coastal Plain NE of the mountain belt. Localized block-faulting and roll-over folds are associated with major faults that separate the Late Campanian to Tertiary sediments from older basement rocks of the Oman Mountains and with Late Cretaceous thrusts reactivated as normal faults. To the SW of the mountains, large NW-SE striking folds are thought to be gravity structures developed above a decollement in Late Cretaceous shales.
Syn-sedimentary tectonic influences are summarized and integrated with the structural analysis to identify the style and timing of tectonism on the S margin of the Gulf of Oman from the Late Campanian/Maastrichtian to present. There is evidence to suggest that penecontemporaneous tectonics controlled rates of subsidence and facies development during this time. A major E-W trending palaeo-high running close to the present-day shoreline affected Palaeogene sedimentation.
Unlike the northern Oman Mountains (Musandam Peninsula), there is no unequivocal evidence of mid-Tertiary (Zagros) compressional structures in the central Oman Mountains. Structural development of the cover sediments in the central mountain belt is believed to be controlled by underlying Late Cretaceous basement structures. In particular the Saih Hatat culmination was a positive structure throughout the Late Cretaceous and Early Tertiary, affecting both the stratigraphic and structural history of adjacent areas. The northern end of the Nakhl culmination seems to have had little effect on sedimentation but did influence deformation in the Tertiary.
Salt removal and sedimentation in Southern Oman
Authors: Heward A. P. 
Published: April 2008

AbstractOn the Eastern Flank of the South Oman Salt Basin lies a Cambrian to Recent sequence much affected by the withdrawal and dissolution of underlying Infracambrian salt. Salt withdrawal began after burial by only a few hundreds of metres of Cambrian continental sands, and salt dissolution has taken place periodically up to the present, initially near-surface and later in the subsurface. Salt removal has (1) resulted in the collapse of masses of dolomite and shale formerly interbedded with the salt, (2) influenced the large-scale geometries of sedimentary bodies within the overlying succession, (3) affected the distribution of sedimentary facies when rates of salt removal balanced or exceeded sedimentation, (4) allowed the preservation of parts of the succession otherwise eroded at this basin margin, and (5) caused folding and fracturing of Cambrian to Recent sediments.More than 2 × 109m3of oil (12 × 109bbls) is estimated to be present in four types of hydrocarbon trap related to salt removal. In terms of importance these are: large turtleback anticlines resulting from the inversion of former peripheral synclines, truncation traps rimming eroded turtle-back anticlines, small anticlines draped over residual masses of dolomite and shale, and porous and fractured dolomites within such residual masses.Comparison of salt removal phenomena from the Eastern Flank of the South Oman Salt Basin, the North Sea, western Canada and the USA suggests that the south Oman features may be typical of the margins of basins where a thick mobile salt sequence is overlain by clastic sediments.
Late Cretaceous and early Tertiary evolution of Jebel Ja’alan and adjacent areas, NE Oman
Authors: Filbrandt J. B. , Nolan S. C. , Ries A. C. 
Published: April 2008

Abstract
Jebel Ja’alan forms the northernmost extremity of the NNE-SSW trending Huqf-Haushi Uplift, a structural high which runs parallel to the SE continental margin of Oman. On Jebel Ja’alan Precambrian rocks, exposed in the core of this structural high, are overlain by a cover sequence of shallow water carbonate and clastic sediments of Maastrichtian to Eocene age. These cover sediments, and the structures which affect them, record a sequence of tectonic events leading to the uplift and inversion of Jebel Ja’alan in post middle Eocene times. In the Maastrichtian an extensional regime resulted in subsidence and the accumulation of fluvial clastic deposits, the Qahlah Formation, overlain by shallow marine limestones, the Simsima Formation, of Maastrichtian age. A post-Maastrichtian normal fault, the East Ja’alan Fault, downthrows Simsima Formation to the east against Precambrian basement to the west and controls the deposition of the Palaeocene/early Eocene Hasad Beds, which form debris fans distributed along the fault plane. The East Ja’alan Fault may have been linked to early extensional movement on the WNW-ESE trending North Ja’alan Fault which partly controlled deposition of the Eocene fluvial/marginal marine Rusayl Formation. A mid-Eocene transgression resulted in the deposition of the Seeb Formation shallow water limestones. All these sediments were deformed by a post middle Eocene compressional event which resulted in the formation of north-south trending asymmetric anticlines, forming a pop-up structure; the latter was controlled by a shallow level detachment dipping east which led to the detachment and removal of the Maastrichtian-Eocene sediments from Jebel Ja’alan. An associated deeper level basement ramp resulted in uplift and inversion of the Precambrian basement of Jebel Ja’alan. These compressional structures are displaced by later left-lateral strike-slip on the North Ja’alan Fault Zone.
The Arabian continental margin in Iran during the Late Cretaceous
Authors: Stoneley R. 
Published: April 2008

Abstract
The events which affected the Iranian sector of the Southern Tethyan margin of the Arabian continent during the Cretaceous differed from those that took place in Oman, although they were clearly related to them. Extensional faulting, parallel to the shelf margin, commenced locally in the Cenomanian and culminated later in the Cretaceous with the expulsion of mantle material to the surface. This engulfed the shelf edge before gliding southwestwards over a complementary intra-shelf basin. These events took place progressively later towards the north-west, and are interpreted as an unsuccessful attempt to develop a spreading axis along the continental margin. They were followed by a return to shelf sedimentation at the southern edge of Tethys, which closed finally in the early Miocene. It is suggested that the Oman and Iranian sectors of the Arabian margin were offset some 300 km by a north-south transform fault, and that the differences between the two regions were therefore due to attempted spreading in different tectonic environments in the late Cretaceous.
Thermal effect of the Tertiary Cuillins Intrusive Complex in the Jurassic of the Hebrides: an organic geochemical study
Authors: Thrasher Jane 
Published: April 2008

Abstract
The Tertiary Cuillins Intrusive Complex is partially located within the Mesozoic depositional basins of the Minch and intrudes a Jurassic sequence including a number of moderately organic-rich horizons. The thermal effect of the central intrusive activity, and related minor intrusions, on the Jurassic sediments has been assessed using organic geochemical molecular maturity parameters. Analysis of more than 60 samples, mainly from the Middle Jurassic Dun Caan and Cullaidh Shales, shows that the thermal effect of the igneous complex is very localized and that Jurassic sediments more than 15 km from the complex margin are extremely immature, except in the immediate vicinity of minor intrusions. Igneous activity similar to the Tertiary of western Britain should therefore not be invoked as an alternative maturation route for shallow-buried sediments.
Aspects of the geology of the Malin Sea area
Authors: Dobson M. R. , Whittington R. J. 
Published: April 2008

Abstract
A complex of sediment-filled graben and half-graben, separated by acoustic basement, occupy much of the northwest shelf of the British Isles. Some were established in the Late Carboniferous, but most were formed during a post-Hercynian tensional phase that adopted Caledonoid-trending structures in the basement. A major graben complex occurs in the Malin Sea area; flanked by the Coll-Tiree-Skerryvore-Stanton Banks basement ridge to the north and by the Islay-Donegal Platform to the south. Rock samples obtained by divers from the two basement ridges confirm their Precambrian character. Limited commercial multichannel reflection seismic data together with BIRPS WIRE lines and structural information supplied by Texaco suggest that the graben complex consists of three major depocentres: the Inner Hebrides Trough, the Malin Basin and the South Donegal Basin. To the west lies the Main Donegal Basin. This basin, in concert with the South Donegal Basin, evolved during the Carboniferous as a result of dextral strike slip movement between the Stanton Banks in the north and the Islay-Donegal Platform to the south. Sea bed core and dredge material and well data recovered from the graben complex indicate that the basin sediments include Upper Carboniferous, Permo-Triassic, Lower Jurassic, Middle Jurassic, with thick Cretaceous and Lower Tertiary in the far west. Periods of uplift and erosion restricted sedimentation during the late Mesozoic, whilst uplift and erosion in the early Tertiary was accompanied by extensive igneous activity, with the development of two plutonic centres and twelve other smaller intrusive igneous bodies. Tertiary sediments are inferred for the Blackstones Basin by analogy with similar sequences elsewhere in the Hebridean area. A thick Quaternary section, dominated by glaciomarine sediments, contains three of the five glacial cycles that constitute the Pleistocene in this area.
Identification of tectonic rotations in boreholes by the integration of core information with Formation MicroScanner and Borehole Televiewer images
Authors: MacLeod C. J. , Parson L. M. , Sager W. W. ,   the ODP Leg 135 Scientific Party
Published: April 2008

AbstractPalaeomagnetic studies on land have shown that block rotations on a variety of scales are commonplace in many tectonic regimes. In the oceans, however, analogous rotations have rarely been documented. This is due principally to the difficulty of their measurement rather than to their likely absence. Palaeomagnetic measurements can be, and are, readily made on borehole cores. However, the difficulty in reliably reorienting these cores, and hence their magnetization vectors, back to geographical coordinates severely hampers their use for the purposes of addressing tectonic rotations. Several techniques for orienting cores are commonly in use, none of which is without its limitations for palaeomagnetic purposes. A technique is outlined here that potentially allows the reliable orientation of sections of core by matching distinctive inclined planar features measured on the core with their images on Formation MicroScanner and Borehole Televiewer wireline logs. Its methodology is described and an example, from Ocean Drilling Program Leg 135, presented to illustrate its application.