bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pore pressure/stress coupling in Brunei Darussalam — implications for shale injection
Authors: Tingay Mark R. P. , Hillis Richard R. , Morley Christopher K. , Swarbrick Richard E. , Okpere Eugene C. 
Published: April 2008

Abstract

Shale dykes, diapirs and mud volcanoes are common in the onshore and offshore regions of Brunei Darussalam. Outcrop examples show that shale has intruded along both faults and tensile fractures. Conventional models of overpressure-induced brittle failure assume that pore pressure and total stresses are independent of one another. However, data worldwide and from Brunei show that changes in pore pressure are coupled with changes in total minimum horizontal stress. The pore pressure/stress-coupling ratio (Δσ
h
/ΔP
p
) describes the rate of change of minimum horizontal stress magnitude with changing pore pressure. Minimum horizontal stress measurements for a major offshore field where undepleted pore pressures range from normal to highly overpressured show a pore pressure/stress-coupling ratio of 0.59. As a consequence of pore pressure/stress coupling, rocks can sustain a greater increase in pore pressure prior to failure than predicted by the prevailing values of pore pressure and stress. Pore pressure/stress-coupling may favour the formation of tensile fractures with increasing pore pressure rather than reactivation of pre-existing faults. Anthropogenically-induced tensile fracturing in offshore Brunei supports this hypothesis.
Re-evaluation of mobile shale occurrences on seismic sections of the Champion and Baram deltas, offshore Brunei
Authors: Van Rensbergen Pieter , Morley Christopher K. 
Published: April 2008

Abstract
3D seismic data in the Baram and Champion delta provinces offshore Brunei show that regions thought to be occupied entirely by chaotic seismic data and conventionally interpreted as shale diapirs, are regions of dimmed, but coherent reflectivity. Such data indicate shale diapir masses are not present, instead dimming can be attributed to sediment intrusive complexes, overpressured fluids and gas clouds, or processing artefacts. In this way significant delta structures are masked on 2D seismic data, which are important to interpret delta tectonic evolution. The Middle Miocene-Recent Champion and Baram deltaic provinces are characterized by typical gravity tectonics-related structures. However, being situated on an active margin they are also affected by episodic development of contractional structures, which are located on older reactive shale bulges and result in inversion of motion on some growth faults. The emplacement of shale pipes, gas clouds and intrusive complexes is generally relatively late (Pliocene) in comparison with the underlying reactive diapirs (Late Miocene) and their emplacement events may be separated in time by several million years. Late overpressured systems may be related to phases of pore fluid pressure increase during or following periods of inversion tectonics, which resulted in phases of enhanced fluid migration in the basin, where fluids were either expelled laterally oceanwards, or vertically.
The role of shale deformation and growth faulting in the Late Cretaceous evolution of the Bight Basin, offshore southern Australia
Authors: Totterdell J.M. , Krassay A.A. 
Published: April 2008

Abstract
The Jurassic-Cretaceous Bight Basin of offshore southern Australia is a large, under-explored basin with little stratigraphic control. Sequence stratigraphic and structural interpretation of regional-scale 2-D seismic data has revealed the presence of two large progradational delta systems of mid-Late Cretaceous age, which are vastly different in terms of geometry and stratal architecture. The Cenomanian White Pointer Delta is characterized by shale deformation and growth faulting. Growth fault-controlled depocentres occupy a wide band across the Ceduna Subbasin of the Bight Basin that records the progradation of the delta across the palaeo-shelf during the Cenomanian. The growth faults are generally listric and basinward dipping (regional). Counter-regional faults are uncommon. The updip extensional features are accompanied downdip by a zone of diapirs that coincides with an outer basin high and, in deeper water at the toe of slope, a region of contractional deformation and toe-thrusts. In comparison, the younger (Late Santonian-Maastrichtian) Hammerhead Delta exhibits strongly progradational stratal geometries with little evidence of shale tectonics except in the SW part of the Ceduna Sub-basin. There, sustained progradation under a high sediment supply regime caused gravitational instability and the formation of listric growth faults at the palaeo-shelf margin with associated down-dip contractional deformation.
The role of shear stress in mobilizing deep-seated mud volcanoes: geological and geomechanical evidence from Trinidad and Taiwan
Authors: Yassir Najwa 
Published: April 2008

Abstract
Deep-seated mud volcanoes are observed in a variety of geological settings, which has led to considerable debate on their origin. This paper summarizes the geological features common to mud volcanoes around the world and possible mechanisms of their extrusion. Field and laboratory data from Trinidad and Taiwan are discussed to assess the possible sources and causes of the volcanoes. A close association between mud volcanoes and compressional tectonics leads to the conclusion that tectonic activity plays an important part in mud volcano development. Experimental data are presented to explain the role of tectonic activity and the association between shear stresses and mud volcanoes. It is demonstrated that shear stresses applied to low permeability sediments can produce a dramatic increase in pore pressure and can cause sediment flow. This is proposed as one possible contributing cause of mud volcanoes.
Boron and boron isotopes as tracers for diagenetic reactions and depth of mobilization, using muds and authigenic carbonates from eastern Mediterranean mud volcanoes
Authors: Deyhle A. , Kopf Achim J. , Aloisi G. 
Published: April 2008

Abstract

Authigenic carbonates and muds from six mud volcanoes in the eastern Mediterranean Sea were recovered during the French/Dutch MEDINAUT cruise utilizing the submersible
Nautile
in November 1998. The mud volcanoes are active seafloor vents in two areas at the plate boundary between the converging African and Eurasian Plates: the Mediterranean Ridge accretionary prism near Crete (Greece) and the Anaximander Mountains south of Turkey. B contents and δ
11
B signatures were measured with the aim of identifying the diagenetic processes and source depths of the material in the collision zone. B concentrations of the carbonate precipitates cover a range of 8–45 ppm and vary isotopically from +15.6 to +22.9‰ (corresponding to a parent solution of 34.9–42.2‰ at pH 7). Both the B-enrichment and a δ
11
B valve slightly lower than seawater suggest the mud domes originate from a moderately deep fluid source, with local admixture of seawater. B contents and δ
11
B of the mud show distinct differences between the areas: the Mediterranean Ridge mud domes have lower B contents and higher δ
11
B (average 3.9‰) compared to Anaximander Mountains mud volcanoes (δ
11
B average −0.6‰). These B results attest the release of structurally-bound B from clay mineral lattices, probably due to stronger deformation near Turkey. These mudstones, which had previously been affected by deep-seated thrusting beneath the Antalya Complex, may have been liquefied and remobilized in their present setting. By contrast, the mud on the Mediterranean Ridge represents offscraped clay-rich strata that was incorporated into the large accretionary wedge.
On the phylogeny and evolutionary history of pterosaurs
Authors: Unwin David M. 
Published: April 2008

Abstract

Previous cladistic studies of pterosaur relationships suffer from restricted numbers of taxa and characters, incomplete data sets and absence of information on characters, tree structure and the robustness of tress. Parsimony analysis of a new character data set (60 characters, 20 terminal taxa, 97.75% complete) yielded six trees. In the strict consensus tree
Preondactylus
is the most basal taxon followed, stepwise, by the Dimorphodontidae and the Anurognathidae. Beyond this basal group, more derived pterosaurs (Campylognathoididae (Rhamphorhynchidae + Pterodactyloidea)) share a suite of characters principally associated with elongation of the rostrum. The Pterodactyloidea consists of four major clades. The Ornithocheiroidea is the most basal taxon consisting, stepwise, of
Istiodactylus
, the Ornithocheiridae,
Nyctosaurus
and the Pteranodontidae. The remaining taxa, Ctenochasmatoidea, Dsungaripteroidea and Azhdarchoidea, are weakly united in a clade of non-ornithocheiroid pterodactyloids, but their inter-relationships are difficult to resolve.
Cycnorhamphus
is the basal-most ctenochasmatoid, while the remaining taxa (
Pterodactylus
, Lonchodectidae, Ctenochasmatidae) form an unresolved trichotomy. The Dsungaripteroidea (
Germanodactylus
+Dsungaripteridae) is strongly supported by features of the skull and dentition. The Azhdarchoidea (
Tapejara
[
Tupuxuara
+ Azhdarchidae]) is united by cranial characters such as elevation of the antorbital region, and relative shortening of the wing finger. The pattern of pterosaur evolution suggested by the results of this analysis is broadly similar to traditional ideas, but has greater resolution, more complexity and reveals several previously unrecognized ‘events’.
Morphological evolution of the pectoral girdle of pterosaurs: myology and function
Authors: Bennett S. Christopher 
Published: April 2008

Abstract

The musculature of the pectoral region of representative rhamphorhynchoid (
Campylognathoides
) and large pterodactyloid (
Anhanguera
) pterosaurs was reconstructed in order to examine the function of various muscles and the functional consequences of the evolution of the advanced pectoral girdle of large pterodactyloids. The reconstructions suggest that
m. supracoracoideus
was not an elevator of the wing, but instead depressed and flexed the humerus.
m. latissimus dorsi, m. teres major, m. deltoides scapularis
, and
m. scapulohumeralis anterior
were wing elevators. Comparison of the origin, insertion and function of muscles in the rhamphorhynchoid and the large pterodactyloid suggests that the evolution of the advanced pectoral girdle: (1) straightened the pull of
m. pectoralis, m. deltoides scapularis
and
m. teres major
, improving their function in wing elevation; (2) allowed ligaments rather than muscles to resist the tendency of those muscles to move the scapula; and (3) braced the pectoral girdle against the vertebral column so that the tendency of
m. latissimus dorsi
and of aerodynamic lift on the wing to move the scapulocoracoid medially and dorsally, thereby compressing the thorax, could be resisted. The osteological and myological complexity of the advanced pectoral girdle, its uniqueness among tetrapods and its association with other complex osteological features argue that the advanced pectoral girdle is a synapomorphy complex of a single clade of large pterodactyloids, rather than a mere correlate of large size evolved convergently in various lineages.
New specimens of Pterosauria (Reptilia) with soft parts with implications for pterosaurian anatomy and locomotion
Authors: Frey Eberhard , Tischlinger Helmut , Buchy Marie-Céline , Martill David M. 
Published: April 2008

Abstract
New specimens of pterosaurs with soft-part preservation from the Solnhofen Lithographic Limestone (S Germany) and the Crato Formation (northeastern Brazil) yield hitherto unknown and unexpected details of pterosaur anatomy: the presence and internal anatomy of softtissue crests, the internal anatomy of the brachiopatagium, including a blood vessel system and structural details of foot and hand. Some consequences for pterosaurian flight, thermoregulation and aspects of evolution are discussed.
Middle- and bottom-decker Cretaceous pterosaurs: unique designs in active flying vertebrates
Authors: Frey Eberhard , Buchy Marie-Céline , Martill David M. 
Published: April 2008

Abstract
Among Pterosauria there are three types of scapulocoracoid construction. In the ornithocheirid scapulocoracoid the scapula is oriented almost horizontally; it is shorter than the coracoid and the glenoid fossa is level with the ventral margin of the vertebral column. In the azhdarchid scapulocoracoid the scapula is curved ventrally and is as long as the coracoid. In this construction the glenoid fossa lies approximately in the mid-horizontal plane of the chest. In the tapejaroid construction, the scapula is about one-third longer than the coracoid, which is oriented subhorizontally, and the glenoid fossa is level with the dorsal rim of the sternal plate. Both latter conditions are hitherto unknown among flying vertebrates and result in an unstable, but manoeuvrable flight, probably powered with wing beats.
Pterosaur swim tracks and other ichnological evidence of behaviour and ecology
Authors: Lockley Martin G. , Wright Joanna L. 
Published: April 2008

Abstract

New finds of pterosaur tracks (cf.
Pteraichnus
) from the Summerville and Sundance formations (Late Jurassic) of western North America associated with elongate scrape marks and small circular paired depressions indicate that pterosaurs could swim, or at least float in water, and that they may have fed on small animals living at the sediment surface in shallow water. In this respect their behaviour resembled certain seabirds. The ichnological evidence for pterosaur ‘swim’ and ‘feeding’ traces consists of scrape marks interpreted as traces left when the paddling limb of a pterosaur registered on the substrate, and small circular paired depressions as traces left when the beak of a pterosaur was probing for food. Such traces resulting from aquatic activity are consistent with the nearshore environments in which pterosaur bones and trackways have been found.

There is growing evidence for an extensive and complex
Pteraichnus
ichnofacies in the Late Jurassic of western North America; over 80 specimens have been collected with many more remaining in the field. In particular we draw attention to the large quantitative data base that is available for morphometric, size-frequency studies and the potential for behavioural studies of individual locomotion and flocking. In addition the sites hold considerable promise for understanding what appears to be the world’s largest pterosaur ichnofacies in the context of ancient depositional environments and regional sequence stratigraphy.
Triassic mid-ocean ridge basalts from the Argolis Peninsula (Greece): new constraints for the early oceanization phases of the Neo-Tethyan Pindos basin
Authors: Saccani Emilio , Padoa Elisa , Photiades Adonis 
Published: April 2008

Abstract
The Middle Unit of the central-northern Argolis Peninsula, in NE Peloponnesus (Greece), is composed of several tectonic slices, locally including intact sequences of mafic volcanic rocks topped by radiolarian cherts. Although some of these sequences are Jurassic in age, many of them display a Triassic age based on biostratigraphical evidence. The petrological studies presented in this paper indicate that the Triassic volcanic rocks were generated in a mid-ocean ridge setting, and that they represent the oldest remnants of the Pindos oceanic crust so far recognized in the Subpelagonian zone. On the basis of immobile trace element analyses, two chemically distinct groups of Triassic lavas can be recognized in the various volcanic sequences. One group is represented by transitional-type mid-ocean ridge basalts (T-MORBs) displaying moderate light rare earth element (LREE) enrichment, and incompatible element abundances very similar to those observed in present-day T-MORBs. The other group exhibits a range of characteristics typical of many normal-type MORBs: that is, variable LREE depletion and flat N-MORB normalized patterns of incompatible element abundance. Moreover, many geochemical characteristics indicate that the various N-MORB type volcanic sequences originated from chemically distinct (heterogeneous) sub-oceanic mantle sources. Analogous to similar basalts from ophiolitic mélanges of the Dinaride-Hellenide belt, the T-MORBs from the Argolis Middle Unit are interpreted as having originated from a primitive mantle source variably enriched by an ocean-island basalt (OIB)-type component. In contrast, the contemporaneous occurrence of N-MORBs implies that, during the Mid-Late Triassic, oceanic spreading of the Pindos basin had already reached, at least in some sectors, a quasi-steady state involving only sub-oceanic mantle sources and their partial melt derivatives. Our model for the Triassic opening of the Pindos oceanic basin and its related tectonomagmatic evolution is largely supported by comparison with the Red Sea embryonic ocean, a modern analogous setting.
Yarlung Zangbo ophiolites (Southern Tibet) revisited: geodynamic implications from the mineral record
Authors: Hébert Réjean , Huot François , Wang Chengshan , Liu Zhifei 
Published: April 2008

Abstract

We present mineral chemistry data and petrological evidence from the Yarlung Zangbo suture zone ophiolites (Southern Tibet) suggesting that they represent a collage of heterogeneous massifs. Mantle sections in these ophiolites consist of harzburgite and lherzolite cut by several generations of gabbroic to diabasic intrusions, all affected by high-temperature deformation. Pyroxenitic bands are parallel to the mantle foliation. Crustal plutonic sections, consisting of dunite, wehrlite and gabbro, are thin or absent and have been observed only in the Dazhuqu massif. Plagioclase is an additional phase associated with crustal peridotites. The mineral chemistry of silicate minerals and spinel in the mantle and crustal rocks varies widely and is believed to reflect complex melt percolation and reaction. The massifs record polybaric exhumation steps from at least 50 km depth to the plagioclase stability field. Pyroxene has re-equilibrated compositions from 1200 °C down to medium-grade metamorphic conditions. The mantle peridotites are interpreted as the residues of 10–40% partial melting of a fertile lherzolitic source. High Cr number, low TiO
2
content and relatively high Fe
3+
number of spinels suggest that the ophiolitic massifs were generated in a suprasubduction zone (arc or back-arc) environment.
Tectonic implications of boninite, arc tholeiite, and MORB magma types in the Josephine Ophiolite, California-Oregon
Authors: Harper Gregory D. 
Published: April 2008

AbstractThe Josephine Ophiolite is a large complete ophiolite flanked by arc complexes, including rifted arc facies, and overlain by volcanopelagic and volcaniclastic sedimentary rocks. The extrusive sequence and sheeted dyke complex record a wide range in magma types and degree of fractionation. The upper part of the extrusive sequence, as well as late dykes in the ophiolite, have mid-ocean ridge basalt (MORB) affinities and include unusual highly fractionated Fe-Ti basalts. The sheeted dyke complex and lower pillow lavas are dominated by transitional island-arc tholeiite (IAT) to MORB, but about 10% consist of low-Ti, high-Mg basalts and andesites. Whole-rock chemistry and Cr-spinel compositions indicate that the low-Ti rocks range from boninite (BON) to primitive arc basalt. The low-Ti samples have trace element characteristics indicating a greater subduction component than the IAT-MORB or MORB samples, as well as derivation from a wide range of sources ranging from depleted to enriched relative to an average N-MORB mantle source. Mixing of low-Ti and MORB magmas may have produced the IAT-MORB magma type that is most characteristic of the ophiolite. Podiform chromites and late magmatic features in the mantle peridotite, described by previous workers, appear to have been formed from the low-Ti magmas. Regional geological relationships and the presence of boninitic magmas suggest that arc rifting and initial sea-floor spreading to form the Josephine Ophiolite occurred in the forearc of a west-facing arc built on edge of the North American plate. Arc magmatism appears to have jumped westward, at which time the Josephine basin became situated in a back-arc setting, analogous to the inferred evolution of the modern Lau back-arc basin. Alternatively, the Josephine Ophiolite may have formed in a setting analogous to the north end of the Tonga Trench or the south end of the North Fiji basin, both sites of modern boninites, where a back-arc spreading centre has propagated across an arc into the forearc. Rift propagation during formation of the Josephine Ophiolite is consistent with the presence of highly fractionated Fe-Ti basalts.
Forearc extension and sea-floor spreading in the Thetford Mines Ophiolite Complex
Authors: Schroetter Jean-Michel , Pagé Philippe , Bédard Jean H. , Tremblay Alain , Bécu Valérie 
Published: April 2008

Abstract

The Ordovician Thetford Mines Ophiolite Complex (TMOC) is an oceanic terrane accreted to the Laurentian margin during the Taconic Orogeny and is affected by syn-obduction (syn-emplacement) deformation and two post-obduction events (Silurian backthrusting and normal faulting, and Acadian folding and reverse faulting). The southern part of the TMOC was tilted to the vertical during post-obduction deformation and preserves a nearly complete cross-section through the crust. From base to top we distinguish cumulate Dunitic, Pyroxenitic and Gabbroic Zones, a hypabyssal unit (either sheeted dykes or a subvolcanic breccia facies), and an ophiolitic extrusive-sedimentary sequence, upon which were deposited sedimentary rocks constituting the base of a piggy-back basin. Our mapping has revealed the presence of subvertically dipping, north-south- to 20°-striking faults, spaced
c.
1 km apart on average. The faults are manifested as sheared or mylonitic dunites and synmagmatic breccias, and correspond to breaks in lithology. The fault breccias are cut by undeformed websteritic to peridotitic intrusions, demonstrating the pre- to synmagmatic nature of the faulting. Assuming that rhythmic cumulate bedding was originally palaeo-horizontal, kinematic analysis indicates that these are normal faults separating a series of tilted blocks. In the upper part of the crust, the north-south-striking fault blocks contain north-south-striking dykes that locally constitute a sheeted complex. The faults correspond to marked lateral changes in the thickness and facies assemblages seen in supracrustal rocks, are locally marked by prominent subvolcanic breccias, and have upward decreasing throws suggesting that they are growth faults. The base of the volcano-sedimentary sequence is a major erosional surface in places, which can penetrate down to the Dunitic Zone. The evidence for coeval extension and magmatism, and the discovery of a locally well-developed sheeted dyke complex, suggest that the TMOC formed by sea-floor spreading. The dominance of a boninitic signature in cumulate and volcanic rocks suggests that spreading occurred in a subduction zone environment, possibly in a forearc setting.