bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiple generations of extensional detachments in the Rhodope Mountains (northern Greece): evidence of episodic exhumation of high-pressure rocks
Authors: Krohe Alexander , Mposkos Evripidis 
Published: April 2008

AbstractAn integrated structural and petrological study shows that exhumation of high-Procks of the Rhodope occurred in several pulses. The structurally uppermost Kimi Complex recording an Early Cretaceous high-Pmetamorphism was exhumed between about 65 and >42 Ma. The Sidironero, Kardamos and Kechros Complexes that record Early Tertiary high-Pmetamorphism (at least 19 kbar at 700 °C) were exhumed at >42–30 Ma. Exhumation occurred with isothermal decompression. Strain episodes depict thrusting of medium/high grade above lower grade high-Procks, syn-thrusting extension and post-thrusting extension. Polyphase extension created several generations of detachment zones, which, in sum, excise about 20 km of material within the crustal profile. This reduction in crustal thickness is consistent with a reduction of the present crustal thickness from more than 40 km to less than 30 km in the eastern Rhodope. We mapped the post-thrusting Xanthi low-angle detachment system over 100 km, from its break up zone above the Sidironero Complex (Central Rhodope) into the eastern Rhodope. This detachment shows an overall ESE-dip with a ramp and flat geometry cutting across the earlier thrust structures. The Kimi Complex is the hanging wall of all syn- and post-thrusting extensional systems. On top of the Kimi Complex, marine basins were formed from the Lutetian (c.48–43 Ma) through the Oligocene, during extension. Successively, atc.26 to 8 Ma, the Thasos/Pangeon metamorphic core complexes were exhumed. In these times representing the early stages of Aegean back-arc extension, the Strymon and Thasos detachment systems caused crustal thinning in the western Rhodope. Renewed heating of the lithosphere associated with magmatism and exhumation of hot middle crust from beneath the Sidironero Complex occurred. We focus on the geometry, timing and kinematics of extension and contraction structures related to the >42–30 Ma interval and how these exhumed high-Procks. We interpret high-Procks exhumed in this interval as a window of the Apulian plate beneath the earlier (in the Cretaceous) accreted Kimi Complex.
Models of Rodinia assembly and fragmentation
Authors: Pisarevsky Sergei A. , Wingate Michael T. D. , Powell Chris McA. , Johnson Simon , Evans David A. D. 
Published: April 2008

Abstract
Amongst existing palaeogeographic models of the Rodinia supercontinent, or portions thereof, arguments have focused upon geological relations or palaeomagnetic results, but rarely both. A new model of Rodinia is proposed, integrating the most recent palaeomagnetic data with current stratigraphic, geochronological and tectonic constraints from around the world. This new model differs from its predecessors in five major aspects: cratonic Australia is positioned in the recently proposed AUSMEX fit against Laurentia; East Gondwanaland is divided among several blocks; the Congo-São Francisco and India-Rayner Cratons are positioned independently from Rodinia; Siberia is reconstructed against northern Laurentia, although in a different position than in all previous models; and Kalahari-Dronning Maud Land is connected with Western Australia. The proposed Rodinia palaeogeography is meant to serve as a working hypothesis for future refinements.
Time, place and mode of propagation of foreland basin systems as recorded by the sedimentary fill: examples of the Late Cretaceous and Eocene retro-foreland basins of the north-eastern Pyrenees
Authors: Christophoul F. , Soula J.-C. , Brusset S. , Elibana B. , Roddaz M. , Bessiere G. , Deramond J. 
Published: April 2008

Abstract

The relationship between tectonics and sedimentary fill has been studied in two syncontractional basins of the western Corbières (eastern North Pyrenean retro-foreland basin). The Late Cretaceous basin formed during
c.
10–12 Ma as a result of left-lateral transpressional deformation, and is composed of forward-younging sub-basins characterized by reworking of the forelimbs of growing fold-propagation folds. Thrust-wedge advance and cratonward migration of the platform are recorded by a deepening-upward stacking pattern indicating increased regional subsidence with a limited contribution of the submarine orogen. Tectonic quiescence and erosional unloading lasting 29–30 Ma are recorded by a shallowing-upward stacking pattern, and fluvial sedimentation issued from widespread sources in the emerging inner orogen. The Early to Middle Eocene basin formed as a result of pure shortening normal to the range. The marine Early Eocene basin developed during
c.
2 Ma by widening of a single basin provoked by the two-step propagation of a basement duplex. This is recorded by growth-stratal patterns and coarsening-upward depositional sequences indicating the increasing contribution of the emerged orogen. The Middle Eocene continental deposits infilled two sub-basins working synchronously and were transported by alluvial fans with a provenance in the inner orogen, during decreasing thrust-wedge advance and increasing erosional unloading.
Active intraplate strike-slip faulting and transpressional uplift in the Mongolian Altai
Authors: Cunningham D. , Dijkstra A. , Howard J. , Quarles A. , Badarch G. 
Published: April 2008

Abstract
The Mongolian Altai is a Late Cenozoic intraplate strike-slip deformation belt which formed as a distant strain response to the Indo-Eurasian collision over 2000 km to the south. We report results from 5 weeks of detailed fieldwork carried out during summer 2000 in northwestern Mongolia investigating the crustal architecture of the Altai at latitude 48°N. The region can be divided into discrete Cenozoic structural domains each dominated by a major dextral strike-slip fault system or range-bounding thrust fault. Gentle bends along the major strike-slip faults are marked by transpressional uplifts including asymmetric thrust ridges, restraining bends, and triangular thrust-bounded massifs. These transpressional uplifts (Tsambagarav Massif, Altun Huhey Uul, Sair Uul, Hoh Serhiyn Nuruu, Omno Hayrhan Uula, Mengildyk Nuruu) comprise the highest mountains in the Mongolian Altai and are structural and metamorphic culminations exposing polydeformed greenschist-amphibolite grade basement recording at least two phases of Palaeozoic ductile deformation overprinted by Cenozoic brittle structures. Cenozoic thrust faults with the greatest amounts of displacement bound the W and SW sides of ranges throughout the region and consistently verge WSW. Each major range is essentially a NE-tilted block and this is reflected by asymmetric internal drainage patterns. Many faults are considered active because they deform surficial deposits, form prominent scarps, and define range fronts with low sinuosity where active alluvial fan deposition takes place. Reactivation of the prevailing NW-striking, NE-dipping Palaeozoic basement anisotropy is a regionally important control on the orientation and kinematics of Cenozoic faults. At first order, the Altai is spatially partitioned into a low-angle thrust belt that overthrusts the Junggar Basin on the Chinese side and a high-angle SW-vergent dextral transpressional belt on the Mongolian side. The mechanically rigid Hangay craton and Junggar basement block which bound the Altai on either side have played a major role in focusing Late Cenozoic deformation along their boundaries and within the Altai. The geometric relationship between rigid block boundaries, Palaeozoic basement structural anisotropy, and the dominantly NE SHmax (derived from India’s continued NE indentation) has dictated the kinematics of Late Cenozoic deformation in the Altai, Gobi Altai, and Sayan regions.
Relationships between Cenozoic strike-slip faulting and basin opening in northern Thailand
Authors: Uttamo Wutti , Elders Chris , Nichols Gary 
Published: April 2008

Abstract
Northern Thailand is located in a structurally complex area between three major tectonic regimes, a region of extensional tectonics to the south and two major strike-slip zones, the Sagaing fault zone to the west and the Red River fault zone to the northeast. Cenozoic tectonics in northern Thailand resulted from the collision between the Indian plate and Eurasia. The continued indentation of the Indian plate into Eurasia caused polyphase extrusion of Sundaland and the movement of major strike-slip faults. The movement of these faults accompanying the regional east-west extension during Late Oligocene to Early Miocene initiated the formation of the Tertiary basins.
Thirty-six major faults and forty-two intra-cratonic depositional basins in northern Thailand have been recognized and delineated using Landsat TM images. More than 70% of these basins are related to strike-slip tectonics. Five basin types have been recognized on the basis of geometric and kinematic considerations. These are fault-tip basins, pull-apart basins, fault-wedge basins, fault zone basins, and extensional basins. The opening and development of these basins was influenced by the movement of NW-trending dextral faults and NE-trending sinistral faults associated with north-south shortening and east-west extension.
An improved regional structural model of the Upper Carboniferous of the Cleaver Bank High based on 3D seismic interpretation
Authors: Schroot B. M. , De Haan H. B. 
Published: April 2008

Abstract

The use of 4500 km
2
of amalgamated 3D seismic surveys allowed for an improved intra-Carboniferous seismic interpretation of the Dutch Cleaver Bank High, which is part of the Southern North Sea Carboniferous Basin. The observations of faults that were active during the Late Carboniferous are reviewed in the context of what is described in literature about the regional structural framework of the basin. The high quality seismic data show at least three distinct fault trends, namely east-west, NE-SW and NW-SE, active before Rotliegend times. All of these trends are inherited from older existing zones of weakness, and furthermore, all three trends have been reactivated again during the Mesozoic or Cenozoic to some extent. The interpretation of major controlling east-west shear zones that have been reactivated in different senses throughout geological history is the result of careful examination of the data. The dominance of such systems is not obvious on simple fault maps. Their role in the regional plate tectonics fits the model of escape tectonics of the North Sea-Baltic plate. The distinction of different styles of Late Carboniferous normal fault systems results in a better understanding of the different tectonic phases during the period from Westphalian D to Autunian.
New aspects of tectonic stress inversion with reference to the TENSOR program
Authors: Delvaux D. , Sperner B. 
Published: April 2008

Abstract

Analysis of tectonic stress from the inversion of fault kinematic and earthquake focal mechanism data is routinely done using a wide variety of direct inversion, iterative and grid search methods. This paper discusses important aspects and new developments of the stress inversion methodology as the critical evaluation and interpretation of the results. The problems of data selection and separation into subsets, choice of optimization function, and the use of non-fault structural elements in stress inversion (tension, shear and compression fractures) are examined. The classical Right Dihedron method is developed in order to estimate the stress ratio
R
, widen its applicability to compression and tension fractures, and provide a compatibility test for data selection and separation. A new Rotational Optimization procedure for interactive kinematic data separation of fault-slip and focal mechanism data and progressive stress tensor optimization is presented. The quality assessment procedure defined for the World Stress Map project is extended in order to take into account the diversity of orientations of structural data used in the inversion. The range of stress regimes is expressed by a stress regime index
R’
, useful for regional comparisons and mapping. All these aspects have been implemented in a computer program TENSOR, which is introduced briefly. The procedures for determination of stress tensor using these new aspects are described using natural sets of fault-slip and focal mechanism data from the Baikal Rift Zone.
Oil and gas production from basement reservoirs: examples from Indonesia, USA and Venezuela
Authors: Koning Tako 
Published: April 2008

Abstract
Basement rocks are important oil and gas reservoirs in various areas of the world. Such reservoirs include fractured or weathered granites, quartzites, or metamorphics. In South America, basement reservoirs occur in Venezuela and Brazil. In North Africa, basement oil and gas production occurs in Morocco, Libya, Algeria and Egypt. Significant basement reservoirs occur in the West Siberia basin as well as in China. In the USA, basement-derived oil production occurs in a number of areas, including California (Wilmington and Edison fields), Kansas (El Dorado and Orth fields) and Texas (Apco field). In Southeast Asia, basement reservoirs are the main contributor of oil production in Vietnam. In Indonesia, to date oil and gas production from basement rocks has been minimal. However, the recent large gas discovery in pre-Tertiary fractured granites in southern Sumatra has led to a focusing of exploration in Indonesia for basement reservoirs.
A review of the occurrence and origin of abiogenic hydrocarbons in igneous rocks
Authors: Potter J. , Konnerup-Madsen J. 
Published: April 2008

Abstract

Reports on the presence of hydrocarbons in igneous rocks have been on the increase and generating greater interest in the scientific community over the last 20 years. Most of the occurrences are due to the incorporation of organic material into the magmatic systems. However, reports on the presence of hydrocarbons formed by abiogenic processes have also increased in recent years, suggesting that these hydrocarbons may not be as rare as previously thought and may have implications for natural gas resources in the future. This paper reviews these occurences and the models proposed for the generation of these hydrocarbons, in particular the nature of the hydrocarbon-bearing fluids in the alkaline complexes Khibina, Lovozero and Ilímaussaq. The origin of these hydrocarbons remains controversial, whether they are (1) derived directly from the mantle, (2) formed during late crystallization stages by respeciation of a C-O-H fluid below 500°C, or (3) formed during postmagmatic alteration processes involving Fisher-Tropsch type reactions catalysed in the presence of Fe-oxides and silicates. The reports suggest that a direct mantle origin for the hydrocarbon fluid is unlikely. A model involving near-solidus reequilibration of a C-O-H fluid to a CH
4
-rich composition is possible, although only for extreme melt compositions that have large crystallization temperature ranges (i.e. hyperagpaitic melts). The Fischer-Tropsch synthesis of hydrocarbons in igneous rocks seems to be a more applicable model for a wide variety of igneous rocks.
Fracture-dominated flow in the Borrowdale Volcanic Group at Sellafield, NW England: the identification of potential flowing features, development of conceptual models and derivation of effective parameters
Authors: Degnan P. J. , Littleboy A. K. , Michie U. McL. , Jackson C. P. , Watson S. P. 
Published: April 2008

Abstract
Between 1989 and 1997 United Kingdom Nirex Limited (Nirex) studied in detail the geology and hydrogeology of a rock volume near Sellafield in Cumbria, NW England. The aim of the study was to determine the suitability, or otherwise, of the site as the location for a deep repository for intermediate-level and certain low-level radioactive wastes. An important factor in determining site suitability was the nature of groundwater flow in the potential repository host rock, the Borrowdale Volcanic Group. In the host rock, interpretation of borehole core, wireline logs and hydrogeological pumping test data indicated that groundwater flow was predominantly through a limited subset of discontinuities, mainly fractures, parts of which form networks of connected channels. Within this overall understanding of the nature of groundwater flow, there is a wide range of possible geometrical descriptions for the flow channels. Determination of one or more appropriate conceptualizations of the flow system must be soundly based on site characterization data as a prerequisite for any numerical modelling study. In the first part of this paper, details of the site characterization studies that were used to identify the location, orientation and mineralogical characteristics of discontinuities, and in particular the set of discontinuities referred to as Potential Flowing Features (PFFs), are provided. These features have either demonstrable present-day open porosity, or display evidence of geologically recent groundwater flow as part of the evolution of the current groundwater system. It is inferred that the PFFs observed in boreholes correspond to flowing features and that the borehole data can be used to infer the distribution and characteristics of flowing features that are present in the unobserved rock mass. On this basis, knowledge of the distribution, orientation and permeability associated with the PFFs provided the framework for developing conceptual models for groundwater flow. Numerical models were constructed to represent the flow. It is not computationally practicable to undertake regional scale groundwater flow and transport calculations in which small-scale variability is explicitly represented. Therefore upscaled effective parameters need to be derived as a precursor to running large-scale numerical model simulations. A summary of the Nirex upscaling procedure applied to the flowing feature network in the Borrowdale Volcanic Group is provided.
Preliminary microfocus X-ray computed tomography survey of echinoid fossil microstructure
Authors: Stock S. R. , Veis A. 
Published: April 2008

Abstract

Microfocus X-ray computed tomography (μCT), a high resolution variant of medical CT, was used to non-invasively examine Jurassic echinoid fossils with spine, demipyramid and test plate fragments serving to assess the extent to which the microstructure remained unaffected by diagenesis. The sizes of the calcite-crystal stereom remains dictated the resolution that could be obtained. The smaller diameter spines were imaged with 9 × 9 ×
c.
25 μm voxels; the larger demipyramids and test plate fragments were imaged with 13 × 13 μm and 17 × 17 μm voxels, respectively, in the plane of reconstruction and with a proportionally larger slice thickness. The stereom structure was not seen in the μCT slices of the fossils. This is not surprising because, for the ossicles studied, the stereom pore dimensions are, for the most part, smaller than the resolution of the μCT system. Tide marks and other low absorption features were found in the spines and appear to be related to diagenetic changes. What appear to be cleavage cracks were observed in the demipyramid and some of the pores for tube feet could be seen in the test fragment.
The genesis of polygonal fault systems: a review
Authors: Cartwright Joe , James David , Bolton Al 
Published: April 2008

Abstract
Polygonal fault systems are widely developed in fine-grained sedimentary successions and have been recognized in over 50 basins worldwide. They are normal faults with modest throw values (typically 10–100 m), organized with a characteristic plan form pattern that is crudely polygonal, but with considerable variation in specific planform patterns. They have been attributed to four genetic mechanisms: gravity collapse, density inversion, syneresis and compactional loading. Their strain characteristics allow them to be distinguished from tectonic normal faults. The strengths and weaknesses of the four genetic mechanisms are considered in the light of these strain characteristics. It is argued that syneresis offers the likeliest mode of genesis and best explains the local and global features of these extraordinary structures. The detailed physical mechanism driving syneresis remains poorly understood.
Arc-trench rollback and forearc accretion: 2. A model template for ophiolites in Albania, Cyprus, and Oman
Authors: Dilek Yildirim , Flower Martin F. J. 
Published: April 2008

Abstract
Ophiolite assemblages record structural, magmatic, and metamorphic processes that preceded their entrapment in orogenic belts by continental plate collisions. Ophiolite genetic models appealing to ‘oceanic’ or ‘suprasubduction’ provenance are still unable to reconcile several basic problems, including: (1) the association of boninites with oceanic ridge-type structural settings; (2) the diachronous ‘patch-like’ distribution of ophiolites in orogenic belts; (3) disparate ages between and within their mantle and crustal sections; (4) the lack of evidence for ‘obduction’ at modern passive margins. In contrast, the proposal that ophiolite genesis is exclusive to intra-oceanic forearc settings is compelling, given their uniquely shared structural, lithological, and stratigraphic attributes. Forearcs are interpreted to record discrete stages of subduction ‘rollback’ cycles, examples of which begin with subduction nucleation and the formation of boninitic ‘proto-arcs’, followed by arc splitting and concomitant retreat of the evolving arc-forearc complex. Forearc assemblages are likely to resist subduction to become entrapped in orogens, in contrast to denser, recently formed back-arc basin lithosphere, which is reconsumed by subduction following collision of the retreating forearc. As a model for Neo-Tethyan ophiolite genesis, this is predicated on the notion that rollback cycles are driven by ductile asthenosphere mobilized prior to and during collisions of Gondwana fragments with accreting Eurasia. It is also consistent with the apparent correlation of ophiolite ages with collisional events and their conjugate plate kinematic adjustments. Here, we use the slab rollback model as a template for interpreting the structural, magmatic, and metamorphic characteristics of well-studied Tethyan ophiolites, in Albania (Mirdita), Cyprus (Troodos), and Oman (Semail).