bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rift to drift evolution in Permian-Jurassic basins of East Africa
Authors: Kreuser Thomas 
Published: April 2008

Abstract
Intracratonic Permo-Triassic grabens developed in eastern Africa (Tanzania, Mozambique, Zimbabwe) in five stages. Isostatic uplift after the demise of the Gondwana glaciation resulted in block faulting and erosion during the Sakmarian in some basins. Initial rift extension occurred at the Artinskian/Kungurian boundary. Half-grabens developed during the Kazanian in deep and shallow water rift lake environments, divided by accommodation zones and limited by alternating boundary faults and flexural margins. The rifts filled up during the Tatarian, separated from the Lower Triassic by a regional unconformity including a hiatus. The Triassic is characterized by increased extension rates during the final thermal subsidence phase, terminated either by abortion or basaltic outflows from Mid-Triassic to Liassic. Tilting, faulting and erosion occurred during the Miocene to recent uplift of the East African Rift margins. A two-phase rifting is witnessed in the Rukwa Basin.
Pericratonic rift evolution (Tanzania, Mozambique, Madagascar, Ethiopia) started at the Lower Jurassic and continued until the Bajocian/Bathonian breakup unconformity at 165 Ma. Drifting is associated with onlapping deltaic to restricted marine, evaporitic and also with open marine carbonates and the formation of oceanic crust.
Organic geochemistry shows a fair source rock potential for the intracratonic rift basins (i.e. the Ruhuhu and Rukwa Rifts) with favourable maturity levels. Coal macerals (liptinites) and bitumen (exsudatinite) indicate a limited liquid hydrocarbon potential for the dominantly gas prone Type III kerogens. The pericratonic coastal basins of eastern Africa and the Madagascar Rift Basins exhibit only a limited source rock potential.
Hydrocarbon habitat in the rift graben of the Central Sumatra Basin, Indonesia
Authors: Williams Harold H. , Eubank Roger T. 
Published: April 2008

Abstract
The geological history of the Central Sumatra Basin, situated between the Bila River to the north and the Kampar River to the south, is discussed. The structural style in Central Sumatra is produced by a tensional regime strongly overprinted by a dextral wrench component. Compression does not appear to have been a dominant force; most compression observed in the Tertiary section can be ascribed to that component of wrench tectonics. Factors that have contributed to the prolific oil production of the Central Sumatra Basin include presence of graben sequences with thick organic-rich lacustrine shales, an overlying marine sag sequence with excellent reservoirs, development of early structures and high basin heat flows. The shallow Pre-Tertiary basement and thin sediments of the Central Sumatra Basin are characterized by a very high geothermal gradient, with an average gradient of 6.1°C/100 m (3.38°F/100′).
Distribution of the oilfields in the Central Sumatra Basin is largely fault controlled. The oil has migrated vertically out of the Eocene-Oligocene age Pematang Group shales and laterally up the flanks of the graben, generally in an easterly direction, filling younger, Miocene age Sihapas Formation reservoirs. Hydrocarbon accumulations are also present within the rift-fill sequence. Migration distance is generally short, ranging up to 20 km. Models are presented to explain the structural evolution and depositional history of the Pematang graben.
Oil, and most of the gas, in the Central Sumatra Basin has been generated from organic-rich shales of lacustrine origin within the Palaeogene Pematang Group. During Palaeogene time, large freshwater lake systems developed within structurally controlled rift graben. Palynology indicates freshwater conditions prevailed, however, occurrences of slightly saline conditions suggest minor climatic changes, chemical stratification, or occasional marine incursions.
Tropical climatic conditions without an annual lake turnover favoured lacustrine anoxia and deposition of non-marine hydrocarbon source beds. Climatic changes strongly influence the stratigraphic position of oil-prone source material in the Pematang Brown Shale Formation. Differences in oils, however, appear to reflect the different depositional and environmental histories of the individual lake systems. Geochemical analyses are used in the identification of source beds, interpretation of their depositional environments, oil to source rock correlations and determining the maturation history of the source rock. Systematic variations in organic matter reflect different depositional environments and largely determine the composition of the hydrocarbons generated.
Application of sequence stratigraphy to coal-bearing coastal plain successions: implications for the UK Coal Measures
Authors: Flint Stephen , Aitken John , Hampson Gary 
Published: April 2008

AbstractAdvances in the understanding of coal depositional environments have led to the notion that thick, low ash deposits in close proximity to siliciclastic sediment inputs are most commonly restricted to the products of raised mires. These mires are initiated, sustained and preserved in conditions of slowly rising base level (relative sea-level). Hence it is possible to consider the stratigraphic significance of economic coal seams within the concept of unconformity bounded depositional sequences (sensuVailet al.). Time-equivalent clastic deposits tend to be minor (commonly with a heterolith fill) channel deposits, with brackish to freshwater lake and crevasse splay sediments, excluded from the peat mire either via the topographically raised nature of the mire or by the landward dislocation of fluvial facies. In this paradigm, spatially related major fluvial channel deposits, major seam splits and even washout deposits may not be time-equivalent to the coal seam. Regional correlations suggest that thick coal seams are time-correlative to significant flooding surfaces at the coeval coastline. Thus coals may be correlated with initial flooding surfaces over incised valley systems and sometimes with parasequence and parasequence set boundaries. This factor may be important in coal exploration. Application of these ideas to the classic Westphalian ‘Coal Measures’ of England indicates that the ‘marine bands’ may be regarded as flooding surfaces or condensed sections, with several being good candidates for maximum flooding surfaces. Between these marine bands the stratigraphy is punctuated by thick, stacked, regionally extensive fluvial units, incised into previously deposited sediments. These are interpreted as incised valley complexes. Systems tract assignment, based on changing accommodation space, indicates that the main coal zones fall dominantly within transgressive systems tracts.
Sedimentary facies of the coal-bearing Westphalian A and B north of the Wales-Brabant High
Authors: Guion Paul D. , Fulton Iain M. , Jones Neil S. 
Published: April 2008

Abstract
Important coal deposits are present in Britain north of the Wales-Brabant High in the Pennine Basin, which was initiated by late Devonian to early Carboniferous extension. The formation of coals of sufficient thickness, quality and continuity to be commercially exploited was favoured during the latest Westphalian A (Langsettian) and much of the Westphalian B (Duckmantian), when deposition took place in an environment similar to an upper delta plain, with limited marine influence. During the early part of the Westphalian A, marine influence was important, with the consequence that the coals were thinner, less persistent and of inferior quality. By the late Westphalian, alluvial deposition became important, and coals of commercial quality are rare.
Accurate determination of facies, lithological attributes and geometry is an important tool in exploration and mine planning. Sedimentary facies have thus been rationalized into those that may be consistently recognizable in boreholes and mine workings. However, facies may be further subdivided when conditions allow, and intermediate facies exist, reflecting the complexities of depositional environments. The characteristics of the following facies are described here: mire, palaeosol, marine, lacustrine, lacustrine delta, major channel, minor channel, overbank and crevasse splay. Channel deposits have a number of adverse effects on mining and the range of channel-fill deposits reflects the operation of many different processes.
A model of sedimentation is presented which emphasizes that local sedimentary and autocyclic processes, local tectonics, subsidence and compaction were important in controlling the distribution of facies at a mine scale.
Determination of trace element affinities in coal by laser ablation microprobe-inductively coupled plasma mass spectrometry
Authors: Querol X. , Chenery S. 
Published: April 2008

Abstract
The occurrence, association and distribution of potentially toxic trace elements (PTTEs) in coal are basic criteria for predicting the forms and amounts of trace elements that are transferred to the environment during coal combustion processes. Previously, the determination of the affinities of PTTEs in coal was carried out by laborious density separation and subsequent analysis of the density fractions. This study has evaluated a new means of directly determining PTTE affinities in coal by laser ablation microprobe-inductively coupled plasma mass spectrometry (LAMP-ICP-MS). The affinities were determined by a rapid semiquantitative methodology. Additionally, some preliminary quantitative concentrations were obtained using a novel calibration strategy. The spatial resolution of the LAMP-ICP-MS technique allows the analysis of single grains of macerals and minerals in polished blocks, leading to a wide range of applications in coal geochemistry.
Review of borehole seismic methods developed for opencast coal exploration
Authors: Goulty N. R. 
Published: April 2008

Abstract
Evaluation of opencast coal reserves in the UK is accomplished by drilling boreholes on a grid spacing of 40–60 m, with even closer spacings across major fault zones and in areas of old mine workings. In spite of this intensive drilling effort, it is difficult to detect small faults with throws of less than about 2 m, which can still present a serious stability hazard at site boundaries. Borehole seismic methods could be used to detect small faults, to give structural detail across major fault zones and to locate old mine workings. Two techniques have been developed for this purpose: cross-hole seismic reflection surveying and hole to surface seismic reflection surveying. Although the cross-hole method produces sections of extremely high resolution, very close source and receiver element spacings are required to image close to the boreholes. Also the borehole separation should be less than half the length of the source and receiver arrays if complete coverage is required between the arrays. The hole to surface method produces high resolution sections and could be extended to three-dimensional surveys, but imaging is limited to a bell-shaped cross-section with its apex just below the water-table. Both methods can be used to yield continuous sections along lines of boreholes and are potentially of value in other applications.
Coal production and coal reserves of the Czech Republic and former Czechoslovakia
Authors: Pešek Jiří , Pešková Jarmila 
Published: April 2008

Abstract
Czechoslovakia, following the communist takeover in 1948, became a member of the former East European COMECON group of countries. Its industrial potential, together with the heavy industry of the former USSR, represented a strategic base for the whole communist block. Concentration on production, with a high energy consumption, created a considerably higher demand for energy raw materials, namely brown coal in the case of Czechoslovakia. Production increased about five times with respect to 1937 levels, whereas the production of bituminous coal increased by only 80%. This created a considerable depletion of coal reserves. Consequently, only 1.9 Gt of mineable reserves of bituminous coal and about 3.1 Gt of brown coal reserves were registered in the former Czechoslovakia by 1 January 1992. These mineable reserves, recorded in the energy balance, can be divided into reserves in recently mined coal deposits and those occurring in the so-called reserve coal fields. The actual volume of mineable reserves in operating mines is equivalent to 822.7 Mt of bituminous coal and 1799.4 Mt of brown coal. Mineable reserves of brown and bituminous coal in the operating mines and open pits of the Czech Republic will be exhausted in the years 2027 and 2031, respectively, taking into consideration both the present and anticipated future production and recovery of coal.
Exploration and exploitation of the East Pennine Coalfield
Authors: Allen M. J. 
Published: April 2008

Abstract
The East Pennine Coalfield is the most important of all British Coal’s resources. Exploration and exploitation are closely related and studies of the coalfield’s past history, present development and future potential are relevant to the whole coal industry in the UK. At a local level the geology is often variable with uncertainty attached to reserves assessments. However, the overall development of the coalfield is substantially controlled by large-scale and easily determined geological features such as the size of the deposit, seam thickness and depth of cover. Studies on a coalfield scale can therefore contribute to assessments of the future of the coal industry.
The future production from this coalfield depends on both the size of the resource and on the proportion that can be recovered. Historical recovery data are discussed and some of the geological features of the deposit that affect coal recovery are reviewed.
Although the East Pennine Coalfield is at a mature stage of exploitation, with output from deep mines currently at about 540f its peak level in the 1950s and 1960s, the resource has not yet been fully developed, even after major investments at Selby and Asfordby. Recent exploration results from the undeveloped eastern margin of the coalfield are briefly reviewed.
Structural geological factors in open pit coal mine design, with special reference to thrusting: case study from the Ffyndaff sites in the South Wales Coalfield
Authors: Gayer Rod , Hathaway Tanya , Davis John 
Published: April 2008

Abstract
A review of the shear strength characteristics of Coal Measures lithologies suggests that major structurally controlled discontinuities in mudrock or coal are likely to show near-residual shear strength values, with minimal cohesion and a friction angle of approximately 12°. The principal structurally controlled discontinuities are those associated with tilting, folding and faulting. The former result from bedding plane slip during flexural folding that smoothes the bedding planes and reduces cohesion. The latter are produced by fault movements that weaken the rock and produce a structural anisotropy in the fault surface. Both are likely to confine the movement of water through the rock, enhancing weathering and further weakening the surface. In open pit design, the stability of the highwall is discussed in relation to the orientation of the various types of structurally controlled discontinuity.
A case study from Ffyndaff Opencast Coal Site in the South Wales Coalfield is analysed, and shows that the major normal faults that cut the site intersect the highwall with a stable orientation. Regional dip in the site also has a stable orientation, but the site is affected by several major north-verging thrusts that have been investigated by computer analysis of borehole and coal extraction data. The results indicate that the thrusts have a ramp-flat geometry and are likely to imbricate upwards from a bed-parallel detachment in a coal seam. The thrusts have generally developed in a piggy-back sequence, although at least one formed as a break-back thrust. The thrust displacement (slip separation) variation along the thrusts is described and suggests a normal displacement gradient of 0.16–0.18. These geometrical characteristics are used to interpret the thrust structure of a potential site from exploratory borehole logs, where the predicted geometry limits the location of the bounding highwall.
Sequence stratigraphy and lithofacies geometry in an early Namurian coal-bearing succession in central Scotland
Authors: Read W. A. 
Published: April 2008

Abstract
High frequency glacial-eustatic allocycles have been identified in the upper part of the early Pendleian Limestone Coal Formation in the north-central Midland Valley of Scotland. Repeated eustatic oscillations caused extensive lateral migrations of a wide spectrum of depositional environments, ranging from quasi-marine to fluvial. This throws doubt on the assumptions that underlie some existing depositional models of similar late Carboniferous cyclic coal-bearing successions.
The study interval can be divided into three facies associations. The distal association was dominantly controlled by glacial-eustatic oscillations, which resulted in a remarkably regular ‘layer cake’ succession with laterally persistent coals. In the more sandy and variable transitional facies association, local episodic fluvial processes tended to obscure the underlying allocycles. Here coals may split and also amalgamate to form thick composite seams. The highly variable proximal association was dominantly controlled by irregular autocyclic fluvial sedimentary processes which largely obscured the background changes in relative sea level. Sequence stratigraphy is easy to apply to the distal facies association, harder to apply to the transitional association and very difficult to apply to the variable proximal association.
An introduction to the techniques, limitations and landmarks of carbonate oxygen isotope palaeothermometry
Authors: Corfield Richard M. 
Published: April 2008

Abstract

The fractionation of oxygen isotopes is temperature dependent. The ratio of the two commonest isotopes (
16
O and
18
O) in carbonate fossils can, in principle, be used to reconstruct the temperature of ancient oceans. Fossil foraminifera are commonly analysed in the Cenozoic and late Mesozoic and, when appropriately identified and separated, seasurface, deeper-water and bottom-water temperatures can be inferred. More ancient carbonate precipitating macrofossils (e.g. molluscs, brachiopods) have also been used, as well as inorganically precipitated carbonate cements. Drawbacks to the oxygen isotope method of palaeotemperature determination are the uncertainties in the isotopic composition of the water of ancient oceans, the occurrence of non-equilibrium fractionation in organically precipitated calcites (especially in macrofossils) and diagenetic alteration to the δ
18
O values of carbonate fossils.

Notwithstanding these limitations, trends in palaeotemperature and/or the δ
18
O of seawater, such as the Palaeozoic
18
O enrichment, the long-term Cretaceous and Tertiary climatic cooling, the middle Miocene
18
O enrichment, as well as the Pleistocene succession of glaciations, are discernible from appropriate studies of fossil carbonates.
Palaeo-oxygenation: effects and recognition
Authors: Allison Peter A. , Wignall Paul B. , Brett Carlton E. 
Published: April 2008

Abstract
Oxygen is a bio-limiting element for metazoa and one of the most important factors influencing species diversity and abundance in the marine realm. Equally, the absence of oxygen is generally considered to be essential for the inhibition of microbial decay and the formation of organic-rich sediments. As such, the determination of depositional palaeo-oxygenation values of ancient rocks has become a fundamental quest for the palaeoecologist and mudrock sedimentologist. In this paper the development of the tripartite anaerobic-dysaerobic-aerobic terminology for oxygen-related biofacies and the recent additions of the exaerobic and poikiloaerobic biofacies are reviewed. The new, non-genetic, oxygen-restricted biofacies (ORB) scheme is also presented. Chemosymbiotic life strategies have been suggested to be important in many extinct black shale taxa but a glance at modern chemosymbionts casts doubt on the significance of this mode of life in ORB. A review of lowest dysaerobic benthic forms throughout the Phanerozoic reveals the repeated occurrence of a few morphologies almost exclusively derived from the brachiopods and bivalves. Geochemical indices of palaeo-oxygen levels are also reviewed.
The recent renaissance in the development of criteria for the determination of palaeo-oxygen values has led to the recognition of a considerably greater variety of dysaerobic biofacies in the geological record. This is illustrated with two case studies, the first, from the celebrated Burgess Shale of British Columbia, shows a depositional environment dominated by a fluctuating oxycline. The second case study, from widely separated earliest Triassic marine sections, illustrates the possibility of a widespread (global) dysoxic event at this time.
Palaeoenvironmental interpretation using bryozoans: a review
Authors: Smith Abigail M. 
Published: April 2008

Abstract
Bryozoans are colonial marine organisms, found in the fossil record since the early Ordovician. They have many possible applications in palaeoenvironmental interpretation. Their presence or absence, diversity and abundance, zooid morphology, colonial plasticity, colonial growth form, and reef-like structures all provide information about habitat. Temperature, salinity, water energy, water depth, substrate character, sedimentation rate, and even tectonic stability, may be indicated by bryozoan faunas. Examples are given to show palaeoecological applications of bryozoans, from shelf and deep-sea sediment studies to interpretation of Tertiary limestones and Palaeozoic environments. Caution is needed, particularly in interpreting very ancient faunas, due to the confounding factors of sampling bias, interdependent controls, taxonomic evolution and taphonomic selectivity. Bryozoans are nevertheless a tool of considerable value in palaeoenvironmental interpretation, particularly if corroborated with other lines of evidence.
Microfossil indicators of ocean water masses, circulation and climate
Authors: Murray John W. 
Published: April 2008

Abstract

Circulation within oceans is closely linked to climate through feedback mechanisms and both are controlled by insolation and the rotation of the Earth. Because the distribution of organisms is related to the water masses in modern oceans their distribution in the fossil record can be used as a proxy of past water masses. For surface waters the main proxies are calcareous nannofossils, diatoms, radiolaria and planktonic foraminifera. Transfer functions have been derived to determine sea surface temperatures from planktonic microfossils from the Pleistocene and Pliocene. Upwelling regions have distinctive characteristics, notably a great abundance of diatoms and a high dominance of
Globigerina bulloides
d’Orbigny. For bottom waters the principal proxies are benthic foraminifera and, to a minor extent, ostracods. Some assemblages of epifaunal benthic foraminifera seem to be correlated with specific bottom-water masses, but this is not so for infaunal assemblages. The development of thermohaline circulation caused benthic taxa to adjust their depth distribution patterns; some species became extinct and were replaced by others. Changes in distribution patterns in the Neogene have been interpreted as indicating changes in bottom-water mass structure and distribution. For instance,
Nuttallides umboniferus
(Cushman) has been used by several authors to map the past distribution of Antarctic Bottom Water. Sometimes processes operating at the ocean surface produce effects on the ocean floor which override benthic processes. Examples of this include seasonal input of phytodetritus which leads to blooms of
Epistominella exigua
(Brady), and deposition of laminated diatom mats which inhibit bioturbators.