No description available.

No description available.

Potential lacustrine source rocks have been recognised in several Cretaceous syn-rift basins including the producing Taranaki Basin, but have not been officially recognised from drill core and seismic data. The late-Cretaceous Paparoa Coal Measures contain three lacustrine mudstone formations which outcrop in several localities and have been extensively drilled for coal mining. These formations are considered to be an easily accessible analogue for late-Cretaceous lacustrine source rocks in New Zealand and also provide valuable information regarding syn-depositional tectonics and basin formation during the late-Cretaceous. Stratigraphic columns and isopach maps were constructed from field work and drill hole descriptions and results showed variations in lithofacies across the basin. The western side of the basin is characterised by sandy lithofacies, abundant proximal turbidites and debris flows. The transition to a sub-aerial environment is marked by thick conglomerate and meter wide rip-up clasts. The central and eastern sections of the basin show massive mudstone, distal turbidites, low energy fluvial sandstones and thin, discontinuous coal. Isopach maps constructed from drill hole data identified three NNE – SSW oriented lakes with lacustrine sediment of up to 180m thick truncated by the eastern Roa – Mt Buckley Fault Zone. It was determined fault control during deposition was to the west and the basin extended further than its current location. Revisions to isopach models highlighted a lack of change in basin orientation during deposition of the Paparoa sediments. Plate reconstructions combined with direct evidence from the basin indicate formation of the Paparoa Coal Measures could have occurred in either a rift or transtensional basin. The mudstones were geochemically assessed for hydrocarbon potential using a Source Rock Analyser (SRA). Preliminary analysis of the three mudstones has shown TOC values ranging from 1.0 to 4.5 wt.%, HI values ranging from 68 to 552 mHC/gTOC and Tmax results show the mudstones to range in maturity from immature to late – mature. A sample from the Waiomo Formation has excellent potential for oil generation and the low maturity results for the Goldlight Formation make it a potential shale gas resource. These results have shown the potential for hydrocarbon bearing lacustrine source rocks to exist in the Greymouth Coalfield. In addition, revisions have been made to basin formation which should be considered. Due to the availability of data from the Paparoa lacustrine source rocks, they should be used as an accessible analogue for Taranaki and other Late Cretaceous basins.

A minor eruption of Mount Saint Helens in Washington State U. S. A. in 1984, triggered the formation of a debris flow in the headwaters of the North Fork Toutle River. As the debris flow progressed downstream it transformed through the incorporation of water and the loss of sediment and within 34 kilometres became a muddy flood. The deposits produced by the transforming flow and associated recessional flows that followed in its wake, exhibited a coarse grained depositional continuum from debris flow to stream flow, including deposits with intermediate sedimentological characteristics termed "hyperconcentrated flow deposits".The systematic and detailed sedimentological analysis of these deposits, combined with information concerning the characteristics of the flow, has allowed the delineation of hyperconcentrated flow deposits within the debris flow/stream flow depositional continuum and hence the establishment of criteria for the recognition of coarse grained hyperconcentrated flow deposits in the volcaniclastic environment of Mount Saint Helens. Hyperconcentrated flow deposits are generally homogeneous, matrix-supported, unstratified (except where defined by sub units), have sorting characteristics intermediate between debris flow and stream flow and can exhibit a bimodal, generally non imbricate, clast fabric as a function of clast size. Coarse-tail inverse grading may occur but it is weak, or restricted to sub units. Use of these criteria enabled the recognition of hyperconcentrated flow deposits within depositional sequences produced earlier in the eruptive history of Mount Saint Helens.The analysis of Permo-Triassic alluvial fan deposits on the Isle of Lewis Scotland, revealed that elements of the debris flow/stream flow depositional continuum could be recognised by the application of the criteria established in the volcaniclastic environment of Mount Saint Helens.

The Ostracoda from nine sections of the Lower Fars Formation, Northern Iraq, Tel-Hajer well-1, Sheikh Ibrahim locality, Dohuk locality, Sheikhan locality, Bashiqa locality, Kirkuk well-208, Bai-Hassan well-33, Hamrin well-2 and the Naft Khana well-34, have been studied in detail.One hundred and nine Ostracod species/subspecies belonging to 50 genera/subgenera are described, of which one genus, one subgenus and 70 species are new. Five species are assigned to species previously described from western India. Five species are compared with other species from W. India, Iran, Turkey and France. Three species are regarded as having affinities with new species described in this thesis and 26 species are left under open nomenclature mainly because of lack of material or the impossibility of observing the internal details.Biostratigraphically, the Lower Fars Formation in the Sinjar area is divided into three Assemblage Zones, these zones are applicable only to N. Iraq, but make a starting point for future work in the area. In the Kirkuk area, the saliferous beds proved completely barren, but the upper Red, Seepage and Transition beds yield Ostracods although the assemblages recognised are at present only regarded as tentative, because the samples are ditch cuttings.Palaeoecology is discussed in terms of oxygenation, alaeoclimate, salinity and the trends in the depositional environment of the Lower Fars Formation.The affinities of the present genera and species are discussed from a palaeogeographical view point in relation to the adjacent and related regions. Three Miocene Ostracod provinces are proposed, namely a western India province, a Zagros shelf province and a southeast Turkey province.

This study is an integrated biostratigraphical and palaeoenvironmental analysis of foraminiferal and radiolarian distribution from all the major Middle and Upper Jurassic marine deposits of Scotland. These sampled sites are divided between two basins with Staffin Bay and Bearreraig Bay within the Inner Hebrides Basin, North West Scotland; and Brora, Balintore, Helmsdale and Eathie Haven representing the Inner Moray Firth Basin, North East Scotland.A detailed taxonomic section is presented, which provides the means of comparison of microfaunal events between sites. A combined total of 212 species are described, of which 183 are foraminifera and 29 radiolaria; this includes a total of 23 species not previously recorded, comprising 16 foraminiferal and 7 radiolarian taxa.A Callovian to Lower Kimmeridgian biozonal scheme, the first detailed attempted for the onshore UK, is constructed primarily using the Staffin Bay succession as the type section. It is based upon an integration of distinct foraminiferal and radiolarian taxa and events. This microbiostratigraphy is implicitly tied to the Boreal type ammonite scheme and comprises a total of 9 biozones and 12 sub-biozones. The new biozones are then correlated and compared with the other Scottish sites as well as other world-wide schemes.A sequential palaeoenvironmental analysis is outlined, firstly by pinpointing microfaunal assemblages that are based upon a combination of the distribution of the major suborders, the species diversity and faunal abundances, as well as integrating the facies types and probable prevalent substrate conditions. These assemblages are then used to define palaeoenvironmental models for each recorded succession, and are related to prevailing substrate and sea water conditions and distance from the 'palaeoshoreline'. As the assemblages are shown to reflect particular conditions this allows a generalised basin development model to be assessed, related to sea-level changes (transgressions and regressions). All the sites are subsequently correlated palaeoenvironmentally.The relevance of facies dependant distribution is also examined, particularly for benthic foraminiferids. The main conclusion reached is that facies dependence restricts the occurrences of taxa. However, this is not a constant feature as some specific taxa show the ability to colonise several facies types. It is this factor that permits a biostratigraphy to be constructed. Overall, assemblages appear to be related directly to a particular facies, which permits palaeoenvironmental changes to be assessed.Finally the extensive Middle and Upper Jurassic literature is examined and a generalised world wide biogeography constructed. Four provinces are defined based on characteristic foraminiferal and radiolarian assemblages.

Correlations between societal development and climate changes have been investigated for a long period of time. At the archaeological site of Beidha, southern Jordan, most studies have focussed on the Late Pleistocene/Holocene, however, the importance of the Beidha region may even reach further back in time. The presence of water in a generally very dry landscape would have been crucial to early modern humans en route from Africa to all other continents. Through sedimentological observations and OSL dating, this study aims to contribute to solving the puzzle of the local landscape development at Beidha during a longer time scale. It is suggested that a long period of calm floodplain conditions took place, approximately during periods of high lake levels in Lake Lisan ~70-21 ka. After that, a period of soil development has been identified between two phases of aeolian deposition. More recently, during the Holocene, phases of mass flow events may have affected the area.

Cerro Rico is the world's largest silver deposit. Hypogene mineralisation is hosted by a sheeted, polymetallic vein system which cross-cuts a pervasively altered rhyodacite dome. The 13.8Ma dome was intruded along a regional dextral strike-slip fault. Subsequent movement focused stress within the dome, creating a closely-spaced fracture system, best described as an extensional duplex. Hydrothermal alteration shows features characteristic of both porphyry and epithermal deposits. Shallow acid-sulphate alteration, comprising sub-horizontal zones of advanced argillic alteration and residual vuggy silica, formed through the neutralisation of a supergene, acid-sulphate fluid derived from the atmospheric oxidation of hypogene H₂S. Deep sericitisation which largely pre-dates the polymetallic vein mineralisation is the product of wall-rock reaction with magmatically-derived volatiles. Localised tourmalinisation resulted from the violent release of boron-rich fluids during early decompression events. A buried magma body is implied for the source of volatiles. Polymetallic vein mineralisation is vertically and laterally zoned from deep Sn-W-Bi-As-Cu assemblages to peripheral Pb-Zn-Sb-Ag. Hypogene silver occurs within complex Pb-Sb sulphosalts, tetrahedrite (freibergite), pyrargyrite and argentite. Mixing of reduced, near-neutral, hypogene Ag-bearing fluids and oxidised, supergene, acid-sulphate fluids caused the precipitation of 'bonanza' silver mineralisation within the acid-sulphate lithocap. Early pre-mineral fluids were hypersaline (34wt. %NaCl equivalent). Main stage ore fluids varied in temperature between 140 and 410°C with salinities averaging 11wt.% NaCl equivalent. Stable isotope data are consistent with a magmatic source both for the ore fluid and sulphur. Following collapse of the hydrothermal system, a fall in the palaeo-water table caused deep oxidation. Silver was released from hypogene sulphosalts and re-precipitated as disseminated acanthite and silver halides. Hypogene Ag₂S remained stable in the weathering environment. The oxide zone, preserved by a semi-arid climate, currently constitutes a world-class silver orebody.

No description available.

The Upper Cretaceous Medicine Hat Member (Niobrara Formation) in western Canada contains abundant reserves of biogenic natural gas. In the Medicine Hat gas field area of southeast Alberta, nineteen cored intervals were examined and classified based on primary physical and biogenic sedimentary structures. Core analysis and stratigraphic mapping determined that the Medicine Hat Member strata consist of stacked, regionally extensive, lobate geobodies that prograde to the north. Employing spot-minipermeametry, the effect of biogenic rock fabrics on the reservoir characteristics was assessed. X-ray micro-computed tomography was conducted on four samples from a reservoir interval to visualize the geometry and distribution of burrow-associated heterogeneity. The results demonstrate that planiform bioturbate textures locally enhance the storage and transmission of natural gas in Medicine Hat reservoirs.