This thesis studied 9 sediment cores from the Bohai Sea (JX91-2A and JX91-3B), the Huanghai Sea (JX91-7m and 7G) and the Arabian Sea (cores 1733, 1734a, 1735, 1736 and 1739) through a multi-disciplinary approach including geochemistry, sedimentology, rock magnetism and radiochemistry. The purpose of this study is to retrieve the sedimentary records, characterise and compare the virtually different sedimentation processes in the Chinese and Arabian regions, and to reconstruct regional and trans-continental palaeoenvironmental changes since the Late Pleistocene. The main conclusions drawn from this study concerning A) the China Seas, B) the Arabian Sea and C) palaeoenvironment in the two regions include: A1. The Huanghe River plays a key role in the sedimentation in the Bohai and Huanghai Seas, and its well documented channel switching can be directly correlated with the lithological changes in the sediments; A2. Estuarine turbidity current can be formed in the Bohai Sea in a different way from that in deepwater, owing to the extremely turbid riverwater and highly diluted seawater; but it cannot in the Huanghai Sea; A3. Huanghe estuarine sediment in the Bohai Sea can be linked to the recent soil erosion on the Loess Plateau through geochemical and palaeomagnetic indicators, viz. P, Ti, REE and magnetic susceptibility; B1. Sediments in the Gulf of Oman in the Arabian Sea are generally of aeolian origin, though coarser sands can be found either as saltation population in nearshore cores or as cyclone deposits on the Murray Ridge; B2. Monsoonal variations since the Late Pleistocene in terms of both wind strength and wind direction are responsible for the lithological changes in the Arabian sediments directly, and biogeochemical changes indirectly, through the wind-driven coastal upwelling system in the Arabian Sea.

A Late Cretaceous-Early Tertiary regressive sedimentary succession is developed in Cyprus. Regression continued in the Neogene, above the active Cyprus plate margin, with pelargic carbonate deposition that was followed by varied clastic and carbonate successions of the Miocene Pakhna Formation. Overlying Messinian evaporites of the Kalavasos Formation mark the peak of regression prior to the Pliocene transgression. Within the Pakhna Formation, two phases of reef growth were developed: the Aquitanian - Burdigalian aged Terra Member, and the Tortonian aged Koronia Member. The Terra Member is exposed only in west and southeasten Cyprus, mainly between pelagic carbonates. The Koronia Member is exposed around the margins of the Troodos Massif in north, south and west Cyprus and on the Akamas Peninsula in northwest Cyprus. There was little tectonic influence on the growth patterns of the reefs of the Terra Member. The reefs of the Koronia Member however, developed on up-faulted blocks. Most of the Koronia Member fore-reef facies and associated clastic input were shed into downfaulted basinal depocentres. The Koronia Member developed in a dominantly extensional re*gime, but with compressional structures developed in southern Cyprus. Limited extension in west Cyprus resulted in gradual reef migration away from a subsiding graben axis, without associated debris flows. Pulsed extension occurred on the north margin of the Troodos Massif. This resulted in mid Miocene channels and debris flows of reef talus, disruption of the evaporites of the Kalavasos Formation and then culminated in an east-west detachment of metre to kilometre-scale blocks of Pliocene sediments. Compartmentalised faulting was constrained by north-south and east-west trending faults. Stacked selenite crystals and laminated gypsum are the main lithologies in the fault localised evaporitic deposition that follows the Koronia member. Primary reef construction and the nature of the background carbonate pelagic sediments distinguishes betwen the first and second Miocene reef phases in Cyprus. The Terra Member reefs are dominantly framestones, comprising faviids and domal poritids with several types of secondary reef-dwelling corals. There is no indication of a connection with the Indo-Pacific coral faunal province. Benthonic foraminifera and fragments of crustose coralline algae are abundant in the off-reef. By contrast, the Koronia Member is a bindstone comprising virtually monospecific, alminar poritrid corals, but with coralline algae also playing a r^ole in encrustation. The Koronia member off-reef facies comprises decimetre-thick beds of bioclastic reef detritus. In north Cyprus however, beds of similar detritus (centimetres in thickness), are overlain by progressively thicker (up to several metres) debris flow sheets. The reefs of the Terra Member exhibit a limited acicular fringe cement, probably aragonitic. This is overlain by an abundant, marine, bladed, formerly high-Mg calcite cement. Later cements present in the reef facies include micritised calcite spars, perhaps indicating microboring within cements during their precipitations. Neomorphism was extensive, converting most cements to low-Mg calcite. Stable isotopic data for all the Cyprus calcites exhibit depletion in the heavier isotopes, <SUP>18</SUP>O and <SUP>13</SUP>C, indicative of meteoric alteration. The Koronia Member limestones show abundant indication of early lithification, with fringing fibrous aragonite and micrite cements. Isotopic analyses of the botryoidal aragonite cements indicate a marine origin. The dolomite, of Pliocene age, is thought to result from marine-freshwater mixing on the basis of stratigraphic, solution-replacive fabric and isotopic data. Dolomite characteristically replaces the Pliocene fissure fill contents in southeast Cyprus and off-reef horizons in the Terra Member and Koronia Member of west and north Cyprus respectively. The growth and burial history of Miocene reefs and related-sediments contribute to the understanding of the tectonic history and palaeogeographical evolution of Cyprus, particularly with respect to sealevel variation.

This research project aims to recognise and understand the relationship between lithology, stratigraphy and structural setting across the hinge-zone between Sirte Basin and Cyrenaica Platform to the northeast. This is the first time that the Tertiary sedimentary rocks in the north-eastern Sirte Basin have been the subject of detailed structural and stratigraphic investigation. The systematic approach through geological and geophysical interpretation using seismic reflection data, aided by synthetic well data, is the most suitable way to attain the research objectives, especially since the study area has only a few real wells. This study integrates structural interpretation of seismic data, velocity analysis, depth conversion, seismic sequence stratigraphy, well correlation and porosity and subsidence analysis. Interpretation of the structural features seen on the seismic sections and their mapping with relation to geological time has defined the structural history in the east Sirte Basin. All the depositional sequences dip toward the southwest (basin direction) and faults are the most prominent structure in the area. Most faults are normal trending NW-SE with downthrow towards the basin. Velocity analysis has been carried out as a useful tool for local stratigraphic interpretation and lithology evaluation and also for the conversion of two-way time to depth to the top of each sequence. The difference between seismic derived velocity, check-shot and sonic log velocities has been examined to establish the effect this difference might make in the determination of the true velocity distribution. Average velocity and interval velocity maps have been constructed for each sequence. Time to depth conversions for complex models including laterally variable velocities and reflector structure have been done. This depth-conversion method results in depth maps with exact well ties and geologically reasonable depth estimates away from wells. By applying seismic sequence stratigraphic techniques in the area, depositional environments are interpreted using the resultant facies analysis and the characterisation of reflections.

No description available.

The Charlestown Main Limestone, of the Dinantian Lower Limestone Group (Brigantian), in the eastern Midland Valley is generally the thickest marine limestone developed within a basin fill otherwise dominated by fluvio-deltaic sediments and volcanics. Field descriptions, enhanced and refined through the collection of samples and subsequent petrographic microfacies analysis, were used to define and map facies, including those comprising buildup complexes. The regional distribution of these facies was found to be controlled by (i) differential subsidence and (ii) the geographical location of two major penecontemporaneous fluvio-deltaic systems. Carbonate buildups present within the Charlestown Main Limestone are restricted to central Fife, an area of reduced subsidence (the Burntisland High) during the Brigantian. Buildup geometry and local facies mosaics reflect the relative water depth and position on the Burntisland High which, because of its slight topographical relief and more distal position with respect to the location of fluvio-deltaic systems, became an area of increased carbonate productivity, away from this structure, in the Midlothian Low, more monotonous argillaceous limestone facies, of low-energy and somewhat deeper water aspect, accumulated. Influxes of terrigenous mud associated with delta progradation from the NE curtailed carbonate deposition earlier in eastern than in western areas and accounts for the thinning of the Charlestown Main Limestone towards East Fife. Moreover, differential subsidence north of the Pentland-Firth of Forth fault zone allowed a thick sequence of prodeltaic sediments to accumulate above the Charlestown Main Limestone in Fife, while delta top sediments succeeded the limestone in Midlothian. Significant diagenetic modification of the Charlestown Main Limestone began immediately after deposition, and continued through shallow and intermediate burial into the deep bural réime. Using a range of integrated petrographic and geochemical techniques, broadly comparable cement stratigraphies (designed Stage A, B etc.) have been identified at several localities. These cement stratigraphies enabled the relative timing of other diagenetic events such as hydrocarbon migration, styolitization, fracturing and dolomitization to be placed within a diagenetic history related to the burial of the Charlestown Main Limestone. The earliest phases of diagenesis, while the Charlestown Main Limestone was still influenced by pore fluids of marine derivation, included several phases of dissolution (of biogenic silica and carbonate) which locally (<i>i.e.</i> within buildup facies) produced large volumes of secondary porosity. Stage A cement, comprising sub-isopachous layers of inclusion rich calcite, are best developed within these early dissolution voids. They are considered to represent altered fibrous or acicular marine cements. Clear, blocky to prismatic calcites succeed Stage A. While the exact sequence of cements varies between each locality, the cements are, nevertheless, considered to have formed during shallow burial from phreatic waters initially of sea-water composition which were gradually diluted by mixing with fresh water associated with delta advance and development of a meteoric lens. Geochemical variation within these cements reflects not only mixing with fresh water associated with delta advance and development of a meteoric lens, but also progressive burial through oxic, suboxic and then reducing zones in the shallow subsurface.

Phangnga Bay is a 2000km<SUP>2</SUP> shallow marine tropical embayment on the peninsula coast of South Thailand. The surrounding catchment area consists of Sn-bearing granites. Permian and Mesozoic sediments and Sn-rich pegmatites intruded in NE-SW trending fault systems. Grain size analysis of surface sediments reveals that mean grain size and sediment sorting show an overall increase southwards towards the more open marine environment. This is thought to reflect the transition from fine grained recent sediments presently settling out in the low energy sheltered conditions in the north to coarse relict sands in the south deposited during Pleistocene low sea-level stands and not covered by recent sedimentation. Geochemical analysis of the sediments reveals that the majority of elements studied (namely, Fe, Mn, AlP<SUB>2</SUB>O<SUB>5</SUB>, K, Rb, Nb, Y, Th, Pb, V, Cr, Zr, Nl, La, Ce Nb and Organic Carbon) are closely associated with clays through adsorption and cation exchange processes. These elements show concentration distributions which mirror that of the clay content. Sn, Zr and Tl when ratioed to Al, show highest values in the south of the area which is thought to reflect the concentration of these elements in heavy minerals which themselves are concentrated in the relict sands of the south. Both Sn and Rb show distributions strongly controlled by the distribution of cassiterite and lepidolite respectively in the catchment area. Both Mg and Sr show distributions partly controlled by clays and partly by carbonates. CaCO<SUB>3</SUB> shows a general increase southwards reflecting improved conditions for carbonate-secreting organisms and a decrease in the diluting effect of terrigenous material. The carbonate mineralogy varies in relation to the biogenic content of the sediments. Kaolinite is the dominant clay mineral due to the intense chemical weathering of granites in the catchment area, however, clay mineral proportions change from north to south as a result of the variations in settling velocities of different clay minerals. The sediments of 8 depositional environments which have been distinguished on the basis of geomorphology and water depth are compared. Different techniques for distinguishing populations from the data are discussed particularly in relation to the 8 depositional environments mentioned above. From radiocarbon dates of core material sediment accumulation rates in the north of the Bay have been calculated and vary between 0.3 and 1.5mm/year. Progradation rates of the main mangrove development in the north of the Bay have been estimated at approximately 1.5m/year. From the study of cored material and the distribution of surface sediments it is concluded that Holocene sedimentation in Phangnga Bay represents a regressive, fining-upward sequence. Comparisons are made between this model of sedimentation in Phangnga Bay and possible analogues in the geological record.

No description available.

The primary aim of this research is to answer some of the questions about the role of Lesmahagow in the Caledonian orogeny. Other important considerations include how it correlates with the other inliers of the southern Midland Valley and why such an unusual fauna should be preserved here. The basin model to emerge from this study shows that the sediments of Lesmahagow accumulated in a narrow, trans-tensional basin within a largely extinct volcanic arc. The basin subsided quickly and was filled by organic rich muds. Arenaceous sediment was supplied by two turbidite sources; a fine to course grained one shed from an active fault scarp along the south-eastern margin, and a very fine grained source which entered the basin axially from the north-west. From fossil evidence it seems unlikely that the basin ever had full and open connection to the 'rump-Iapetus' ocean that remained between Laurentia and Avalonia. Whatever connection did exist became gradually more tenuous as the basin was filled and uplifted. The animals that inhabited these environments (which became progressively more lacustrine) must have had to cope with water chemistry that departed from what is regarded as 'normal' marine and this may indicate that these were the first vertebrates to colonise non-marine environments. These conclusions re-write the Silurian stratigraphy of the Midland Valley of Scotland and may have an important bearing on the history of vertebrate evolution. They also show that, during the Silurian, the stresses produced by the collision of the Laurentian and Avalonian plates were being accommodated through strike-slip processes, which ultimately led to the dismemberment of the northern margin of Iapetus and its reconstitution as a patchwork of unrelated 'suspect' terranes.

Planktonic foraminifera recovered from nine cores in the Benguela Current system are used to ascertain the variability of upwelling intensity for the Late Quaternary and its impact on atmosphere-ocean-cryosphere linkages. The analyses from high-resolution planktonic foraminiferal records for cores GeoB 1706, GeoB 1711 and PG/PC 12, reveal striking variations in upwelling intensity during the last 160,000 years. Four species make up over 95% of the variation within the cores, and enable the record to be divided into episodes characterised by particular planktonic foraminiferal assemblages which have meaningful ecological significance when compared to those of the present-day and the relationship to their environment. The cold-water planktonic foraminifer, <I>Neogloboquadrina pachyderma </I>sinistral [<I>N. pachyderma </I>(s))], dominates the modern-day, coastal upwelling centres, and <I>Neogloboquadrina pachyderma </I>dextral and <I>Globigerina bulloides </I>characterise the fringes of the upwelling cells. <I>Globorotalia inflata </I>is representative of the offshore boundary between newly upwelled waters and the transitional, reduced nutrient levels of the sub-tropical waters. In the fossil record, episodes of high <I>N. pachyderma </I>(s) abundances are interpreted as evidence of increased upwelling intensity and the associated increase in nutrients. The <I>N. pachyderma </I>(s) record suggests rapid shifts in the intensity of upwelling, and corresponding trophic domains, that do not follow the typical glacial - interglacial pattern, but instead reflect the shifts of the Angola-Benguela front situated to the north of the Walvis Ridge. Absence of high abundances of <I>N. pachyderma </I>(s) from the continental slope of the southern Cape Basin indicate that Southern Ocean surface water advection has not exerted a major influence on the Benguela Current system. The periods of high abundance in <I>N. pachyderma </I>(s) are referred to as 'PS events' and indicate increased intensity and zonality of the South Atlantic trade winds controlling the Benguela upwelling system. During these intense upwelling phases, total organic carbon, abundance of <I>N. pachyderma </I>(s) and the benthic/planktonic foraminiferal ratio, provide the best indicators for palaeoproductivity away from coastal re-suspension. The offshore record of GeoB 1711 is used as the indicator for maximum offshore divergence and shelf-edge upwelling and is regarded as the best indicator for palaeoceanographic and palaeoproductivity variability.

An integrated approach, combining sedimentology, structural geology and geomorphology, has been used to reconstruct the Pliocene and Quaternary evolution of the Aksu basin, located on the Mediterranean coast of Turkey. The present basin opened in the Lower Miocene (Flecker, PhD, 1995). The shallow marine, bioclastic Gebiz Limestone, originally thought to be Messinian in age is believed to date from the late Miocene (late Tortonian/early Messinian). Selenitic gypsum in the Aksu basin is related to the Messinian dessication of the Mediterranean Sea, which produced widespread evaporite deposits. Right-lateral shear is recognised during the late Miocene-early Pliocene. Pre-existing structural lineaments, that were orientated sub-parallel to the shear direction, were reactivated as right-lateral shear zones. Between these defined lineaments broader zones of distributed shear are thought to have deformed by clockwise rotation of small blocks bounded by sinistral fault planes. Flooding of the Mediterranean at the beginning of the Pliocene resulted in deposition of the Yenimahalle Formation. The onshore sediments of the Yenimahalle Formation are dated as <I>Globorotalia puncticulata-Globorotalia margaritae</I> zone, using planktic foraminifera. Benthic foraminifera assemblages show that maximum water depth at this time was of the order of 150m. Seismic profiles in Antalya Bay indicate that the Pliocene sediment package is approximately 500m thick and that it was deposited onto a block-faulted topography. Three transgressive phases are recognised, that can be related to eustatic sea-level changes during the Lower Pliocene highstand. The Yenimahalle Formation shallows and coarsens upwards in the upper 25m of section. The sediments change from blue-grey silts to yellow sands containing gravel lenses, shallow-water burrows and large macrofossils. The benthic foraminifera assemblage of the upper part of the section indicates a water depth of 50m or less. The Yenimahalle Formation grades into the Çalkaya Formation. This consists of non-marine fanglomerates in the far north; braided stream deposits in the northern Aksu basin; and deltaic marine and transitional marine deposits (marine sands and conglomerates, muds, soils and coals) in the south. A tuff deposit in the Çalkaya Formation is interpreted as the basal surge deposit of a small phreatomagmatic eruption. K-Ar dates from biotites extracted from pumice clasts in the tuff were inconclusive, due to excess atmospheric argon.