Seismic stratigraphic analyses of the late Palaeocene-Present transitional to post-rift succession in the Faroe-Shetland Basin and Faroe Graben (FSC) on the NE Atlantic volcanic passive continental margin have revealed the occurrence of a early Eocene dendritic palaeo-drainage system and Middle Eocene-Miocene contractional inversion structures. The palaeo-drainage system consists of a significant NNW-SSE trending distributary channel (40km long, 5km wide and up to 400m deep), fed by numerous tributaries (100m deep). The drainage system incised into a major delta system (Colsay Sandstone Member) and was subsequently unfilled and draped by estuarine deposits (Hildasay Sandstone Member and Balder Formation). The excellent preservation of the palaeo-valleys indicates that uplift, incision and subsequent infilling of the drainage system occurred relatively rapid (biostratigraphically constrained to 1.45 My). The uplifting responsible for the incision event at c. 54.75 Ma, earliest Ypresian) was widespread and extends as far as the North Sea (Bressay area) and SE England (London Basin). Furthermore, coeval volcanic activity is consistent with the drainage system having resulted from transient uplift driven by a mantle-plume. This transient uplift event (incision and infill) in the FSC provides important new evidence for the evolution of the ancestral Iceland mantle plume and its influence on stratigraphic development. The inversion structures, developed in Middle Eocene, Oligocene and Middle Miocene, are marked by folding with the syn/post inversion stratigraphy onlapping and thinning over the structures. The location and orientation of the inversion structures suggest that the underlying Mesozoic structural configuration, especially the NW-SE transfer zones, influenced their development. The timing and nature of the movement of the inversion structures in the FSC provide new temporal constraints which help to understand better the controlling mechanism of passive continental margins.

The Neogene to Quaternary sedimentary succession of the southern North Sea Basin, which is generally considered to consist of deltaic sediments, has been studied in an 80 by 170km area off the north-west coast of the Netherlands. The total thickness of the succession here varies from 450 to 1,200m, and is thickest at the southern end of the North Sea Central Graben. The sediments were studied using about 2500km of regional seismic data, 58 commercial well logs and 7 high resolution, site investigation, reflection seismic data-sets, the latter covering areas no larger than 6km<SUP>2</SUP>. From this database a preliminary litho-stratigraphic scheme for the study area has been constructed. This has been fully integrated with existing, offshore stratigraphic schemes. The limited bio-stratigraphic data available has been used to give age estimates of the units which make up the succession. Only sediments deposited between the Netherlands' Praetiglian and the Waalian stages (late Pliocene to early Pleistocene, 2.5 to 1.4Ma) can be assigned ages with any confidence. The base of the Neogene to Recent succession is marked by an unconformity generated by a minor phase of late Oligocene to early Miocene inversion. The oldest part of the succession is made up of 80m of clay, deposited along the southern end of the North Sea Central Graben axis during the ?early to middle Miocene. Following this, there was a major depositional hiatus lasting from ?middle Miocene to ?Brunsummian (middle Pliocene) times. This hiatus, which is marine, is an important marker horizon in both well and seismic data. Sedimentation resumed in the ?early Reuverian (middle Pliocene) in the north-east of the study area, and gradually expanded westward across the hiatal surface to cover the entire study area by the middle of the Tiglian (late Pliocene, ˜1.9Ma). Outer shelf, clay deposition dominated at first, shallowing to middle/inner shelf, coastal and fluvial sedimentation from the beginning of the Praetiglian onward. After a large transgression in the middle Tiglian, a major regression occurred in the late Tiglian (latest Pliocene, ˜1.8Ma), possibly displacing the sea to the far north-west of the study area. Estuarine and fluvial environments probably dominated the study area from then until the ?mid "Cromerian" (˜0.5Ma). A combination of glacial and marine conditions dominated deposition from ?Elsterian times (0.3-0.4Ma) to the present, resulting in large scale erosion and in very complex depositional architecture for sediments of this age.

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For appropriate management of any stretch of coastline, it is desirable to understand (and ultimately to be able to predict) the exchange, transfer and storage of material at the landocean boundary. To this end, the multidisciplinary Land-Ocean Interaction Study (LOIS) was set up by the UK Natural Environment Research Council (NERC), focusing chiefly on eastern England as an example. Distinction between short-term fluctuations and long-term trends is particularly important when devising predictive models of coastal change. Within LOIS, the Land-Ocean Evolution Perspective Study (LOEPS) provided data on a Holocene time scale using evidence from the sediment record of east coast sinks including the Humber, the Fens and the North Norfolk coast. As part of LOEPS, the present study centred on the Wash-Fenland Embayment, the largest accumulation of Holocene tidal sediments in Britain. Since initial marine inundation of the area around 7,000 years BP, approximately 24 km' of sand and mud have been deposited by vertical and lateral accretion under varying rates of sea-level rise. However, in the last 50 years, parts of the shoreline have started to erode, raising questions over sediment supply and other conditions necessary for maintaining the position of the intertidal zone. The main aim of the work presented in this thesis was to ascertain the main sources of sediment supplied to the Fenland and adjacent Lincolnshire coast. Selected tidal sediments from early Holocene to recent age were compared with a range of potential source lithologies. The latter included sections of eroding coast between Holderness and North Norfolk and local strata exposed within the embayment and its river catchments. In the Fens, use of chemical ratios showed the majority of Holocene sediment to be well mixed and very homogeneous, variations in bulk chemical data mainly being a function of sediment grade. However, samples with anomalous chemical ratios were identified at the base of the succession close to the landward margins. Grain-size specific analyses of these samples suggest that they have a similar composition to lithologies from Fenland river catchments and the floor of the embayment. For example, clay mineralogy indicated an early Holocene fluvial input of Oxford Clay at Adventurer's Land. In a similar way, surface area, mineral magnetic analyses, optical mineralogy and SEM of anomalous sand samples show quantitatively and qualitatively the links between selected non-marine sources and these early Holocene sediments. The bulk of the Fenland sediment appears to have been well mixed in the North Sea sediment pool prior to deposition. Comparisons of the potential marine source lithologies showed the fine fraction of the glacial tills to the north and east of the embayment to be chemically very similar. On the basis of clay mineralogy, subtle differences between Devensian and Anglian Tills were identified, and Fenland sediment was found to have an intermediate composition. The sand fraction of most Devensian Till samples could be distinguished from the more quartz-rich sand fraction of the Anglian Tills, and quantitative analyses of surface area and magnetic properties of selected Fenland samples suggest till eroding from the Lincolnshire foreshore is the most likely source. Particle size analysis, summarised using Principal Components Analysis (PCA), proved successful in characterising sediments according to depositional environment. Grain-size data indicated a general fining-upwards trend in the sand fraction. In the embayment as a whole, vertical accretion was accompanied by lateral progradation indicating that sediment supply was more than sufficient to keep pace with sea-level rise. The use of particle size analysis together with PCA seems widely applicable to studies of modern and Holocene sedimentary environments, estuarine sedimentation history and consideration of long term sediment budgets. Chemical ratios appear to have potential as first indicators of changing sediment source.

The present research is on the Cretaceous microbio- and litho-stratigraphy of the Cauvery Basin, Southeast India. The planktonic and benthonic foraminifera are used to establish microbiostratigraphic zonations for the mid-Cretaceous succession in the Basin; leading to the first proposal of a benthonic foraminiferal zonation scheme. The schemes are primarily defined for regional application. In the absence of a formal lithostratigraphic classification for the Cretaceous succession in the Basin, a revised lithostratigraphy, in line with standard stratigraphic procedure, is proposed. The systematic taxonomy of the foraminifera studied is documented and revised in line with Western standards. The study shows that, in contrast to the standard European forms, the fauna from the Cauvery Basin is composed of more robust individuals. The study also shows some interesting differences in the planktonic foraminifera from the standard Tethyan assemblage. Comparative studies indicate a longer time range for some of the &quot;index&quot; species and more ornamented forms in the Cauvery Basin. The study records two levels, ( I ) in the late Albian and (2) from the late Cenomanian to mid-Turonian, when anoxic conditions developed in the Basin. These anoxic events record major taxonomic changes in the planktonic foraminiferal assemblage. The study shows that the anoxic events had a major affect on the microfaunal community and that the post anoxic microfaunal population was dominated by more robust and heavily ornamented individuals. The planktonic foraminifera are used to identify the mid-Cretaceous sea-level changes in the Basin. The pattern of evolution and expansion of the planktonic foraminifera suggest a continuously rising sea-level in the mid-Cretaceous; with four periods of major transgressions. These levels are, at the late Albian, mid-Cenomanian, late Cenomanian-early Turonian and mid-Turonian. The pattern of sea-level changes in the Cauvery Basin followed , in general, the global sea-level curve, but has been influenced by local factors particularly tectonics. A pilot study demonstrates how palaeontology (including ichnology) in conjunction with sedimentology and stratigraphy is used to apply sequence stratigraphy concepts to the late Turonian-Coniacian succession in the Basin. A comprehensive study of Teredolites-infested fossil wood documents the morphological characters of the wood and its palaeoenvironmental significance. The study shows that there exists a close link between the influx of the fossil wood and sea-level dynamics.

A revised Lower and Middle Pleistocene stratigraphy and palaeoenvironmental history of south-east Suffolk is proposed as a result of field and laboratory examination of 15 sites and several temporary exposures by analyses of particle size distributions, clast roundedness, stone counts, till macrofabrics, palaeocurrents and facies assemblages. The oldest unit consists of intertidal sands and silty clays of the Creeting Formation. Pollen evidence suggests a date earlier than the Pastonian. The situation of the deposits suggests that early Pleistocene marine conditions were more extensive than previously thought and their altitude and distribution indicate significant Pleistocene tectonic activity. Overlying these, the Kesgrave Formation comprises three terraces of sand and gravel deposited by a northeastward flowing braided river. The exotic components of the gravel indicate an extensive drainage basin, though some may have been introduced into the catchment by ice. These deposits represent the earliest course of the Thames, of Beestonian and Pre-Pastonian age and possibly earlier. The uppermost 1.0m or more of the terrace deposits have been altered by humid, temperate pedogenic activity to form the Valley Farm-Rubified Sol Lessive during a succession of interglacials of which the Cromerian is the youngest. The succeeding Anglian periglacial phase is marked initially by aeolian deposits and then by ground-ice activity, which disturbed the temperate palaeosol and formed the Barham Arctic Structure Soil. The ensuing glacigenic suite, the Lowestoft Formation, starts with outwash sands and gravels. Basal flow tills appear to occur preferentially in the valleys and to be overlain by slumped till which passes laterally into lodgement till in the plateau area. During deglaciation a further flow till and gravels were deposited. The formations and their members are separated on the basis of variations in their lithological, sedimentological and structural characteristics. The fluvial facies assemblages conform to the Scott, Donjek and South Saskatchewan type models of Miall and, in addition to glacitectonic and hydroplastic disturbances, brittle and ductile deformation is identified as a response to settling on an unstable base such as melting ice or saturated clay or to downslope gravitational movement.

The fluvial Organ Rock Formation, which forms part of the Pennsylvanian-Permian Cutler Group of the Paradox foreland basin, is exposed across much of SE Utah and adjoining parts of northern Arizona and represents a wedge of coarse-grained fluvial strata that progressively fines south-westwards (distally) away from its source area, the Uncompahgre Uplift. By the time of onset of Organ Rock deposition (Leonardian/Artins kian), the Paradox basin was in an overfilled state, resulting in the progradation of a 100 m-thick wedge of fluvial strata across a wide part of the basin floor. These deposits record a downstream transition from a proximal fluvial system that was dominated by in-channel sedimentation in which evidence for repeated nodal avulsions is common, through a medial zone in which channels lay within belts that were subject to a variety of lateral accretion, avulsion and anabranching processes, to a distal zone where evidence for in-channel sedimentation is less abundant and in which sheet flood and aeolian dune elements are dominant. This research presents the first detailed sedimentological and stratigraphic analysis of the Organ Rock Formation. Gross-scale facies distributions and sedimentary architecture have been analysed using a comprehensive set of regionally and more locally distributed sedimentary logs acquired throughout the outcrop belt of the Organ Rock Formation within SE Utah. These data have formed the basis for more detailed architectu ral analyses enabling the development of a suite of two-dimensional and three-dimensional depositional models that account for the detailed and complex vertical and lateral facies relationships observed throughout the Organ Rock Formation. It is likely that the spatial and temporal evolution of the Organ Rock fluvial system was controlled by a combination of intrinsic and extrinsic processes, which acted at a range of scales and which are represented by a hierarchy of cyclicity observed at outcrop.

Differential compaction within alluvial sediments results from the inherent juxtaposition of sand, si It, clay and peat on the floodplain. Differential compaction is primarily dependent on (a) the nature of overbank mudstone compaction, and (b) the relative timing of channel and adjacent overbank sediment deposition. Results from the analysis of modern overbank sediments indicate that the near-surface porosity of alluvial overbank sediment Is controlled by the complex interaction of grain shape, grain size, clay content, groundwater fluctuations, evaporation and transpiration, suggesting that the subsequent compaction of these sediments would be an extremely heterogeneous process, with n'o single controlling parameter. Porosity-depth curves derived from modern sediment analysis indicate that a significant amount of compaction occurs during the first few metres of burial. Examination of samples suggest that ·porosity loss may be due to the expulsion of water from the sediment pores, and the rearrangement of grains from an unstable packing arrangement to a more stable one. Early differential compaction will affect floodplain topography, and therefore directly influence the subsequent pattern of facies distribution. However, as significant amounts of compaction have occurred during very early burial, later stages of compaction will have a less marked effect on alluvial stratigraphy than has been previously suggested. In particular, simulation models such as Bridge & Leeder (1979) which suggest that channel "packing" increases with depth may not be entirely correct. If, within an alluvial sequence, there is no compactional deformation of features such as alluvial channel wings, it is unlikely that channel packing will have increased with depth. Studies of the Middle Jurassic alluvial sediments of North Yorkshire and the Cretaceous of the Isle of Wight, illustrate that the effects of differential compaction can be observed on several scale~: (a) channel belt, (b) individual channel or bedform, and (c) microscopic

No description available.

No description available.