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No description available.

The Upper Jurassic sediments of the East Coast of Sutherland and the South Brae Oilfield were deposited during the late Jurassic taphrogenic episode in which there was rapid subsidence in the grabens and uplift of the adjacent areas. The initiation of coarse-grained sedimentation in the grabens was directly related to an increase in subsidence rates. At Sutherland the most sand-rich sequences were deposited during the cymodoce zone of the Kimmeridgian, immediately after the increase in subsidence rates. Depositional environments varied from a relatively shallow water and sand-rich submarine slope during the early Kimmeridgian to a deeper water sediment starved submarine slope during the early Volgian. The sediments of the South Brae Oilfield were deposited in the channelised part of a submarine fan system which was sourced from a point which lay to the west of the 16/7a-8 well and to the southwest of the 16/7a-12 well. The South Brae sequences are part of a much larger complex which was composed of at least seven different submarine fan systems. Sediment entry points occurred along the western margin of the South Viking Graben from the T-Block in the south to East Brae in the north and each of these fed a submarine fan system. The reservoir sequences will tend to be vertically stacked and spatially restricted in proximal areas and will become less stacked and less restricted distally. Stratigraphically trapped "Brae-like" plays probably exist at the margins of many North Atlantic Continental Shelf grabens. The eastern margins of the Vøring and Træna Basins have especially high prospectivity.

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Mass-transport deposits (MTDs) are virtually ubiquitous on the modern seafloor and common in ancient slope successions. Their upper surfaces are often irregular due to surface topography, which may vary significantly in wavelength and geometry. Turbidity currents are highly sensitive to topography, resulting in the modification of their density and velocity profiles during topographic interaction, thus affecting their depositional architecture. It is therefore expected that supra-MTD turbidite systems are also affected so. Previous analysis of the upper surface of MTDs and conformable overlying turbidite systems suggests that the upper surface of MTDs support irregularities that vary in wavelength, from 10 m to greater than 1000 m, by which longer length-scales may compartmentalise turbidite systems. But such studies do not investigate in detail the mechanisms by which topography is generated and the effect of the three-dimensional form of topography on supra-MTD turbidite systems. This study therefore addresses these aspects by the application of spectral analysis methods, synthetic modelling of three-dimensional topography, and architectural and lithofacies relationships of turbidite systems with the upper surface of MTDs, illustrated using an ancient slope succession cropping out at Cerro Bola, Argentina, and a modern deepwater system of the Sabah slope, offshore Brunei. In this thesis, an analytical model is described that characterises the three-dimensional form of the upper surface of MTDs in to two types: isolated topographic highs (termed positive topography) and isolated topographic lows (termed negative topography), which describe topography with a low and high degree of confinement, respectively. The geometry of these 'types' of topography are illustrated to vary significantly depending on the variability in the confinement across the surface in question, the degree of anisotropy and the obliquity of the flow direction to its orientation, which are similarly quantified using the analytical model described. Such topographic variability and anisotropy are demonstrated to relate to horizontal variations in thickness of the underlying MTD, generated by various mechanisms, including: internal structure, basal shear surface topography and post-emplacement creep and compaction. Each mechanism may support a variety of wavelengths that typically vary in length-scale and are generated simultaneously upon syn- and post-MTD emplacement. As a consequence, a turbidity current may interact with multiple length-scales of topography that might be produced contemporaneously with deposition. Topographic interaction may therefore not occur over the same length-scale as topographic ponding and, thus, supra-MTD ponded turbidite systems may have vertical and horizontal facies transitions that occur over similar length and height scales to the underlying topography despite ponding over a longer wavelength. Due to the three-dimensional complexity and variability of MTD topography, facies and architectures of supra-MTD reservoirs cannot be generalised in two-dimensions or extrapolated with ease into the third-dimension from isolated exposures/data.

No description available.

The “deltaic” geomorphology in the Eberswalde Crater is often considered a “smoking gun” for the warm-and-wet ancient climate of Mars. The Crater displays sedimentary features, which many argue, can only be found in a river-delta system (Bhattacharya et al., 2005). However, with the advent of high-resolution images, the Eberswalde Crater delta’s geomorphology has been revealed to be more complicated than could be seen previously. These high-resolution data suggest that the development of the Eberswalde delta is likely more episodic (Schieber 2007). While better resolution data has placed doubt on the wet Mars hypothesis at the Eberswalde Crater, the opposite is true of the Gale Crater. Recent images acquired by the Mars Curiosity Rover have revolutionized the hypotheses explaining the formation of Mount Sharp in the Gale Crater. The new prevailing hypothesis is that Mount Sharp was formed by a series of crater lakes (NASA, 2014). This study provides evidence supporting the crater lake hypothesis, using bedding architecture diagrams, facies diagrams, lithologic logs, paleocurrent map and rose diagram, and minimum water depth estimations of the exposed sedimentary layers. Reconstructing a detailed depositional history of the Gale Crater Lake provides a window into a more ancient Mars where life could have evolved in a wet habitable climate that is absent today.

A Dissertation Submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in Fulfilment of the Requirements of the Degree of Doctor of Philosophy. / The Gariep Belt is an arcuate north-south trending tectonic unit extending ;along the western coast of southern Namibia and northwestern South Africa. It forms part of the Pan-African Damara Oragert, which consists of a north-south trending coastal branch (Kaoko and Gariep Belts) and an east-west trending inland branch. The Gariep Belt is subdivided into an eastern parautochthonous passive continental margin on the western edge of the Kalahari Craton, the Port Nolloth Zone, and a western allochthonous ophiolitic terrane, the Marmora Superterrane, thrusted on the Port Nolloth Zone. The sedimentary evolution of the Gariep Belt was initiated with the deposition of sediments of the Rosh Pinah Formation into fluvial, alluvial and lacustrine depositional systems, which are associated with bimodal volcanic activity and related Zn-Pb-Cu-Ag- (+Ba) sulphide mineralization. The overlying mixed continental/shallow marine deposits of the Gumchavib Formation are overlain by the carbonate dominated Pickelhaube Formation, which was deposited in shallow marine to pelagic depositional settings. The Rosh Pinah, Gumchavib and lower Pickelhaube Formations are intruded by basic volcanic sills of the "Gannakouriep dyke swarm", The conformably overlying Obib Peak Formation was deposited into a fluvial/alluvial palaeoenvlronrnent, The Numees Formation unconformably overlies the underlying stratigraphic units and consists predominantly of glaciomarine massive diamictites and occasionally interbedded iron formations, which are occasionally interbedded with interglacial sediments and volcanics. The regional structural pattern is characterized by three phases of deformation. The earliest deformational event, D1, comprises intrafolial small scale recumbent and isoclinal F1 folds, a penetratlve beddlnq-subparatel 81 cleavage and a preferred elongation of boulders, pebbles, grains and minerals (11). Associated with D1 are bedding-subparallel thrust faults. The D2 deformational phase is characterized by small to large scale, north to northwest trending F2 folds with a generally easterly vergence, which can change into a westerly direction due to backfolding. The F2 folds are associated with a penetrative axial planar S2 cleavage. Thrusting continued during the D2 deformational phase. The latest deformational event, D3, is characterized by small to large scale open F3 folds with southerly to south-westerly trending fold axes. The metamorphic evolution of the Gariep Belt during the Damara Orogeny was associated with barrovtan-type metamorphism with a geothermal gradient of about 20oC/km, reaching greenschist to lower amphibolite facies metamorphism. The sedimentological and structural features are explained in a tectono-sedimentery model, which started with rift initiation during the deposition of Rosh Plnah Formation lithologies along old tectonic weakness zones of Middle Proterozoic age at about 780Ma. Supercontinenta! breakup is documented by the initial transgression of Gumchavib Formation sediments and the continuous trensgression of the Pickelhaube Formation, which is related to thermal subsidence after the initiation of oceanic spreading of the Adamastor Ocean. Renewed rifting and/or glacial outwash heralding' the advance of the Numees glaciation and associated seale': :'changes may be responsible for the sudden break in marine sedimentation during the deposition of the Ohio Peak Formation. The Numees glaciation is probably contemporaneous with the 670Ma old Varangian glacial and the Rapitan glacial episodes and provides a minimum age for the deposition of Gariep Group lithologies. Rifting and spreading was followed by the closure of the Adamastor Ocean, associated with. a southeastward directed subduction. of oceanic crust under the Kalahari Craton and was accompanied by intense southeastward and subsequently eastward directed tectonic transport during 01 and D2. During D3, a late Sinistral movement developed along tre defined fault zones in the late stages of the Adamastor Orogeny.Metamorphic ages from the Nama and Vanrhynsdorp Groups indicate that that the tectonic evolution of the Gariep Belt only ceased at about 500Ma. / Andrew Chakane 2018

This study focuses on the development o f provenance signatures for sediments accumulating in Prince William Sound, with an emphasis on interpreting mechanisms of sediment deposition using historical earthquake, wave, river discharge, and glacial outburst flood records. A highresolution sedimentary sequence in Prince William Sound, Alaska contains sediments sourced from local watersheds as a result of seasonal and event-driven sedimentation. This study contributes to the development of paleo-proxies for sediment provenance, earthquakes, shelf sediment resuspension, and Copper River discharge. Geochemical studies of sediment cores and end-member samples using X-ray fluorescence and inductively coupled plasma mass spectrometry allows for the development of elemental proxies for sediment provenance during the past ~ 100 years. Seasonal sedimentation is resolved at Hinchinbrook Entrance as a result of high sediment accumulation rates and distinct textural and geochemical changes. Sediments deposited during the winter are derived from shelf sediment resuspension and sediments deposited during the summers are sourced from a complex mixture of the Copper River plume and direct discharge within Prince William Sound. Analyses of a continuous 18-year (1995—2013) wave record reveal that shelf sediment resuspension has a strong seasonality with large waves in the winters compared to the summers. More than 65 % of the sediments at Hinchinbrook Entrance accumulate during the winters, and those sediments are sourced from the shelf with distinct provenance signatures from the Copper River Basin. A north-south transect of sediment cores in Prince William Sound reveal that provenance signatures can be used to identify deposits in the Sound that were initiated by different mechanisms. Deposits in northern Prince William Sound that correspond to large earthquakes occurred in 1912, 1964, and 1983. A similar deposit from ~ 1895 in northern Prince William Sound, prior to historical earthquake records, may also have been initiated from a large earthquake in the 1890’s. Additional deposits in southern Prince William Sound from 1977 and 1992 were likely formed due to an increase in Copper River discharge. The 1977 deposit occurred during a shift to abruptly warmer climate conditions in Alaska that resulted from the well-documented climate regime shift in the North Pacific in 1976—1977. The most recent identifiable deposit in the north-south transect has an age of 2001 with sediments that contain distinct Prince William Sound provenance signatures. Relative to any other season in the 18-year record, the winter of 2001 experienced the highest bottom wave orbital velocity on the Gulf of Alaska continental shelf, the largest area of the shelf with sediment in resuspension, and the shortest time between resuspension events. During a time of minimal seismicity, slope failure within the southern portion of the central channel in Prince William Sound may have occurred due to the extreme waves in the winter of 2001 and could explain the occurrence of this deposit in southern Prince William Sound.