Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: James E. Pizzuto, Dept. of Geological Sciences. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 124-128). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 117-134).

Thesis (Ph. D.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by Carolyn Ruppel. / Vita. Includes bibliographical references (leaves 179-191).

The amount of carbon trapped in hydrates is estimated to be larger than in conventional oil and gas reservoirs, thus methane hydrate is a promising energy resource. The high water pressure and the relatively low temperature needed for hydrate stability restrict the distribution of methane hydrates to continental shelves and permafrost regions. Stability conditions add inherent complexity to coring, sampling, handling, testing and data interpretation, and have profound implications on potential production strategies. New guidelines are identified for sampling equipment and protocols. Then a novel technology is developed for handling, transfering, and testing of natural hydrate bearing sediments without depressurization in order to preserve the sediment structure. Natural samples from the Nankai Trough, Japan, are tested as part of this study. In-situ testing prevents dissociation and the consequences of sampling and handling disturbance. A new multi-sensor in-situ characterization tool is designed and prototyped as part of this research. The tool includes advanced electronics and allows for automated stand-alone operation. Finally, a robust analytical model is developed to estimate the amount of gas that can be recovered from hydrate bearing sediments using depressurization driven dissociation. Results highlight the complexity of gas extraction from deep sediments, and inherent limitations.

This thesis aims to assess the response of invertebrate assemblages to fine sediment in the River Isábena, a catchment generating unusually high sediment loads due to the presence of badland areas. First, a spatial approach was taken in order to assess evidence of sedimentrelated patterns in invertebrate assemblages across the catchment under stable flow conditions. This provided a “snap‐shot” of the spatial variability on the assemblages in relation to sediment stored in the channel, as well as the relative influence of physical habitat conditions of different spatial scales. Fine sediment proved to be driving invertebrate assemblages distribution, structure and trait composition, filtering‐out sensitive species and thus promoting nested patterns across the catchment. Strong interactions between spatial scales were found, emphasizing the existence of catchment scale controls (such as geology and rainfall) on reach physical habitat conditions and, in turn, on invertebrate assemblages distribution. This spatial approach was complemented with the study of the temporal dynamics, which focussed on understanding the dominant drivers in the catchment hydrosedimentary behaviour and the relationship between physical processes and the ecological response. Temporal distribution of rainfall (and thus the occurrence of floods), along with the sediment availability (both in the source and in the channel) were driving the intra‐annual suspended sediment dynamics. Turnover of invertebrate assemblages was jointly driven by taxon life cycles and the temporal dynamics in hydrosedimentary conditions (i.e. occurrence of floods and episodes of high sedimentation). Despite the intra‐annual variability, assemblages proved to be resilient, most likely as a result of the selection of pre‐adapted traits. Overall, these findings emphasize the importance of assessing the geomorphological and hydrological processes that control sediment production, delivery and permanence in the channel, in order to better understand the ecological impacts of excessive fine sediment loads.

The Buzzard Field lies within outer Moray Firth (Central North Sea) and is part of a Late Jurassic, syn-rift, deep water depositional system that comprises deep-water sandstones interbedded with ‘expanded’ hemipelagic mudstones, and mud-rich mass transport deposits, sourced from basin margin highs. Sandstones are interpreted mainly as the deposits of large volume, sustained high density turbidity currents sourced axially through linear systems aligned with the west-to-east regional structural trend. The extensive core database has formed the basis for the sedimentological interpretation of the field, which has been extended into uncored wells using a new lithofacies recognition technique pioneered within this study. Dipmeter data have been used to supplement lithofacies interpretation of conventional wireline logs. Neural net analysis of these log signatures, calibrated to core description, has revealed the lithofacies present in uncored section and allowed an improved understanding of lithofacies variability across the field. The depositional history of the Buzzard system, based on fieldwide correlation and a regional biostratigraphic framework, is interpreted to consist of seismically triggered flow events, which were initially confined by structurally generated basin floor topography; later, more frequent flows encountered simpler bathymetry and were weakly confined, depositing lobe shaped sandstone bodies. This sequence is summarised by several depositional cartoons. The field is described here as a three-way stratigraphic trap with a down-dip oil-water contact despite being deposited in a tectonically active period. The sedimentological factors that contribute to the trapping mechanism are discussed in detail including: flow divergence; slope angle; and basin margin interaction. This study has implications for the interpretation of flow processes in (and sediment delivery mechanisms to) the deep-water environment, recognition of lithofacies from wireline data, and for future exploration in syn-rift, deep-water settings. Analysis of the extensive core dataset has revealed that sands were transported to the deep basin as part of large-scale flow events and were deposited rapid mainly through fallout from suspension. These infrequent but catastrophic flow events moved large volumes of sediment from a shallow marine staging area to the deeper setting, eventually depositing a characteristically thick-bedded sandstone succession. The coarsest-grained portions of individual event beds have been identified as high permeability layers and are essential to understand from a production perspective. The geometry and distribution of these high permeability zones is controlled by depositional process and are iii located in the axial, updip parts of event beds. Therefore, accurate correlation of thick event beds is particularly important for reservoir characterisation. The updip depositional limit of these sands defines a stratigraphic pinchout margin that corresponds to an Upper Jurassic isochron which may be used to define the limit of Upper Jurassic sandstones in other areas of the North Sea. Furthermore, the pinch out limit is defined at a transition from high structural complexity updip to lower complexity downdip. Crucially, this transition allowed flows that were routed through the complex updip palaeobathymetry to diverge downdip, thus rapidly depositing their sediment load. Well established sediment gravity flow pathways such as those interpreted to feed the Buzzard basin are rare in the Upper Jurassic of the North Sea. Despite that, this combination of flow pathway, shallow marine source area and structural configuration we essential factors in producing a reservoir of the quality of Buzzard;similar tectono-stratigraphic settings may also produce Buzzard-style reservoir and should be considered exploration targets.

The bathyal continental margins (200 – 3000 m) account for 7 % of global sea floor area, but are responsible for recycling 30 % of sedimentary organic matter (OM) within the oceans. Climate-change driven expansion of oxygen minimum zones and increasing frequency of extreme weather events (storms) may have implications for OM processing at the continental margins, resulting in decreased oxygen availability and increases in terrigenous OM inputs. The present thesis tests how changes in oxygen availability influence sea floor community structure and OM processing across the OMZ-impacted Indian continental margin. Megafaunal and macrofaunal assemblages exhibit a distinct zonation, with faunal distributions controlled by changes in oxygen availability and sediment OM content. In situ stable-isotope pulse-chase experiments reveal that, following phytodetritus deposition, macrofaunal feeding responses were influenced by oxygen availability through changes in macrofaunal assemblage structure. Macrofaunal feeding was governed at the organismal level, with fauna maximising organic nitrogen assimilation against an internal carbon-nitrogen budget. Bacterial feeding responses were not directly influenced by changes in oxygen availability and instead were regulated by the macrofaunal assemblage. This thesis proposes that the macrofauna may control the availability of labile organic matter in OMZ-sediments, limiting bacterial activity. The thesis also investigates the differential fates of marine and terrigenous phytodetritus in the sediments of the Whittard canyon (NE Atlantic). In situ pulse-chase experiments reveal nitrogen demand to control macrofaunal feeding responses, inhibiting the utilisation of the nitrogen-poor terrigenous phytodetritus. Bacteria exhibit similar feeding responses to the fauna, whilst bacterial biomass was negatively correlated to increasing faunal activity. This demonstrates that increased inputs of terrigenous organic matter may alter ecosystem-scale carbon cycling pathways and trophic interactions within continental margin sediments.

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