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Sedimentology and Geochemistry of Gas Hydrate-rich sediments from the Oregon Margin (Ocean Drilling Program Leg 204)

Other TitlesSedimentologia i Geoquímica de Sediments rics en Hidrats de Gas del Marge d’Oregon (Ocean Drilling Program Leg 204)
AuthorsPiñero, Elena
AdvisorGràcia, Eulàlia ; Martínez-Ruiz, Francisca
Issue DateMay-2009
PublisherUniversidad de Barcelona
AbstractGas hydrates have been recently recognized as a key factor affecting a number of global processes such as the climatic change, sea floor stability, etc. In this thesis we present the multidisciplinary study of gas hydrate rich sediments recovered during ODP Leg 204 “Drilling gas hydrates at Hydrate Ridge”. The main objective of this thesis is to study how the textural characteristics of marine sediments can affect the main pathways and intensity of fluid flow and how fluid flow determines the distribution of gas hydrates in the continental margins, as well as the main geochemical processes that occur during early diagenesis. To reach these objectives, a complete sedimentary and geochemical study of 581 sediment samples from southern Hydrate Ridge was carried out. The methods and techniques that were applied include: complete textural analyses (grain size, granulometric distribution curve, statistical parameters, identification of the coarse-grained particles, carbonate content…), mineralogy (bulk sediment and clay minerals), physical properties (magnetic susceptibility) and geochemistry (major and trace elementary composition, total organic carbon). The southern Hydrate Ridge sediments are mainly made up of four lithofacies defined as: hemipelagites, turbidites, ash layers and debrites. Mass-transport deposits such as turbidites and debrites are more abundant in Lithostratigraphic Unit III and II, as well as in Lithostratigraphic Unit IA in the slope basin of southern Hydrate Ridge. Some increasing trends with depth can be observed in the smectite content in the clay mineral assemblages of southern Hydrate Ridge sediments. These features suggests that the transport in suspension of fine sediments through the California Current was more effective during the Pliocene and early Pleistocene period. Bedload transport of coarse material from local and distal areas was more effective during the middle Pleistocene and Holocene due to the tectonic reactivation of the southern Hydrate Ridge uplift. During the Pleistocene and owing to the pervasive fluctuation of sea-level, gas hydrate dissociation together with the seismic movements in the Oregon margin seems a plausible triggering mechanism for mass-movements. Thus, the results presented here confirm that the sedimentation patterns in the Hydrate Ridge region are controlled by climate and tectonic parameters such as the regional intensity of the California Current or the local tectonic movements that lead to the uplift of the Ridge. These parameters mainly control the clay mineral distribution as well as the sedimentary facies that are produced [...]
DescriptionMemòria de tesi doctoral presentada per Elena Piñero Melgar per a optar al grau de Doctora per la Universitat de Barcelona (UB) dins del programa en Ciències de la Terra del bienni 2003-2005, realizada sota la direcció de la Dra. Eulàlia Gràcia i Mont de la Unitat de Tecnologia Marina (UTM-CSIC) y de la Dra. Francisca Martínez-Ruiz del Insituto Andaluz de Ciencias de la Tierra (IACT-CSIC)
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