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University of Aberdeen (2009)

Tectono-stratigraphic and climatic record of the NE Arabian Sea

Calvès, Gérôme

Titre : Tectono-stratigraphic and climatic record of the NE Arabian Sea

Auteur : Calvès, Gérôme

Université de soutenance : University of Aberdeen

Grade : Doctor of Philosophy (PhD) 2009

This study describes the tectono-stratigraphic and climatic record of the NE Arabian Sea during the Cenozoic. Compilation of regional knowledge and subsurface observations has in this thesis provided new interpretations and insights into the records present along this passive margin. The first is the rifting period (80-65 Ma) and the identification of a syn-rift volcanic sequence, comparable to other volcanic rifted margins. This is followed by the record of a drift sequence ( 65 Ma to present day), composed of extensive carbonate platforms and an infill sequence of siliciclastic deposits. The analysed drift sequence (sink) is partly the result of the erosion of the hinterland (source) characterised by the India-Eurasia continent-continent collision. Influence of regional climate and/or tectonic forces on the accumulation rate in the sink was tested, but not conclusive as the study area (Upper Indus Fan) covers only a limited part of the sedimentary record of the Indus Fan. The thermal regime of the western margin of India is sparsely sampled, but once analysed, allows the definition of first order constraints on multiple rifting events. The post-rift subsidence of the margin is slow and anomalous for >28 m.y. after break-up, potentially in relation with vigorous asthenospheric convection and a sharp ocean-continent boundary. Past and present fluid flow is recorded in the sedimentary sequence of the Upper Indus Fan. The first is related to gas hydrate occurrence and is the result of the migration of fluids by a plumbing system to the shallow subsurface, expressed by bottom-simulating reflections crosscutting stratal reflections. A longer term fluid migration is recorded in this basin by the longest lived ( 22 m.y.) mud volcano field recorded to date.

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