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Architecture and processes of deep-marine sandbodies, Ainsa basin, Spanish Pyrenees

Bayliss, N.J.; (2011) Architecture and processes of deep-marine sandbodies, Ainsa basin, Spanish Pyrenees. Doctoral thesis, UCL (University College London). Green open access

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Abstract

The integration of sedimentology, architectural element analysis and stratigraphy has been applied to characterise the complex depositional history of the Ainsa basin fill, and document the evolution of the proximal parts of eight, channelised deep-marine systems of the Hecho Group. The Eocene Ainsa basin provides an opportunity to research three-dimensional organisation through an entire deep-marine slope to proximal basin-floor fill, and records a range of depositional processes and sedimentary environments in a spatio-temporal framework. The Hecho Group can be divided into two tectono-sequences, TS-I and TS-II. TS-I accumulated during a period of strong flexural subsidence ahead of the main thrust front during a foredeep setting, whereas TS-II represents a more mature stage of basin development, characterised by anticlinal uplift as the basin became detached and evolved into a complex thrust-top basin. Four discrete systems and their constituent sandy sequences compose each tectono-sequence. The sequences comprising TS-I show very little lateral migration due to high basin-scale accommodation; however, westward lateral offset stacking is observed in the sandy sequences of TS-II due to the development of intrabasinal growth anticlines. These structurally controlled trends demonstrate that the timing of tectonic processes operated at frequencies consistent with the accumulation of the depositional systems. Depositional systems range between ~60–700 m thick, and were deposited in a number of deep-marine settings that include mid-slope canyons, lower-slope erosional channels and proximal basin-floor channel systems. Temporal variation in depositional style and architecture between systems reflects the tectonic regimes operating during the accumulation of the tectono-sequences. Alternatively, the 22 sandy sequences were controlled by the ~400 kyr Milankovitch frequency with higher-frequency orbital bands influencing the accumulation of channel complexes and channel fill elements. An important outcome of this study is the recognition of a complex hierarchical interaction between global climatic and tectonic drivers, operating at a variety of time scales to control the timing of coarse clastic sediment supply and the architectural styles of depositional systems.

Type:Thesis (Doctoral)
Title:Architecture and processes of deep-marine sandbodies, Ainsa basin, Spanish Pyrenees
Open access status:An open access version is available from UCL Discovery
Language:English
Additional information:Appendix D: Published work (pp 379-383) has been removed from the digital copy of this thesis due to copyright restrictions.
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences

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