--> Abstract: Ainsa Submarine Fans, Middle Eocene, South Spanish Pyrenees: Integrated Outcrop - Subsurface Study of Architecture and Processes; #90063 (2007)

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Ainsa Submarine Fans, Middle Eocene, South Spanish Pyrenees: Integrated Outcrop - Subsurface Study of Architecture and Processes

 

Pickering, Kevin Thomas1, Julian Clark2, Nicole Bayliss3, Jordi Corregidor4 (1) UCL (University College LOndon), London, United Kingdom (2) Chevron Energy Technology Company, San Ramon, CA (3) UCL (University College London, Department of Earth Sciences), London, United Kingdom (4) ERM (Environmental Resources Management), Barcelona, Spain

 

We present unprecedented detail of the internal architecture and facies types that characterise the proximal parts of three laterally offset-stacked sandy submarine fans in the Middle Eocene Ainsa basin, Spanish Pyrenees, from an integrated outcrop and subsurface study based on eight wells drilled through ~220-250 m of section with typical inter-well spacing of ~400 m (including seismic lines, wireline logs, essentially continuous coring, sandstone petrography, micropalaeontological and palynomorph analyses). Mapping of the Ainsa, and other, deep-marine clastic systems shows the lateral stepwise migration of the fans, as a foreland-propagating clastic wedge. Each fan contains channels, typically 5-30 m deep and hundreds of metres wide (~100-600 m). Each discrete fan and channel is initiate by the development of a mass transport complex (MTC) or mass transport deposit (MTD), typically a pebbly mudstone horizon. By combining the outcrop and subsurface data, it is possible to develop a detailed understanding of the proximal to distal, and axial to lateral, changes in facies associations, the lateral continuity of beds in a proximal setting, and the influence of syn-sedimentary tectonics in controlling fan development. We discuss the interplay between tectonics, eustacy, and basin topography, in driving these depositional systems at time scales from 2-3 million years for the "tectono-stratigraphic units", to hundreds of thousands of years, probably at ~400 ka Milankovitch mode (Ainsa depositional system), with discrete fans, channels and smaller architectural elements at time intervals ranging from in the order of a hundred thousand years to tens of thousands of years and less.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California