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A Comprehensive Classification Scheme for the Mass Transport Deposits in the Ainsa Slope Complex, Southern Pyrenees, Spain

Pau Arbués1, Oriol Falivene1, Oscar Fernandez2, Mariano Marzo1, and Josep Anton Muñoz1
1 Universitat de Barcelona, Barcelona, Spain
2 Midland Valley Exploration, Glasgow, United Kingdom

The Ainsa slope complex developed in a foredeep to piggy back setting. It is mostly expressed as thin-bedded mudstones, but includes also turbidite systems expressed as coarser-grained sediments deposited from turbidity currents and a variety of mass-transport deposits (MTD's). Siliciclastic MTD's include slumps and debris flows. Slumps are mostly composed of thin-bedded slope mudstone. Some moved down the main basin axis, others travelled from the active slope margin and invaded the main basin axis occupied by turbidite deposition. Slumping had a double effect on turbidite sandstone distribution: substraction of previously deposited turbidite sandstone, and creation of topography preventing deposition of sand from turbidity currents. Debris flows can be sandstone-dominated or mudstone-dominated and in general include gravel-sized clasts. They are the resedimentation product of the coarsest-grained turbidites and mud plugs formerly deposited within the confines of erosional channels. Carbonate MTD's are those in which the majority of clasts derive from penecontemporaneous carbonate shelf or slope. For most cases they are debris flows that were deposited towards the foreland margin of the basin. In other cases, they were deposited on the flanks of active intrabasinal anticlines. The largest accumulations of MTD's overlie basinwide unconformities that formed during one episode of thrust-driven basin reorganization.