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Pau Arbués1, John Gjelberg2, Marta Puig3, Santiago Sánchez-Villanueva3, Cai Puigdefàbregas2, Josep Anton Muñoz3, Mariano Marzo3
(1) University of Barcelona, Barcelona, Spain
(2) Norsk Hydro Research Centre
(3) University of Barcelona, Spain

Abstract: Anatomy and evolution of an intra-slope turbidite system in a foredeep basin: the Ainsa system (Eocene, Spanish Pyrenees)

The Ainsa turbidite system is a slice of the slope fill of a, basin-scale, elongate depression, which was excavated by gravitational collapses and promoted by thrust induced oversteppening. The system is 320 m thick, 8 Km wide, and has a preserved length of 9 Km parallel to NW directed downslope paleoflow. Its geometry is that of an inverted trapezoidal prism and occurs embedded into comparatively thick slope mudstone units. The base corresponds to an angular unconformity, whereas the top and the margins are gradual. The elementary architectural constituents of the system are: 1) sandstone dominated channel fills; 2) channel margin and frontal splay deposits, essentially made of thin sandstone/mudstone beds; and 3) mudstone dominated slump scar fills. The system evolved through two cycles of channel complex development and abandonment. The lower cycle is characterized by two parallel synclinal fairways; both accommodated their own suite of vertically stacked channel fills up to 2 Km wide and 40 m thick. By the upper cycle, the main synclinal conduit recorded deposition along strongly erosive channels that are juxtaposed to the southwest, in agreement with the vergency of the anticlinal divide. Towards the anticline, merely depositional channel fills and channel margin facies prevailed. The resultant sandstone body is a prism up to 5 Km wide and 50 m thick. Prior to the definitive abandonment of the system, a few late channel fills stacked vertically.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana