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Source-to-Sink Study and Grain Size Model of the Escanilla Sediment Routing System, Tremp-Graus and Ainsa Basins, South Central Pyrenees, Spain

Michael, Nikolas *1; Allen, Philip 1; Whittaker, Alexander 1
(1) Earth Sciences and Engineering, Imperial College London, London, United Kingdom.

Understanding how the tectonic controls on accommodation generation affect grain size trends, depositional facies and stratigraphic architecture remains a key challenge for sedimentologists and petreoleum geologists. We tackle this issue using a case study in the Escanilla Formation an upper Eocene clastic sedimentary system, sourced primarily from the Axial Zone of the Pyrenees and deposited in wedge top basins of the South Central Pyrenees. This system consists of a variety of depositional environments from proximal fanglomerates and fluvial deposits to distal slope and deep marine turbidites [1-3]. We focus on the fluvial segment of the sediment routing system. We present a source-to-sink analysis by teleconnecting mountain catchment areas, basin margin fans acting as proximal feeder systems [3-6] and braided river systems of the Escanilla Formation in the Tremp-Graus and Ainsa basins [2].

Within the fluvial segment, distinct point sources for sediment supply to the wedge-top basins existed in the mid-late Eocene. Excellently exposed remnants of these major feeder systems are found in the Pobla de Segur-Gurb and Sis regions close to the southern edge of the Pyrenean Axial Zone. The deposits of the fluvial system are best observed in the Isabena Valley close to Lascuarre, the Viacamp region, and in the southeastern Ainsa Basin. We present new sedimentological data from the Gurb and Viacamp regions in the Tremp-Graus basin and make a correlation panel for the entire fluvial segment. Linkages within the fluvial segment are aided by a range of provenance tools (paleoflow determinations, clast composition data, detrital U/Pb zircon ages and Apatite Fission track data) and palaeomagnetic data[1].

The sediment budget for the Escanilla routing system can be estimated by mapping the fairway of the system and interpolating sediment thicknesses of its constituent units. We model the downsystem trends in grain size [6] in relation to deposited sediment volumes for these time intervals. Our results demonstrate that it is now possible to derive quantitative relationships between the spatial distribution of subsidence, down-system grain size, sediment volume and stratigraphic architecture in this common type of sediment routing system.

1.Beamud et al., 2010, Basin Research

2.Bentham and Burbank 1996,p.144- 152,CUP.

3.Vincent, 2001, Sedimentology.

4.Whittaker et al. 2011, GSA bulletin

5.Whitchurch, et al. in press. Am. J. Science.

6.Duller et al. 2010, JGR

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California