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Three-Dimensional Reconstruction of Growth Strata from Field Data: the Sant Miquel Del Montclar Alluvial System Case Study (SE Ebro Basin, Spain)

Marin, Miquel 1; Caumon, Guillaume 2; Cabrera, Lluís 1; Roca, Eduard 3
1 Dept. Estratigrafia, Paleontologia i Geociències Marines, University of Barcelona, Barcelona, Spain.
2 Gocad Research Group, Institut national polytechnique de Lorraine, Nancy, France.
3 Dept. Geodinàmica i Geofísica, University of Barcelona, Barcelona, Spain.

Three-dimensional (3D) reconstruction of growth strata permits the understanding of the relationships between fold-and-thrust belts and their related basins. Strata deformed by the propagation of a thrust and their related unconformities hold explicit records of fault activity. In addition, it is known that ancient alluvial fan systems may be good hydrocarbon reservoirs.

The Ebro Basin has special relevance for the study of growth strata analogs because of high-quality exposures of growth outcrops. Our study illustrates the case of the Sant Miquel del Montclar Alluvial system, located in the south-eastern margin of the Ebro Basin and deformed by the Paleogene tectonic activity of the Catalan Coastal Ranges (CCR). The map pattern of this system shows a fan-shaped geometry with a basinward lateral passage from proximal massive conglomerates to middle-distal red sandstones and mudstones. Moreover, the erosion allows the lower syn-tectonic units (highly-deformed, even overturned) to be displayed at the surface.

We introduced a field dataset (1:5000 geological mapping and punctual dip data) into the Gocad© earth modeling package. After picking geological contacts and other geomorphological markers on top of a 5-meters-resolution DEM, a tetrahedral 3D mesh was built and the 3D stratigraphy was interpolated using Discrete Smooth Interpolation (DSI). Key horizons are then extracted as isovalues of the stratigraphic property.

Taking into account geometrical constraints derived from field observations, the analysis of our 3D model enables to decipher important aspects about the kinematic evolution of the CCR frontal thrust, as well as sedimentary architectures and thicknesses of the syn-kinematic sequences. Using this geometric model, we discuss the spatial and temporal relationships between sedimentary sequences and Paleogene growing structures in the Ebro Basin.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009