The Influence of Tectonics on Temporal and Spatial Variations in Sandbody Architecture; Cretaceous Gosau Basin, Western Calcareous Alps, Austria

Paton, Douglas¹, Mary Carr², Hugo Ortner³, Robert Amerman², Jamers Borer⁴, Piret Plink-Bjorklund², David, R. Pyles², Bruce Trudgill², Richard J. Wild⁵ (1) Colorado School of Mines, Golden, CO (2) Colorado School of Mines, (3) University of Innsbruck, Innsbruck, Austria (4) El Paso Corporation, Denver, CO (5) Chevron ETC, Houston, TX

The Cretaceous Gosau deep water basin, western Austria, provides an exceptional example of syn-depositional structural influence on sandbody architecture. Significant variations in sandbody architecture are observed in both proximal to distal and axis to margin settings; these can be attributed to the basin's structural configuration. The west of the basin (proximal) is structurally confined and characterized by amalgamated coarse-grained channels. In contrast, structural deformation increases towards the east (distal) generating significantly greater accommodation space that results in both a deepening of the basin and an increase in basin width (from ~ 0.5 to 3 km). There is a corresponding change in strata to repetitive couplets of high-aspect ratio lobeform conglomeratic Mass Transport Complexes (MTCs) overlain by thinly bedded turbidites. The axis to margin variation is most pronounced in the medial portion of the basin where superb exposure of progressive rotation of strata is associated with structural growth of the basin margin fold. Immediately adjacent to the growth fold the basin fill is dominated by re-mobilized coarse grained facies and MTCs (~ 90 % of gross stratigraphy). Coeval strata in the axis are more finely bedded turbidites (coarser grained facies ~ 30 % of gross stratigraphy). The basin axis migrates to the north away from the deforming basin margin through time; this reflects progressive growth on the southern confining structure.

The Gosau Basin, therefore, provides a setting with a demonstrable structural control; in addition the effect of variations in the style of deformation on sandbody architecture and stratigraphy can be ascertained.