Ground Penetrating Radar and Outcrop Interpretation of Achitecturally Complex Carbonate Platforms: Analogs for Deciphering Seismic Profiles

Leonardo Piccoli and J. A. Toni Simo
University of Wiscosin, Madison, WI

The Hueco Canyon Formation (Lower Permian) in west Texas is characterized by highly complex internal architectures and rapid facies offsets. Ground penetrating radar surveys (GPR, 25 and 50 MHz with penetration depths of >50 m), photo-panorama and meter-scale outcrop descriptions are integrated to establish the geometries of bounding discontinuities and facies distribution. The result is the recognition of six geomorphological facies associations (bioclastic shoals, Tubiphytes mounds, fusulinid-crinoid shoals, Phylloid mounds, bioclastic (grain-prone) tabular wedges and bioclastic (micrite) prone tabular wedges) that have been assigned to depositional environments and cycle set systems tracts, and three types of bounding surfaces (cycle set boundaries, regressive surfaces of marine erosion and maximum flooding surfaces). The facies are grouped into two GPR facies geometry: a) large-scale mounded packages volumetrically dominated by mounds and shoals and b) large-scale clinoformal packages dominated by tabular wedges and always underlying mounded packages. Bounding surfaces perpetuate mounded and clinoformal geometries. This two-fold geometry bridges the gap with seismic-scale observations; seismic shows clinoformal and mounded geometries as the two major geomorphological seismic facies, with clinoforms underlying mounds. This suggests self-similarity between outcrop-scale patterns and seismic-scale geometries even though they are 1 or 2 orders of magnitude different. The comparison can be used to speculate on the internal distribution of rock types, depositional and sequence stratigraphic interpretations at the seismic scale. Regardless of their dimensions, we propose to rename carbonate platforms sharing a two-fold geometric pattern and a similar geologic origin as clino-mounded platforms replacing the classical rimmed shelf and ramp classifications.