Print this pageOfflap Profile of Cyclic Mixed Lithofacies and Comparison with Computer Simulations, Late Permian, Guadalupe Mountains, Southern New Mexico
OSLEGER, DAVID A.
A detailed transect of seismic-scale, laterally continuous, dip-oriented exposures of the Yates Formation in Slaughter Canyon in the Guadalupe Mountains permits the quantification of several depositional variables such as progradation aggradation ratios, offlap angles, platform progradation rates, accumulation rates per platform position, and a range of sea-level amplitudes. The Yates consists of four complete depositional sequences and the lower half of a fifth sequence that continues into the overlying Tansill Formation. Within each individual sequence of the Yates, the depositional profile flattens from 10-12 degrees early in each sequence to 1-2 degrees along each upper sequence boundary. During overall Yates deposition in the study area, almost 200 m of cumulative aggradation occurred at a position 2 km from the contact of the uppermost Yates with the Capitan reef for a long-term growth angle of approx. 5.5 degrees. The progradation:aggradation ratio increases upward with each successive sequence of the Yates, yielding systematically decreasing apparent angles of offlap from +1.2 degrees for the earliest sequence to +0.3 degrees for the latest full sequence.
Comparison of depositional variables measured from field observations with values predicted from published computer simulations of the Yates reveal a reasonable degree of corroboration. Porosity and permeability measurements determined from core plugs of field samples provide an additional scale of information, linking together the seismic-scale geometries with the pore-scale attributes of the component lithofacies. This integrated field and petrophysical study will ultimately contribute toward improved visualization of the two-dimensional architecture of mixed carbonate-siliciclastic reservoirs and component fluid flow pathways.