Abstract: Lower Campanian Shannon Sandstone (Hartzog Draw): A Template for Regional Correlation

Katherine M. Bergman

Extensive studies of the Shannon Sandstone in the Salt Creek Anticline and Hartzog Draw areas define isolated sand bodies encased in marine mudstones, punctuated by depositional discontinuities. In the absence of core control, correlation based solely on well logs between these areas and with the contemporaneous shoreface deposits at Lucerne is difficult, and depends on interpretive assumptions, particularly in areas of abrupt facies changes. The morphology of the depositional discontinuities and the facies changes across them can be explained by fluctuations of relative sea level, and suggest that the isolated sand bodies are detached lowstand shoreface deposits, truncated by erosional transgressions. The facies and discontinuities at Hartzog Draw can be idealized into a template, wh ch can be used to correlate between Hartzog Draw and Salt Creek Anticline. The template aids in local correlation, and predicts regional correlations in landward and seaward directions. The template helps to identify the bounding discontinuities and the sand bodies contained between these discontinuities. The bounding discontinuities link the isolated sand bodies and the contemporaneous shoreline deposits, and define a stratigraphic basis for the interpretation of the depositional history and relative sea level changes. Six regressions and transgressions have been defined; they suggest that the isolated sand bodies are detached lowstand shoreface deposits controlled by sea level fluctuations, and not shelf ridge complexes.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994