Three Orders of Depositional Cyclicity Within the Cherry Canyon Formation, Dimmitt Field, Delaware Basin, West Texas

Thomas R. Loftin Jr.

Deepwater sedimentary units of the Cherry Canyon Formation were deposited during Permian (Guadalupian) time in the Delaware Basin, a shallow, semi-restricted, epicontinental sea. This formation is composed of fine-grained sandstones, siltstones, basinal carbonates, and organic rich, fine-grained siltstones deposited in submarine fan systems. The study was undertaken to define limits on subsurface interpretations of submarine fan architecture in this basin and to produce a model for application to similar deposits. The DB-03 well, drilled by Gulf Research and Development Company in 1985, was the primary data base for this work.

In this study, three orders of depositional building blocks could be defined and their stacking patterns documented. "Subcycles" are small-scale coarsening-upward packages likely produced by short-term depositional processes. "Cycles" are intermediate order building blocks, bound by periods of sediment starvation. Approximately 30 of these "cycles" were developed during the nearly three million year time frame of Cherry Canyon deposition. Based on lithologic stacking patterns, "cycles" are best interpreted as representing relative sea-level change with an ~100,000 year cyclicity (fifth-order). This cyclicity was tested using time series analysis of gamma ray and sonic logs. Potential reservoir sandstones are isolated within "cycles" and vary in lateral extent. "Supercycles," coarsenin - or fining-upward packages of several "cycles", represent longer term relative sea-level variation.

The resulting depositional model is strongly linked to a sequence stratigraphic framework and is useful for predicting sandstone distribution in deepwater deposits from similar environmental settings.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995