ABSTRACT

The Council Grove Group (Lower Permian) in Grant and Haskell Counties, Kansas, represents a series of shallowing-upward carbonate cycles each of which is capped by terrigenous clastic red beds. There is a direct relationship between original depositional lithofacies and favorable reservoir properties. The carbonate packstone lithofacies has good porosity (17 percent maximum and 8 percent average) and permeability (average 84 md), whereas the red bed siltstones are tight.

In ascending order, Council Grove cycles and interpreted depositional environments consist of: (a) mixed skeletal fragment, algal packstone of a shallow-water open-shelf lagoon environment, (b) silty, sparsely skeletal wackestone to mudstone, intertidal, (c) dolomitic, silty, sparsely skeletal wackestone to mudstone, intertidal, (d) dolomitic, stromatolitic boundstone, supratidal, (e) sparsely skeletal, calcareous siltstone to shale, supratidal, and (f) calcareous, hematitic, quartz siltstone to shale, subaerial.

Nodular anhydrite is found throughout the Council Grove section, suggesting that eogenetic subaerial exposure was a frequent phenomenon.