Govert J.A. Buijs¹, Robert H. Goldstein¹

(1) University of Kansas, Lawrence, KS

ABSTRACT: Climatic and Sequence Architectural Controls on Diagenesis of Permo-Carboniferous Carbonates, Hugoton Embayment, Western Kansas

Many Permo-Carboniferous carbonate reservoirs from western Kansas were deposited during sea-level falls and are directly overlain by fine-siliciclastic intervals. The tops of most carbonates lack paleosol or paleokarst horizons, but the overlying siliciclastics contain peds, horizonation, root molds, and calcareous nodules indicative of paleosols.

The diagenesis of many of the carbonates is dominated by post-compactional phases consisting of calcite, dolomite, quartz and anhydrite cements that can be correlated across many cycles. Less abundant pre-compactional features consist of marine phases like micritic rims and isopachous fibrous calcite rims, but early meteoric cements are unusual. The lack of meteoric cementation might suggest that the duration of subaerial exposure on limestones was too short for significant cementation. Early influx of fine siliciclastics may have prevented percolation of meteoric water to underlying limestones. This model suggests that carbonate reservoirs farther from sources of siliciclastics may be more likely to show intense meteoric diagenesis. This is contrary to many predictive models in which carbonates are expected to show more intense meteoric diagenesis in upslope areas.

The dominant diagenesis in these cycles is closely related to increasing aridity from Pennsylvanian to Permian. Fluid inclusions and petrographic data in late-stage calcite and dolomite cements indicate that this increased aridity resulted in major events of brine reflux. Ultimately, the diagenesis of the Permo-Carboniferous carbonates of western Kansas is controlled by distance from source of siliciclastic sediments and climate. Similar mixed cycles elsewhere in the world may have responded similarly.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado