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Kansas Geological Survey, Lawrence, Kansas 66047

Abstract: Regional Stratigraphic Analysis of A Pennsylvanian Carbonate Shelf and Margin in Kansas

A 220 mile (354 km) cross-section through the Upper Pennsylvanian section from west-central to south-central Kansas was produced using computer techniques. The section crosses a carbonate-dominated shelf of the Virgilian and Missourian Series in south-central Kansas that borders the Anadarko Basin. Correlations are resolved to 0.5 ft (15 cm) over distances of many miles. User control provided by correlation of cyclothemic-scale genetic units. High-resolution petrophysical correlations are then defined by computer procedures. Stratal units resolved in this study include: 1) longer-term sets of cyclothemic-scale genetic units (10s to 100s of meters), 2) cyclothemic-scale genetic units (10s of meters), and 3) stratal elements within genetic units (meter-scale).

The computer method establishes stratal elements within a lithofacies and between contrasting lithologies: genetic units showing classic onlap, offlap, and toplap relationships. Gaps in correlation between wells and use of false coloring further emphasize stratal relationships. The resulting stacking patterns dramatically increase our resolution of relative sea-level history and lead to improved predictive models.

Although local controls are important in lithofacies distribution, results suggest allogenic controls influence distinct stratal elements as small as meter by km size. Such stratal units have been well established by outcrop and seismic investigations, but have been difficult to substantiate from wireline logs.

Abrupt variations in sediment accumulation occur along km-sized regions reflecting differential subsidence along basement heterogeneities. Distribution of favorable reservoir properties and petroleum production appears to be linked to these features. This approach should help focus exploration efforts.

AAPG Search and Discovery Article #90921©1999 AAPG Mid-Continent Section Meeting, Wichita, Kansas