Jason R. Cansler¹, Timothy R. Carr¹

(1) University of Kansas, Lawrence, KS

ABSTRACT: Paleogeomorphology of the Pre-Pennsylvanian Unconformity on the Arbuckle Group (Cambrian-Lower Ordovician)

The Pre-Pennsylvanian unconformity is an important control on the distribution of oil and gas in Kansas. Understanding the paleogeomorphology of the erosional surface, the influence of Precambrian structure, and the relationship of karst landform development to pre-existing structure and stratigraphy are components to continued hydrocarbon exploration and production. The karst geomorphology of the Arbuckle Group rocks (Cambrian and Lower Ordovician) was examined at various scales, from regional mapping to core, over the southern extent of the Central Kansas uplift (Barton, Ellsworth, Rice and Stafford counties). Structure and interval isopach maps were produced to reconstruct the paleotopography using abundant well information where the well density in the studied counties exceeds 24 wells per square kilometer. Major karst landform geometries (dolines, and multigenerational karst) were identified and landform development was related to the basement structure of the area. Arbuckle karst erosional features also show the influence of ground-water sapping processes. Scalloped-shaped escarpment edges, stubby U-shaped channels, pirated drainages, and basin head widening on the down-dip side of local highs are characteristic of mature stages of ground-water sapping on the Arbuckle exposure surface. In contrast, up-dip scarp edges are relatively straight and form the divides between drainage basins. Differences in paleogeomorphic patterns are attributed to structural and stratigraphic constraints that determine the relative effectiveness of ground water (sapping) processes. Integration of the core and well data provided a basis to develop a model of reservoir formation and performance within the Arbuckle Group of Kansas, and insight to genesis and geomorphology of large-scale early Paleozoic karst terrains.

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