Regional Fault Control of Shelf Margin

Shelf margins of the Middle Mississippian and Upper Pennsylvanian are distinctively developed in southern Kansas.

Interval isopachs were previously mapped for a succession of Upper Pennsylvanian 4th order genetic units (mapped from flooding unit to flooding unit, see maps below). Composite sequences (3rd order Muncie Creek and Nuyaka Creek) were recognized through examination of the stacking pattern along the shelf margin (see well log and regional cross section below).

The 3rd order sequences exhibit a transgressive-regressive behavior whereby initial 4th-order cycles in the composite sequence extend farther landward. Recognized onlap lies beyond study area, but higher sea level at beginning of 3rd order cycle is suggested by abrupt landward migration (10's to 100's of km) of thicker cycles and peritidal lithofacies. This landward shift in lithofacies is paralleled by km-scale backstepping of carbonate shelf margin (see cross section).

 

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