ENIGMATIC STRUCTURE OF THE SOUTH FLANK OF THE WICHITA UPLIFT

Major structures in the southwest-central part of the North American continent are mainly compressional, and of Late Paleozoic age. The style of deformation is similar to that of the Laramide foreland of the northern Rocky Mountains. The Wichita - Amarillo Uplift is one of the larger structures of the region. It is generally agreed that the uplift is bounded on the north by a south-dipping, basement-rooted thrust fault. However, the structure of the south flank of the uplift is less well-understood, and interpretations vary.

Study of single-fold seismic records in the 1960s resulted in the interpretation of the Burch Fault as a down-to-the-south normal fault. Related faults were interpreted as normal faults as well. However, no subsequent published interpretation has been in agreement with that work.

Subsequent authors:

a) Have been noncommittal, showing all faults as vertical faults.

b) Have shown tectonic diagrams with a north-dipping reverse fault, but without a structure section to illustrate how that may occur.

c) Have interpreted the Burch Fault a north-dipping reverse fault (difficult to do in light of the previously published seismic profiles).

d) Have shown faults with “nature undetermined” on a map, but declared in text that both north and south boundaries (of the Wichita Uplift) are “ . . . probably reverse faults.”

The ambiguities can be resolved by a reverse (backthrust) fault at depth, with antithetic normal faults at shallower depths, on the south flank of the Wichita Uplift. However, no published geological or geophysical studies resolve the enigma entirely. What is the structure of the south flank of the Wichita Uplift?