Structures of types somewhat unusual for the Mid-Continent region which occur in the Ardmore district of Oklahoma include the following.

Pseudo-plastic folding, with extensive axial thickening of major shale sections.

Synclines much deeper than the stratigraphic thickness of their enclosed sediments.

Fan folds, with both limbs locally overturned.

"Rabbit-ears" anticlinoria, in which lateral anticlines paralleling the central arch may be very sharp in shallow sediments which unconformably overlie truncated shales dipping away from the central fold, but may have no reflection in the more competent rocks beneath those shales.

Hinge faults along which stratigraphic displacement varies in a very short distance.

Steep faults which are normal along part of their length, reverse at another part.

A "propeller" fault, warped into thrust position in opposite directions along different parts of its trace.

Horst-grabens: fault blocks which toward one end are higher, toward the other end lower, than the bordering masses on either side.

The writer regards all these features as results of regional crustal compression.