Application of Fault-Related Fold Theory to an “Odd Structure”

Paul Genovese
Grizzly Energy Resources, Llc, Columbia Falls, MT

C. W. Tomlinson (“Odd Geologic Structures of Southern Oklahoma,” 1952) observed that Late Paleozoic “Structures of types somewhat unusual for the Mid-Continent region occur in the Ardmore district of Oklahoma.” Despite structural peculiarity, application of fault-related fold theory to a 2D seismic profile can explain the geometry of one of Tomlinson's “odd structures.”

The purpose of this endeavor is not to offer an explanation of interest only to regional geoscientists; rather it is to present a “case study” of how disciplined application of quantitative structural theories can yield a balanced, tractable, kinematically-viable solution that honors well and seismic data…even for “odd” structures. Moreover, the exercise illustrates that rigorous structural solutions can be obtained without the use of expensive specialized software. Indeed, for such a 2D solution, all one needs is data, suitable computer graphics software; and most importantly, a command of applicable structural theories. A stepwise structural solution along a 2D transect is presented, highlighting key observations and decision points, to illustrate utility of fault-related fold theory.

Structural “oddity” of the Ardmore Basin is a product of an Eocambrian rift prehistory followed by punctuated Carboniferous-Permian contraction spanning a continental regressive to transgressive sequence. The Pennsylvanian and Permian growth sediments are well-imaged seismically relative to older Paleozoic strata beneath the pre-Penn unconformity and do not directly betray the complexity of the older deformation. Nonetheless, deformation recorded by growth sediments plus the shape of major unconformities is the key to identifying controlling faults and guides the complete structural solution.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005