Abstract

Wrench faulting to explain the Permian basin structures was first promulgated by John M. Hills (1963, 1970). At that time he knew that he had not presented positive proof of wrenching, and he only considered it a working hypothesis. Unfortunately, over the years, this has become the dogma, and geologists today no longer consider it necessary to further validate his hypothesis.

New discoveries in the field of plate tectonics and structural mechanics have revolutionized the entire field of structural geology, and few old structural ideas have remained intact through this revolution.

This paper discusses the use of those tools to make a structural analysis of the Permian basin. The greatest advance has been in understanding thermal deformation. That is possible because we now have a satisfactory earth model. A study of the field evidence indicates that a single thermal event, analagous to that occuring in northern New Mexico today, can explain almost all the structural phenomena; no external stress system is necessary to form the structures. During the period of high heat flow, the crust bulged, dilated, and failed along pre-existing lines of weakness. However, most of the differential vertical movement we map today is related to the cooling and contracting cycle that continued throughout the Permian. It also explains why old structures can be located by mapping the young rocks.