Deformation in Footwall of Clinchport Thrust, Valley and Ridge of Northwest Georgia

William Lee Morris

The footwall of the Clinchport thrust in northwest Georgia contains small-displacement reverse faults, blind thrusts, and related small anticlines involving the Lower Silurian Red Mountain Formation which, because of its erosion resistance, has given rise to a distinctive topographic pattern.

The eastern limb of a large syncline, adjacent to and overridden by the Clinchport thrust, is overturned in places and is faulted throughout its length. Deformation increases with proximity to the Clinchport thrust. Petrographic analyses show twinned carbonate crystals and veinlets in carbonate units and microfaults in sandstone units near the Clinchport thrust, whereas samples from the same horizon 3-5 mi westward, away from the Clinchport thrust, have no similar features.

Smaller scale anticlines adjacent to the Clinchport thrust are superimposed on the eastern limb of the major syncline. Thin-skinned tectonic interpretation and unique fold axial directions support their origin by blind thrusting. Some of these anticlines are faulted by small-displacement reverse faults, which are prevalent in the footwall along the length of the Clinchport thrust. All features are interpreted as having formed in the footwall during a single deformational event as a response to continued movement on the Clinchport thrust plane.

This type of footwall deformation probably exists adjacent to other Valley and Ridge thrusts. The presence of the Clinchport thrust near the highly resistant Red Mountain Formation results in topographic relief which makes the structure discernible.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.