Recent Salt Related Uplift and Subsidence at Sour Lake Salt Dome, Hardin County, Texas
K. M. Looff
Geologic Consultant, Lovelady, Texas
Sour Lake is a large piercement salt dome located in southern Hardin County, Texas. Recent deformation of the cellar and wellhead of one of the salt cavern storage wells initiated a geologic investigation into the cause of the deformation and its future impact. Unlike many of the other Gulf Coast salt diapers that have a flat or inclined upper salt surface, the upper surface of the salt at Sour Lake is strongly domed with over 1000 feet of relief. The geologic investigation showed that the diapir has maintained a near-surface position since at least Yegua time and appears to be characterized by a passive or “down building” state of growth. However, the central area of the diapir has been an area of active uplift since late Frio time resulting in a complex graben system forming over the central area of the dome. The cause of a 1929 sinkhole occurrence at Sour Lake was reevaluated and provided the basis for mapping the changes in ground level between 1923 and 1965. These changes in elevation show areas of uplift and subsidence that correspond to the underlying graben system. In addition to being located in the area of active uplift, the storage well experiencing the deformation is also located on a smaller and more active area of salt uplift or a salt spine. Since the late 1960’s, this spine has begun moving and has resulted in the overpressuring of the caprock and adjacent sands. Active salt movement at Sour Lake has also resulted in uplift and extension of the overlying strata and produced surface subsidence.
AAPG Search and Discovery Article #90901©2001 GCAGS, Annual Meeting, Shreveport, Louisiana