Integrated Gravity, Magnetic, Seismic, and Geologic Study of Triassic Riddleville Basin, Georgia

Elizabeth Fisher, Daniel G. Ziegler, C. L. V. Aiken

An integrated approach was taken in assessing the basement configuration of the Riddleville basin, a Triassic rift structure in central Georgia. The basin is within Piedmont metamorphic and igneous rocks and is overlain by a veneer of Cretaceous and younger sediments. Generally, these basins yield poor seismic data, as in this case where much of the seismic energy is absorbed at the Triassic-Cretaceous unconformity and where little velocity contrast exists between the deeper Triassic sediments and basement. The problem is further compounded by large-amplitude gravity and magnetic contrasts caused by intrabasement lithologic changes and by the presence of basic intrusions. Detailed gravity and USGS aeromagnetic surveys were utilized as well as a singular seismic line and s veral nearby wells of which two penetrate basement. The complications were handily resolved by powerful potential field inverse modeling techniques where gravity and magnetic models verified the seismic interpretation. It is shown that the basin has far more sediment than previously conjectured, and bodies that were considered to be shallow are now found to be intrabasement effects. It is also established that the basin consists of a series of tilted fault blocks, each of which displays contrasting stratigraphic sections seismically where one could infer that the sedimentary architecture of the basin was at least partially controlled by the local tectonic regime.

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