Ian R. Duddy, Andrew J. W. Gleadow, Paul F. Green, Kerry A. Hegarty, Susan A. Marshallsea, Peter R. Tingate, John F. Lovering
A record of thermal history in sedimentary basins improves estimates of hydrocarbon potential and provides critical constraints required to test basin models. AFTA is a unique and powerful method designed to quantitatively evaluate the temporal variation of temperature at any horizon in a sedimentary column. AFTA uses the annealing characteristics of fission tracks to unveil the magnitude and timing of temperature variations below 130°C. To illustrate the versatility of the AFTA technique, we have selected results from several different tectonic settings. As part of an ongoing series of basin studies around the world, we present analyses from both extensional and foreland basinal types, tectonic settings where most of the world's oil and gas are found.
The Bowen and Amadeus basins (Australia) and northern Appalachian basins are selected as example of compressional basins where AFTA has provided new insight in identifying the timing of tectonic events and thermal history. Fission track data from the Bowen basin shows a strong correlation with vitrinite reflectance values and points to a two-phase thermal history where elevated temperatures peaked in the Early Cretaceous followed by a prolonged cooling phase. Results from the Amadeus basin indicate that the cessation of uplift and compression associated with the Alice Springs orogeny did not occur until at least 260 Ma, much younger than previously suggested by other workers. Apparent apatite ages from Devonian sediments in the northern Appalachian basin are consistent with a Cretaceo s or Late Jurassic uplift. This uplift event, which has not previously been recognized, delimits the end of oil generation.
AFTA results from two extensional terrains and environs in southeast Australia, the Otway and Gippsland basins, show that the time of maximum heat flow is about 95 Ma (approximately the age of breakup along the southern margin) and are used to constrain thermomechanical models of extensional basin formation and to estimate the maturation history of the sediments.
AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.