ABSTRACT: The Thermal History of the Arkoma Basin and the Eastern Ouachita Mountains from AFTA (Apatite Fission Track Analysis)

D. C. Arne, I. R. Duddy, P. F. Green

Results of an Apatite Fission Track Analysis (AFTA) study indicate that regional cooling commencing around the middle Cretaceous (^sim100 Ma) has affected both the relatively undeformed Arkoma basin sediments and the folded rocks of the eastern Ouachita Mountains (Benton uplift). Outcropping Pennsylvanian rocks of the Arkoma basin sequence in a section along the Arkansas River between Little Rock and Ozark, Arkansas, as well as Mississippian and older rocks in a section across the Ouachitas between Russellville and Hot Springs, Arkansas, experienced paleotemperatures between about 90 and 110°C immediately prior to middle Cretaceous cooling. Cretaceous intrusive rocks have apatite fission track ages indistinguishable from K-Ar and Rb-Sr ages at about 95 Ma, with mean rack lengths greater than 14 µm indicating rapid cooling from temperatures greater than approximately 110-50°C or less at this time.

AFTA data from Missouri also show evidence of cooling from elevated paleotemperatures during the middle Cretaceous and suggest the possibility of raised thermal gradients (^sim50°C/km). These data emphasize the regional extent of the observed cooling episode, which appears to have involved uplift and erosion of at least 1-2 km of section from across the region since the middle Cretaceous.

Comparison of these results with published vitrinite reflectance data suggests that the Arkoma basin sequence achieved maximum paleotemperatures during late Paleozoic burial, and that paleo- temperatures reached in the Mesozoic, during rifting in the Mississippi Embayment, were of lower magnitude. These observations have important implications for hydrocarbon generation and exploration in the Arkoma basin.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990