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AAPG Bulletin

Abstract


Volume: 76 (1992)

Issue: 3. (March)

First Page: 392

Last Page: 402

Title: Evidence from Apatite Fission-Track Analysis for Regional Cretaceous Cooling in the Ouachita Mountain Fold Belt and Arkoma Basin of Arkansas: Geologic Note (1)

Author(s): DENNIS C. ARNE (2)

Abstract:

A reconnaissance study involving apatite fission-track analysis of surface Paleozoic sedimentary and Cretaceous intrusive rocks was undertaken to evaluate the low-temperature thermal history of the Ouachita Mountain fold belt and Arkoma basin of Arkansas. Paleozoic rocks have apparent apatite-fission-track ages ranging from 184 + or - 12 Ma to 95 + or - 11 Ma with mean track lengths in the range of 12.95 + or - 0.17 micrometers to 13.51 + or - 0.13 micrometers, indicating that these samples have undergone significant postdepositional annealing. Cretaceous samples have apatite fission-track ages between 104 + or - 4 and 88 + or - 6 Ma that are concordant with Rb-Sr and K-Ar ages, and mean track lengths in the range 14.69 + or - 0.16 micrometers to 15.36 + or - 0.10 microme ers, indicating that these rocks cooled rapidly to paleotemperatures below 50-60 degrees C following their emplacement and have subsequently remained cool.

Paleozoic strata of the Ouachita Mountain fold belt and Arkoma basin in Arkansas are inferred to have undergone regional cooling from paleotemperatures greater than 110 degrees C beginning in the Early Cretaceous to paleotemperatures generally less than 80-90 degrees C prior to the intrusion of alkaline plutons along the western margin of the Mississippi embayment during the middle Cretaceous. Whether regional cooling during the Cretaceous was caused by uplift and erosion or whether a dramatic reduction in the paleogeothermal gradient was involved remains uncertain, although a significant component of uplift and erosion is inferred from independent geological observations. The results of this study indicate that Paleozoic rocks of the Ouachita Mountain fold belt and Arkoma basin of Ar ansas were exposed to maximum paleotemperatures during late Paleozoic burial, prior to the emplacement of Cretaceous plutons in the region.

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