--> ABSTRACT: Determination of Paleoheat Flux from Pollen Translucency Data, by I. Lerche and T. McKenna; #91038 (2010)

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Determination of Paleoheat Flux from Pollen Translucency Data

I. Lerche, T. McKenna

We show that pollen translucency with depth can be used as a quantitative tool to determine, by inversion, the thermal history of sedimentary sequences. The overall trend of translucency is a decrease with increasing depth.

Three neighboring wells in southwest Louisiana were examined, each having carya (a pollen taxa) translucency measurements with depth and one of the wells containing measurements of vitrinite reflectance with depth. High sedimentation rates (300 ft/m.y. of shale) require the use of a one-dimensional fluid flow/compaction burial history program linked with the carya inversion algorithm. Thermal history is estimated by the interaction of a heat flow taken to be linear in time and a time-temperature integral for the inversion of carya translucency. The former involves, ß, a linear heat-flow coefficient to be determined, while the latter involves two previously unknown constants: Tc, a critical temperature, below which the translucency is stable, and TD, a scali g constant, roughly analogous to a doubling temperature. Grid searches for an acceptable solution in Tc vs. TD vs. ß space were conducted independently for each of the three wells to determine the best TD, Tc, and ß. A goodness of fit criterion, contoured in TD vs. Tc vs. ß space, defines a volume of solution families within fixed error limits. Estimates of TD = 75K ± 30 and Tc = 290K ± 20 for the taxa carya are consistent for all of the wells. Acceptable ß ranges, determined by the carya inversion, overlap for the neighboring wells; and the ranges are consistent with ß, determined by the independent inversion of vitrinite reflectance in one of the wells.

We conclude that carya translucency can be used as a quantitative thermal indicator. Application of the inverse method to translucency measurements on other palynomorphs having longer, or different, age ranges than the Eocene-Holocene lifetime for carya is recommended.

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