--> Effects of Diagenesis on the Geochemistry of Pedogenic Carbonates: Implications of Using Paleosols for Paleoclimatological and Paleoenvironmental Reconstructions, by P. Deutz, I. P. Montanez, G. H. Mack, and H. C. Monger; #90986 (1994).

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Abstract: Effects of Diagenesis on the Geochemistry of Pedogenic Carbonates: Implications of Using Paleosols for Paleoclimatological and Paleoenvironmental Reconstructions

Pauline Deutz, Isabel P. Montanez, Greg H. Mack, H. Curtis Monger

Many recent studies have utilized stable isotope values from paleosol carbonates to make paleoclimatological and paleoenvironmental reconstructions. These studies, however, typically overlook the potential effects of diagenesis. Recent documentation of low magnesium calcite recrystallization suggests that stable isotope values and trace element concentrations of paleosol carbonates may reflect the composition of diagenetic fluids, rather than the physio-chemical conditions that governed pedogenesis. This study of pedogenic carbonates from soils and Pliocene-Pleistocene, Cretaceous and Permian paleosols developed in non-calcareous terrestrial deposits in southern New Mexico investigates the effects of diagenetic modification on the textural and geochemical composition of paleosol carbo ates, and addresses the implication of chemical alteration on the use of their geochemical composition for paleoclimatological and paleoenvironmental reconstructions.

Plane light, cathodoluminescent, and epi-fluorescent petrography and scanning electron microscopy suggest that the textures associated with pedogenic carbonates in soils may not be preserved in all paleosols. Paleosol carbonates exhibit textural heterogeneity on a micron scale, characterized by neomorphic textures and complex luminescence. Silicification of pedogenic carbonates and association with ferroan calcites records exposure to a burial fluids. Preliminary data indicate that geochemical heterogeneities are consistent with the scale of textural variations. These variations are typically beyond the resolution of standard geochemical sampling techniques, implying that "whole rock" and microsamples may yield homogenized values, which do not record the conditions of precipitation. T is study indicates the need for high resolution studies addressing the post-pedogenic history of paleosol carbonates prior to applying their geochemical compositions to paleoclimatological and paleoenvironmental reconstructions.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994