2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 3
Presentation Time: 8:00 AM-4:45 PM

Hydrologic Controls on the Distribution of Authigenic Minerals In the Plio-Pleistocene Lake Tecopa Beds, Southeastern California, USA

LARSEN, Daniel, Department of Earth Sciences, University of Memphis, Rm 1 Johnson Hall, Memphis, TN 38152, dlarsen@memphis.edu

The distribution of authigenic silicate minerals in the Plio-Pleistocene Lake Tecopa Beds in southeastern California is controlled by several factors, including sediment composition, pore-water chemistry evolution, lake level, and basin hydrology. Recent evaluation of conceptual models describing the primary controls on authigenic mineral composition and distribution in the central part of the basin indicate that basin hydrology plays an important role. The hydrologic processes principally involved are thought to be free convection during low- and intermediate-lake stands and vertical migration of the central brine body during long-term lake level change. The effect of these processes within the central part of the Lake Tecopa is replacement of primary and early-formed authigenic silicate minerals by potassium feldspar, illite, and searlesite, presumably by interaction with a potassic chloride-rich brine. The general hydrologic conditions favoring free convection in the Tecopa Basin are presented as well as the more broad application of basin hydrology in understanding authigenic silicate mineral distributions in saline, alkaline lake deposits.