Date of Award
Master of Science (MS)
Daniel M. Deocampo
W. Crawford Elliott
Authigenic clays are potential proxies for paleoclimate change when formed under saline conditions. Between 1.9 -1.7 mya, Olduvai was a closed-hydrologic basin into which Al- and Fe- rich detrital clays were transported from surrounding soils. Authigenic Mg-rich smectite formed within the basin due to chemical alteration in alkaline and saline conditions. 40 samples were chosen from a stratigraphic section in the center of the paleolake and analyzed to characterize the geochemical facies of the material using XRD, EMPA, and FTIR. ~70% of samples were Mg-rich with clay d060 XRD peaks between 1.506-1.523Å. EMPA indicated (Al2O3 + Fe2O3)/MgO ratios ranged from 0.2-4.8, 21 had ratios >1.0, indicating higher (Al2O3 + Fe2O3) content. These clay data correlated with bulk XRF data, indicating diagenetic controls on bulk composition. Therefore, bulk geochemistry can potentially indicate paleoclimate change when influenced by Mg-rich phyllosilicate formation.
Simpson, Alexandra M., "Authigenic Clays used as Terrestrial Climate Proxies: Locality 80, Olduvai Gorge, Tanzania." Thesis, Georgia State University, 2016.