T167 Exploring Changes in Climate, Flora, and Fauna of Africa through the Cenozoic (Posters)

Tuesday, 17 October 2023
8:00 AM - 5:30 PM
Hall B

PALEOENVIRONMENTAL AND PALEOCLIMATIC RECONSTRUCTION OF A MIDDLE MIOCENE PRIMATE FOSSIL SITE IN WEST TURKANA, KENYA

Paper number: T167-6
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

Abstract

The Turkana Basin of northern Kenya in eastern Africa hosts sedimentary archives that preserve environmental and climatic information critical to understanding hominid evolution. In this study, we analyzed paleosols to reconstruct the paleoenvironment associated with the Esha fossil site (13.8 Ma) in the Lothidok Formation, West Turkana. Paleosols were systematically described from a stratigraphic interval that includes newly discovered ape and monkey fossils. Macroscopic features described in the field include paleosol horizons, structure, Munsell color, mottling, presence of root traces or burrows, grain size, and mineralogy. A total of 19 samples were recovered in the summers of 2022 and 2023 for elemental and isotopic analysis from four different paleosols— two are correlated laterally and directly underlie the new primate fossil layer, and two are stratigraphically higher than the fossil layer. Elemental weathering for each profile was estimated using X-ray fluorescence (XRF) on prepared bulk samples. The random forest proxy for mean annual precipitation (RF-MAP) indicates that precipitation levels at the time of soil development were 500-1000 mm. Similar climate zones across modern Africa support woodland and savanna environments, suggesting that the paleoenvironment of Esha was neither a grassland nor a closed canopy forest. Elevated calcium and sodium oxide concentrations in some samples are attributed to diagenetic zeolitization and calcite cementation, which produce artificially low rainfall estimates compared to unaltered samples. Our ongoing work includes organic carbon stable isotope analysis for paleovegetation reconstruction, and petrographic and mineralogical analysis to better differentiate well preserved versus diagenetically altered samples. These initial results suggest that the Middle Miocene Esha locality was dryer and less forested than Early Miocene localities of the Lothidok Formation in West Turkana.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-394327

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