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

PALEOSOL CORE-LATIONS AND STABLE ISOTOPES IN THE EASTERN AFRICAN RIFT

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

Authors

Abstract

Baringo Basin, Kenya is located within the East African Rift and preserves the most continuous record of fossiliferous Neogene strata in equatorial Eastern Africa. The BTB13 sediment core was drilled in the Baringo Basin through 222.6 meters of the Pliocene-Pleistocene Chemeron Formation dated from 3.29 Ma to 2.56 Ma. The mid-Pliocene Warming Period (mPWP), an important analogue for modern climate change, occurred from 3.26 to 2.95 Ma. Major Northern Hemisphere Glaciation (NHG) began shortly afterward at 2.7Ma. These units consist of alternating lacustrine and fluvial units, with paleosol units composing 57% of the core length. Pedogenic carbonates (δ13CPC) from these paleosols are used to track environmental changes through changes in vegetation (C3 vs. C4 plants) and fractional woody cover (fwc). Values of fwc >0.8 indicate predominantly C3 closed settings, while values <0.2 indicate predominantly C4 open settings. These preliminary results indicate an overall decrease in woody cover in the Baringo Basin from 3.4 to 2.7 Ma. The Baringo Basin was a shrubland (fwc= 0.4 to 0.8) from 3.26 to 3.22 Ma, a wooded grassland (fwc= 0.1 to 0.4) from 3.22 to 2.84 Ma, and a dominantly C4 grassland from 2.84 to 2.7 Ma. These transitions in the vegetation appear to correlate with the onset of the mPWP, mPWP intensification, and transition toward NHG respectively. A rapid spike in fwc to shrubland vegetation from 2.7 to 2.6 Ma, before a return to wooded grassland from 2.6 to 2.58 Ma, may be related to the onset of Northern Hemispheric Glaciation. A steep dip in woody cover can be observed at 3.1 Ma that correlates to a known decline in CO2. Previous applications of fractional woody cover in the East African Rift (Lake Turkana and Awash Valley) show similar transitions with marginally higher fwc values. δ18OPC values from BTB13 (-1‰ to -15‰) are more varied than values previously observed in the Baringo Basin (-4‰ to -8‰) and other East African Rift sites. Future research will focus on using clumped isotopes (Δ47) to refine the effects of temperature on δ18OPC fractionation in these pedogenic carbonates.

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

doi: 10.1130/abs/2023AM-394198

© Copyright 2023 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.