152 Integrating 20 Years of Scientific Drilling in the East African-Syrian Rift: A Session In Honor of Andrew Cohen (Posters)

Continental drilling extending from the East African Rift into western Asia has yielded transformative discoveries, altering our understanding of paleoenvironments, paleoclimatology, paleoecology, and paleoanthropology. This session, in honor of Andrew Cohen, will celebrate these successes and define new directions.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Common Ground: Understanding Changes in Paleoclimate using a Multi-Proxy Paleosol Approach in Baringo Basin, Kenya

Paper number: 152-1
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Early hominins relied on lake margin paleoenvironments in the Eastern African Rift for food, water, and habitat. The Eastern African Monsoon provides ~70% of the region’s annual precipitation and rift lakes are highly sensitive to changes in precipitation. Understanding changes in water availability is important for recognizing the impact of climate change for early hominins and modern humans affected by anthropogenic climate change. A sediment core (HSPDP-BTB-13, 3.29-2.56 Ma) was drilled in Baringo Basin, Kenya, through the Pliocene-Pleistocene Chemeron Formation and includes the mid-Pliocene Warming Period (mPWP; 3.25-2.95 Ma) and the onset of global cooling leading to Northern Hemisphere Glaciation (NHG; ~2.75 Ma). 

Paleosols (n=78) compose 57% of HSPDP-BTB-13 and are intercalated between lacustrine, fluvial, alluvial, and tephra units. Most of these paleosols are weakly to moderately developed and many contain pedogenic carbonates, which were used for stable isotope analyses to reconstruct woody cover (δ13CPC), paleoprecipitation (δ18OPC), and paleotemperature (Δ47). Paleosol B-horizons and parent material samples (n=98) were sampled to examine changes in maturity and bulk mineralogy through time. Maturity was quantified using a paleosol maturity index based on soil characteristics such as horizonation, bioturbation, and degree of carbonate development, and mineralogy was analyzed using X-Ray Diffraction (XRD). These paleosols are interpreted to be paleo-Entisols, Inceptisols, or Vertisols. The δ18OPC values of carbonates from well-developed paleo-Vertisols at the base of the core suggest that precipitation from the Eastern African Monsoon decreased during the mPWP, which is supported by increased abundance of vertic features that indicate increased seasonality. The paleosols consist of mainly feldspathic minerals and clay minerals, as well as quartz, zeolites, and carbonate. Older paleosols in the mPWP contain more quartz and less feldspar, with more abundant feldspars in the younger paleosols during the onset of the NHG. Isotope analyses during the mPWP coeval increases in temperature, precipitation, and C3 plant coverage, while feldspar abundance decreased. Increased weathering of less resistant  feldspars, which weather to clay minerals supports our interpretation of increased Eastern African Monsoon precipitation. Future XRD work will focus on identifying the clay minerals. This multi-proxy study indicates that the paleoclimate in the Baringo Basin was highly dynamic and suggests both short- and long-term changes in hominin habitats.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-414436

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