δ13C records from fish fossils as paleo-indicators of ecosystem responses to lake levels in the Plio-Pleistocene lakes of Tugen Hills, Kenya

High‐Latitude, Indian Ocean, and Orbital Influences on Eastern African Hydroclimate Across the Plio‐Pleistocene Boundary

“…Assuming little temperature or elevation change in the late Pliocene Baringo Basin, variations in moisture source (i.e., Congo vs. IO) are the only other plausible driver of δ 2 H H2O change (Levin et al., 2009; Tierney et al., 2011), but the strong positive correlation and in‐phase spectral coherence of δ 2 H C31 values and MS (Figure S4a in Supporting Information ) suggest that deuterium‐depleted rainfall is indeed associated with higher erosion and runoff. The δ 2 H C31 changepoint at 3 Ma also coincides with the first appearance of diatomites (Westover et al., 2021) and fish fossils (Billingsley et al., 2021) and thus deeper lakes in the region. These physical proxies should be insensitive to δ 2 H H2O change; this implies that enhanced precipitation drove fluctuations in lake levels, and therefore that δ 2 H C31 values are a robust indicator of rainfall amount and actual changes in the local water budget.…”

“…Based on paleoecological proxies such as biomarker δ 13 C C28 values (Lupien et al., 2019) and phytolith ratios (Yost et al., 2021), C 4 grasses increased relative to forest by 3.05–3 Ma. Ichthyolites (Billingsley et al., 2021) and diatomite strata (Westover et al., 2021) increase in abundance between 3.04 and 2.95, indicating lake highstands favorable to diatoms and fish; diatom assemblages (Kingston et al., 2007; Westover et al., 2021) and fish fossil δ 13 C values (Billingsley et al., 2021) are both characteristic of deep lacustrine environments. Alternating diatomites and analcime‐bearing sedimentary strata diagnostic of alkaline, highly‐evaporated brines imply repeated and abrupt wet‐dry transitions from 2.99 Ma onwards (Minkara, 2017).…”