Orbital Influence on Precipitation, Fire, and Grass Community Composition From 1.87 to 1.38 Ma in the Turkana Basin, Kenya

A 216-meter drill core from the Turkana Basin reveals that orbital forcing significantly influenced precipitation, fire activity, and grass community composition between 1.87 to 1.38 million years ago (Ma). Microcharcoal analysis showed that fire variability correlated with precessional cycles (~21 kyr), linking elevated precipitation to increased landscape fires. Phytolith data indicated alternating dominance of mesic and xeric C4 grasses, also influenced by orbital forcing but mediated by basin geometry. Two high eccentricity intervals at ~1.72 Ma and ~1.50 Ma marked abrupt environmental shifts, with the latter transitioning to a seasonally wet, open landscape dominated by xeric C4 grasses—conditions similar to those when Homo erectus/ergaster fossils were discovered nearby.

Yost, C. L., Lupien, R. L., Beck, C., Feibel, C. S., Archer, S. R., & Cohen, A. S. (2021). Orbital Influence on Precipitation, Fire, and Grass Community Composition From 1.87 to 1.38 Ma in the Turkana Basin, Kenya. Frontiers in Earth Science, 9. https://doi.org/10.3389/feart.2021.568646