Paleoenvironmental Reconstruction of the Turkana Basin through pedogenic
carbonate analyses (1.9 to 1.2 Ma)
Abstract
Eastern Africa contains a well-preserved pedogenic carbonate record,
useful for contextualizing the paleoenvironment associated with key
fossil and archeological evidence. One significant paleoanthropological
discovery from the Turkana Basin in Kenya was Nariokotome Boy, one of
the most complete examples of Homo erectus discovered to date. This site
is directly associated with a paleo-Vertisol and the Natoo tuff,
enabling stratigraphic correlation into outcrop records. Leveraging this
opportunity, we analyzed stable isotopes of pedogenic carbonates (n=74)
to study the paleoenvironmental conditions in the Turkana Basin for
three time slices between 1.9 and 1.2 Ma. We interpret that the narrow
range of δ18O values implies the presence of one main water source
throughout the time interval. Variation in δ13C, with a standard
deviation of 1.5‰ and range of 6.9‰, can thus be considered a function
of landscape heterogeneity rather than changing water source. Woody
cover estimates from the paleosols within this study interval suggest
this area was a wooded grassland despite a significant first-order
paleoenvironmental change from a marginal lacustrine environment to a
fluvially-dominated one. While our record cannot resolve variability on
a millennial scale, the lack of significant long term trends in percent
woody cover suggest that Nariokotome Boy and other hominin communities
inhabited a paleoenvironment which was relatively stable in terms of
vegetation composition despite a major lacustrine regression.