Evidence for rapid faunal change in the early Miocene of East Africa based on revised biostratigraphic and radiometric dating of Bukwa, Uganda
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Human Evolution
Abstract
Field expeditions to Bukwa in the late 1960s and early 1970s established that the
site had a small but diverse early Miocene fauna, including the catarrhine primate
Limnopithecus legetet. Initial potassium-argon radiometric dating indicated that Bukwa
was 22 Ma, making it the oldest of the East African early Miocene fossil localities known
at the time. In contrast, the fauna collected from Bukwa was similar to other fossil
localities in the region that were several million years younger. This discrepancy was
never resolved, and due to the paucity of primate remains at the site, little subsequent
research took place.
We collected new fossils at Bukwa, reanalyzed the existing fossil collections, and
provided new radiometric dating. 40Ar/39Ar incremental heating ages on lavas bracketing
the site indicate that the Bukwa fossils were deposited ~19 Ma, roughly 3 Ma younger
than the original radiometric age. Our radiometric dating results are corroborated by a
thorough reanalysis of the faunal assemblage. Bukwa shares taxa with both
stratigraphically older localities (Tinderet, Napak) and with stratigraphically younger
localities (Kisingiri, Turkana Basin) perfectly corresponding to our revised radiometric
age.
This revised age for Bukwa is important because it indicates that significant
faunal turnover may have occurred in East Africa between 20 and 19 Ma. Bukwa
samples immigrant taxa such as large suids, large ruminants, and ochotonids that are
absent from stratigraphically older but well-sampled localities in the region, such as
Tinderet (~20 Ma) and Napak (20 Ma). Further age refinements for Bukwa and the
entire East African early Miocene sequence will help to constrain the timing of this
faunal turnover event, of particular importance in paleoanthropology since this
temporal sequence also provides us with what is currently our best window into the
early evolution of cercopithecoid and hominoid primates.
Description
Keywords
Africa, Neogene, Limnopithecus, 40-argon 39-argon dating, Biochronology, Faunal list
Citation
Cote, S., Kingston, J., Deino, A., Winkler, A., Kityo, R., & MacLatchy, L. (2018). Evidence for rapid faunal change in the early Miocene of East Africa based on revised biostratigraphic and radiometric dating of Bukwa, Uganda. Journal of Human Evolution, 116, 95-107.