Chronostratigraphy and age modeling of Pleistocene drill cores from the Olduvai Basin, Tanzania (Olduvai Gorge Coring Project)

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2021-06, Vol.571, p.109990, Article 109990
• Main Authors: Deino, Alan L., Heil, Clifford, King, John, McHenry, Lindsay J., Stanistreet, Ian G., Stollhofen, Harald, Njau, Jackson K., Mwankunda, Joshua, Schick, Kathy D., Toth, Nicholas
• Format: Article
• Language: English
• Subjects: 40Ar/39Ar dating; Bayesian; East Africa; Magnetostratigraphy; Tephrostratigraphy
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2020.109990

The Olduvai Gorge Coring Project drilled a total of 611.72 m of core (575.48 m recovered) of mostly fluvio-lacustrine and fan-delta volcaniclastic Pleistocene strata at three sites in the Olduvai Basin, Tanzania, in 2014. We have developed a chronostratigraphic framework for three of the cores based on 40Ar/39Ar dating of core and outcrop volcanic and volcaniclastic units, core paleomagnetic stratigraphy, and tephrochemical correlation between cores and from core to outcrop. This framework is then used to constrain Bayesian stratigraphic age models which permit age estimates for desired core levels with realistic confidence intervals. The age models reveal that the deepest core level reached at 245 mbs is ~2.24 Ma, ~210 kyr older than the oldest strata exposed at Olduvai Gorge. Strata net accretion rates in this early phase of basin history were relatively rapid (57–69 cm/kyr), but decreased within ~250 kyr to ~15 cm/kyr in Lower Bed I. Rates rebounded partially in Upper Bed I, but subsequently declined to