Seismic imaging of the Olduvai Basin, Tanzania

Kai Lu, Sherif Hanafy, Ian Stanistreet, Jackson Njau, Kathy Schick, Nicholas Toth, Harald Stollhofen, Gerard T. Schuster

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Abstract

A 5.6-km-long line of refraction and reflection seismic data spanning the Pliocene-Pleistocene fill of the Olduvai Basin, Tanzania is presented. The line is oriented along a northwest-southeast profile through the position of Olduvai Gorge Coring Project (OGCP) Borehole 2A. Our aims are to (1) delineate the geometry of the basin floor by tracing bedrock topography of the metaquartzitic and gneissic basement, (2) map synsedimentary normal faults and trace individual strata at depth, and (3) provide context for the sequence observed in OGCP cores. Results with refraction tomography and poststack migration show that the maximum basin depth is around 405 m (±25 m) in the deepest portion, which quadruples the thickness of the basin-fill previously known from outcrops. Variations in seismic velocities show the positions of lower density lake claystones and higher density well-cemented sedimentary sequences. The Bed I Basalt lava is a prominent marker in the refraction seismic results. Bottom-most sediments are dated to >2.2 Ma near where Borehole 2A bottoms out at the depth of 245 m. However, the seismic line shows that the basin-fill reaches a maximum stratigraphic thickness of around 380 m deep at Borehole 2A, in the western basin where the subsidence was greatest. This further suggests that potential hominin palaeoenvironments were available and preserved within the basin-fill possibly as far back as around 4 Ma, applying a temporal extrapolation using the average sediment accretion rate.
Original languageEnglish (US)
Pages (from-to)109246
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume533
DOIs
StatePublished - Jun 26 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OCRF-2014-CRG3-2300
Acknowledgements: The geophysical research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST) and grant agreement number OCRF-2014-CRG3-2300. The KAUST Shaheen computing resources were used for computing the seismic images. The authors would like to acknowledge the Tanzanian Commission for Science and Technology (COSTECH), the Department of Antiquities, Ngorongoro Conservation Area Authority (NCAA) for research permits. Financial support for the Olduvai Gorge Coring Project (OGCP) and subsequent analysis was provided by the Stone Age Institute (which was primarily responsible for the planning and logistics of the project), the Charles H. Kaman Charitable Foundation, the Fred Maytag Family Foundation, the Ann and Gordon Getty Foundation, Carl and Marcy Cook, Kay and Frank Woods, the John Templeton Foundation, the Springcreek Foundation, the L.S.B. Leakey Foundation. Additional field and travel expenses were provided to HS by the German Research Foundation DFG (STO 275/9), to JN, IS by the Palaeontological Scientific Trust (PAST), and to LM by the European Research Council (ERC Starting Grants-283366 to de la Torre).

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