Skip to Main Content
Book Chapter

Sedimentation Patterns in a Plio-Pleistocene Volcaniclastic Rift-Platform Basin, Olduvai Gorge, Tanzania

Gail M. Ashley
Gail M. Ashley
Department of Geological Sciences, Rutgers University, Piscataway, New Jersey 08854, U.S.A.
Search for other works by this author on:
Richard L. Hay
Richard L. Hay
Department of Geosciences, University of Arizona, Tucson, Arizona 85721 U.S.A.
Search for other works by this author on:
January 01, 2002


The Plio-Pleistocene sedimentary deposits of upper Bed I and lowermost Bed II in the Olduvai basin, Tanzania, are analyzed in terms of sedimentary processes, paleoenvironments, and paleoclimate. The sedimentary basin was a shallow, closed depression (∼ 50 km wide with strata ∼ 100 m thick) located adjacent to the East African Rift between Precambrian basement rocks to the west and the large Plio-Pleistocene Ngorongoro volcanic complex to the east. Olduvai lies on the west flank of the main rift valley, and this rift platform area was subjected to crustal extension resu I ting in normal block faulting and block tilting. Through time the axial part of the sedimentary basin episodically migrated eastward toward the main rift valley. Syndepositional volcanism included basalt flows, pyroclastic air falls, ground surges, and ignimbrites from eruptive centers of the Ngorongoro volcanic complex. Hay (1976) interpreted the paleolandscape to have had a central lake basin that was filled with detrital sediment, carbonate rocks, and tephra. Detrital sediment was provided both by rivers sourced in the Ngorongoro complex and by Precambrian rocks of the Serengeti to the north and west. Recent high-resolution stratigraphic studies of paleoenvironments in a time slice (1.85-1.75 Ma) found that the sedimentary facies vary temporally and spatially because of the interplay among five independent variables affecting the sedimentary record: (1) sediment flux (pyroclastic air fall, intermittent fluvial runoff and mudflows, and eolian), (2) sediment composition (Precambrian source rocks vs. volcanic source rocks), (3) hydrology and chemistry (lake water, surface water, and groundwater), (4) soil formation, and (5) tectonics associated with rift extension. Lake cycles, ephemeral fluvial systems, soil formation on the interfluves and lake margin, well as a large groundwater-fed wetland (> 3 km2) are all part of the Olduvai rift-margin basin record and provide insights into the Plio-Pleistocene paleoclimate history of East Africa.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables


SEPM Special Publication

Sedimentation in Continental Rifts

Robin W. Renaut
Robin W. Renaut
Department of Geological Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
Search for other works by this author on:
Gail M. Ashley
Gail M. Ashley
Department of Geological Sciences, Rutgers University, Piscataway, New Jersey 08854-8066, U.S.A.
Search for other works by this author on:
SEPM Society for Sedimentary Geology
ISBN electronic:
Publication date:
January 01, 2002




A comprehensive resource of eBooks for researchers in the Earth Sciences

This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

View Article Abstract & Purchase Options

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Subscribe Now