ABSTRACT: Comparison of the Baikal Rift, Siberia with the Tanganyika and Malawi (Nyasa) Rifts, East Africa: Insights from Multichannel Seismic Reflection Data

SCHOLZ, C. A., Duke University Marine Laboratory, Beaufort, NC, D. R. HUTCHINSON, U.S. Geological Survey-Atlantic Branch of Marine Geology, Woods Hole, MA, T. C. MOORE, CGLAS-University of Michigan, Ann Arbor, MI, L. ZONENSHAIN, and A. GOLMSTOK, Institute of Oceanology, U.S.S.R. Academy of Sciences, Moscow, U.S.S.R., and B. R. ROSENDAHL, RSMAS-University of Miami, Miami, FL

Seismic reflection data reveal important similarities and differences between the two largest lake basins of the western branch of the East African rift system and the basins of Lake Baikal in the Baikal rift. All three lake basins have thick accumulations of synrift sediment, estimated to be as thick as 8 km in Baikal, 6 km in Tanganyika, and 5 km in Malawi. The basal synrift strata were deposited in the Miocene in the African basins, and possibly as early as the Oligocene in the Baikal rift. All three rifts display an asymmetric geometry. Whereas the two African rifts are composed of ~120 km long half-graben units that alternate polarity down the rift axis, the Lake Baikal rift consists of three asymmetric rift segments 160-260 km long, and dominated by border faults on the northwes ern side of each basin. Three major depositional packages are recognized in Lake Baikal data, and 3-4 sequences are observed on multichannel seismic data from Malawi and Tanganyika. Well-developed erosional truncation surfaces that are widespread in the east African lakes are not prevalent in Baikal. This may be in part because the mean water depth of Lake Baikal is far greater than the other lakes, thus even drastic drops in water level would not result in extensive erosional surfaces. The first freshwater Bottom Simulating Reflector has been reported in Lake Baikal, mostly in water depths greater than 1200 m. Similar features are absent in the African lakes, presumably because of warmer bottom waters and shallower water depths.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)