--> Mesozoic-Cenozoic Stratigraphy and Rifting History of the Anza Rift, Kenya, by R. D. Winn Jr., J. C Steinmetz, and W. L. Kerekgyarto; #90986 (1994).

Datapages, Inc.Print this page

Abstract: Mesozoic-Cenozoic Stratigraphy and Rifting History of the Anza Rift, Kenya

Robert D. Winn Jr., John C Steinmetz, William L. Kerekgyarto

Lithological and compositional relationships, thicknesses, and palynological data based on drill cuttings from five wells in the Anza rift, Kenya, indicate probable active rifting during the Late Cretaceous and Eocene-Oligocene. The earlier rifting possibly started in the Santonian to Coniacian, primarily occurred in the Campanian, and likely extended into the Maastrichtian. Anza rift sedimentation was in lacustrine, lacustrine-deltaic, fluvial, and flood-basin environments. Inferred syn-rift intervals in wells are shalier, thicker, more compositionally immature, and more poorly sorted than Lower Cretaceous (?)-lower Upper Cretaceous and upper Oligocene (?)-Miocene deposits. Syn-rift sandstone is mostly feldspathic or arkosic wacke. Sandstone deposited during non-rift periods is quart ose, cleaner, coarser, and has a high proportion of probable fluvial deposits. Volcanic debris is absent in strata older than Pliocene-Recent, although small Cretaceous intrusions are present. Cretaceous sandstone is partially cemented by laumontite, possibly recording Campanian extension. Early Cretaceous history of the Anza basin is poorly known because of limited sampling; Jurassic strata were not reached.

Cretaceous rifting in the Anza basin was broadly synchronous with rifting in Sudan and with break-up and separation of Africa and South America. These events were likely related, although Sudan and Kenya rifting was partially out-of-phase with tectonism in Central African basins. Eocene-Oligocene extension in east Africa reflects stresses unrelated to South America-Africa separation. The transition from active rifting to passive subsidence in the Anza basin at the end of the Neogene and formation of the East African Rift records a reconfigured response of east Africa to plate stress.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994