Crustal structure and tectonic evolution of the anza rift, northern Kenya

L. C. Greene, D. R. Richards, Roy A Johnson

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The Anza trough is a Mesozoic rift located in northern Kenya that appears to be the failed third arm of a paleo-triple junction which allowed the separation of Madagascar from Africa during the Jurassic. The rift is oriented NW-SE and its tectonic evolution is related to that of the Mesozoic southern Sudan rift system. We analyzed seismic and gravity data from the southwestern side of the Anza rift including the Chalbi Desert to gain a better understanding of rift structure. Gravity data delineate the main rift basins as well as a small sub-basin on the southwest side of the main rift. Normal faulting evident on the NW end of a 42-km-long, NW-SE oriented Vibroseis® profile, marks the western boundary of the sub-basin. This sub-basin is offset from the trend of the main Anza trough; the western boundary may be a complex fault zone accommodating a change in direction of the main rift trend. Gravity values increase to the NW in the faulted area, suggesting shallowing of basement. A strong NW-dipping reflection from 0.5 s to almost 3 s is interpreted as a pre- to mid-Cretaceous unconformity. The configuration of the unconformity and the normal faulting strongly resembles the half-graben geometry imaged in the East African Rift. Numerous discontinuous reflections can be seen deeper in the section between 6 and 9 s, but a distinct reflection Moho cannot be interpreted with certainty. In addition to seismic and gravity data, regional geologic and well data lead us to conclude that there are probably Jurassic marine sediments in the bottom of the Anza rift.

Original languageEnglish (US)
Pages (from-to)203-211
Number of pages9
JournalTectonophysics
Volume197
Issue number2-4
DOIs
StatePublished - Oct 30 1991

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Kenya
crustal structure
tectonic evolution
tectonics
gravity
basin
unconformity
faulting
trough
Jurassic
vibroseis
triple junction
gravitation
Moho
graben
marine sediment
fault zone
troughs
desert
Cretaceous

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Geophysics

Cite this

Crustal structure and tectonic evolution of the anza rift, northern Kenya. / Greene, L. C.; Richards, D. R.; Johnson, Roy A.

In: Tectonophysics, Vol. 197, No. 2-4, 30.10.1991, p. 203-211.

Research output: Contribution to journalArticle

Greene, L. C. ; Richards, D. R. ; Johnson, Roy A. / Crustal structure and tectonic evolution of the anza rift, northern Kenya. In: Tectonophysics. 1991 ; Vol. 197, No. 2-4. pp. 203-211.
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