A 1.3 million year record of synchronous faulting in the hangingwall and border fault of a half-graben in the Malawi (Nyasa) Rift

Tannis McCartney, Christopher A. Scholz

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Abstract

This paper analyzes throw-depth (T-z) profiles from a high resolution 2D reflection seismic grid in the central basin of Lake Malawi to investigate whether evidence exists: 1) for migration of faulting away from the border fault of the half-graben; and 2) that faults in the hangingwall lengthened over the last 1.3 million years. We use the high-precision age model from a 2005 scientific drilling project in our study area to constrain the ages of our seismic horizons and examine a fault array and two individual faults within the hangingwall of the central basin border fault. We account for climatic and sedimentological controls on stratal growth with a lake-level curve that accompanies the age model. A comparison of our hangingwall T-z profiles with published throw-distance (T-x) profiles for the border fault shows synchronous faulting over the last 1.3 m.y. rather than basinward migration of faulting. Furthermore, we find no evidence for significant propagation of the tips of the hangingwall faults in the last 1.3 m.y. and conclude that the lack of basinward migration of faulting is a consequence of strain localization on faults established at an early stage in basin development.

LanguageEnglish (US)
Pages114-129
Number of pages16
JournalJournal of Structural Geology
Volume91
DOIs
StatePublished - Oct 1 2016

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graben
faulting
border
basin
lake level
basin evolution
seismic reflection
drilling
lake
comparison
project

Keywords

  • Border fault migration
  • East African Rift System
  • Half-graben
  • Malawi (Nyasa) Rift
  • Syndepositional faulting

ASJC Scopus subject areas

  • Geology

Cite this

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abstract = "This paper analyzes throw-depth (T-z) profiles from a high resolution 2D reflection seismic grid in the central basin of Lake Malawi to investigate whether evidence exists: 1) for migration of faulting away from the border fault of the half-graben; and 2) that faults in the hangingwall lengthened over the last 1.3 million years. We use the high-precision age model from a 2005 scientific drilling project in our study area to constrain the ages of our seismic horizons and examine a fault array and two individual faults within the hangingwall of the central basin border fault. We account for climatic and sedimentological controls on stratal growth with a lake-level curve that accompanies the age model. A comparison of our hangingwall T-z profiles with published throw-distance (T-x) profiles for the border fault shows synchronous faulting over the last 1.3 m.y. rather than basinward migration of faulting. Furthermore, we find no evidence for significant propagation of the tips of the hangingwall faults in the last 1.3 m.y. and conclude that the lack of basinward migration of faulting is a consequence of strain localization on faults established at an early stage in basin development.",
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