Anatomy of a Half Graben: Structural Style and Stratigraphic Fill -- A Case Study from the Sinai Margin of the Suez Rift, Egypt
By
Ian Sharp1, Rob Gawthorpe2, Ian Carr3, John Underhill4
(1) Norsk Hydro Research Center, Bergen, Norway (2) University of Manchester, Manchester, United Kingdom (3) The University of Manchester, Manchester, United Kingdom (4) Grant Institute, Edinburgh, United Kingdom
The past decade has seen increasing research on the interaction between
fault
growth and stratigraphic architecture in extensional basins. In
particular, variations in accommodation development associated with the vertical
and lateral propagation and linkage of originally isolated normal
fault
segments
have been investigated as a primary control on sediment dispersal and
stratigraphic architecture. The aim of this contribution is to document the
structural style and stratigraphic fill of a well exposed half graben from the
Suez Rift, with emphasis on understanding the dynamic interaction.
The Wadi Nukhul half graben is a well exposed example of a “rift initiation”
depocenter. The segmented border fault
system to the half graben is exposed over
6 km, and comprises distinct NW-SE and N-S striking elements. Displacement is at
a maximum in the south and decreases northwards towards a well defined tip point
and
fault
-tip monoclinal fold. Folds are evident parallel and perpendicular to
the border
fault
.
Fault
perpendicular folds are associated with distinct
fault
segments, while folding parallel to the boarder
fault
is associated with a
faulted monocline configuration.
Contemporaneous syn-rift sediments show marked thickness and facies
variations about the structural elements. The non-marine Abu Zenima Fm is
thickest in hangingwall depocenters adjacent to NW-SE striking segments of the
border fault
, and is thinnest over transverse anticlines associated with N-S
striking segments. In contrast, the estuarinal Nukhul Formation is thickest and
more “marine” in nature at the southern tip of the Nukhul
Fault
, and shows
progressive northwards thinning, onlap and overstep parallel to decreasing
fault
displacement.