Inproceedings,
The Dead Sea Transform and the Dead Sea Basin -- Structure and dynamics
EOS Transactions, American Geophysical Union. Fall Meeting Supplement, 88, page T12B-08+. (December 2007)
Abstract
DESERT and DESIRE, two multi-national, interdisciplinary research
efforts by teams from Germany, Israel, Jordan and Palestine focused
on the Dead Sea Transform (DST) and the Dead Sea Basin (DSB), respectively.The
DST has accommodated left-lateral transform motion of 105 km between
the African and Arabian plates since early Miocene (ca. 20 My), creating
during this process also the prime example of a pull-apart basin,
the DSB. Within DESERT the DST segment between the Dead Sea and the
Red Sea called Arava/Araba Fault (AF) was studied with the following
results. On plate tectonic scale the AF is a narrow, sub-vertical
zone cutting through crust and lithosphere to more than 50 km depth,
while the Moho depth increases smoothly from 26 km to 39 km from
W to E under the DST. Several faults exist in the upper crust in
a ca. 40 km wide zone around the AF, but none has kilometer-size
zones of decreased seismic velocities/zones of high electrical conductivities
typical for damage zones. Across the sub-vertical AF abrupt changes
in lithology can be identified to a depth of 4 kilometers. The AF
also acts as a barrier to fluids. The AF is the main active fault
of the DST system but it has only accommodated a limited part (up
to 60 km) of the overall 105 km of sinistral plate motion. Now inactive
fault strands in the vicinity of the present day AF took up lateral
motion until about 5 Ma ago, when the main, active fault trace shifted
ca. 1 km westward to its present position. In the top few hundred
meters of the AF a locally transpressional regime occurs in a 100
to 300 m wide zone of deformed and displaced material, bordered by
sub-parallel faults forming positive flower structures. The damage
zones of the individual faults are only 5 to 20 m wide. This narrow
width is significantly smaller than at other major strike-slip faults
of similar magnitude. Most of these findings are corroborated by
thermo-mechanical modeling that show shear deformation in the lithosphere
under the DST/AF first localizes in a 20 to 40 km wide zone with
a mechanically weak decoupling zone extending sub-vertically through
the entire lithosphere. As time progressed upper crustal deformation
became quickly focused in a few faults. Within DESIRE the DSB, the
largest basin along the DST, is studied using again a multi-disciplinary
and multi-scale approach. Some of the open questions presently being
addressed in the DESIRE project which started in 2006, are: (1) What
is the fault pattern of the DSB at depth? and (2) What is the deep
structure of the DSB and the depth and configuration of the major
crustal interfaces, e.g. the Moho beneath the basin? We will also
report results of DESIRE, with an emphasis on the findings from geophysical
studies and modeling.
