Our other team (Taufeeq, Olma, Khaya and Michelle) went out looking for big thrust faults,
specifically around the basal thrust zone of the Gariep Belt. After the
deposition of the Gariep Belt rocks (associated with the breakup of Rodinia ca.
750 Ma); this package was obducted onto the basement Vioolsdrift rocks during
the amalgamation of Gondwana. In order to better understand the scale of this
process, Olma, Khaya and Michelle (our esteemed guest from the office of the
COO) traversed across one of the major thrust faults in a zone of major faults
separating the Gariep from the basement. This was no easy feat, and highly
dangerous- we of course maintain the highest levels of safety and security (and
not just when we have guests from the office of the COO…).
The entire fault zone extends for several kilometres and
increases in topographically high peaks toward the top of the thrust succession.
This provides some idea of the thrust direction, kinematics and strain
partitioning throughout this sequence. Ductile deformation was present in the
diamicitite, with now rotated clasts illustrating thrust transport direction
along a top-to-the-west sense of motion. In addition, the quartzite of the
Stinkfontein suffered under the strain partitioning and displayed very high
levels of shearing and the formation of thin foliated layers. Finally, within
each thrusted block (bounded by metre-thick vein quartz brecciation), a
tectonic melange was present, where rocks buckled under the immense pressures.
Jumping for Joy: Olma and Khaya hunt for thrust tectonics. Bottom left: Olma showing one of the thrusts
With the temperature reaching above 40 degrees Celsius the
team did not attempt trying to get down the steep thrust. Did not try to get
down today, I should add. Tomorrow is a new day and likely to be a better day
to attempt this! This will unfortunately have to be done without Michelle, who
will return to Pretoria tomorrow. Michelle admitted that she enjoyed her visit
to the Field School: “I would love to come back…” she said. And she will always
be welcomed!
Until tomorrow- the final day of field mapping, here’s
hoping to go out with a Bang!
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