11th CGS Field School - Mapping the Gariep Belt

And so, finally we have completed another highly successful CGS Field School. This was arguably the most grueling and challenging field school yet. It all came to an end where our team set out to map in the Gariep fold and thrust belt. This of course represents a period spanning the existence of the Supercontinents' Rodinia and Gondwana. Read more about the Gariep Belt here.

Rocks

The team was split into three separate groups and allocated three different maps across the southern portion of the Gariep Belt. Each sheet was unique in its own right and required varying degrees of focus from the various groups. Throughout the mapping period the teams were exposed to several different rocks types characteristic of this region. Some of these include:

TL: Sheared 1,800 Ma Vioolsdrift (Richtersveld Suite) grano-diorite, note the development of spaced cleavage; TR: Magnetite-bearing quartzite of the Stinkfontein Group; ML: Kaigas diamictite with characteristic carbonate clasts; MR: Marble of the Hilda Subgroup; BL: Sheared Numees diamicitite; BR: Iron stone of the Jakkalsberg Member of the Numees.

Tectonics

For those who took the time to hike and closely examine the rocks, there was a continuous sense of dejavu. This was of course due to the continuous repetition of the Gariep sequence. This duplication allowed the team to really consider the tectonic history of this region. 

The tectonics characterises the period after Rodinia broke up, and in the process, formed the mighty Adamastor Ocean; and eventually the growth of Gondwana. This ocean could somewhat be synonymous to the present-day Atlantic, separating the Kalahari (KC) and Rio de la Plata (RC) Cratons. It was within the Adamastor Ocean where much of the Gariep rocks were deposited.

Imagination, and some walking is needed - But, after some time you may begin to exist in a strange space-time continuum bubble where you begin to visualise everything.

Tectonic inversion c. 555 Ma saw the RC and KC encroach, closing the Adamastor Ocean and eventually culminating with the RC accreting atop the KC during the formation of Gondwana. Several structural features were also seen characterising this event:

TL: Fault breccia within Numees diamictite; TR: Pseudotachylite development along the frontal thrust zone; BL: What was the Kaigas diamicitite, now highly deformed schist; BR: Mylonite developed along thrust zone.

Life

Another great thing about spending time in the Richtersveld is interacting with the local people, and clearing your troubled mind in vast and endless landscape.

Sometimes the roads are long and tough. Only for you to discover that this is only half the journey.

Sometimes you chose the easiest path home. Only to discover this means walking over isoclinally folded carbonates interlayered with thrust-bounded phyllite.

But, there's a story to be founded...

And history to be uncovered...

And, some crazy weather to Moer you

Come the third day of battle, look to the East!

And you'll find yourself sad to leave, because you've left a part of yourself behind...