Day 11 (Saturday Sept. 16th ) Snowballs!
Kuruman to Hotazel to Postmastberg.
We started bright and early from Kuruman, and went first to an exposure of
stromatillites in the late Archean to early Proterozoic Campbelrand Platform.
One of our alumni, Dawn Sumner, has worked extensively on the small
stromatillites from this locality, showing that they appear to have the ability
to photosynthetically fix the bicarbonate ion (HCO3-). We even found the
volcanic ash which she and Sam Bowring (at MIT) used to date the sequence at
2.521 +/- 3 myr. At that point, Oscar von Antwerpen, a geologist at the
Mamatwan Manganese mine, met us on the outcrop and drove us to their open pit
operations. As the mines don't operate on the weekends, we were able to drive
right up to the active ore body, a 20-m thick layer of nearly pure manganese
oxides, formed in the aftermath of the worst glaciation in Earth history
(snowball #1). Unfortunately, the weather was not cooperating, and as the
mist and rain came pouring down we turned South from the Hotazel area to the
massive Sichen Iron Mine, stopping for a superb discourse on BIFs from Laura.
As the rain and lightning thundered down on us once again, we decided to stay at the
Postmastberg Hotel that evening rather than risking our tents being washed
away. Dinner at a local restaurant was also interesting, interrupted by one of
the heaviest downpours in memory. Even some of the rooms in the hotel leaked
that evening, and we were glad to have opted out of the tents!
Written by JLK
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