Oorlogskloof Glacial Floor EarthCache
Oorlogskloof Glacial Floor
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The glacial floor exposed on the farm Oorlogkloof south of Nieuwoudtville is easily reached by
following the main road through the town and driving on a reasonable dirt road for about 7 km. The
site is about 300m wide.
About 300 million years ago, glacial conditions prevailed over Southern Africa when it migrated with
the rest of the Gondwana supercontinent over the South Pole. The ridges and striations in the
sandstone were formed as a result of ice movement during this time. The grooves were not made
on bedrock, but in a thin layer of sandy debris trapped between bedrock and the glacier base. This
veneer of glacial detritus, which was eroded from sandstone bedrock and carried along by the ice,
is preserved as a pebbly quartzose sandstone. The grooves were made by rock and pebbles held in
the ice. The bedrock consists of upper Table Mountain Group (i.e. Nardouw Formation) sandstone,
dating back to about 420 million years, whereas the glaciation occurred some 100 million years later,
well after lithification of the bedrock and partial erosion of the rocky surfaces. Glacial erosion was
followed by melting of the ice and deposition of its debris load as the diamictite blanket of the
Dwyka Formation over the eroded land surface.
It is clear that many of the delicate structures formed in quiet water when the ice front retreated or
was lifted clear of the sediments by buoyancy during a rise in sea-level. These beds were
eventually covered by fine suspended mud settling on them, leaving sufficient time for compaction
to take place before meltwater currents and rain-out debris from the glacier formed a blanket
deposit over.
Thanks to Western Cape Branch of the Geological Society of South Africa for information.
Please close the gate as you go to or leave the site - Thank you.
To claim this cache:
Please tick the box to send along your e-mail address with your answers.
1. Post a picture of yourself and your GPS at the site with your log (this has now become optional, but makes it interesting)
2. E-mail me with the following information -
(a) In which direction was the glacial flow at oorlogskloof
(b) what direction was the larger glacial flow over Bushmanland.
Additional Hints
(Decrypt)
Cyrnfr gvpx gur obk gb fraq nybat lbhe r-znvy jvgu lbhe nafjref
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