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Author Topic: Geography of klein karoo and surrounding area.  (Read 132 times)

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Offline FarScape

Geography of klein karoo and surrounding area.
« on: September 13, 2021, 11:21:08 pm »
I wish someone can explain to me how the red cliffs have formed in that area. Its almost if they where formed by water. You can even see stones in that sand hills that came out of river beds. I have seen these formations as far as baviaans. I have heard the great karoo was once an lake. So how big could it possibly have been?
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Offline Karoo Rider

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Re: Geography of klein karoo and surrounding area.
« Reply #1 on: September 14, 2021, 05:48:37 am »
This might explain to some degree: https://en.wikipedia.org/wiki/Enon_Formation  Things must have been rather different a few million years ago.
 
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Re: Geography of klein karoo and surrounding area.
« Reply #2 on: September 14, 2021, 07:32:24 am »
 
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Offline tok-tokkie

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Re: Geography of klein karoo and surrounding area.
« Reply #3 on: September 14, 2021, 09:18:18 am »
This is more about the geology of the Great Karoo but it will help   http://www.wilddog.za.net/forum/index.php?topic=39072.0
 
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Offline Kortbroek

Re: Geography of klein karoo and surrounding area.
« Reply #4 on: September 14, 2021, 10:27:59 am »
I wish someone can explain to me how the red cliffs have formed in that area. Its almost if they where formed by water. You can even see stones in that sand hills that came out of river beds. I have seen these formations as far as baviaans. I have heard the great karoo was once an lake. So how big could it possibly have been?

It depends which cliffs you are referring to. If those that form part of the swartberge then you need to read up on the Cape Supergroup, the same rocks that make up all the mountains from the Cederberg all along the WC to PE. They were deposited between about 500Ma to 350Ma ago in a "ocean" that formed in a rift valley in the previous supercontinent Gondwanaland. As this ocean closed up due to tectonic events they we're folded which is why you see these layers of rocks that are folded and turned on end. This makes the red cliffs you'll see for instance in the swartberg pass. During this tectonic event and with the folding of the Cape Supergroup sediments a mountain range was formed the remnants of which endures to this day. This event would have happened around 330 million years ago and this process formed the main Karoo basin north of the Swartberge. This great karoo during this time evolved to become an inland sea in which the sediments of the Karoo supergroup were deposited. This inland sea filled up with sediments over a roughly 100Ma period and eventually in the final stages there would have been a series of shallow lakes remaining in a sandy desert. The remnants of this can be seen in the eastern Free State below and in the Clarens formation which would have been massive sand dunes around 200Ma ago. Subsequent to this from about 190Ma the Gondwana supercontinent started breaking up which is recorded by the intrusions of dolerite (ysterklip) throughout the Karoo and by the Drakensberg basalts.

In the Klein Karoo and south Cape the Cape fold belt was being put under tension during this breakup and as the mountains and rock we're being pulled apart large sections would fracture forming fault lines. Along these faults blocks of crust/rock would "sink/slip down" forming basins/valleys into which rivers would deposit sediments eroded from the Karoo and the mountains of the Cape fold belt. This is what formed the Enon formation which is likely the red cliffs you refer to that have boulders in them. These rocks are know as conglomerates and are typical of sediments that weren't transported very far from their source. The boulders are rounded, just like we see in the modern cape rivers, but there is a lot of finer material in between cementing it together. The Enon formation would like have been deposted around 100-150Ma ago.

So in summary, the great Karoo was once a inland ocean that stretched up into Botswana and Zim, before that the klein karoo was in an ocean as well. Later during and after the breakup of Gondwanaland the Klein Karoo would have been a series of mountains with mini eskarpments and deep valleys when the Enon fm was deposited.

For further reading:
Cape Fold Belt: https://en.wikipedia.org/wiki/Cape_Fold_Belt
Karoo Supergroup: https://en.wikipedia.org/wiki/Karoo_Supergroup
Enon fm: https://en.wikipedia.org/wiki/Enon_Formation
Gondwanaland: https://en.wikipedia.org/wiki/Gondwana

If you are interested in the landscape and geology, two really good books that are geared towards the layperson are "Geological Journeys" and "Geology off the beaten track", both by Nick Norman. They are great travel companions when driving around South Africa as they explain the geology along main routes and then along the back roads of the country.
https://www.exclusivebooks.co.za/product/9781770070622
https://www.exclusivebooks.co.za/search?keyword=9781431700820
« Last Edit: September 14, 2021, 10:32:26 am by Kortbroek »
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Online Captain Zef

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Re: Geography of klein karoo and surrounding area.
« Reply #5 on: September 14, 2021, 12:48:11 pm »
Wow this is fascinating stuff. I know what i am reading today. Thanks for the thread.
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