Red Stone Hills EarthCache
Hidden : 4/16/2015
Difficulty:
3 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

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Geocache Description:

The aim of this Earth Cache is to teach you something about the colour and formation of these hills.  

At the beginning of the Cretaccous Period, the super continent of Gondwana split up and Africa was finally separated from the other continents.
In a period characterized by warm humid conditions with lush vegetation and the big lizards, the earth crust underwent major change as it stretched and split. It was accompanied by violent earthquakes and torrential downpours as rocks fractured and ruptured along the fault lines. Crustal extension was also responsible for the formation of elongate basins such as the Oudtshoorn Basin of the Eastern Little Karoo which extends as far west as Calitzdorp. This basin developed mainly along a deep fracture running from East to West along the base of the Swartberg called the "Kango Fault" (also an important ground water conduit). The basin floor subsided mainly along it's Northern Margin, as rocks were crushed and fractured along the Kango fault line.
Accompanying this, rejuvenated rivers on the new highlands of Gamkasberg and Rooiberg as well as from the uplifted area to the North, flowed into the Oudtshoorn basin. They carried with them vast amounts of scree and rock, fractured from the Table Mountain sandstone and Quartzite's from the mountain chains surrounding the Little Karoo, and deposited them on the emerging lake shores. These course continental sediments are unique in being one of the first truly African sediments, having been laid down during the time that the African continent was being formed. They were previously known as Enon Conglomerates but are now called the "Buffelskloof Formation", after a nearby farm. The rounded cobbles and pebbles were laid down in silica rich gravels and sediments and are known as conglomerates. The angular rock scree on the slopes covered by these same sediments are known as Breccias.

Along the Northern shores the sediments are rich in an iron mineral called Hematite which oxidized in the warm humid climate to a reddish colour , giving Red Stone Hills it's name. Originally this belt of red, gravel sediments formed the Nothern margin of the Oudtshoorn basin but 100 million years of erosion has left isolated koppies in a band stretching from De Rust almost to Calitzdorp. Initially they eroding quickly, but they then formed an outer crust which was more resistant to weathering. However weathering has broken through some of this resulting in small caves and overhangs as well as a rather spectacular Hole-in-the Wall. Due to the highly oxidizing conditions prevalent at the time of their formation, fossil remains are virtually non existent although found elsewhere in other Cretaceous deposits on the shores of the ancient Kango basin as well as in older Jurassic deposits. This has resulted in some difficulties in establishing the exact age of these deposits of red gravel.
In order to log your find please email the CO with your own answers to the following questions. You are welcome to log your find before emailing the answers, but any logs unaccompanied by an email with suitable answers will be deleted:
  • 1) What is the name of the fracture that runs from East to West along the foot of the Swartberg?
  • 2) Where does the red colour in these hills come from.
  • 3) Why is it difficult establishing the exact age of these deposits of red gravel?
  • 4) At the second way point, just around the bend, park at a safe spot, and examine the rock face. Describe what you see. (Width of cliff, height, coloring, composite)
  • 5) Optionally, but would be appreciated, submit a photo of you or your team with the "hole in the wall" in the background.
>References: Geology of the Klein Karoo (by Geoff Wyatt-Goodall)

Additional Hints (Decrypt)

Erzrzore gb rznvy lbhe nafjref!

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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