Cliffhanger EarthCache
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The N3 highway passes through this wonderful exposed portion of rock at Inchanga between Pietermaritzburg and Durban, affording us to the opportunity to look at some of South Africa’s early history.
As the N3 passes through this kloof – the Natal Group sandstones are exposed and shown to their full advantage in these prominent cliffs on both sides of the highway. From the cache site on the R103 – you can really get up close and personal with these exposures.
The Natal Group is the oldest sedimentary group in the area, and a number of mesas (table mountains) are visible in the region of exposure (between Durban and Pietermaritzburg, the Bishopstowe mountain is the most obvious). These sandstones were deposited onto the basement granites around 490 million years ago, and is the time equivalent of the quartzitic sandstones of the Table Mountain Group of rocks in the Western Cape. The sand that forms this group, was deposited within the coastal stretches of ancient rivers that drained the long gone highlands towards the north east. The deposits eventually formed a continuous layer across much of what we know as KwaZulu Natal today. This was to be covered, in a much later sedimentary event, by the Karoo sediments (around the time of the dinosaurs) and finally by the Drakensberg lavas. After the break up of Gondwana and the erosion that followed, the continuous sandstone layer was dissected into separate table lands that we see around KwaZulu Natal currently.
These sandstones are visible across large parts of the province, and in areas in and around Durban, cross bedding and distinct layers can be seen (e.g. on Fields Hill near Pinetown). Good exposures are used close by at Monteseel (“Monties”) by climbers that overlooks the Valley of a Thousand Hills. The relatively stable rock and strength of the Natal Group sandstones make idea climbing rock in comparison to the Drakensberg basalts that weather and crumble for easier making Berg climbing far more dangerous, although the setting is far more spectacular.
(Acknowledgements to Google.com and Geological Journeys.; Norman & Whitfield; 2006).
In order to qualify to log this cache, you need to answer the following questions and email the cache owner. Any logs not accompanied by an email will be deleted.
1) Take a photo of you and your GPSr at this spot with the cliffs visible in the background [Optional].
2) Look at the rocks making the cliff and describe the rock structure (grains – colour – cracks etc.).
3) How do you think this kloof (gorge) was formed?
4) What is Gondwana?
Additional Hints
(Decrypt)
Erzrzore gb fraq lbhe rznvy!