We have put together a series of earthcaches along the N2 in the Eastern Cape and this is just one of them. We got really excited at the prospect of putting together these earthcaches after doing some research. Little did we know just how varied our possibilities were and how diverse the geology is in this province! We hope you enjoy them and learn a great deal of our beautiful part of our planet.
A word of caution however – this cache is not for children and extra care needs to be exercised when walking along the road as it is extremely busy. There is parking at this cache, on the west side of the cutting, and make sure that your vehicle is parked well off the road.
An Earth cache is a special type of Virtual Cache that is meant to be educational. Therefore to log a find you must demonstrate that you have learnt something from the site and experience.
Send your answers to us in an email via our profile page.
Any logs not accompanied by an email will be deleted.
Logging Tasks:
Take a walk along the opposite side of the road and view the cutting at S33 22.168 E026 28.642.
No spoiler pictures to be posted!
1) What band formation is in the rock-face starts behind the road marker at the base?
2) Estimate how wide and long it is – the portion that is visible.
3) Would you say this is a dyke, sill or inclined sheet?>
The Witteberg comprise mostly quartzitic sandstone, thin-bedded reddish-grey siltstone and interbedded thin beds of sandstones. Many of the latter show well developed ripple marks on the bedding plains. A dusting of shiny silver-hued mica flakes characterises much of the Witteberg siltstones. A conspicuous white quartzite, the Witpoort formation, occurs towards the top of the group; its bright white quartzite outcrops having given the name to the Witteberg Group.
The best exposures of the Witteberg Group occur in the Howieson’s Poort and other road cuts near Grahamstown. The siltstone beds, which form the bulk of the Witteberg Group in the Eastern Cape, normally weather away and tend to form rolling hilly country. Witteberg sediments underlie much of the land between Alicedale, Highlands, Salem, Kasouga Road, Port Alfred and Kleinemond.
The Witteberg Group has little economic use except for small burrow pits for road making. Most of the Witteberg is poor aquifer, except for the prominent quartzite zones, which can yield strong supplies of good quality water.
The Witteberg Group rocks of the Cape Supergroup were deposited about 400 million years ago during the Devonian Period. It is geologically the youngest unit of the Cape Supergroup. The Devonian Period coincides with the evolution of the first land plants and marine fish. These would have both been fairly primitive specimens, with the zoological record dominated by marine invertebrates. The Witteberg Group was deposited in a tidal flat environment. The quartzitic sandstone and sandstone rock types would have been deposited in the intertidal zone, where clean sands were being reworked by marine action. The darker (and softer) shale was formed within the mudflat environment.
Acknowledgments and recognition
Addo Geology
A field guide to the Eastern Cape Coast by RA Lubke FW Gess & MN Bruton