Topsy Turvy Highland Quartzite EarthCache
Topsy Turvy Highland Quartzite
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Located next to the Scottish War Memorial in Kensington. There is a traditional cache close to this Earthcache, and lovely views of the western part of downtown Joburg (Marshalltown).
This hill is formed by quartzites of the Brixton Quartzite Formation, the same layer that forms the Observatory Ridge to the north. At this locality, the quartzite dips northward at about 70°, but is UPSID-DOWN! This can be seen from the cross bedding (the lines of deposition in the rocks) which is very well developed to the south west of the paved plinth around the monument (i.e. towards the school down the hill).
These strata (lines) were overturned as a result of faulting. The fault itself can not be seen at the surface, but is located in the lower laying ground to the north of the Scottish memorial hill, probably around Roberts Avenue in the “valley” below. The zone of disturbance induced by this fault is several hundred metres wide and extends all the way south of the M2 highway.
There are no major faults south of the locality within this geological “area”. This was fortunate because it meant that the Main Reef, on which all the concentrated auriferous (gold bearing) layers lie, and on which the gold mining industry developed, was not affected. The Main Reef lies just north of the M2 highway, and the line of mine dumps to the south shows the extent of mining operations that took place in earlier days of gold mining on the Witwatersrand.
(Acknowledgments: guidebook to Sites of Geological & Mining Interest on the Central Witwatersrand.; Geological Society of South Africa; 1986).
1) Take a photo of you and your GPSr at this spot with the Quartzite outcrop visible and include in your log. [Optional]
2) Look around the cache area, and surrounding areas. Explain the significance of the quartzite in this area. Make observations based on roads, buildings, influence on the human habitation etc. Include a paragraph or so on this in your email.
3) Look at the strata on the quartzite. Explain what you see – form, size, colours, shapes etc. If you have done the Earthcache below the Brixton Tower, please comment on similarities and differences that you may see between the sites.
Additional Hints
(Decrypt)
Erzrzore gb fraq lbhe rznvy! Jngpu sbe intenag zhttyrf!