The Ecca Pass on the Queen’s Road is situated in the Eastern Cape on the R67 between Grahamstown and Fort Beaufort. Logging requirements edited 08/10/2015 as the toposcope is no longer accessible.
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Logging Tasks:
1) Name two sedimentary rocks found in this pass.
2) At the given waypoint in the road cutting on the north/east side you will notice a number of round circles formed in the rock face. How do you think these circles were formed?
3) What important boundary does the Winterberg Escarpment form?
4) There is a blue road marker near the listed co-ordinates what is on it? (Location question)
As an optional extra - in the cuttings see if you are able to find subtle trace fossil marks left by small soft-bodied animals, crustaceans and fish which foraged on the deep sea floor of Permian time and share the coordinates and pictures with us.
Here we view the geological rock formation of the Ecca Group that Andrew Geddes Bain first identified as well as the Winterberg Escarpment. We strongly recommend that you drive the whole pass. At S33 13.679 E26 37.986 there is a Toposcope (no longer accessible as it has been vandalized) and a Memorial to Andrew Geddes Bain, which can be seen from the road - plaque removed though
Some History
Andrew Geddes Bain (1797-1864) for his geological work earned himself the title of Father of South African Geology. During the construction of the Ecca Pass section of the Queen’s Road between Grahamstown and Fort Beaufort he became interested in Geology discovering that the sedimentary rock of the Beaufort Group contained fossil reptiles. The Queen’s Road was built as a military road between Fort Beaufort and Grahamstown to provide the British with a quick access to the troubled frontier and was completed around 1843.
Geology
The Ecca Pass is the type area for the Ecca Group and by far the best place to view these rocks. The road cuts along the pass show how the beds dip fairly uniformly northwards; the various individual parts of the Ecca stratigraphic succession can be traced with ease in the road cuts. The Ecca consists of a succession of dark grey shale units with interbedded sandstone. Some parts are more shaly, others more sandy.
The Ecca was deposited in fairly deep sea water as large, submarine, fan-shaped deposits. The rivers providing the sediment drained a Himalaya-like Gondwana mountain range in the South. Careful inspection of the beds reveals subtle trace fossil marks left by small soft-bodied animals, crustaceans and fish which foraged on the deep sea floor of Permian time. The Ecca formation tend to produce poor soils supporting a dwarf succulent thicket. Groundwater is mostly brackish and the Ecca Group is a poor aquifer. The shaly units of the Ecca Group are used for the construction of gravel roads.
The Ecca Group is the name given to the sedimentary geological formations found in Karoo Basin region of Southern Africa, immediately beneath the Beaufort Group. It consists mainly of shales and sandstones, laid down in the sandy shorelines of swamplands, during the Permian Period (299 to 251 million years ago).
The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup of geological strata in Southern Africa. It follows conformably after the Ecca Group and consists essentially of sandstones and shales, deposited in the Karoo Basin from the Middle Permian to the early part of the Middle Triassic Periods (245 to 228 million years ago).
The Winterberg Escarpment
Along the northern horizon is the Winterberg escarpment, carved out of relatively soft sedimentary rocks of the Beaufort Group. It owes its preservation to the resistant Dolerite (ironstone) dykes, sills and sheets, which intruded the area in the volcanic period during Jurassic period 190 to 180 million years ago. The Winterberg escarpment also forms an important climatological boundary.
Acknowledgements and recognition:
Google books – Field Guide to the Eastern and Southern Cape Coasts By Roy Lubke, Irene De Moor, I. De Moor
Wikipedia