Back Tafelbergsandstein German Tafelberggroep Dutch

Table Mountain Sandstone

Main article: Cape Fold Belt § Cape Supergroup
Table Mountain seen from Signal Hill, across the Cape Town city bowl. The portion of the mountain made up of Table Mountain Sandstone is indicated on the right.[1] It is this mountain that has given its name to the geological structure that occurs in the mountains throughout the Western Cape

Table Mountain Sandstone (TMS), formally known by its geological name the Peninsula Formation Sandstone, is a group of rock formations within the Cape Supergroup sequence. While the term "Table Mountain Sandstone" remains widely used, it is no longer formally recognized; the correct geological name is "Peninsula Formation Sandstone," which is part of the Table Mountain Group. The name originates from Table Mountain, the famous landmark in Cape Town, South Africa. For consistency with common usage, the term "Table Mountain Sandstone" will continue to be used throughout this article.

Schematic diagram of an approximate 100 km west-east (left to right) geological cross-section through the Cedarberg portion of the Cape Fold Belt (South Africa). The rocky layers (in different colors) belong to the Cape Supergroup. Not to scale. The green layer is the Pakhuis diamictite formation which divides the Table Mountain Sandstone (or Peninsula Formation Sandstone) into a lower and upper portion. It is the lower (older) portion that is particularly hard and erosion resistant, and, therefore, forms most of the highest and most conspicuous peaks in the Western Cape, as well as the steepest cliffs of the Cape Fold Mountains (including Table Mountain - see upper illustration).[2] The Upper Table Mountain Sandstone Formation, above the Pakhuis tillite layer, is considerably softer and more easily eroded than the lower Formation. In the Cederberg Mountains This formation has been sculpted by wind erosion into many fantastic shapes and caverns, for which these mountains have become famous.[3] The Graafwater Formation forms the lowermost layer of the Cape Supergroup in this region, but is, for simplicity, incorporated into the Table Mountain Sandstone Formation in this diagram.
Schematic geological west-east cross section through Cape Peninsula, based on a section through the Back Table just south of Table Mountain. Not to scale. On the Peninsula the basement layer consists in the main of Cape Granite. The Table Mountain Sandstone (in the same colour as in the diagram on the left) forms the steep escarpments that surround the approximately 5 km-wide central plateau. It consists of the layer below the "Pakhuis diamictite", of which there is only a trace at the highest point on Table Mountain at 1085 m above sea level. The lowermost formation of the Table Mountain Group is the "Graafwater Formation", which rests unconformally on the Cape Granite base, as opposed to the Malmesbury Formation base in most of the rest of the extent of Cape Supergroup in the Western Cape (see illustration above, on the left). Kirstenbosch Botanical Gardens, and all the major wines estates on the Peninsula are situated on the fertile (weathered) granite slopes on the east side of the mountain. The soils derived from Table Mountain Sandstone are very poor in nutrition.

Composed primarily of quartzitic sandstone, Table Mountain Sandstone was deposited between 510 million years ago (Cambrian Period) and 400 million years ago (Silurian Period). It is the hardest and most erosion-resistant layer of the Cape Supergroup, making it responsible for the highest peaks and steepest cliffs of the Cape Fold Belt. Despite being the oldest and lowermost layer of the Cape Supergroup, its resistance to erosion has allowed it to persist as the dominant rock formation in many prominent landscapes across the Western Cape.[2]

The folding of the Cape Supergroup into the parallel mountain ranges of the Western Cape began approximately 330 million years ago, shaping the landscape from Clanwilliam (about 200 km north of Cape Town) to Port Elizabeth (about 650 km east of Cape Town). Beyond these points, the Cape Supergroup sediments are not folded into mountain ranges but instead form steep cliffs and gorges, where surrounding sediments have been eroded away, as seen in locations like Oribi Gorge in KwaZulu-Natal.[4][5]

  1. ^ Compton, J.S. (2004).The Rocks and Mountains of Cape Town. p. 24-26, 44-70. Double Storey Books, Cape Town. ISBN 1-919930-70-1.
  2. ^ a b Norman, N., Whitfield, G. (2006). "Geological Journeys. A Traveller’s Guide to South Africa’s Rocks and Landforms". pp. 208-212. Cape Town, Struik Publishers. ISBN 1-77007-062-1.
  3. ^ Cite error: The named reference whitfield was invoked but never defined (see the help page).
  4. ^ McCarthy, T., Rubridge, B. (2005). The Story of Earth and Life. pp. 159–161, 182, 187–195, 202–207, 267–269, 302. Struik Publishers, Cape Town. ISBN 1-77007-148-2
  5. ^ Truswell, J.F. (1977). The Geological Evolution of South Africa. pp. 93-96, 114-159. Purnell, Cape Town. ISBN 0-360-00290-0.

Table Mountain Sandstone

Dodaje.pl - Ogłoszenia lokalne