page_title: Cape Peninsula
section_title: Geology
hierarchical_section_title: Cape Peninsula / Geology
caption_attribution_description: English: A schematic W-E geological cross section of the Cape Peninsula, roughly based on a section through the Back table just south of Table Mountain. Not to scale.
context_page_description: The Cape Peninsula is a generally rocky peninsula that juts out into the Atlantic Ocean at the south-western extremity of the African continent. At the southern end of the peninsula are Cape Point and the Cape of Good Hope. On the northern end is Table Mountain, overlooking Cape Town, South Africa. The peninsula is 52 km long from Mouille point in the north to Cape Point in the south.
  The Peninsula has been an island on and off for the past 5 million years, as sea levels fell and rose with the ice age and interglacial global warming cycles of, particularly, the Pleistocene. The last time that the Peninsula was an island was about 1.5 million years ago. Soon afterwards it was joined to the mainland by the emergence from the sea of the sandy area now known as the Cape Flats. The towns and villages of the Cape Peninsula and Cape Flats now form part of the City of Cape Town Metropolitan Municipality.
  The Cape of Good Hope is sometimes erroneously identified as the meeting point of the Atlantic and Indian Oceans.
context_section_description: The Cape Peninsula is underlain by the oldest rocks in the area, the Malmesbury Group, and the granite intrusions of the Peninsula pluton.
  The Malmesbury Group has been dated from between 830 and 980 Mya, and was deformed during the Saldanian orogenic cycle, both before and during the granite intrusions of 630 to 500 Mya, and there are minor intrusions which precede the granite. The base of this group has not been exposed. The basal rocks were eroded to a relatively featureless peneplain with exposed granites covering most of the peninsula south of Lion's Head and Devil's Peak. The Sea-Point contact zone, described by Charles Darwin is a well known region of metamorphic rocks formed by the (originally very hot) granite intrusion into the Malmesbury rocks.
  These rocks were later unconformably covered by the Cape Supergroup. The Cape Supergroup is divided into eight formations, the three oldest of which are present on the Peninsula. The lowest present is the reddish Graafwater formation which consist of shales and sandstone. The Graafwater Formation can be clearly seen in the cutting on the second hairpin bend as the Ou Kaapse Weg (road) goes up the slope from Westlake on to the Silvermine plateau. In the cutting one can also see the abrupt and obvious transition into the Table Mountain Sandstone (or, as it is currently known, the Peninsula Formation Sandstone) above it. Looking up the slope from below to the first hairpin bend, the granite basement on which the Graafwater formation rests is visible. And in the cutting at the first hairpin bend, the ocher-colored, gritty clay into which the granite weathers is clearly displayed. The relatively thin Graafwater layer (no more than about 60–70 m thick on the Cape Peninsula) is overlain by the prominent Peninsula Formation, which consist mainly of hard, erosion resistant, quartzitic sandstone, which form the high, prominent, almost vertical cliffs of the Cape Peninsula. At the very top of Table Mountain, at Maclear's Beacon, is a small remnant of the Pakhuis Diamictites, better represented in the Cederberg Mountains, 200 km to the north of Cape Town.
caption: Schematic West-East geological cross section through the Cape Peninsula to illustrate its general structure. It closely resembles a W–E section through the Back Table, immediately south of Table Mountain, but is not to scale. The height of the "plateau" varies from 1000 m on Table Mountain, in the north, to about 150 m close to Cape Point, 50 km to the south. The colour-coding is the same as on the geological map 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.
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