TOUR:
Cape Peninsula Field Trip
LED BY:
Dr John Rogers
Department of Geological Sciences
University of Cape Town
DURATION:
1 Day
DATE:
13 September 2005
TIMES:
08:00 - 17:00
COST:
R400.00 per person
Including lunch pack, boat trip and entrance fees
MAXIMUM PAX:
This tour is limited to 40 people
DESCRIPTION:
The aim of the excursion is to understand the
geological history of the Cape Peninsula and to show
how a multitude of geological principles are illustrated
in a relatively small area.
ITINERARY:
Stop 1: Three Anchor Bay
Late Proterozoic (560 Ma) Malmesbury Group.
Oldest rocks in the Cape Peninsula. Well-preserved
turbidites. Steeply tilted to the S on N limb of Signal
Hill Syncline. Minor sinistral faulting.
Stop 2: Sea Point Contact
(Walk from Sunset Beach to Queens Beach and the
Darwin Plaque). Spotted hornfels of the contactmetamorphic aureole around the Cape Granite Pluton
(540 Ma). Migmatite at the Sea Point Contact.
Xenoliths of spotted hornfels. Lion's Head with
igneous (granite), metamorphic (hornfels) and
sedimentary (sandstone) rocks in one hill.
Stop 3: Clifton First Beach
(Walk down to beach and back up to the road via
steps). Early Cretaceous (130 Ma) dolerite dykes
intruding the Cape Granite.
Stop 4: Disa Estuary and Hout Bay Beach
(Walk beside estuary to beach and dunes)
Estuary of the Disa River and its interaction with Hout
Bay beach and coastal dunes.
Stop 5: Hout Bay and Chapman's Peak Drive from
the Sea
(CALYPSO - one hour boat trip; glass-bottomed boat)
Boat trip to view debris flows on the slopes of
Constantiaberg and the nonconformity between the
older (540 Ma) Cape Granite and the younger
Table Mountain Group sandstones (<520 Ma), both
intruded by the even younger dolerite dykes (130 Ma)
of the False Bay Dolerite Dyke Swarm, mapped by
airborne and seagoing magnetometers. Recently
installed engineering structures (catch nets and halftunnel) clearly visible from the sea.
Stop 6: Viewsite at the N end of Chapman's Peak
Drive
(Short walk between bus stop and viewsite)
Sedimentary structures, e.g. crossbedding, ripple
marks and parting lineation in the Graafwater
Formation of the Table Mountain Group (Ordovician)
of the Cape Supergroup
Stop 7: Chapman's Peak Drive - Noordhoek
Beach Viewsite
(Short Walk from Bus Stop to Viewsite)
View over a variety of coastal and nearshore
environments. Wreck of the KAKAPO proof of
progradation of the coastline since 1900 by over
100m.
Stop 8: Misty Cliffs, N of Scarborough
Proof of higher sea level, cemented boulder beach
below cemented talus.
Probably Early Pleistocene.
Stop 9: Smitswinkel Bay
Evidence of Cretaceous block-faulting as Gondwana
broke up. Dolerite dyke with granite xenoliths.
Stop 10: Froggy Pond, south of Simon's Town.
Most accessible dolerite dykes. Good example of
differential weathering. Most abundant xenoliths of
spotted hornfels.