Lets continue!
Overview of the route along the Cape Fold Belt
Day 3
On this third day we continue through the Natal Sector of
the NNMB as we depart PMB and travel across the Mzumbe Terrain. As we continue
along the coast we’ll cross the Mellville
Thrust Zone and enter the granulite-facies Margate Terrain. Here we encounter more granites and exotic
varieties of the charnockite of the Oribi Gorge Suite. Charnockites are
granitoids that contain orthopyroxene. In order to allow for the stabilisation
of orthopyroxene, the bulk rock composition must have low water content and
exist at high temperatures, i.e. in granulite facies space. One of the
charnockite we’ll be visiting is the Port
Edward Enderbite. This is a charnockite that consists of quartz,
antiperthite, orthopyroxene and magnetite. The name Enderbite is derived from
the type locality of this rock, in Enderby Land, Antarctica. For now, this is
as close as we can get – however we should have some Antarctic alumni on our
team, so remember to ask them about Enderby Land!
We will then continue south and exit the NNMB, for now, and
enter the Karoo Supergroup once again. This time we now travel through the
Adelaide Subgroup of the Beaufort Group. We will have a chance to look at this
more carefully once we cross the historical Kei River. Soon after entering the
Eastern Cape we’ll find our way to the overnight destination of East London.
Day 4
By now I’m sure everybody’s heads will be spinning (like
mine, for example, while typing all this geology); and this will thus be the
ideal time to travel west and into the Cape
Fold Belt (CFB). The rocks encompassed within the CFB were deposited ca.
485 – 300 Ma under continental shelf to beach marine environments. The Cape Supergroup comprises of three
distinct lithostratigraphic groups. These include: The quartzite and shale of
the Table Mountain Group; shale of
the Bokkeveld and sandstone and
shale of the Witteberg Group.
These rocks were later deformed to form the CFB. This was in
response to compression associated with the formation of Gondwana. The CFB can
be separated into three tectonic domains, including; the western and eastern
limbs, separated by the Syntaxis
situated north of Cape Town. Our journey will take us from East London to Port
Elizabeth, across the CFB and along the Zuurberg
Pass. Here we will be able to investigate the intricate structural features
defining the Western Limb of the CFB. Perhaps we may also get the compasses out
and get everybody to measure some strikes and dips!
After crossing the CFB we join the Garden Route and travel
along the vast quartzite of the Peninsula Formation. For our engineering
geology friends, we’ll stop and have a look at some of the incredible bridges
build over the mammoth gorges. Our overnight stop on this day is Knysna.
Day 5
This is the final leg of this phase of the journey. Today we
travel from Knysna to the Council for Geoscience regional office in Bellville. First, our journey continues
out of this picturesque town and continues down the Garden Route toward George.
Before this, we may have a quick stop at the famous Knysna Estuary and
potentially some calc-silicate rocks associated with the Cape Granite Suite. Upon arriving in George, we’ll cut back across
the CFB once again and head toward Oudtshoorn. In Oudtshoorn we’ll note a Cango Precambrian inlier of ca. 900 Ma
rocks and one of the large E-W faults that define much of the CFB. These faults
are often synonymous for the Enon
Formation of red beds residing along the scarp. Also, these faults are
renowned for controlling the development of numerous hot springs. Perhaps one
day we’ll harness this heat and generate energy from it!
From Oudtshoorn we’ll take the R62 and see lots of cool
stuff! Basically many, many more structural features, e.g. the Huis River Thrust Zone and Cogmanskloof. Eventually we’ll near
the, now even more famous, Syntaxis and we’ll get to see how much more
intensely the CFB features are around here. The remainder of this trip will
take us through most of the Table Mountain Group, and eventually onto the Malmesbury shale. Sadly, these shale mark
the approach of Bellville and the end of this first leg of our South African
geological tour.
Our group Our group will now get to learn some remote sensing, GIS and participate in several lectures and short courses in Bellville. In addition, we’ll have a tour of the Cape Peninsula before starting the next leg of our geological tour. This next leg will take us from Cape Town, up the western Limb of the CFB and into the Namaqualand-sector of the NNMB. Stay tuned for that!
