unfossiliferous formations > Archaean to
\ of pre-Devonian age / Silurian(?)

The general structure of the colony is simple. It may be regarded as a
shallow basin occupied by the almost horizontal rocks of the Karroo.
These form the plains and plateaus of the interior. Rocks of pre-Cape
age rise from beneath them on the north and west; on the south and east
the Lower Karroo and Cape systems are bent up into sharp folds, beneath
which, but in quite limited areas, the pre-Cape rocks emerge. In the
folded regions the strike conforms to the coastal outline on the south
and east.

Pre-Cape rocks occur in three regions, presenting a different
development in each:--

+-------------------------+-------------------------+-------------+
| North. | West. | South. |
+-------------------------+-------------------------+-------------+
| Matsap Series | Nieuwerust Beds | Cango Beds |
| Ongeluk Volcanic Series | | |
| Griquatown Series | Ibiquas Beds | |
| Campbell Rand Series | | |
| Black Reef Series | | |
| Pniel Volcanic Series | | |
| Keis Series | | |
| Namaqualand Schists | Namaqualand Schists and | Malmesbury |
| | Malmesbury Beds | Beds |
+-------------------------+-------------------------+-------------+

The pre-Cape rocks are but little understood. They no doubt represent
formations of widely different ages, but all that can be said is that
they are greatly older than the Cape System. The hope that they will
yield fossils has been held out but not yet fulfilled. Their total
thickness amounts to several thousand feet. The rocks have been greatly
changed by pressure in most cases and by the intrusion of great masses
of igneous material, the Namaqualand schists and Malmesbury beds being
most altered.

The most prominent member of the Cango series is a coarse conglomerate;
the other rocks include slates, limestone and porphyroids. The Ibiquas
beds consist of conglomerates and grits. Both the Cango and Ibiquas
series have been invaded by granite of older date than the Table
Mountain series. The Nieuwerust beds contain quartzite, arkose