Geological Notes on Griqualand West
Authors: Stow G. W. 
Published: October 2009

The geological results of a journey made by Mr. G. W. Stow and Mr. F. H. S. Orpen from the Orange Free State into Griqualand West are communicated by Mr. Stow in this paper, with numerous carefully executed sections and a geological map based on the survey map prepared by Mr. Orpen for the Government. From the junction of the Riet and Modder rivers (south of the Panneveldt Diamond-fields) westward to the junction of the Vaal and the Orange, over the Great Campbell Plateau to Griquatown, Ongeluk, Matsáp, Potgieter, the Langeberg, Witte Zand, and to Kheis and the Schurwe Bergen, the track traversed three degrees of longitude, but nearly 300 miles of road. The return route north-east to Mount Huxley and Daniel's Kuil, and eastward to Likatlong, on the Hart or Kolang River, was nearly as long; and its results form part of the present communication. A subsequent portion of the journey up the Hart, across to the Vaal, down the valley by the diamond-diggings of Hebron and Klipdrift to the Panneveldt, will be treated of in another paper.

From the Modder, first south-westward and then westward, to the junction of the Vaal and Orange, the olive shales of the
Dicynodon
-or Karoo-series, traversed frequently by igneous rocks, form the country, and are seen in some places to lie uncomfortably on older rocks. The shales reach to the edge of the Campbell Randt, on the other side of the Orange River, and have been, it seems, to a great extent, formed of the débris of those old hills. The oldest rocks of the locality are seen cropping out here and there in the gorges at the foot of the Randt, and consist of metamorphic rocks, greatly denuded, on which the massive and extensive siliceo-calcareous strata of the Great Campbell Plateau lie uncomfortably. These latter and the breccias of their slopes are coated thickly with enormous travertine deposits. Beyond the Plateau, at Griquatown, a long parallel range of jaspideous rocks comes out from beneath the Campbell Plateau, presenting a wonderful group of yellow, brown, chocolate and red jaspers, with magnetic and other ironstone, and beautiful seams of blue and yellow crocidolite. The southern portion of this range has long been known as the “Asbestos Mountains” and the “Doornberg.” Igneous rock-masses occur around Ongeluk, west of the Jasper range; and then bright-red Jasper rocks crop up near Matsáp, succeeded to the west by the parallel quartzite range of Matsáp, and again by other bedded jaspers, which seem to lie in a synclinal of the quartzite rocks, which come up again in the Langeberg. These are succeeded by lower rocks, consisting largely of sandstone, grit, and quartzite, with more or less pervading mica, as far as the journey extended in the Schurwe Bergen, also parallel to the former ranges. The maximum thickness of the successive strata is calculated by the author at 24,000 feet; allowing for possible reduplications, the mininmum is regarded as not less than 9000 feet. The details of stratification, successive upheavals, denudation, nature and origin of the salt-pans, escarpments, river-valleys, and other features were treated of by the author, who has supplied a very large collection of specimens illustrative of the phenomena observed in the line of march, and of his numerous sections, maps, and sketches.