Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/706

 table-tops of such mountains* as the Winterberg, the Groot Tafelberg, the Twee Tafelbergen, Honder Neck, the Mostert Hoek mountains, and Hangklip, near Queenstown, are the evident monuments) to the excavation of the deepest valleys in the existing flats.

Whether or not all these Karoo strata were deposited under a uniform climate it is difficult to prove ; but that there was some difference between the climate of the Dicynodon period and the present seems to be indicated by the section (fig. 8) of the Upper Stormberg, exposed near Dordrecht. These strata are now about 5000 feet above the level of the sea. One bed, 10 feet thick, is composed of a fine conglomerate of small fragments of quartz, and can be traced wherever the side of the mountain is sufficiently bare. The only locality, at present known, whence such quantities of quartz could be derived is the Washbank. Immediately above and below this band of conglomerate is a coarse gritty sandstone. The one above is of a yellowish ochre colour, containing coarse nodules, such as Nos. D. S. 2 (D. S. 1 is a specimen of the quartz-grit) ; in many places it is discoloured with ferruginous patches. The one below is the zone of fossil wood, which is found in abundance, evidently the remains of a primaeval forest. In some places there are trunks of trees between 20 and 30 feet long, and great numbers of segments erect in the position in which they grew ; these latter are often more than 8 or 9 feet in circumference. The fossil wood is found wherever this coarse sandstone makes its appearance. The specimens that have been examined are pronounced to belong to the Coniferae. These last-mentioned strata are amongst some of the latest of the Stormberg formation ; and the wide-spread remains of coniferous forests found there seem to point to climatal conditions different from the present, and still more different from those of the old Carboniferous formations of Europe and elsewhere, the plentiful remains of coniferous trees here most probably indicating that such forests flourished in a more temperate climate. In such a climate and in deposits formed under such circumstances it is not probable that such abundant coal-measures would be found as those accumulated in the northern hemisphere. From the wide extent of this fossil wood it is evident that immense tracts of forest must have existed in those ancient times ; but from that time to the present an interval has intervened of incalculable duration, during portions of which agencies (yet to be explained) have been in operation that have not only occasioned the denudation above referred to, but have also rendered the country a treeless region. Trees introduced by human agency thrive well ; and it is not, therefore, the present climate that has caused the annihilation of forests : we must look to a remote period for an explanation of this as well as the other peculiar features of the country.

Denudation of the Karoo Beds. — The encroachment and retreat of the sea cannot have effected the vast denudation, either during the subsidence or the upheaval of the land ; for there is no evidence that any of the strata, except those on the immediate sea-coast, have


 * These are all mountains of denudation and not of elevation.