Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/704

 the mountains, but may have even constituted unknown thicknesses above their present tops.

With regard to the rocks themselves, of which these mountain- ranges are composed, much is yet to be learnt, and to arrive at a satisfactory conclusion about them will yet be the life-study of some future geologist. Many questions of great interest and importance have yet to be answered, thus : — "Were these strata really of lacustrine origin? and if so, were these extensive and thick deposits formed during a subsidence ? If so, what were the outer barriers of such wide-spread "lacustrine" deposits, effectually cutting off all communication with the ocean during the deposition of sediments, it is said, of some 6000 feet ? Or were they laid down when the region was considerably above the level of the sea ? The Dicynodon formation is cut across by the oblique sea-coast near the Gualana River, and extends northward thence into Natal; its boundary therefore on the south-east has disappeared in the present ocean.

Proceeding from the sea inland, through Albany, the country rises in a succession of vast steps, as shown in the outline-section, fig. 13.

The most recent of the Karoo deposits are to be found in the Stormberg* ; and the whole face of this range (as is plainly seen on approaching it) is composed of horizontal strata. Here, again, the question arises, "What could have formed the boundary of a formation that shows so little evidence of displacement as the elevated strata of these mountains? Again, Do these constitute one continuous formation? Were they the vast deposits of a single lake, or, rather, of many successive lakes ? It is probable that, on a closer examination, the latter will prove to be the case, and that this extensive series of strata may be divisible into several limited and overlapping groups of deposits. To explain this, I have sent a section (fig. 14) of that part of the formation to which this paper principally refers. The synclinal structure indicates that one basin must have extended from the neighbourhood of the Katberg on the south to near the Washbank on the north. Thus the dip of the strata of the Queenstown hills is from 5° to 6°, and at the Bongolo Neck 5° N.N.W. ; on an offshoot of the Stormberg, near the Buffel-Doorns Flat, 5° N.N.E. ; at the foot of the Stormberg 4° to 5° N.N.E. ; while at Dordrecht, on the other side of the mountains, at one spot the dip is 4° to 5° S.E., at another 6° to 7° in the same direction, and some twelve miles nearer the Washbank it is 5° to 6° S.S.E. These dips seem to prove this particular basin to have its synclinal axis somewhere about the centre of the Stormberg range, and that, should the strata be continuous, the deposit must be of enormous thickness.

Not only must the period of deposition of such rocks have been of immense duration, but so also must that of their denudation, from the time of the breaking of the original plateau† (of which the


 * Quart. Journ. Geol. Soc. vol. xxiii. pp. 143 and 172. — T. R. J.

† Such a plateau must have been similar to that in Dr. Livingstone's ideal section of South Central Africa.