Part III.—The Climatical changes of South Africa (Eastern Province an the Vicinity), as indicated by its Geology and Fossils; and specially the Glacial Denudation of the Kaboo Strata.

Abstract

The consideration of the climatal changes that have taken place in this portion of the ancient world during the deposition of the various formations treated of in the first part of this memoir will lead me to make some remarks upon the probable cause of the denudation of a large portion of the Dicynodon-rocks in the Eastern Province. Tertiary Climates .—The evidence of the Pliocene shells of the superficial limestone of the Zwartkops heights and elsewhere leads us to believe that the climate of South Africa must have been of a far more tropical character than at present. Take, for instance, the characteristic Venericardia of that limestone: this has migrated along the coast some 29 or 30 degrees, and is now found within a few degrees of the equator, near Zanzibar, gradually driven, as I presume it must have been, further and further north by a gradual lowering of the temperature of the more southern parts of this coast since the limestone was deposited. During the formation of the shell-banks in the Zwartkops estuary, younger than the Pliocene limestone, the immense number of certain species of shells, which have as yet been found living only in latitudes nearer the equator, point to a somewhat similar though a more modified change of temperature. These, however, do not seem to have been the only periods when this part of the world had a temperature different from that it now possesses. In the Jurassic times the shells of the Trigonia -beds indicate a tropical or