The Pasoemah region S of the Goemai Mts. in W. Palembang is largely occupied by Quaternary volcanics, which form a sharply dissected plateaulike country, whose surface gradually slopes downward in an ENE direction from ± 1000 m to ± 300 m above sea-level, conformably to the courses of the Selangis and Lematang Rivers above their point of confluence. Where the Lematang River unites with the Moelak River, the acid welded tuffs of the Pasoemah highland, to which attention will be drawn in this paper, are cut off by a steep bluff, formed undoubtedly by retrogressive erosion, which was substantially facilitated by the presence of vertical cleavage planes in the rhyolitic tuff series. In the Goemai Mts., described elsewhere in detail by K.A.F.R. Musper (1937)... |