A CENTRAL AFRICAN GLACIER OF TRIASSIC AGE 691 



Before the formation of the great interior lake or sea in which 

 the Lubilache was deposited the Congo Valley was probably a 

 most important depression and after the subsidence the upper 

 portion of the valley formed a wide but rather shallow gulf with 

 arms reaching in instances into valleys of the eastern mountain 

 range itself. A small isolated remnant of flat-lying sandstone 

 having the general lithologic character of the upper beds of the 

 Lubilache, as exposed in the Maniema, was found in the Eastern 

 Mountains in the Luiko Valley. This o'utlier is only a few feet 

 in thickness, and lies in a small tributary valley on an uneven, 

 eroded surface of gneiss. Its elevation above sea-level is about 

 4,800 feet, or nearly 2,000 feet above the highest horizontal rocks 

 known in the region, the sandstone forming Niembo Mountain 

 near Niembo (Fig. 2). This great difference in elevation is due 

 to profound north-and-south faulting along the western front of 

 the Eastern Mountains, but the presence of horizontal sandstone 

 beds in a small valley at a considerable distance from the main area 

 of flat-lying rocks is unquestionably due to its having been deposited 

 in an antecedent valley, the sides of which protected it from com- 

 plete removal by erosion. This outlier, and the residuals of apparent 

 Lubilache in the Bas-Congo, show that this formation once had 

 much wider distribution than at present. 



A type of the Lualaba River basal beds is exposed along the 

 Lulindi River, just downstream from the crossing of the telegraph 

 line, and near the village of Plana Lusuna. This is fifteen miles 

 from the present Lualaba River, and 275 feet above it at Kasongo. 

 The older rocks unconformably underlying the Lubilache are not 

 exposed here, but t3^ical basal beds occur for 200 feet laterally 

 along the river. The matrix of the conglomerate is a yellow, inco- 

 herent, fine-grained, slightly argillaceous sandstone. The exposure 

 is apparently flat-lying. Small bodies are wholly without bedding, 

 others are thinly laminated, while still others have a swirly bedding, 

 the thin laminae curving in concentric bands. Cross-bedding is 

 not rare. The distribution of the bowlders and pebbles is patchy; 

 areas 2 to 40 feet across being without pebbles, while between are 

 heavily conglomeratic areas. In the same conglomeratic mass 

 coarse sand and bowlders 4 feet across occur. The smaller pebbles 



