696 SYDNEY H. BALL AND MILLARD K. SEALER 



subangular, and are frequently large and fresh. Further, at 

 several places the bowlders are in excess of what can be considered 

 the load of one tree. In shales elsewhere in the world which are 

 known to have been deposited in lakes or seas with tree-lined shores, 

 similar bowlders occur in but few instances. 



We believe, then, that these bowlders were transported by 

 icebergs, derived from glaciers, and which melted where perhaps 

 arrested in their courses by cross-currents. 



Nyangwe was apparently the northern limit to which these 

 icebergs reached, although below Nyangwe the immediate Lualaba 

 (Congo) Valley only was examined. From Nyangwe to 5° S., 

 however, in almost every mile of Lubilache exposures traversed, 

 these erratics were noted. As the morainal conglomerate extends 

 south of Nyangwe, we have perhaps evidence here of the south- 

 ward retreat of the glacier in early Lubilache times. 



RESUME OP EVIDENCES OF GLACIATION 



It is concluded from the evidence given above that during 

 Triassic time at the beginning of the deposition of the Lubilache 

 series, a glacier, or glaciers pushed in a tongue down the present 

 valley of the Lualaba River; from the fact that large bowlders, 

 probably dropped by icebergs, are found at least 200 feet above 

 the base of the formation, it is believed that long after the glacier 

 had retreated toward the south, glaciers still existed to the south- 

 east. This glacial epoch, therefore, must have been of a con- 

 siderable duration. 



The glacial features presented by the Lubilache formation con- 

 tiguous to the Lualaba Valley in the Maniema are : 



1. Striations, having the characteristics of glacial striations, 

 on pebbles in the basal conglomerate of this series, indicating 

 morainal origin.- 



2. The tongue-like form of the basal Lubilache beds in the 

 Lualaba Valley, and the character of this conglomerate, including 

 the size of the bowlders, the lack of assortment, the patchy arrange- 

 ment of the material, and the preponderance of bowlders of local 

 origin. 



3. Erratic bowlders, presumably dropped by icebergs, occurring 



