A CENTRAL AFRICAN GLACIER OF TRIASSIC AGE 693 



PROBABLE GLACIAL SCRATCHES 



Plana Mulambo is situated on the Lualaba River about fifty 

 miles northwest of Kasongo (Fig. 2). One-quarter mile east of the 

 house of the transport agent of the Grand Lakes Railroad at this 

 village is a swift rapid in the river. On the west bank of the river, 

 at the lower end of the rapids, highly inclined slaty quartzite beds 

 are at the same elevation as the base of the Lubilache at the house 

 mentioned. Fig. 3B represents the contact one mile south of the 

 house. The slaty quartzites, owing to the differences in resistance 

 to erosion of their beds, usually weather as sharp-crested ridges and 

 saddles, but here and there are flat surfaces. On the upper sur- 

 faces and never on the sides of these flat exposures of the older rocks 

 are peculiar gouges and scratches (see Fig. 4). 



[••'■•'■■1 River sand 



W&\ Lubilache formation 



K Older folded rocks 



Fig. 3. — Contacts of Lubilache and older rocks on Lualaba River. A, Kitete 

 Rapids; B, Plana Mulambo Rapids. 



Coursing a little east of north and west of south these gouges 

 and scratches have a rude parallelism. Some are cylindrical depres- 

 sions from one to five feet long, and from one-half to three inches 

 wide and deep. The ends are as a rule cigar-shaped and the 

 surfaces of the grooves are striated with fine scratches from y^-g to 

 J inch apart. At the southern end is frequently a bowl-like depres- 

 sion, more deeply cut than the rest of the gouge. Local smoothings 

 of the rocks occur finely striated with parallel scratches and in 

 direction similar to the gouges described. At one place are three 

 crescent-shaped gouges which course from east to west, with the 

 concavity to the south. These, which resemble "crescentric 

 gouges," are four inches in length, the central one being deepest 

 and broadest (see Fig. 4). 



