698 SYDNEY H. BALL AND MILLARD K. SEALER 



PROBABLE ELEVATION OF LUBILACHE BEDS WHEN DEPOSITED 



The base of the Lubilache formation at Luebo at the present 

 day is 1,475 f^^t above sea-level. In the Maniema, due to uplift 

 by north-and-south faults, the basal beds lie at a higher elevation 

 (1,800 to 2,400 feet), while near Lake Leopold II (1,110 feet), 

 through subsidence of the beds, the country rock is well up in 

 the Lubilache. It is believed that the elevation of the basal beds 

 at Luebo is considerably above that of the lake bottom in which the 

 Lubilache was deposited. It has before been mentioned that 

 residuals of what appears to be the Lubilache formation were 

 found in the Lower Congo, indicating that the lake was probably 

 .once connected with the ocean. Other evidence also points to the 

 uplift in later geological times of the Crystal Mountain region to 

 an elevation of 3,400 feet above sea-level. On the coast there is an 

 indistinct zonal distribution of the Tertiary and Cretaceous sedi- 

 mentary rocks, the later being farther inland. The Crystal 

 Mountains themselves are a peneplain, which has been uplifted 

 presumably by faults coursing west of north and east of south. 

 The Congo River valley through the Crystal Mountains is young 

 topographically and indicates recent uplift, and yet the amount 

 of erosion which the peneplain has suffered would lead one to 

 place its development back at least as far as the Cretaceous. At 

 some time then during or prior to the Cretaceous we may believe 

 the Congo basin to have been practically at sea-level. All evidence 

 at hand indicates that the Lubilache formation was laid down in 

 a lake of which the bed was at, or but shghtly above, sea-level. 



Only to the east did high hills arise, and from the lack of bowlders 

 in the Lubilache immediately surrounding these hills, it is doubted 

 if they reached a maximum elevation of over 2,000 feet above the 

 lake surface. 



SIZE OE GLACIER 



The known extent of the morainal basal conglomerate in the 

 Maniema (at least 100 miles from north to south) is many times 

 greater than any tropical glacier now existing. Further, if the 

 bottom of the Lubilache lake was at as low an elevation as we 

 believe it to have been, we must rank this glacier in size with 

 glaciers of the Malaspina type, if not with continental glaciers. 



