A CENTRAL AFRICAN GLACIER OF TRIASSIC AGE 683 

 GENERAL GEOLOGY (Fig. l) 



The coastal plain is underlain by marine sandstones which are 

 inclined gently toward the ocean. The sandstones, which are 

 covered by recent alluvium at the Congo mouth, are considered by 

 geologists who are familiar with them to be of Tertiary and Cre- 

 taceous age. 



Fig. I. — Showing approximate geological boundaries in the Belgian Congo 



The so-called Crystal Mountains consist of older rocks, the 

 age of which has not yet been satisfactorily determined. The 

 older members of the series consist of mica schists and sericitic 

 quartzites, interbedded with which are chlorite and epidote schists, 

 representing either basic lavas contemporaneous with the sedi- 

 mentary rocks, or very ancient intrusive bodies of igneous rocks. 



Of later origin are intrusive masses of granite and gabbro, now 



