114 SIERRA DE UMANGO 
convenient to charaterize in short terms the lithological habit of 
the conglomerate. 
The quantity of the boulders in relation to that of the cement is 
very considerable. The size of the boulders is always large, and 
badly rounded forms dominate. They consist entirely of old crys- 
talline rocks, gneisses, schists and granitic varieties of almost the 
Fig. 20. Sunken erosion remnant of a young (tertiary) conglomerate, lying with great unconformity 
over a zone of strongly dislocated, continental strata. The vertically striated part of the picture 
signs conglomerate, the dark wills are basement crystalline rocks. The continental strata are buried. 
— A graben in the high ridge of the Sierra de Umango. Looking south toward the Cumbre de 
Umango. 
same kind as in many parts of the Umango crystalline area. The 
conglomerate is clearly waterworn, and the cement seems to be a 
calcareous sand (it is now considerably endurated). Stratification 
is not conspicuous in all parts, but somewhere a distinct one can 
be observed. The sediment is jointed to vertical cliffs of great 
height, a test of a considerable cementation. Interstratifications of 
sandy layers have not been observed. The whole formation is 
evidently an ancient mountain shingle deposit, formed during con- 
ditions of steeper gradients. The material does not seem to be of 
a distant origin. 
This conglomerate lies but in slightly tilted position. It ends 
ey wy  ” 
