416 
MINERALOGICAL GEOLOGY 
It overcomes the intrinsic objections of previous formation of 
ulexite in playas, and especially the almost unsurmountable one 
that the colemanite is a playa deposit. It harmonizes perfectly 
with all known geological features. If metasomatic replacement 
be urged the process must take place while the calcareous forma¬ 
tion is still a horizontally lying bed, normally reclining on other 
sedimental beds. It is, therefore, in no sense a vein formation. 
By no possible interpretation can it be misconstrued into vein de¬ 
velopment. The two processes are wholly distinct, unrelated, and 
incomparable. 
Ki;ye:s. 
Death Valley Section of Boraciferous Terranes. In the con¬ 
sideration of the divers aspects of the colemanite deposits and their 
origin the great succession of Tertiaries exposed in Furnace Can¬ 
yon leading out of Death Valley is not without fundamental bear¬ 
ing. The general features are as follows: 
Feet 
18. Basalt . SO 
Unconforinity 
17. Shales, gray, boraciferous. 40 
16. Shales, yellowish. 500 
15. Sandstone, pebbly, brown. 500 
14. Conglomerate, irregular. 60 
Unconformity 
13. Shales, argillaceous, yellow. 200 
Unconformity ■' 
12. Basalt . 30 
11. Shales, pale yellow. 500 
10. Sandstone, friable, reddish. 25 
9. Shales, argillaceous, olive. 150 
Unconformity 
8. Basalt . 100 
7. Shales, olive green to yellow. 60 
6. Shales, bluish, abundant colemanite. 50 
5. Shales, buff. 300 
Unconformity 
4. Basalt . 200 
3. Conglomerate .300 
Unconformity 
2. Shales, bluish, argillaceous.1000 
Unconformity 
1. Andesite (exposed). 5(X) 
The suggestion that some of the section might be repeated be¬ 
cause of faulting finds no substantiation from observation; yet this 
is not beyond possibility. 
Keyes. 
