Mar. 1899. THE OREs OF COLOMBIA—NICHOLS. 129 
is succeeded by Odlitic ranges, which, in turn, overlie Permian and 
Triassic strata, while the central regions are of Devonian and Silurian 
age. The mountains, he says, were raised in four upheavals, of which 
the first occurred+in the Permian or Triassic. John C. Randolph 
' (see p. 159) finds, in the Magdalena valley, Archean schists, on which 
lie Triassic sandstones and Jurassic limestones. The author of the 
article on Colombia in the Encyclopedia Britannica,* says: ‘‘ The 
fundamental formations of Colombia are igneous and metamorphic, ° 
the great masses of the Cordilleras consisting of gneiss, granite, por- 
phyry and basalt. In many places the Carboniferous strata have 
‘attained considerable development, though they have been thrown 
into strange confusion by some unknown disturbance.” With the 
Museum collection there is a specimen of encrinal limestone from the 
Department of Santander which appears to be of Subcarboniferous 
age, although none of the fossils are in such condition that they can 
be determined positively. There is also a very fair specimen of bitu- 
minous coal from Titiribf, in Antioquia, and coal is reported from 
many localities. The sedimentary rocks in the Departments under 
consideration, Antioquia and Tolima, are everywhere mingled with 
and penetrated by eruptives, said to be largely andesites. According 
to Robert White,+ the Eastern Cordillera is almost all volcanic, while 
the rest of the Cordilleras are composed of granites, granitoid rocks 
and diorites. From specimens inthe collection it would appear that 
dacites, trachytes and rhyolites are not uncommon. The earlier of 
these lavas were erupted during the great disturbance closing the 
Tertiary. There has been much volcanic activity in the region ever 
since. At the present time there are a number of active and dor- 
mant volcanoes there. Fora fuller account of the geology, see the 
article by Randolph referred to above, and also ‘‘The Manganese 
Deposits of the Department of Panama, Republic of Colombia.’’ } 
zs _—_— 


*As quoted in the Handbook of Colombia, p. 9. 
+Rep. Br. Assn. Adv. Sci., 1882, p. 552. 
tEduardo J. Chibas. Tr. A. I. M. E., vol. xxvii., 1897, p. 63. 
