20 
ORIGIN OF THE ANDES 
in the Caupolican district of Bolivia Steinmann ® records Early 
Paleozoic strata in southeastern Bolivia. Keidel ® considers the 
pre-Cordillera of northwest Argentina as having a basement of 
rock folded in pre-Cambrian times. 
(3.) Evidences indicate that the marine Late Carbonic trans¬ 
gression came from the east, and that the plant-bearing Carbonic 
beds of Paracas peninsula, in about latitude 14“ S., on the Peru¬ 
vian coast, were littoral in character and on the eastern margin of 
an ancient land-mass. 
(4.) There is total dissimilarity between the early Miocene 
fauna of northern Peru and southern Chile, showing an entire 
lack of communication between the two regions at that time, and 
an arrangement of the land which prevented the prototype of the 
present Humbolt current from reaching Peru. 
(5.) There is complete absence of marine Eocene, Oligocene 
and Miocene deposits between latitudes 6° and 34® S. 
(6.) By the presence, between these latitudes, of a deep longi¬ 
tudinal trough (Peruvian and Chilean deeps) immediately off the 
present coast the consequent gradient being one of the steepest in 
the world, and indicating a fault-scarp. This interpretation is 
emphasized by the great seismic and volcanic band of the Western 
Andes, and the recency of this faulting is indicated by the fact 
that adjustments throughout the whole length of the Western 
Andes are still actively taking place. Earth tremors are constant 
and the numerous disastrous quakes are a matter of human history. 
The next item of Andean history is the transgression of the 
Siluric and Devonic sediments which form so considerable a part 
of the rocks of the Eastern Andes in Peru and Bolivia, and whose 
folded hog-backs gradually disappear beneath the detrital deposits 
that cover the altaplanicie of Bolivia. 
Late Devonic and Early Carbonic fossils have not been dis¬ 
covered in the Andes and there is some evidence that marked 
folding and emergence occurred at this time, in the discordance 
between Devonic and Late Carbonic (Ouralian) observed by H. 
Gerth in the Eastern Andes. 
Next followed transgression of Late Carbonic rocks correlated 
7 Quart. Jour. Geol. Soc. London, Vol. LXII, p. 425, 1906. 
8 Neues Jahrb,, Beil. Bd. 34, pp. 176-252, 1912. 
9 Op. cit. 
10 Geol. Rundschau, Bd. 6, pp. 129-153, 1915. 
