HILL : GEOLOGY OF THE ISTHMUS OF PANAMA. 247 



Isthmian section are largely developed throughout this region. The 

 formations of the River Tuyra described by Maack, 1 are almost identical 

 in character with that of Vamos a Vamos and lie directly within their 

 line of strike, and are much nearer the Caribbean than the Pacific. 



From the mouth of the Atrato eastward ta the Mouth of the Gulf of 

 Maracaibo, and thence in the parallel fringing islands along the northern 

 shore of South America, the record of continuity seems quite complete. 

 Maack 2 found the formations around Turbo, near the southern end of the 

 east shore of the Gulf of Darien, to consist of clays with coal which he 

 thought to belong to the Tertiary period. 



The low chain of hills near Cartagena, according to Hermann Karsten, 3 

 are composed entirely of Tertiary and Quaternary deposits, and they 

 contain thick agglomerated limestone beds alternating with sands and 

 marls, containing beds of argillaceous sandstone very much like those of 

 the Isthmus of Panama. Karsten also gives many other localities from 

 Cartagena eastward. 



Sievers 4 in his recent map of Venezuela, has shown the continuation 

 of the possibly Eocene and " Miocene " formations east of the Gulf of 

 Maracaibo, near the northernmost point of South America, latitude 12°, 

 on the mainland and the peculiar peninsula of Paraguana. East of this 

 peninsula the east and west coast of the northern end of South America 

 drops southward over a degree of latitude, and from Puerto Cabello be- 

 comes granitic. The strike of the "Miocene" formations of Paraguana 

 continued eastward is north of the main continental outline, and the 

 formation outcrops in the islands of Curacoa and Trinidad. 



The foregoing observations certainly indicate the existence of a con- 

 tinuous littoral of older Tertiary sediments around the Caribbean side of 

 the Tropical American region, and incidentally a pre-existing land which 

 they bordered. Of course it is impossible, from the lack of paleontologic 

 evidence, to state that these older Tertiary beds are exactly synchronous, 

 but they probably belong to the continuous series of sediments of the 

 Eocene and Oligocene epochs. Sapper shows from their position that 

 they are Pre-Pliocene in Yucatan and Guatemala. Dr. Dall's studies of 

 my own collection, as given in the Appendix, show that they are Eocene 

 and Caribbean Oligocene along the Isthmian and Costa Rican coasts, 



1 Previously cited. 



- Op. cit., page 160. 



3 Geologie de l'Ancienne Colombie, Boliviarienne, Venezuela, Nouvelle-Grenade 

 et Ecuador, 1886, p. 23. 



* Petermann's Mitteilungen, 1896, Bonn, Vol. XLII. Part 6, p. 125. 



