CHANGES IN KELATIONS OF OCEANIC WATERS. loo 



tKroughout the whole region varies from a few luiiKh'ed to al)out 3,000 

 feet. Accordingly the Pliocene deformation may have been about this 

 amount, thus allowing the drainage of the Pliocene continent to reach 

 the Pacific through contracted seas, as before suggested. Moreover, from 

 the geomorphy and the features of denudation* in Cuba and Jamaica, it 

 is apparent that a very considerable if not indeed the greatest amount 

 of orogenic upUll lias 1)ecn during the Pleistocene i)eriod ; l)ut the ter- 

 restrial movements which have almost obliterated the Antillcan conti- 

 nent have depressed the Antillean area without submerging tbe Central 

 American bridge. 



The deep-sea Echini and other forms of deep-sea invertebrates of the 

 Antillean waters belong to old and Pacific types (Agassiz) '•', and geo- 

 morphically there was no known deep-sea connection with the Pacific 

 ocean since the Miocene period. Again, the Pacific contours do not sup- 

 port the hypothesis of a post-^Iiocene extension of the basin of the sea 

 of Honduras to that ocean, as do those of the gulf of Mexico and Carib- 

 bean sea, as shown on map. It would a})pear that the latter basins 

 drained directly into the western ocean in the earlier part of the Pleisto- 

 cene period. 



The Matanzas (or late Pliocene) depression admitted the Atlantic cur- 

 rents with greater depths than at present to the Antillean seas. The 

 Pacific waters probably had access by one or two straits with depths of 

 about 200 feet, according to Crawford's report on the altitude of recent 

 fossils in Nicaragua, for they rise high above the low divide between the 

 waters. The Panama divide is now 287 feet and the Nicaragua is 150 

 feet above tide, with Matanzas limestones at Panama at an elevation of 

 at least 150 feet. On this question we need more investigation. In the 

 Antilles the terrestrial movements, whether orogenic or epeirogenic, have 

 recently raised the mountain ridges higher than the synchronous eleva- 

 tions of the deposits on the coast. The same, probably true in Central 

 America, also affected by the recent volcanic action, would favor the 

 existence of shallow straits at the close of the Pliocene period between 

 the Antillean waters and the Pacific. With the earlier Pleistocene eleva- 

 tion tlie drainage of the Antillean continent was again restored to the 

 Pacific ocean between the barriers of Central America, which were now 

 being brought into prominence by combined epeirogenic, orogenic and 

 volcanic movements, thus turning the Cariljbcan and Gulf plains into 

 basins which became seas at the end of tlic i)()st-Matanzas elevation ; l)ut 

 this Pleistocene continent was not obstructed Ijy barriers to the drain- 

 age so as to )»revent the general recxcavation of tlie valleys wliieli had 

 been partly filled during the Matanzas subsidence. 



♦ Am. Jour. Sci., vol. xxvil, 1884, p. 187. 



