284 Geological Society : — 



characteristics of Jamaica which bear upon the problem of its late 

 high elevation and former connexion with the continent, and to 

 trace across the neighbouring seas and islands to the mainland the 

 evidences of the former linking of Jamaica to North and South 

 America. The first part of the paper treats of the growth of the 

 island, and the following events are described. After the formation 

 of the mechanical sediments, limestones, and igneous rocks which 

 constitute the basement of the ' White Limestones/ the latter group 

 was accumulated in later Eocene and early Miocene times to a 

 thickness of 2000 feet, and they indicate a subsidence of 3000 feet 

 below sea-level. Their formation was followed by a Pliocene or 

 Mio-Pliocene elevation in an epoch of long duration ; the uplift was 

 inferior to a later (post-Lay ton) one, but sufficient for the removal 

 of Miocene limestone below sea-level. The period was one of 

 general elevation, general dislocation of strata, and great erosion. 

 The formation of the Layton marly beds with loams and gravels 

 which succeeded this period is referred to the end of Pliocene times. 

 In early Pleistocene times the ' post-Layton ' elevation occurred, 

 causing an uplift of from 7000 to 11,000 feet above sea-level. The 

 strata were not greatly deformed, but the epoch was one of enormous 

 erosion. A subsidence somewhat resembling that of the Layton 

 formation followed this erosion in late Pleistocene times, and caused 

 the accumulation of the loams and gravels of the Liguanea forma- 

 tion. In modern times minor changes have occurred, causing the 

 formation of terraces, of channels over banks, of coralline limestone, 

 and of the modern coral terraces. 



The second part of the paper treats of the continental connexions 

 of Jamaica. The author gives details of the submerged plateaux 

 and drowned valleys which are analogous to those still existing 

 above sea-level. TLey indicate that the former altitude of the 

 West Indian plateau, and some portions of the adjoining continent, 

 reached 2| miles. -But the floors of the Mexican Gulf and Honduras 

 aud the Caribbean Sea formed low plains draining into the 

 Pacific Ocean, for at that time the eastern region was high, while 

 the Mexican area was generally low. 



There was a generally high elevation of the Antillean region during 

 the great Mio-Pliocene period, with probable continental connexion ; 

 at the close of the Pliocene period a general subsidence flooded the 

 coastal plains of the continent, and reduced the West Indies to 

 fewer and much smaller islands than those which now exist. But 

 the earlier portion of the Pleistocene period was that of the great 

 continental elevation, when the lately formed Pliocene topography 

 was deeply dissected by rain and rivers, yet there were apparently 

 several pauses of terrestrial movements at different altitudes, as 

 indicated by the various base-levels of erosion. At this time 

 Jamaica and other islands formed a mountainous tableland bordering 

 the Mexican and Caribbean plains. Afterwards the later Pliocene 

 continent was depressed, so as to flood most of the coastal plains of 

 the continent and reduce the islands to small proportions, and 



