HILL: GEOLOGY OF JAMAICA, 161 
Blue Mountain ridges, was elevated some 500 feet or more, bringing up 
With it, not only the present marginal border composed of the new made 
Sediments of the Bowden epoch, but a now slightly submerged area 
towards tho south, which extended at least as far as the present 500 
fathom line, embracing the Pedro banks and keys. This upward move- 
Ment, while accompanied by slight deformation, was less orogenic than 
those of the preceding epoch, probably representing the last throes of 
the Antillean uplifts. It is very certain that the large area of Jamaica 
Was expanded during this epoch (late Miocene) beyond its present borders 
% least as far as the present 500 fathom line. 
Accompanying or closely following the time of this elevation in late 
locene or early Pliocene time was a period of great erosion and de- 
Audation, which largely produced the minor relief of the surface con- 
figuration of to-day. During the Pre-Bowden elevation the headwaters 
9f the marginal drainage of the south coast, which then flowed out to 
ca across the present submerged banks, were actively engaged in cut- 
ting ont, as headwater amphitheatres, the embryo embayments of the 
Present Liguanea type of plains, and the older sink-holes in the summit 
of the limestone arch by dissolving through the soluble limestone. In 
the Post-Bowden epoch the sink holes were cut downward to the insolu- 
le Strata, underlying the limestone, producing the first of the present 
Steat interior basins, which also commenced to expand laterally by 
"Tosion of their soluble margins. Meanwhile, the coastal drainage 
“pidly extended interiorward by headwater erosion, and the country 
adjacent to its lower portions became extensive base-levelled plains, and 
Neluded then what are now the submerged benches of the island, and 
Which were veneered with the aggradational Kingston formation dur- 
Ng a subsequent subsidence. This period of erosion was late Miocene 
or early Pliocene, corresponding in time almost exactly with the great 
!e-Lafayotte erosion epoch of the North American continent, 
During this late emergence the middle series of terraces (now from 
00 to 700 feet high) were cut around the coastward face of the back 
“ast country, 
Possibly there was another subsidence in late Pliocene time, — the 
tet of a cycle of epeirogenic oscillations that characterized the later 
"story of the island. The island once more underwent partial subsi- 
“nee; the pre-eroded coastal plains and base-levelled bights bordering 
* island became in their seaward extension submerged platforms, 
dle their interior borders constitute deeply indented estuarios at the 
uths of the great rivers of the south coast and Montego Bay of the 
VOL. xxxıv. 11 
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