162 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY, 
north side. The platforms were covered with littoral formations and 
the estuaries filled with aggradational débris. This submerged the 
island to the foot of the back coast country. It clearly took place 
i during the late Pliocene and beginning of Pleistocene time. 
i The next and last event was the epeirogenic elevation, or series of 
elevations, which have continued until the present time, restoring t? 
Ay the island the belt of land now forming the fringing coastal border 
including the elevated reefs. 
The continuity of this uplift may have been interrupted by a mino! 
subsidence in early Pleistocene time. Unfortunately paleontologists have 
not sufficiently analyzed the West Indian marine faunas to enable us t0 
discriminate between the Pliocene, Pleistocene, and recent faunas, espe” 
cially the last. Hence the differentiation of the stages of Post-Pliocen® 
chronology is still vague. As the pre-submerged platforms of the preced- 
ing epoch of subsidence were brought up within the zone of reef cor? 
growth, the first true coral reefs began to fringe the island and formed 
outlying and fringing reefs. As elevation progressed, the oldest of these 
were first raised above the sea into a bench of Soboruco, while ne" 
living reefs were installed upon that portion of the submerged platform 
which the elevation in turn brought up to a position favorable for reel 
growth. Thus successive reefs were elevated into coastal benches, while 
living reefs continued to grow in the adjacent waters, as are found t0 
day. In this manner, as the island was constantly rising, the terrace? 
of reef rock now found at altitudes of 60, 25, and 15 feet, as describe 
in the geologic portion of this paper, were made. Similar living reels 
continued to grow as now in the adjacent waters, which in turn ma 
some day be elevated into marginal terraces. Inasmuch as the elevate 
reefs are made up entirely of living species, there is no reason to assig” 
this elevation to a more remote period than late Pleistocene and recent 
time, 
Accompanying their elevation the lagoonal débris behind the barri 
reefs was also converted into low coastal swampy lands, and the streams 
renewed their channels to the sea across the old alluvial plains. This 
elevation completed the geographic evolution of Jamaica into the la? 
area it presents to-day. f 
From the foregoing statements it will be secn that the evolution ° 
Jamaica has resulted from varied processes of land construction, inclut" 
ing, first, piling up of volcanic ejecta in the beginning of its history 
which we shall not further mention at present; and two kinds of up 
lifts, orogenic and epeirogenic movements respectively, 
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