142 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vo.. VIII. 
deposition ot any sediment in them; all loose material, whether eroded from 
the sides or transported by currents from elsewhere, being immediately 
carried away to deeper water outside. Not less clear is the testimony 
of the wide and compatatively shallow valleys of Carenage and Diego- 
martin, originally much deeper but now to a great extent filled up with 
alluvium. As we go eastward from Diegomartin, the valleys become steep- 
er and narrower, assuming the form of mere ditches in their lower portions 
but having immense delta-like deposits of alluvium at their mouths 
ranging from 80 to 200 feet in height above the level of the Caroni Plain, 
which lies to the south all along the base of the northern or Parian Range. | 
Fig. 3 shows the condition of things in the miocene period after the 
Parian Range had been raised to its maximum height and when movements 
of depression had dislocated and faulted it. The miocene rocks were now 
in course of being laid down in the sea to the south of the Parian Range, 
while the eocene rocks had been partly uplifted. This state of things 
continued until the post-pliocene period, movements of depression taking 
place in the Parian Range, while elevation was going on in the middle and 
southern portions of the island, the result being as shown in Fig. 4, where 
the tertiary formations are seen elevated much above their present height 
leaving two valleys, one in the line of the present Caroni and Oropuch(N.E.) 
Rivers and the other in the line of the Pitch Lake and Oropuch (S.W.) 
Lagoon and Ortoir River. Through these valleys flowed rivers which had 
their origin in the mountain ranges of South America, and their outlets 
to the eastward of the present shore line of the east coast of the island. 
Up to this time Trinidad was not a separate land from Venezuela. When 
the Caribean formation rose above the level of the sea, the Parian Range 
was continuous with that of Venezuela, and the subsequent growth of the 
island by the deposition and upheaval of the cretaceous and tertiary beds 
was continuous likewise across what is now the Gulf of Paria. 
In the valleys mentioned which are shown in the diagram, (Fig. 4), 
large estuarine formations were developed, and in these were deposited 
extensive layers of vegetable matter now converted into lignite, manjak 
and asphalt. But before this, and indeed during the whole time when the 
movements of elevation which raised the oceanic deposits from deep water 
were going on, there was a continual laying-down of fine clastic matter, 
accompanied by vegetable remains, all through the tertiary period. 
The relationships of the various deposits, mostly of tertiary age, form- 
ing all that part of Trinidad south of Latitude 10° 40’ North, are extremely 
complicated. But by aid of the key given by the elucidation of the phe- 
nomena described in this paper, they will sooner or later be completely: 
unravelled. No good exposure of the relations between the strata con- 
taining Orbitoides Echinolampas and Terebratula, and the oceanic beds 
