[ELLS] NOTES ON GEOLOGY OF TRINIDAD AND BARBADOS 123 
like structure of the lake itself, the underlying shales being struck at 
fifty feet or even less. With the large output of over 100,000 tons per 
year, it is conceivable that under present conditions this deposit will ulti- 
mately be exhausted. Such a possibility is, however, remote, and even in 
that case the enormous amounts found along the beach as the result of 
former outflows, as well as between the shore and the lake itself, will 
enable the mining of the asphalt to be carried on to an almost indefinite 
period. 
The northern slope of this anticline can be readily seen in railway 
cuttings on a tram line connecting the north-west side of the lake with 
the village of La Brea, which is a shipping point. Here curious out- 
flows of the asphalt are associated with the surrounding shales, sometimes 
as injected sheets between the strata, sometimes as large masses which 
have pushed up the beds after the fashion of an igneous laccolith. In 
places the blackish shales have been changed to a red colour as if the 
contained bituminous matter had been eliminated through the action of 
heat. 
Along that part of the coast south of the shipping pier and extend- 
ing for a mile the strata where seen are much disturbed. Small faults 
also occur and some portions of the shore asphalt may have been derived 
from the exudation of the petroleum along such lines of fracture. A 
boring made here many years ago still discharges a thick black petroleum 
at the rate of about a barrel per day, and the discharge from this well, 
which is quite shallow, has spread over a large surface in the form of 
tarry asphalt in which are small pools of the liquid petroleum. The 
presence of the anticline at this place can also be noted in rocky islets 
which lie a few hundred yards off from the shore with a marked dip 
to the north-west while the southerly dips are seen on the coast a short 
distance south of the boring. 
Between this anticline and that which shows near Guaypo point a 
few miles to the south there are also local foldings, but the dips are com- 
paratively low and portions of the shore in this distance are sand covered. 
A curious feature in this direction as in other places, is the present red 
colour of much of the ordinary grey and dark shales, and their alteration 
from a soft rock to a hard and sometimes cherty character. Certain 
portions of these altered shales closely resemble a hard red felsite in 
general aspect, as if the mass had been acted upon by volcanic intrusions. 
No such igneous rocks were anywhere observed, and the alteration seems 
to be due to the fact that at some time the contained bitumen of these 
sediments had become ignited and eventually destroyed, the resulting 
heat being sufficient to entirely alter their original characters. This 
red or burned condition of the soft Tertiary shales and oil-sands was 
