MINERAL OIL 201 
Trinidad has yielded many wells chiefly from the Lower 
Kainozoic rocks which have been intensely folded and 
disturbed. The folds run E. and W., continuing those of 
the Cordillera of Venezuela into the Atlantic. Some of the 
Trinidad oil is high-grade and can be at once used as petrol ; 
it was doubtless naturally refined from crude petroleum and 
has migrated into beds of sand. The foundation of Barbados 
consists of deltaic deposits of Lower Kainozoic age covered 
by deep-sea deposits and coral reefs. The foundation beds 
yield manjak or Barbados tar, and bores have obtained some 
petroleum. 
Cuba consists of Jurassic to Oligocene limestones which 
rest on a basal serpentine; the rocks have been folded and 
fractured, and oil distilled from the limestone has travelled 
through the porous rocks, depositing in some places seams of 
asphalte and in some places impregnating the sand with 
colourless petrol (sp. gr. -72; 62°-65° B.), and at Bacuranao 
near Havana, impregnating the serpentine with a heavy 
oil (sp. gr. *88; 28°B.). 
Sout AMERIcA—The extensive pitch lakes in Eastern 
Venezuela have long encouraged hopes of the existence 
there of important oilfields. Prolific fields have been 
found in Western Venezuela near the Gulf of Maracaibo. 
The rocks of Venezuela include a folded foundation of 
pre-Paleozoic metamorphic rocks, on which rest 5000 feet 
of Cretaceous limestones and dolomites, 7000 feet of Eocene 
to Oligocene shales with coal and oil, and 5000 feet of 
Pliocene sandstone, gravels, and shales.. The whole series 
has been folded by post-Miocene movements, which in Eastern 
Venezuela trend E. and W. parallel to the main West 
Indian trend ; but in Western Venezuela they bend round 
to the S.W. and S., and pass into the Andes. The general 
sequence offers many resemblances to that in Mexico; but 
the oilfields have not been affected by volcanic action and 
igneous intrusions, and the gushing wells are more easily 
controlled. Some of the oil may be derived from Cretaceous 
limestone, but apparently most of it has come from the 
Oligocene shales and has been stored in the Miocene beds. 
The oil is usually heavy (about sp. gr. -93 and 21° B.). 
The oilfields of Peru occur in Kainozoic beds at least 
17,000 feet thick (Negritos, Eocene, 7000 feet; Lobitos,