The Elements of economic geology

Bibliographic data

Monograph

Identifikator:: 1773832379

URN:: urn:nbn:de:zbw-retromon-172798

Document type:: Monograph

Author:: Gregory, John W. http://d-nb.info/gnd/11683014X

Title:: The Elements of economic geology

Place of publication:: London

Publisher:: Methuen

Year of publication:: 1928

Scope:: XIV, 312 S.; graph. Darst.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Part V. Mineral fuels

Collection:: Economics Books

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,

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