This paper is a summary account of the structural conditions under which oil and gas have accumulated in the Rocky Mountain region, supplemented with data on the diastrophic history and tectonic pattern, the origin of the producing structures, the age and character of the productive zones, and copious citations of relevant literature. Maps, charts, and tables are substituted for lengthy discussions of many topics.
A graph shows that since 1927 there has been a marked decline in the number of oil and gas fields discovered in the region. Regional maps show the main structural elements and the locations of the oil and gas fields in the physiographic provinces. State maps show the geographic relations of the oil and gas fields to the main structural elements. Maps of typical producing structures are included, and a chart shows columnar sections in representative oil and gas fields. Tables give many geologic details on all fields.
Oils of highly divergent character have been produced from strata ranging in age from lower Mississippian to Oligocene, and strong showings of oil have been found in several pre-Mississippian series. The oldest oils tend to be heavy and the youngest oils light. Some of the natural gases are rich in helium and carbon dioxide. The productive zones are highly variable in character, and the quality of the oil bears no demonstrable relation to the dynamic metamorphism that the region has undergone. The carbon-ratio theory can not be indiscriminately applied to the Rocky Mountain region, where most of the Cretaceous and early Tertiary coals are low in rank.