"Analyses of 103 crude oils from Big Horn Basin fields have been compiled and tabulated in an abridged form according to the geological time periods of productive formations. The analyses, made by the Bureau of Mines routine method at the petroleum and oil-shale experiment station at Laramie, Wyoming, represent most of the fields and productive formations within the basin. All low-sulfur oils were produced from Cretaceous formations while all oils with more than 0.5 percent sulfur were produced from formations older than Cretaceous. Further correlations between type of oil and geological source are suggested. Similar correlations have been made in neighboring areas in the Rocky Mountains. The information presented is useful from the standpoint of the geologist in predicting types of oils to be found and in correlating geological information, and from the standpoint of the production man and refinery man in judging value and utilization."