Detailed Cross Sections of the Eocene Green River Formation along the North and East Margins of the Piceance Basin, Western Colorado Using Measured Sections and Drill Hole Information

摘要

The Eocene Green River Formation was deposited in Lake Uinta, a long-lived saline lake that covered much of the Piceance Basin in northwestern Colorado and the Uinta Basin in eastern Utah. This report presents 2 detailed cross sections of the Eocene Green River Formation in the Piceance Basin constructed from 8 detailed measured sections, 14 core holes, and 2 rotary holes. The cross sections extend across the northern and eastern margins of the basin and are intended to aid in correlating between surface sections and the nearby subsurface. Detailed measured sections new to this report are: (1) Smith Gulch, (2) Hay Gulch, and (3) Rio Blanco. Detailed measured sections that were previously published include: (1) Fletcher Gulch (Johnson and others, 1988), (2) Anvil Points (Self and others, 2010), (3) Spring Creek (Self and others, 2010), (4) Yellow Creek (Self and others, 2010), and (5) Lower Piceance Creek (Johnson, 2012). Core holes and rotary holes used include oil-yield histograms from Fischer assay analysis, a standardized laboratory test for determining the oil yield from oil shale that has been almost universally used to determine oil yields for Green River Formation oil shales (Stanfield and Frost, 1949; ASTM, 1984). In addition, all measured sections except Anvil Points and Smith Gulch include estimates of oil yield based on appearance and density. According to Cashion (1967, p. 25) estimated oil yields from surface samples can give moderately accurate results when sampling is done by an experienced investigator, but should only be used if data are not available.