Energy Resources Program
The identification of organic materials in shale is complicated by fine grain size and dispersion into the mineral matrix. Organic petrographic analysis of shale generally employs both incident white light and fluorescence illumination techniques. This site provides labeled images of organic materials in shale as an aid for generic identification and as a supplement to ASTM D7708-11 (ASTM, 2011).
Note: In some cases, maceral identifications labeled in the photomicrographs herein are based on information that may not be apparent in the photographs. For instance, measured reflectance values are used in some cases to make identifications. Such observations sometimes are included in the comments field in photomicrograph metadata.
Click on the shale formation links below to see representative examples based on photomicrographs taken in the USGS Organic Petrology Laboratory:
Green River Shale
Eagle Ford Shale
ASTM, 2011, D7708-11 Standard test method for microscopical determination of the reflectance of vitrinite dispersed in sedimentary rocks: Annual book of ASTM standards: Petroleum products, lubricants, and fossil fuels; Gaseous fuels; coal and coke, sec. 5, v. 5.06: ASTM International, West Conshohocken, PA, p. 823-830, doi: 10.1520/D7708-11, http://www.astm.org/Standards/D7708.htm.
Disclaimer for a Provisional Database: The data you have secured from this USGS database are provisional and subject to revision. The data are released on the condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use.
Page Last Modified: Wednesday, November 16, 2016