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Paul Hackley
Lead Geologist
703.648.6458

Sharon Swanson
Lead Geologist
703.648.6453

Peter Warwick
Lead Geologist
703.648.6469

Organic Petrology: Introduction

Organic petrology is the comprehensive investigation of organic materials occurring in sedimentary rocks; in particular, coal and petroleum source rocks. Organic petrology also includes study of the utilization products of coal and petroleum source rocks, for instance, coke, fly ash, and liquefaction residue. Studies of the origin, occurrence, structure, and history of sedimentary organic matter typically are pursued through techniques of optical microscopy. Complementary geochemical methods of investigation include pyrolysis, gas and liquid chromatography, solvent extraction, and mass spectroscopy.

Organic petrology research is used to understand and predict the behavior of coal in utilization and/or thermal maturity of petroleum source rocks, and to understand and predict hydrocarbon generation.  Other important themes of organic petrology research include the impact of coal composition on coalbed gas generation and storage. Research in the USGS Organic Petrology Laboratory at the National Center in Reston includes all of these themes.

Photomicrograph of high volatile bituminous coal, showing the inertinite maceral fusinite, carbonized (charred) wood.  The coal sample is from the open-pit Paso Diablo mine in western Venezuela (in the Paleocene Marcelina Formation).