The Devonian Marcellus Shale and Millboro Shale
The recent development of unconventional oil and natural gas resources in the United States builds upon many decades of research, which included resource assessment and the development of well completion and extraction technology. The Eastern Gas Shales Project, funded by the U.S. Department of Energy in the 1980s, investigated the gas potential of organic-rich, Devonian black shales in the Appalachian, Michigan, and Illinois basins. One of these eastern shales is the Middle Devonian Marcellus Shale, which has been extensively developed for natural gas and natural gas liquids since 2007. The Marcellus is one of the basal units in a thick Devonian shale sedimentary sequence in the Appalachian basin. The Marcellus rests on the Onondaga Limestone throughout most of the basin, or on the time-equivalent Needmore Shale in the southeastern parts of the basin. Another basal unit, the Huntersville Chert, underlies the Marcellus in the southern part of the basin. The Devonian section is compressed to the south, and the Marcellus Shale, along with several overlying units, grades into the age-equivalent Millboro Shale in Virginia. The Marcellus-Millboro interval is far from a uniform slab of black rock. This field trip will examine a number of natural and engineered exposures in the vicinity of the West Virginia–Virginia state line, where participants will have the opportunity to view a variety of sedimentary facies within the shale itself, sedimentary structures, tectonic structures, fossils, overlying and underlying formations, volcaniclastic ash beds, and to view a basaltic intrusion.
|The Devonian Marcellus Shale and Millboro Shale
|Daniel J. Soeder, Catherine B. Enomoto, John A. Chermak
|GSA Field Guides
|USGS Publications Warehouse
|Eastern Energy Resources Science Center