Rock asphalt (bitumen-saturated sandstone) was produced from the Big Clifty Sandstone near Tar Hill and Big Clifty in northeastern Grayson County, and at Summit in adjacent Hardin County, from 1889 to 1940. Noncommercial amounts of oil were distilled from Big Clifty rock asphalt before 1930. Resource assessments conducted throughout the area during the mid-1920's described substantial rock-asphalt deposits. Later assessments in 1951, 1965, and the early 1980's, however, overlooked the northeastern Grayson County area. A new evaluation in 2015 estimated that the historically developed area between Clifty Creek and meeting Creek, and between the Summit Fault and Eveleigh Fault Zone, contained 200.3 million barrels of heavy oil and bitumen in place in the Big Clifty Sandstone. This study estimates an additional 29.6 million barrels of heavy oil and bitumen in place in less than 9,600 ha of the Big Clifty southwest of Clifty Creek, or about 7,600 barrels per hectare.
The rock-asphalt industry in the northeastern Grayson County area left substantial surface damage that is still visible, especially at Summit, more than 70 yr later. Although leaching of hydrocarbons from rock-asphalt mine-spoil piles is a reasonable environmental concern, tests have shown no leaching of hydrocarbons using a synthetic rainwater at a pH above 3.5; natural rainwater has a pH of about 5.5.
Report of Investigations 35
Digital Object Identifier (DOI)
Bowersox, J. Richard, "Heavy-Oil and Bitumen Resources of the Big Clifty Sandstone, Northeastern Grayson County and Adjacent Hardin County, Kentucky" (2016). Kentucky Geological Survey Report of Investigations. 36.