An isoreflectance map, based on the average maximum reflectance of the vitrinite macerals, was compiled from 329 coal samples from Kentucky (75 samples), Virginia (14 samples), West Virginia (200 samples), Ohio (10 samples), Maryland (15 samples), and southern Pennsylvania (15 samples). This map shows that coalification increases toward the Allegheny Front (or in west-to-east and northwest-to-southeast directions) in the northern part of the Appalachian coal basin. The dry-ash-free fixed carbon contents of the coals show the same general trends.

The isoreflectance map shows that the rank increases to a maximum in two directions: (1) from Ohio eastward to the Allegheny Front in southern Pennsylvania, Maryland, and Mineral County, West Virginia; and (2) from Ohio and northeastern Kentucky to the central part of McDowell County, West Virginia. This increase in rank can be attributed to the eastward thickening of the strata, but the major factor in the coalification was probably the increase of thermal activity and temperatures coupled with the Appalachian orogeny.

An attempt to determine the temperatures of coalification by using the level of metamorphism of P. J. Hood showed that the temperatures during the effective times for coalification were approximately 85 to 90°C near the northwestern boundary of the coalfield and approximately 180°C in central McDowell County where the highest reflectance of 1.80% R_max occurred.

End_of_Article - Last_Page 1577------------