INTRODUCTION 217 



states of Pennsylvania and. West Virginia. This has been in large 

 measure due to the fact that the study of the Maryland Coal Measures 

 has been mainly confined to the Georges Creek basin, a deep synclinal 

 trough that presents the only full representation of the formations of 

 the Coal Measures within the limits of the state. The consequent lack 

 of continuity in many of the coal seams of this basin with those of other 

 regions in Maryland and adjacent states has led to the establishment of 

 local terms in denominating these seams, with the result that much con- 

 fusion exists as to their equivalents in the other areas. Even the rela- 

 tively small amount of consideration hitherto given to the Garrett 

 County basins has been chiefly confined to the local occurrences, without 

 regard to the correlation of the seams with those of Pennsylvania and 

 West Virginia. 



The writers of this article have been engaged for several years in a 

 study of the Coal Measures of Maryland, and are satisfied, both from 

 an intimate comparison of the sequence of deposits found represented 

 in Maryland with those of other areas, and from the continuity of certain 

 of the beds with those of adjacent regions in Pennsylvania and West 

 Virginia, that the same seams of coal, early described and named in 

 Pennsylvania, West Virginia, and Ohio, are present in Maryland, and 

 that these names must be accepted for the Maryland coalbeds. The 

 accuracy of these conclusions is still further shown by a study of the 

 floras and faunas, which at several horizons are highly distinctive, and 

 prove the identity of many of the seams beyond all question. The 

 authors have been very much impressed with the wide geographical 

 range of the several members of the formations of the Coal Measures, 

 many of the beds being traced without difficulty over thousands of 

 square miles and for a great distance along the Appalachian unlift, with 

 very little change in physical characteristics. The coalbeds especially 

 show certain marked features that admit of their ready determination. 

 This is seen both in the characteristic position of the partings, as well as 

 in the physical constitution of the coal itself. 



The Coal Measures of Maryland are divided into five formations, 

 which from below upward are known as the Pottsville formation, the 

 Allegheny formation, the Conemaugh formation, the Monongahela for- 

 mation, and the Dunkard formation, the latter perhaps of Permian age. 



The formations of the Coal Measures are limited to Allegan}^ and 

 Garrett counties, Maryland, the only full representation of formations 

 being found in the Georges Creek basin of western Allegany and eastern 

 Garrett counties. The upper Potomac basin, which is the southwesterly 

 extension of the Georges Creek basin, lacks in its Maryland portion, 

 except in two small areas, everything above the Conemaugh formation. 



