430 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



According to Cummins,"'' later studies have shown that the beds to which 

 the name "Albany" formation was applied are the same as the Wichita formation, 

 'with which they are stratigraphically continuous, the "Albany" being simply 

 deposits in deeper water. 



I 16. ALABAMA. 



Plant remains, probably of Pennsylvanian age, are recorded by Smith ''*'' 

 from the metamorphosed rocks near Moseley (now Erin), Clay County, Ala., which 

 have heretofore been regarded as a part of the Ocoee group of Safford. (See Chap- 

 ter III, p. 88.) 



I-J 16, J-K 17-18. APPALACHIAN COAL FIELD. 



The following statement on the Appalachian coal field was prepared for this 

 work in 1910 by David White: 



GENERAL FEATURES OF THE PENNSYLYANIAN IN THE APPALACHIAN PEOVINCE. 



Conditions of deposition. — The Pennsylvanian (upper Carboniferous) rocks of the Appala- 

 chian trough or province lie unconformably upon a portion of the eroded and soruewhat warped 

 Mississippian surface. The initial invasion of the old basin by the Pennsylvanian sea formed 

 a relatively narrow and elongated estuary extending from the southern anthracite field in 

 Pennsylvania southwestward along or near the eastern margin of the central and southern 

 Appalachian coal fields ^"^ to the Gulf region in southern Tennessee or northern Alabama, 

 where, becoming confluent with the eastern interior lobe, it opened into the broader sea to 

 the southwest. 



Later the basin expanded both to the north and the west, broadening out in these directions 

 to dnd beyond the limits of the present coal fields. There was, therefore, encroachment of 

 the sea on the land and overlapping of the terranes during at least the earher divisions of 

 Pennsylvanian time. Nearly everywhere the Pennsylvanian-Mississippian contact exhibits 

 sharply contrasting sediments, though at a few points, such as the Bluestone section "' in, 

 southwestern Virginia, there is an absence of conglomerates and a less abrupt change in the 

 rock-forming material. Along the eastern portion of the basin the Pennsylvanian deposits 

 lie on the Mauch Chunk formation (regarded as of Chester age); but farther northwest they 

 are found resting bassetwise on rocks nearly if not quite as old as the Pocono. Farther along 

 the western margin of the bituminous coal field they come into contact with the Cuyahoga 

 shale, Logan formation, Blackhand formation, and MaxviUe limestone. ^'^ Yet there is a 

 remarkable absence of local topographic relief, the Mississippian floor having been apparently 

 a base-level coastal plain over most of the area. 



Character of sediments. — The rock-forming materials are mainly terrigenous, brought down 

 by rivers chiefly from eastward lands, which were probably the site of nearly continuous though 

 variable epeirogenic action. Consequently the formations are in general thicker and more 

 arenaceous toward the east side of the basin. The greatest thickening is toward the southeast, 

 where at the edge of the Cretaceous overlap in Alabama the Pottsville, or lower division, 

 probably exceeded 7,500 feet. Marine or brackish-water faunas, extending over wide areas, 

 occur at numerous stages except in the later Pennsylvanian, thus showing frequent accessibility 

 to marine life, though the conditions of sedimentation in the Appalachian trough were generally 

 less favorable for open-water marine ]\IoUusca than in the eastern interior arm. The subsidence 

 kept, on the whole, relatively close pace with loading, so that, though the warping was unequal, 

 there is slight evidence of the contemporaneous formation of new basins as the result of the 

 orogenic changes. 



General structure. — In the western portion of the basin the beds lie nearly horizontal, but 

 toward the eastern margin — that is, the eastern escarpment — of the bituminous regions, open 

 folds with more marked anticlines were developed, from some of wliich the Pennsylvanian 



