STRATIGRAPHY 635 



Kentuclcy. — The principal producing sands of Kentucky are the Salt 

 sands of the Pottsville, the Squaw sand of the Pocono, the Berea and 

 Gantz of the C*atskill horizon, and the Trenton Corniferous or limestones. 



Tennessee. — Oil is found in this State mainly in the ISTewman (Green 

 brier) limestone of the Mauch Chunk horizon and in the Trenton. 



Alabama. — There is no separately recorded production in Alabama, but 

 oil shows occur in the Pennsylvanian sandstones, the Mississippian sand- 

 stones and limestones, and in the Trenton limestone. 



Structure of the Appalachian Oil Field 

 general relations 



The Appalachian oil field lies in the east half of a broad synclinorium 

 which is bounded on the north by the pre-Devonian formations of south- 

 ern New York and Ontario, on the east by the Appalachian Mountains, 

 and on the west by the Ohio and Tennessee domes of the Cincinnati anti- 

 cline. 



The synclinorium is broadest at its northern limit, where the portion 

 of the basin occupied by Carboniferous rocks approaches a width of 300 

 miles. From here it tapers gradually southward until in northern Ala- 

 bama it is less than 30 miles from the outermost strong fold of the Appa- 

 lachians to the Ordovician area of the Tennessee dome. 



STRUCTURE IN PENNSYLVANIA 



In northeastern Pennsylvania the strong folds of the anthracite coal 

 fields die off northward and northwestward through a series of pro- 

 gressively weaker folds into the gently undulating or almost flat struc- 

 tures of the Elmira region of south-central New York. Substantially 

 the same sequence is found in central Pennsylvania, the folds becoming 

 progressively weaker northwestward from the Allegheny Front to the 

 flat district north of Bradford, Pennsylvania, and in Cattaraugus County, 

 New York. 



In southwestern Pennsylvania two strong and sliar]:» outlying folds, 

 giving rise to what are known as Chestnut and Laurel ridges, are found 

 west of the Allegheny Front, the outermost l)eing o\cr 30 miles away. 

 West of these structures the dips flatten materially, tlie fokls being com- 

 ))aratively low and irregular. The change from the mountainous to basin 

 structure is not associated with noticeable faulting in Pennsylvania, 

 ^fost of the pools occur on anticlines, with a few on structural terraces, 

 or, in the absence of water, in synclines. 



XLVIII— Bull. Geol. Soc. Am., Vol. 28, 1910 



