THE MISNAMED INDIANA ANTICLINE. 1 



Recent work by the United States geological survey in 

 western Pennsylvania has revealed a number of unsuspected facts 

 of geologic structure. The results are being published in folios 

 in which the lay of the rocks is shown by deformation contours, 

 but it is thought desirable to call attention here to the finding 

 of a syncline where formerly there was considered to be an 

 anticline. 



The map of Indiana county issued by the second geological 

 survey of Pennsylvania shows the Indiana anticline to extend in 

 a straight line through the town of Indiana. This supposed 

 fold has been thought to be continuous on the southwest with 

 the Fayette anticline in Westmoreland county and on the north- 

 east with the anticline which is well marked near Richmond, on 

 Little Mahoning Creek. The name Indiana anticline, therefore, 

 has been applied to the entire fold. This term has passed into 

 geologic literature and is still being used. 



In the area adjacent to the type locality of the fold, how- 

 ever, the structure, as indicated by the accompanying sketch 

 map, is quite different than previously interpreted. The Rich- 

 mond and Fayette anticlines are not continuous, but the former 

 pitches southwestward and the latter pitches northeastward, and 

 the area between the Conemaugh River and Crooked Creek, along 

 the extension of the axes of these folds is occupied by the 

 Latrobe syncline. It is an odd coincidence that the axes of the 

 Richmond and Fayette anticlines fall in line with each other, 

 and it is not surprising that these folds have been thought to be 

 continuous, for in the intervening region surface exposures are 

 poor and the structure can be deciphered only by detailed work. 

 The present determination is fully proved by the records of 

 some fifty diamond drill holes lately put down by the Rochester 

 and Pittsburg Coal and Iron Company. 



Structural details will be published in the forthcoming Indiana 



1 Published by permission of the director of the United States geological survey. 



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