26 



PROCEEDINGS OF THE ACADEMY OF 



[Part I 



to the S. W.^ The basal layer here is a hmestone conglomerate. 

 Sandstones, shale and conglomerates occm- in the succeeding layers 

 and farther north a large intrusion of diabase. This forms the 

 elevation known as the Conewago hills. All of the rocks examined 

 dip N. W. at an angle varying from 15 to 24 degrees. No evidences 

 of faulting or folding were observed. 



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Fig. 1. — Localities of triassic exposures mentioned herein. 



The localities described in this paper are about three miles north 

 of Emigsville (fig. 1). Taking the average dip as 20 degrees and 

 calculating from the dip and horizontal distances, the productive 

 layers are, approximately, 6600 feet above the basal conglomerate.' 

 Correlation and definite location of these layers is difficult without 

 a section across the Trias. 



Two columnar sections are given (figs. 2 and 3) showing the rela- 

 tive positions of the productive strata. These sections are of interest 

 because they show the rapid alternation of the sediments. The 

 physical and lithological character of the shale varies considerabty 

 even in the same layer. In one place it may be hard and compact 



* Frazer, P. Penna. Geol. Survey, Report C 3, Sec. 2, 1876. 



« Russell, I. C. The Newark System. U. S. Geol. Survey, Bull. 85, p. 34, 

 1892. 



'Ehrenfeld, F. A study of the igneous rocks at York Haven and Stony 

 Brook, Pa. Univ. of Penna., 1898. Wanner, A. Triassic flora of York County, 

 Pa. U. S. Geol. Survey, Ann. Rept., pp. 233-255, 1898-99. 



