Maryland Geological Survey 435 



It has long been recognized by geologists engaged in the study of the 

 Upper Devonian of Pennsylvania that it represents in a general way the 

 Genesee, Portage, Chemung, and Catskill formations of New York. The 

 limits of the formations were drawn, however, at very different horizons 

 by different students. I. C. White,' who made an extended study of 

 these strata in Pennsylvania, recognized the presence of two conglomer- 

 ates which he correlated throughout most of the state by means of their 

 stratigraphic position and lithological characters. He called the upper 

 of these the Lackawaxen conglomerate from a locality on the Delaware 

 River, and stated that it is formed of flat pebbles, some of which are 

 jasper. He named the lower the Allegrippus conglomerate from Alle- 

 grippus, Huntingdon County, Pennsylvania. The section exposed in 

 Huntingdon County, Pennsylvania, was interpreted as follows by White: ' 



Catskill Formation Thickness 



Non-marine beds 2525 



Hauns Bridge beds (marine fossils) 1000 



Lacltawaxen conglomerate (3G50 feet above base of Upper Devonian). 

 Strata below conglomerate, with a fish bed at base 100 



CATSKILL-CIIEMUNG TKANSITION BEDS 



Containing some bright-red sediments 700 



Chemung Formation 



Arenaceous sediments, containing the Allegrippus conglomerate 2700 



feet above the base of Upper Devonian 1550 



Portage flags 1100 



Genesee formation 200 



The base of the Catskill of Huntingdon County is made by White 

 to correspond, as far as possible, with the base of the Catskill as de- 

 termined by him on the Delaware Eiver. The fact that the section 

 studied by White in Huntingdon County is on the strike of the Jennings 

 strata west of Green Ridge in Maryland and the close agreement of his 

 measurements with those of the Jennings in the latter area renders it not 

 improbable that the base of White's Chemung occupies approximately 

 the position of the base of the Parkhead sandstone member of Maryland, 

 that the Allegrippus conglomerate which occurs 2700 feet above the base 



' Rept. 2d Geol. Survey, Pa., vol. T3, 1885, p. 102. 



