Feb. 16, 1877.] OiJ [Ashburner, 



A measured section of the Palmozoic Bocks of Central Pennsylvania, from 

 the top of the Allegheny Eioer Coal Series, down to the Trenton Limestone 

 in the Lower, or Cambro-Silurian System. 



By Charles A. Ashburner, 



Asst. 2cl Geol. Surv. Pa. 



{Bead before the American Philosophical Society, February 16, 1877.) 



The following long section of the Palseozoic strata of Huntingdon County, 

 Pennsylvania, is the result of an instrumental study of a district bounded 

 on the west by Broad Top Mountain ; on the north by the East Broad Top 

 Railroad ; on the east by Blacklog Valley ; on the south by Sideling Hill 

 Creek. 



Two vertical sections were constructed along cross section lines, in a 

 north-west direction, from the Trenton limestone of Blacklog Valley to 

 the Broad Top coal basin, a number of other shorter sections were made 

 along selected portions of the district between the two longer lines. 



The results of the measurements made on these several lines of survey, 

 sufficiently near together to check one another, are given in the following 

 pages. 



The whole height of the vertical section, from the top of the Mahoning 

 sandstone in the Coal Measures down to the bottom of the Trenton lime- 

 stone, is eighteen thousand three hundred and ninety-four feet (18,394'), 

 distributed as follows : 



Carboniferous Strata* at least. 3,777' 



Devonian Strata 7,975' 



Oriskany Sandstone^ 58' [ = 18,394':^ 



Upper and Middle Silurian 4, 214' 



Lower or Cambro-Silurian at least. 2,370' . 



This section would therefore represent the record of a shaft or bore hole 

 3^ miles deep, sunk from the surface of the land of the Broad Top Coal 

 Basin at Broad Top City. 



Carboniferous. 



No. XIII. 



Alleghany Biver {Lower Productive) Coal Mensxires 264' 



267. Mahoning Sandstone. A white conglomerate sandstone, 

 containing a softer shaly mass and a coal bed 90' 



*The base of the carboniferous being in dispute, the term is here made to in- 

 clude the Pocono, Vespertine, or Upper Catskill, X, for reasons evident in the 

 section. 



t Geologists may include the Oriskany in the Devonian or in the Silurian as 

 they see proper. 



XTo get this total the measurements of the rocks above the Clinton lower olive 

 shale at Saltillo are added to those of the rocks below that horizon at Orbisonia. 



