1877.] O^O [Ashburner. 



associate strata may have been based upon observed dips in the loAver 

 member. 



The epoch is valley making and has three horizons of more or less 

 economical importance. 



The Marcellus iron ore bed is of great importance from the Juniata River 

 to the Maryland State line and supports a large iron industry. It varies 

 in thickness from 3 and 4 up to 10 feet, occurring as a series of solid gray 

 layers separated by thin seams of slate. In its native proto-carbonate 

 condition it is a bluish-gray or lead colored ore, sometimes massive, 

 breaking into squai'e pieces, and at other times of a slaty or laminated 

 structure. Where the ore has not been thoroughly subjected to atmospheric 

 action the change to brown peroxide is only partial, a solid nucleus form- 

 ing the interior of the lump, while the peroxide occurs on the surface as a 

 crust of greater or less thickness. 



The following are two partial analyses made by Mr. A. S. McCreath, 

 Chemist of the survey, of ores from the end of Jack's Mountain : 



Fleck's bank. McCarthy's bank. 



Iron 46.5 39.100 



Manganese .301 



Sulphur trace .430 



Phosphorus 133 .060 



Insoluble residue 17.120 



Tipper Helderhurg or Corniferous Limestone [Post Meridian). 



Thickness : Three Springs and Saltillo (Nos. 55 to 47 inclusive), 60 feet. 



Character : Consists of dark blue and gray argillaceous limestone alter- 

 nating with green, olive and gray calcareous shale. Prof. Rogers, in tlie 

 first report, says : "That the post meridian series may scarcely be called a 

 Pennsylvania deposit as it only enters the eastern borders of the State near 

 the Delaware Water Gap. " He includes the calcareous beds which have 

 been placed in the section as Upper Helderberg in the Marcellus Epocli ; 

 but as the limestone strata S3em to be very generally distributed through 

 the centre of the State and as they must owe their origin to dynamical con- 

 ditions entirely different from those existing during the black slate depo- 

 sition above, from which they differ so widely lithologically it seems more 

 reasonable to consider the limestone as representative of the New York 

 Upper Helderberg until the division can be established palaeontologically, 

 or on other than purely lithological grounds. 



These rocks form one flank of the ridge made by the Oriskany. Some of 

 the more massive limestone strata are quarried, the stone on being burned 

 making a poor lean lime. In some places the formation contains a rather 

 poor argillaceous carbonate of iron (ore bed). The Hawk Mine, worked 

 by the Rockhill Iron and Coal Co. north of Orbisonia, is located on this 

 bed, which appears to be a local deposit. 



The petroleum of Canada, according to Prof. T. S. Hunt, is indigenous 

 to this formation. 



