DETAILS OF THE SECTIONS 483 



estimate of 1,000 feet would probably be considerably below the mark. 

 . . . It is more probable that 2,000 feet of concealed shale exists." 82 

 This would place the thickness of the Longwood series over 2,275 and 

 under 3,275 feet, a thickness greater than that found anywhere else in 

 the State. In the Lehigh, as at the Delaware Water Gap, these shales 

 were classed as combined Clinton and Salina, while the Shawangunk was 

 arbitrarily subdivided into Medina and Oneida. 



On the Schuylkill, where the Shawangunk is only 500 feet thick, the 

 Longwood has a thickness of more than 2,600 feet. The section as meas- 

 ured by Doctor Chance was summarized by Lesley as follows: 



Feet 



Upper red shale 750 



Upper red shale and sandstone 630 



Upper olive shales 680 



Ore sandstone '. 96 



Lower olive shale 450 



2,606 



To this Lesley would add several hundred feet for the eroded top rocks, 

 making the whole thickness about 3,000 feet. 



Throughout the region from Culvers Gap, New Jersey, to the Schuyl- 

 kill Gap in Pennsylvania no fossils have been found in the shales of this 

 series. The sections are terminated by the Lewistown limestone series, 

 which throughout the more northerly portion seems to succeed the shales 

 rather abruptly. In New Jersey and adjoining districts of Pennsylvania 

 these beds have been differentiated into their components and given dis- 

 tinct names. They can with more or less certainty be traced into the 

 New York series, and some of them have also been recognized farther 

 south along the Front Eidge. 



In the Delaware Water Gap region the red Salina shales (Longwood) 

 are succeeded by a 5-foot bed of fossiliferous limestone, the Poxino Island 

 limestone of I. C. White. This is followed by the Poxino Island lime 

 shales, which are more or less magnesian, but wholly unfossiliferous and 

 have a thickness of 200 feet. They are in turn succeeded by 90 feet of 

 Bossardville limestone, a gray to bine calcilutyte, well banded and com- 

 posed of lime mud, most probably derived from the erosion of older lime- 

 stones. Fossils are scarce in this formation, but those thai are known 

 are of Lower Monroe age. The limestone is followed by abotri L5 feel of 

 greenish shales, which constitute the terminal member o\' the Lower 



88 Summary Final Report Geol. Pennsylvania, vol. II, p. 732. 



