DETAILS OF THE SECTIONS 479 



Kittatinny Valley, however, is succeeded by upper members of the Lower 

 Monroe group, the Poxino Island shale and Bossardville limestone. Be- 

 tween the latter and the more recent Decker Ferry beds is sometimes 

 found a quartz sandstone composed largely of well rounded quartz grains, 

 suggesting eolian origin. This quartzite, the Croasdale quartzite, appar- 

 ently represents the Sylvania horizon of Michigan and suggests a break 

 of some magnitude between the Lower and Upper Monroe. 78 Apparently 

 throughout the whole of Lower Monroan time the red shales of the pres- 

 ent outlier were subject to erosion, the eroded material furnishing the 

 Lower Monroe sediments farther west and south. When finally this area 

 was covered by the sea in Upper Monroe time, the upper layers of the 

 remaining red series may have been in part incorporated as reworked 

 material in the base of the Decker Ferry series. The occurrence of 

 crinoidal fragments and of a few pelcypods 79 in the higher red strata at 

 Cornwall suggests such a reworking in Upper Monroe time. 



Ulrich and Schuchert in their paper on "Paleozoic seas and barriers in 

 eastern North America," 80 page 654, give the impression that they advo- 

 cate the accumulation of the deposits in the Green Pond-Skunnemunk 

 area in a basin or trough distinct from those in which the corresponding 

 deposits across the Kittatinny Valley accumulated. Their statements 

 are rather vague and this may not be what they intended to say. Still 

 they speak of the "Skunnemunk trough," which is apparently a syncline 

 and holds a series of formations aggregating in the southern section 5,400 

 feet. 



That the Siluric strata of this section accumulated separately from 

 those of the more western area can not for a moment be maintained, 

 especially when the basal elastics are considered. It ought not to be nec- 

 essary at this stage of stratigraphic science to have to argue for the 

 former continuity of extensive series of elastics which at the present time 

 are discontinuous, but parallel, as in the present case, especially when it 

 must be apparent that the only source from which the material of the 

 elastics of both areas is derived is a land-mass which lay east of the east- 

 ernmost of the two. Certainly no fact in the purely physical stratigraphy 

 of this region stands out more boldly than that the separation of the 

 formations on opposite sides of the Kittatinny Valley is due to erosion. 

 It is for this reason that such misleading terms as "Skunnemunk trough" 

 should be discarded. 



78 A detailed study of the formations as exposed in the Broadhead Creek Bection of 

 Pennsylvania will soon he puhlished by Miss E. Kurtz, a graduate student in Columbia 

 University. 



79 Recorded by Hartnagel. 



80 Bull. N. Y. State Museum, No. 52, 1901, pp. C33-663. 



