C. Callaicmj — L. Selderherg Group of N. York. 271 



VI. — On the Cobkelation of the Lower Helderbeeg Group of 



New York. 

 By C. Callaway, M.A., B.Sc, F.G.S. 



IPEOPOSE in this paper to give the evidences for the strati - 

 graphical position of this interesting group, both because the 

 task, so far as I am aware, has not been attempted in detail, and 

 because American geologists themselves are not altogether agreed on 

 the subject, some maintaining the equivalence of the group with our 

 Ludlow, while there are a few who regard it as an easterly exten- 

 sion of the Niagara series of Western New York. Having had an 

 extensive practical acquaintance with the fossils of New York, in 

 the State Museum, and having supplemented cabinet study by worlc 

 in the field, I venture to hope that I may be able to determine the 

 question to the satisfaction of geologists. 



1. Sketch of the group in the typical area in Neio TorJc. — The Hel- 

 derberg Mountains form a low range striking in a comparatively 

 straight line from the valley of the Hudson south of Albany on the 

 east through Albany county to Schoharie county on the west. 

 They present a steep escarpment to the north, overlooking the 

 Mohawk, a western tributary of the Hudson. To the south, the 

 ground gradually slopes downwards for several miles, then rises 

 more abruptly into the bold masses of the Catskills. The base of 

 the Helderberg escarpment generally rests upon the unconformable 

 beds of the Hudson Eiver group. The escarpment itself mainly con- 

 sists of limestones of Lower and Upper Helderberg age, with a thiu 

 basement of Clinton and Niagara rocks, and a considerable capping 

 of arenaceous shales of the Hamilton group. The following cut 

 represents the section from the valley of the Mohawk on the north 

 to the Catskills on the south. 



Section 1. 



Mohawk R. 



Helderberg Mts. 



Catskill Mts. 



a = Hudson Eiver group. 



b = Clinton shales. 



c = Niao'ara Limestone. 



«f = Lower Helderberg group. 

 e = Upper ditto (Lower Devonian) . 

 /= Middle and Upper Devonian. 



The above section shows the relation of the Lower Helderberg 

 to the formations above and below. The next is on a larger scale, 

 and is designed to display the subdivisions of the group. The section 

 is taken through the escarpment overlooking the village of Schoharie, 

 to the south-west of Albany. 



Ascending the escarpment from Schoharie, we find at its base a 

 thin bed of greenish shale charged with iron pyrites, the probable 

 easterly attenuation of the Clinton (Upper Llandovery) series. Form- 



