THE SHALES WEST OP THE HUDSON. 345 



it is, as a whole, characteristic of the upper portion of the Utica shale in 

 the Mohawk valley and of the passage beds between the Utica shale zone 

 and the lower portion of the Lorraine shales in the section at Lorraine, 

 Jefferson county, New. York. 



Professor R. P. Whitfield concluded from his study of the graptolitic 

 fauna at Norman's kill, uear Albany, that the graptolite-bearing layers there 

 are of the age of the Utica shale. He mentions four or five species of grap- 

 tolites that are common to the Norman's kill fauna and the Utica shale in 

 the valley of the Mohawk.* 



When studying the strata on the east side of the Hudson valley, I was 

 brought in direct contact with the disturbed strata that had been referred to 

 the Hudson River group by Mather and Hall, to the Taconic system by Em- 

 mons, and to the Quebec group by Logan. For the purpose of obtaining a more 

 intimate knowledge of the strata assigned to the Hudson River group 

 west of the Hudson, I began by examining, during the field season of 1887, 

 the contact of the Trenton limestone and Utica shale at the falls of the 

 the Hudson, near Sandy Hill. This is the only point known to me where an 

 undisturbed contact is shown between the Trenton limestone and the shales 

 of the Hudson river valley. From this point the shales may be traced, 

 with little interruption, to the neighborhood of Albany, where they are 

 very much disturbed and stand at a high angle. In this vicinity the 

 noted graptolite beds of Norman's kill occur ; also the locality where Mr. 

 Beecher discovered the upper fauna of the Utica shale zone. Following up 

 Norman's kill, alternating shales and sandstones are passed over, all of 

 which are highly inclined to the eastward. Crossing the line of disturbance, 

 the shales and sandstones, of precisely the same lithologic character, are 

 met with in a horizontal position. This series may be followed up until the 

 superjacent Lower Helderberg limestone is met with, resting conformably 

 upon the sandy layers capping the section of the Hudson series. 



At the Indian Ladder, a few miles west of Albany, about 300 feet of the 

 Hudson series is shown in the section. The rocks here consist of alternating 

 shales and sandstones. Near the summit a massive belt of sandstone, 

 thirty feet or more in thickness, occurs just beneath the Tentacidite limestone 

 of the Lower Helderberg. This sandstone and the sandstone beds inter- 

 bedded in the shales are the grits of the older writers. The only fossils I 

 found at this locality were Orthis testudinaria and Trinucleus co7icentricus. 



At Knowersville, about seventeen miles from Albany, the Lower Helder- 

 berg limestone is conformably superjacent to the Hudson shale. The section, 

 so far as it goes, is essentially the same as at the Indian Ladder. In ex- 

 plorations for gas in Albany county, a deep well was drilled at Knowersville, 



* Reports upon the Geographical and Geological Explorations and Surveys West of the 100th Me- 

 ridian, under Wheeler, vol. IV, 1875, pp. 19, 20. 



