MIDDLE AND UPPER OEDOVICIAN. 



189 



Table showing the Hvdson formation as exposed in Rensselaer County and the northeastern part of 



Columbia County, N. Y. 



a See Ruedemann, Rudolf, Bull: New York State Mus. No. 42, 1901, pp. 535-537, stations 24, 25, 26. 



6 See Ruedemann, op. cit., for other fossils. 



c Rarely with small beds of quartzite. 



<J The pebbles of this conglomerate contain Trenton, Chazy, and Lower Cambrian fossils. See Ruedemann, Rudolf, 

 Bull. New York State Mus. No 49, 1901, and Ford, S. W., Am. Jour. Sci., 3d eer., vol. 28, 1884, pp. 206-208. [Regard 

 this zone as overlying the true Normans Kill.] 



« The vertical relations of the colored shale and the black siliceous shale to each other and to the black and gray 

 shale with Normans Kill graptolite fauna are not clear. They are all intimately associated. The greenish shale some- 

 times includes small limestone beds. 



The presence of strata of Chazy, Trenton, and Lorraine age constituting the 

 upper part of the Stockbridge dolomite in the compressed syncUne near Rutland, 

 Vt., was shown by the discovery of fossils by Wing in 1877.^''' and has been con- 

 firmed by Wolff »« and by Dale.'"' 



The faunal horizons of the "Hudson shales" in the vicinity of Albany have 

 been worked out by Ruedemann,"^* who sums up his results as follows: 



This paper purports to demonstrate the presence of four zones of shales in the "Hudson 

 River shales" of the Hudson Valley region about Albany. These zones, which extend from 

 north-northeast to south-southwest, consist, going from west to east, of shales containing the 

 Lorraine, Utica, middle Trenton and Normans KiU graptohte faunas. The shales last named 

 include lower Trenton conglomerate and rest on lower Trenton limestone. This succession of 

 zones places the Normans Kill graptolite beds, which form the mass of the "Hudson River 

 shales" in the Hudson River vaUey, between the middle and lower Trenton and determine, 

 together with other facts, the lower Trenton age of these shales. 



The beds lie conformably inverted, on account of their being the remnant of the 

 undertumed wing of an overturned fold of Appalachian type. This fold has turned into an 

 overthrust fault, which brought the Cambric beds as the next succeeding terrane above the 

 Normans Kill shales. 



On account of the fact that the mass of beds hitherto called Hudson River shales and 

 correlated with the Lorraine beds of central New York is composed of terranes ranging from 

 the Lorraine to the lower Trenton, and on account of the lack of a fuUy representative fauna 

 and of a complete section of the Lorraine portion of these terranes, it is proposed to drop the 

 term "Hudson River shales" for the uppermost part of the Lower SUuric and the term "Hudson 

 River group" for the Utica and Lorraine beds and to employ the term Normans KiU shales for 

 the classic facies of a part of the lower Trenton which is characterized by the graptolite fauna 

 at the Normans KiU. 



