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NEW YORK STATE MUSEUM 



skirting the eastern foot of the mountain. This belt also terminates 

 abruptly against the Georgian rocks of Louse hill, which have 

 overridden its northern continuation in the over-thrust movement. 



The boundaries between the grit zone, shale zone and white- 

 chert bed zone are not sharply delimited, and in one place all three 

 were found to alternate in typical beds several times in a thickness 

 of 17 feet. As the coarse clastic material in the grit indicates, 

 shallow marine conditions prevailed at times during the deposition 

 of the beds and the supply of siliceous and argillaceous mud 

 changed at times very rapidly. 



The true stratigraphic relation of the shales, white-weathering 

 beds and grit, owing to the intensely folded and faulted condition 

 of the region, is nowhere shown conclusively. Dale in 1899 (chart 

 facing page 178) gave the following succession in descending 

 order : Ig Hudson grits, . Hw Hudson white beds, G Hudson 

 shales; placing the grits on top of the series. In 1904 (page 37) 

 however, he published the following table showing the Hudson 

 formation as exposed in Rensselaer county and the northeastern 

 part of Columbia county, N. Y. : 



ESTIMATED 

 DESCRIPTION OF STRATA FAUNA THICKNESS IN FEET 



1 Black shale with arenaceous lime- 



stone (Ruedemann's stations 24-26) Diplograptus amplexi- 



caulis 



2 Black and gray shale with inter- 



bedded grit Normanskill graptoHte 



fauna 



3 Similar shale with limestone and 



limestone conglomerate Trenton fauna in lime- 

 stone and cement of 

 conglomerate 



4 Black, siliceous, white-weathering, 



cherty-looking shale 1 



5 Reddish, purplish, greenish shale with 



small quartzite bands 



'1200-2500? 



Number i are the beds here described as the Snake Hill forma- 

 tion, and no. 3 those here referred to the Rysedorph Hill con- 

 glomerate, and placed now, on faunal evidence, above or near the 

 top of the Normanskill beds; while no. 5, the colored shales, are 

 not exposed, if present, on the Schuylerville quadrangle. It will 

 be seen that here the grits are also placed above the white beds, 

 while the dark shales are not recognized as a separate subdivision. 



