280 NEW YORK STATE MUSEUM 



surface of the present Adirondack region. It was deposited in 

 shallow water under conditions of sufficiently vigorous wave and 

 current action to remove all fine mud particles, whieh were swept 

 away and deposited elsewhere in deeper water. In Clinton county 

 a thickness in excess of 800 feet, perhaps more than double that 

 amount, of this sand accumulated before changing conditions 

 brought about a change in the character of the deposit. The water 

 must have been shallow throughout, hence the rate of subsidence 

 could not have exceeded the rate of accumulation. This thickness 

 diminishes westward and southAvard, and the sands are mostly 

 absent from the west side of the region, as has just been stated. 

 With diminishing thickness, it is apparently the lower beds that 

 disappear. The basal portion of the formation in Clinton county 

 seems to be the oldest of the deposits in the Adirondack region, 

 and its often coarsely pebbly character and abundant content of 

 undecayed feldspars indicate vigorous wave action on rocky shores 

 of resistant, unrotted rocks. The upper portion of the formation 

 here, and most of it elsewhere, consists of pretty pure quartz 

 ■sand, indicative of prevailing different conditions from those 

 above, namely that either the feldspars had been pretty thoroughly 

 rotted previous to submergence, or else that they experienced the 

 triturating action of the waves for a sufficient length of time to 

 be wholly ground fine, while the somewhat harder quartz yet 

 remained coarse, implying a slower rate of subsidence. The 

 former is much the more probable cause, though no doubt the 

 latter had some influence also. 



The present Adirondack region must have supplied much of 

 the rock material thus spread on the sea floor, and the drainage 

 of the district must have been mainly to the north and east. The 

 present western border of the region was but slightly submerged 

 during this time, and for part of the time the waters were clear, 

 with deposit of limestone instead of sand. The upper part of 

 the formation around the Adirondacks is certainly a marine 

 deposit and holds marine fossils. These are lacking in the larger 

 part of the formation, and this, together with its character, sug- 



