GEOLOGY OF THE SCHROON LAKE QUADRANGLE 69 



pieces by numerous normal faults, the most prominent of which 

 usually strike from north-south to northeast-southwest, with known 

 displacements ranging from a few hundred to 2000 feet or more. 

 It is important to note that the outliers above listed, except pos- 

 sibly nos. 2, 3 and 4, lie on the downthrow sides of such faults. 

 Thus a prominent fault bounds the Schroon Lake valley on the 

 west. It appears, therefore, that the valleys containing these out- 

 liers have been largely produced by faulting, and that the Paleozoic 

 strata formerly lay at much higher levels, that is, the general level 

 of the surface of Precambrian rocks of the region. 



Were the early Paleozoic sediments deposited in embayments or 

 estuaries of the sea extending well into the area of Precambrian 

 rocks, or were they deposited as a general mantle over the Pre- 

 cambrian rocks of the whole southeastern Adirondack region? As 

 a result of detailed studies it has been established that the southern 

 half or two-thirds of the Adirondack area was, by the beginning 

 of Potsdam time of the late Cambrian period, worn down to the 

 condition of a peneplain upon whose surface only a few minor 

 knobs or prominences existed. This being the case, notable embay- 

 ments or estuaries could scarcely have existed. Still further evi- 

 dence against the embayment idea comes out of the character of 

 the sediments. Thus the rocks of the outliers, including those of 

 Schroon Lake and Wells, are distinctly marine forma':ions of exactly 

 the same character as those of the same age in the general Pale- 

 ozoic rock area of the Champlain and Mohawk valleys. Estuarine 

 deposits would show certain distinct local variations and hence the 

 very uniformity of the marine sediments in the outliers precludes 

 the possibility of their deposition in estuaries. Thus we conclude 

 that when the early Paleozoic, or more precisely late Cambrian, 

 sea encroached upon the southeastern Adirondack area a general 

 mantle of sediments was deposited over the whole region includ- 

 ing much at least of the area of the Schroon Lake quadrangle, and 

 that, subsequent to the emergence of the region, normal faulting 

 took place whereby portions of the Paleozoic strata were, in many 

 places, carried so far down that remnants have to this day been 

 protected against complete removal by erosion. Thus we explain 

 the existence of the outliers of early Paleozoic marine strata in 

 the Schroon valley. 



Early and Middle Cambrian strata are unknown in northern New 

 York, and there is no evidence that early and middle Cambrian 

 seas ever spread over any portion of that area. But with the late 



