GEOLOGY OF LAKE PLEASANT QUADRANGLE 43 



directly across the strike the beds outcrop continuously so that a 

 thickness of some 51 feet is shown. The beds are generally heavy, 

 ranging up to 2 feet in thickness, with the upper two-thirds of the 

 beds rich in light to dark gray chert which is often arranged in 

 very irregular thin layers, but at other times it is irregularly 

 scattered. From this ledge southward for about 100 yards a 10 foot 

 wide outcrop continues with the same dip and strike. 



Northward, within the belt as mapped, the first dolomite exposure 

 occurs about one-fourth of a mile from the river and thence for 

 one-half of a mile there is a practically continuous exposure, though 

 at no one place is a thickness of more than 6 or 8 feet visible. Along 

 this slope, however, the outcrops are so arranged that no less than 

 30 feet of thickness of dolomite is present with a slight westward 

 dip. None of these dolomite exposures are visible from the road. 



Black River limestone. In an old quarry close to a limekiln, a 

 small wedge of Lowville limestone (see map) is sharply faulted 

 against the dolomite. The fault plane is clearly visible for a few 

 feet in the quarry and a thickness of only 6 or 7 feet of limestone 

 is shown in place. The rock is only sparingly fossiliferous, the 

 Tetradium tubulosum proving the limestone to be of 

 Lowville age. 



Significance of the Paleozoic rock outliers 



These and other outliers (see below) of the southeastern Adiron- 

 dack region afford positive evidence that the waters of the early 

 Paleozoic sea spread over part or all of the region. Did these waters 

 occupy distinct embayments or estuaries as has been suggested or 

 did they form a more regular shore line?^ Along the eastern side 

 of the Adirondacks where the topography was moderately rugged, 

 such embayments were quite likely physiographic features of some 

 importance due to a drowning of the valleys which had been cut out 

 along the belts of weaker Grenville strata. In the southern Adiron- 

 dacks, however, the evidence is decidedly against the encroachment 

 of the late Cambric sea by setting up anything like well-defined 

 embayments or estuaries extending into the area of Precambric rock. 



The outliers of Paleozoic rock in the southeastern Adirondacks 

 are of first importance in this connection. All the definitely known 



1 For a rather full discussion of the " Early Paleozoic Physiography of 

 the Southern Adirondacks " see paper by the writer in N. Y. State Mus. 

 Bui. 164, 1913, P- 80-94. 



