﻿86 NEW YORK STATE MUSEUM 



Ulrich is inclined to unite it with the Seven foot tier or Watertown 

 limestone. We adopt here this view, leaving the final decision as to 

 the exact boundaries to a future close study of the faunas involved, 

 but consider the difficulty of an easy recognition of this boundary 

 — located within a lithologic unit — in the field as another practical 

 reason for mapping and discussing here the Leray and Watertown 

 limestones together. 



Finally, it was found in studying last summer, in company with 

 Dr Ami, Professor Cushing and Dr Ulrich, the section at Klock's 

 quarry at Watertown [see below p. 90], that there is properly 

 referred to the Watertown also a bed 1^/2-2 feet thick, of black 

 limestone, that still overlies the Seven foot tier. 



With these upward and downward extensions of the formation, 

 the limestone will be about 15 feet thick in its type region 

 while the Leray limestone is about 13 feet thick, consisting of dark 

 gray to black, heavily bedded, dove limestone, with layers of black 

 chert nodules. The nodules are more or less scattered through the 

 chert beds, forming here and there strings in the section and a dis- 

 tinct horizon over the whole mapped area near the base of the beds. 

 Since large rock exposures of the surface oithe Leray limestone are 

 frequent in the region, one has often opportunity to observe large 

 quantities of these cherts, half weathered out, on the rocks, pre- 

 senting a flat, cakelike form. Some of the chert beds present, when 

 weathered, a peculiarly fucoidal surface through intricate intermix- 

 ing of the limestone with earthy films, and others are distinctly 

 cross-striated. 



The contrast between the massive chert beds and the thinner 

 bedded underlying Lowville strata is well shown in plate 20. In 

 natural exposures or where the quarry face is weathered, the Water- 

 town and Leray formations are readily distinguished from the 

 lower Lowville beds by their breaking up into small cubic blocks 

 the size of a fist. The beginning of this breaking up, which is ap- 

 parently due to a reticulate system of mud seams, is seen in plate 

 20 and farther progressed in plate 21. Here the rock is so 

 weathered that it can be brought down with the pick and is of con- 

 venient size for road metal. It is also well shown on plate 19, 

 where the hat lies just above the boundary line. This picture ex- 

 hibits especially well the contrast between the evenly and thinner 

 bedded typical Lowville limestone and the thick bedded blocky 

 weathering Leray and Watertown beds. 



In plate 22 will be found an excellent illustration of the uncon- 

 formity between the Lowville and Leray limestones. The lower of 



