GEOLOGY OF LAKE PLEASANT QUADRANGLE 37 



albln and Saratoga quadrangles, we may be reasonably certain that 

 neither the Beekmantown nor Chazy is represented in the Wells 

 outlier. Thus the very distinct unconformity between the Little 

 Falls dolomite and Black River limestone of the Mohawk valley 

 is also shown at Wells. 



Black River limestone. In actual outcrop the Black River 

 series of limestones is represented wholly by the Lowville, including 

 an upper, dark, dove-colored, cherty limestone which is probably 

 to be classed with the Leray member of the Lowville. The only 

 exposures occur along the small creek which cuts through the 

 southern end of the narrow belt of Black River-Trenton limestones 

 shown on the geologic map. The beds strike east-west and dip 

 north 10°. In the creek just east of the quarry the following sec- 

 tion was measured : 



ft. in. 

 7 Trenton limestone with fossils — In situ? 3 



6 Concealed, about 20 



5 Dark, dove-colored limestone with smooth fracture. Rather 

 massive, but with occasional stratification planes visible. Con- 

 tains a distinct layer of black chert. Leray? limestone 6 



4 Smooth, black limestone in layers from i to 4 inches thick and 



with thin shale partings. Lowville 4 6 



3 Smooth, dove-colored limestone fairly well separated into layers 



from ^ to 8 inches thick. Lowville 4 



2 Smooth, dove-colored limestone layers with small dove-colored 



pebbles of limestone. Lowville 3 



I Dove-colored limestone with large and distinct vertical tubes. 

 (Phytopsis tubulosum). Stratification planes divide 

 the mass into layers several inches thick. Lowville 2 



Bottom of creek. 



Thus a thickness of i6 feet and 9 inches of Lowville, including 

 the Leray? layer with chert, is exposed but with neither top nor 

 bottom shown. The exposure is a small one and no fossils except 

 Phytopsis tubulosum were found. Because it answers 

 so well to the descriptions given by Gushing ^ and Ruedemann,^ the 

 six-foot cherty bed is thought to represent the upper or Leray 

 member of the Lowville. 



If the Amsterdam limestone is present it should come between 

 the cherty bed and the Trenton, but this part of the section is com- 

 pletely concealed so that the presence or absence of the Amsterdam 

 can not be determined. 



1 A. J. S.. Feb. 1911, p. 139-42. 



2 N. Y. State Mus. Bui. 145, p. 85-86. 



