GEOLOGY OF THE BROADALBIN QUADRANGLE 31 



pretty well exposed and the transition character of the beds is 

 shown. The dip is from 3 to 5 degrees southwestward and the 

 thickness is estimated at 150 feet. 



LITTLE FALLS DOLOMITE 



Of the Paleozoic formations, the Little Falls dolomite (upper 

 Cambric) is the most prominent and widespread within the quad- 

 rangle. With certain minor exceptions the formation presents a 

 remarkably uniform character throughout. Typically the rock is 

 pale bluish-gray, fine-grained, crystalline, dolomitic limestone, which 

 when freshly broken exhibits a glimmering surface. The rock is 

 often rather arenaceous and in a few cases a pale pink tint has been 

 noted. The weathered surface is generally light gray to pale buff 

 in color. The rock is distinctly bedded, the layers ranging in thick- 

 ness from less than an inch to eighteen inches, with a usual thick- 

 ness of six to twelve inches. A striking feature, which may nearly 

 always be observed in the outcrops, is the occurrence of cavities 

 lined with quartz crystals and frequently accompanied by dolomite 

 or calcite crystals. The quartz crystals, remarkable for clearness 

 and perfection of form, are popularly but erroneously called 

 diamonds. 



A rather persistent feature of the dolomite is the presence of 

 angular chert fragments about twenty to forty feet above the base 

 of the formation. This chert is sometimes white and sometimes 

 dark colored and is often a prominent constituent of the rock 

 through a thickness of several feet. Some of the localities where 

 the chert is well shown are : in the creek at Parks Mill and on the 

 hillside just to the south; two-thirds of a mile west of Galway; one 

 mile east-northeast of Mayfield ; on the west side of Bunker hill; 

 two miles northwest of Cranberry Creek; just southeast of North- 

 ville; in the north end of Gifford valley; on the river two miles 

 south-southeast of Northville ; and two and one-half miles north of 

 Batchellerville. 



A mile east, as well as a mile and a half southwest, of Galway 

 several feet of thin calcareous, sandy shaly beds have been noted 

 near the summit of the formation and these are probably the same 

 as similar beds described in other sections of the lower Mohawk 

 valley. 



Since no complete section of the Little Falls dolomite is exposed 

 within the map limits the thickness can only be approximated. 

 Eastward from Galway the dip and extent of the formation appear 



