30 NEW YORK STATE MUSEUM 





there a little over fifty feet thick. On this basis the passage beds 

 rapidly thicken westward to two hundred feet on the Broadalbin 

 sheet. If, however, we regard the Hoyt limestone as an upper 

 phase of the passage series, and this is a very possible view since 

 Ulrich and Cushing say that the same trilobite fauna ranges through 

 both the Hoyt and the Theresa, the strata between the Potsdam and 

 Little Falls show an increased thickness of only fifty feet westward 

 to the Broadalbin sheet. 



In the vicinity of North Galway there are many good outcrops of 

 the Theresa formation and this locality is of special interest be- 

 cause there the passage beds may be seen resting directly upon 

 the Precambric. Three-fourths of a mile northeast of North Gal- 

 way dolomitic limestone beds, with occasional small quartz pebbles, 

 are practically in contact with the Grenville while two hundred 

 yards west of this a two foot layer of sandstone occurs very close 

 to the Grenville. It is clear that the Potsdam is not present here 

 and that the passage beds rest directly upon the Precambric. The 

 significance of this overlap is discussed on page 51. 



Along the road just east of North Galway the section is as 

 follows : 



Feet 



I. Oolitic and cryptozoon limestone beds 

 14. Alternating dolomitic limestone and sandstone beds 

 7. Interval — but doubtless alternating limestone and sandstone 

 3. Thin-bedded sandstone, rather calcareous 

 25. Dolomitic limestone, sometimes sandy to pebbly 



Potsdam conglomerate not exposed and very thin if present 

 Precambric Grenville quartzite 



Between Northampton and West Galway the line separating the 

 Theresa and Little Falls formations is difficult to draw because of 

 heavy drift. One mile south-southeast of Northville there are large 

 exposures of typical passage beds. Near Edinburg no outcrops 

 were noted but, judging by the distribution of Potsdam and dolo- 

 mite ledges and the drift fragments, the Theresa formation must 

 swing around something as shown on the geologic map. In Gif- 

 ford's valley upper beds of the formation are well exposed, espe- 

 cially along the road by Mr Gifford's house, where the heavy bed of 

 sandstone and immediately overlying dolomite are shown. Two 

 miles north-northwest of Cranberry Creek a small area of these 

 rocks comes against the Noses fault. One and one-half miles 

 northeast of Mayfield, and along Roberts creek, the formation is 



