40 NEW YORK STATE MUSEUM 



limestone both strike east-west and dip northward from lo to 20 

 degrees, the field relations being such that it would not be possible 

 for a thickness of over 20 to 25 feet of Trenton to intervene. 



Where the little stream coming down from Mount Rouge crosses 

 the limestone belt (see geologic map), there is a small quarry also 

 showing a few feet of hard, dark, limey shale or shaly limestone 

 at the base of the Canajoharie or the summit of the Trenton, hence 

 we can be sure of the mapping at that locality. 



Canajoharie (Trenton) shale. As shown on the geologic map, 

 the Canajoharie shale is wholly confined to a single area on the 

 western side of the valley, it being bounded on the west by the fault 

 and on the east by the narrow belt of Black River-Trenton lime- 

 stones. The typical rock is always black, distinctly stratified, some- 

 what calcareous, and thin-bedded, the maximum thickness of layers 

 noted being 5 or 6 inches. Toward the base of the formation the 

 rock is much more calcareous and not so black, so that it might more 

 properly be called a very shaly or impure limestone. . 



Good exposures of the shale occur along the small stream which 

 comes down from Mount Rouge. Within a few hundred feet of 

 the fault there is a good outcrop, showing a thickness of 15 to 20 

 feet, rich in fossils, and with strike north 50° east and dip 20° 

 east. This sharp eastward dip is the updrag effect produced at the 

 time of the faulting. At a point about midway between the fault 

 and the limestone belt an axis of a distinct syncline is crossed (in 

 the creek) because eastward from this point several exposures 

 show a gradually increasing dip of from 5° to 10° to the west. In 

 the small quarry (already mentioned) at the edge of the limestone 

 belt, the shale is very limey and with fossils much like those of 

 the Trenton limestone so that this rock clearly belongs either at 

 the base of the Canajoharie or at the summit of the Trenton. 



Along the next stream course to the south, which comes down 

 from Mount Orrey, the greatest thickness of shaje occurs. About 

 450 feet from the fault there is a good outcrop with numerous 

 fossils. It shows strike north 60° east and dip 15° east. Then 

 comes an interval, and about 1000 feet from the fault a more or 

 less continuous exposure begins and extends several hundred feet 

 along the creek. It shows a strike north 50° east, dip 5° west, and 

 a thickness of 35 or 40 feet. Thus a synclinal axis is also crossed 

 here which is doubtless the same as the one already described as 

 crossing the creek just to the north. This syncline is well shown in 

 the accompanying structure section. The quarry (see map) north of 

 the creek and close to the road, shows a thickness of 20 feet of not 



