48 Report of the State Geologist. 



Fonda Fault — The small uplift east of Fonda brings up a 

 small area of Trenton limestone in the Mohawk valley, mainly 

 in the north bank, where the formation rises thirty or forty feet 

 above the river. The fault plane was not precisely located nor 

 were any attendant phenomena observed. Its relations were 

 shown in section A, plate 3, and on plate 2. The upthrow is on 

 the western side, and the displacement amounts to about 125 

 feet. Heavy drift hides its northern extension. It may pass 

 through the Utica slate area northward, and possibly be con- 

 tinuous with the fault at Mayfield, but I have no positive 

 evidence on this point. 



Tribes Hill Fault. — This fault is not of great prominence, but 

 the limestone beds which it brings up have been extensively 

 quarried, so that it is of considerable economic importance. The 

 relations of the fault are shown in section A, plate 3, and in 

 plate 2. The exposures are quite clear in the vicinity of the 

 river and for some distance northward. To the south it is soon 

 lost in the drift of the Schoharie valley or the adjacent hills of 

 Utica slate and Hudson river. The Utica slate is exposed in the 

 immediate vicinity of the fault at several points along its course, 

 with the usual narrow zone of upturned beds varying in dip from 

 40° to 60°, which die out gradually to the eastward. The amount 

 of the displacement on the Mohawk river is about 200 feet. In 

 the high hills about Perth the fault is heavily covered by drift, 

 and its northern extension could not be traced. It appears to die 

 out in this region. 



BroadaTbin Fault. — This fault is similar to the uplifts east of 

 Ephratah and near Dolgeville, in having the downthrow on the 

 northwestern side. Its location is shown in plates 1 and 2. It 

 is somewhat north of section B, plate 3. It trends east-north- 

 east' and west-northwest, passing half a mile north of Fonda's 

 Bush, and apparently it soon dies out to the east and west. 

 Owing to heavy drift along its scarp its relations are for 

 the most part concealed. In the creek, a half mile north of 

 Fonda's Bush, the slate is seen tilted northeastward or obliquely 

 away from the fault at an angle of 40°. The amount of disloca- 

 tion at Fonda's Bush is about 200 feet. The Calciferous is 

 exposed on the hill a few rods to the southwest of the village, 



