GEOLOGY OF OGDEXSBURG 53 



about Ogdensburg, partly because sharply contrasting, thin forma- 

 tions are not present here, and partly because of drift-covering. 

 The areal mapping suggests that the axes of the folds have swung 

 to northeast and northwest directions, and that the northeast set is 

 much more prominent than the northwest set in the Ogdensburg 

 region. 



Faults. Faults are scarce in the Paleozoic rocks of this north- 

 Avestern region, though they increase in number and importance in 

 passing to the east. In the Ogdensburg region Ave have noted but 

 one fault of any prominence, at Point Comfort, 3 miles up the 

 river from ]\IorristOAvn, Brier Hill sheet. The fault bears east and 

 the south is the doAA'nthroAv side. Above Point Comfort the river 

 cliff is composed of the Potsdam and Theresa formations, 10 feet 

 of Potsdam which has increased to 20 feet at Oak point, overlaid by 

 the thin-bedded, calcareous sandstones of the typical Theresa. 

 This is the section south of the fault, the doAA'nthrow side. North 

 of the fault the Potsdam extends up to 50 feet above the river, Avith 

 a great bed of its characteristic coarse conglomerate, the same bed 

 that occurs in the river cliff in Hammond tOAA^nship. At the fault 

 25 feet' of sandstone shoAv beloAv it, and 20 feet above it, foUoAved 

 by the Theresa. The throAv of the fault here is about 40 feet. 

 The fault zone shoAvs no outcrops but is occupied by a drift-filled 

 depression, as is apt to be the case. It can not be definitely traced 

 inland, aAA'ay from the river because of infrequent outcrops and of 

 similar Theresa beds on both sides. But 2 miles to the east, along 

 its supposed trend, there is CAddence of misfit in the strike of the 

 bed of 20 foot (Heuvelton) sandstone, on the tAvo sides of the line, 

 so that in all likelihood the fault extends east at least to this point. 



A very trifling fault is shoAA'n along the riA'er road 2Y2 miles 

 beloAv MorristoAvn, Avhere the road runs over a shalloAV gully and 

 small stream. The 20 foot sandstone of the Heuvelton is dropped 

 in level about 15 feet on the east side of the gully as compared Avith 

 its level on the west side, and is apparently faulted doAvn. It is a 

 trifling break and can not be traced to the south. 



Except for these tAvo, no faults have been noted. 



HISTORICAL GEOLOGY 



PRECAMBRIAN TIME 



Recorded geologic history began in Ncav York Avith the deposition 

 of the Grenville series. That this AA'as not the actual beginning of 

 the history of the region is shoAvn by the fact that the Grenville, 



