52 NEW YORK STATE MUSEUM 



the past fifteen years on the Paleozoic rocks which rim the Adiron- 

 dacks has shown clearly that they consist largely of the thinned, 

 near-shore edges of a great number of formations, and that there 

 is a great lack of correspondence between the formations on the 

 different sides of the region. The Heuvelton division found here 

 adds yet another unexpected member to the group. Or, as Ulrich 

 writes, '' Evidently the western flank of the Adirondack uplift 

 carries more of these thin wedges than we supposed." No doubt 

 yet others remain to be found. 



Structures of the Paleozoic rocks 

 Dip. The dips of the Paleozoic rocks of the Ogdensburg region 

 are low, seldom exceeding 5°, and are in a general northerly direc- 

 tion. On the Brier Hill quadrangle they average somewhat to the 

 west of north ; on Ogdensburg they are more nearly north. Along 

 the river between Morristown and Ogdensburg the Heuvelton 

 and Ogdensburg beds disappear under the river at a rate of from 

 25 to 30 feet a mile; that is, a mile in a northerly direction; in the 

 northeasterly direction of the river's course the rate is slower. 

 This is not a high dip, but a very low one, and has no particular 

 interest except in its contrast with the southwest dip which the 

 Paleozoic rocks of the Theresa and Clayton quadrangles, on the 

 other side of the Frontenac axis, possess. 



Folds. In the Thousand Islands report it was shown that the 

 gently inclined Paleozoic rocks of the region had been somewhat 

 folded, and that there were two sets of gentle folds whose axes cut 

 one another almost at right angles, the one set trending somewhat 

 east of north, and the other somewhat north of west.^ The effect of 

 this double folding was to produce an alternating series of low 

 domes and low basins in the rocks, domes at the intersections of 

 anticlines, and basins at the intersections of synclines of the two 

 sets of folds. 



This same type of folding carries over into the Ogdensburg 

 region, though the evidence is not so clean-cut here because of less 

 frequent exposures. But low domes of rock, from the summit of 

 which the dip falls away to all points of the compass, are of quite 

 frequent occurrence. The corresponding basins, occupied by out- 

 liers of younger formations, which were such a feature of the 

 geology of the Theresa and Clayton sheets, are not easily detected 



IN. Y. State Mus. Bui. 145, p. 1 12-15. 



