REPORT OF THE DIRECTOR I913 67 



Similar white saccharoidal sandstone, usually but little disturbed 

 and with dips no greater than have been seen over the northern 

 belts, occurs as outliers in separate localities along the east side of 

 the Grasse river 2 and 3 miles respectively south of Canton. At 

 the nearer of these the actual contact with the adjacent Grenville 

 quartzite is excellently revealed, the latter beds standing vertically. 

 Not far away are exposures of a more indurated and disturbed red 

 or reddish sandstone of typical Potsdam character and revealing 

 extensive brecciation and microfaulting. Often this rbck is vir- 

 tually a quartzite, though quite distinct in character from the 

 thoroughly metamorphic Grenville. Small thrusts and monoclines 

 are common. Some of the rock is highly autoclastic. These 

 two types of rocks, with their color contrast even more pronounced 

 perhaps, occur in very close proximity at the more southerly 

 locality, where the red one is seen (as at several other points) in 

 an equally unconformable but strikingly different type of contact 

 with the Grenville quartzite and marble. The relations here are 

 such that pertinence of the white and the red sandstones to the 

 same formation seems open to question, though positive evidence of 

 difference of age is not yet discovered. And these doubts intrude 

 themselves at all the other localities examined, including the ex- 

 posures north and south of Potsdam village. A distinction between 

 these beds has been suggested by Gushing ^ for the Theresa quad- 

 rangle, with an erosion interval postulated on the basis of red 

 pebbles incorporated m the white beds. It appears to us that no 

 considerable age difference is indicated by the accumulating data 

 and that Winchell's suggestion '^ of lower or middle Cambric age 

 for the true red Potsdam sandstone of the Hannawa quarries (type 

 locality) is hardly acceptable, though still possible. 



SURFICIAL GEOLOGY 

 During the year past Professor Fairchild has continued his obser- 

 vations upon the changes in the postglacial waters. In the summer 

 of 1913 his work was partly in the Champlain valley and partly, for 

 purposes of comparison, in the valley of the Connecticut river. 

 The manuscript copy of the forthcoming Churubusco or Ellenburg 

 quadrangle sheet gave opportunity for determination of altitudes 

 in the area near the Canadian boundary east and southeast of 

 Covey hill. With the help of [his map, it was found that the series 



1 N. Y. State Mus. Bui. 145, p. 62. 



2 Vide N. Y. State Mus. Bui. 95, p. 360. 



