PLEISTOCENE MARINE SUBMERGENCE 49 



shown in a broad way in plate 5. This quadrangle was made the 

 subject of a special paper by Woodworth (81), and was also cov- 

 ered in his more comprehensive Bulletin 84 (82). At the time of 

 Woodworth's study no territory adjacent to the Mooers quadrangle 

 had been mapped and definite correlation of features could not be 

 made. It becomes necessary to republish the sheet in order to 

 locate the summit shore line of the sea-level waters, to show the 

 relation of features to adjacent territory, and to reveal graphically 

 the sequence of events or the later Pleistocene history — the very 

 latest glacial events of New York State. 



Much study has been given to this area, long ago by Woodworth 

 and later by the writer. Many visits have been made and some 

 localities have been visited several times. Some of the features 

 are so peculiar or equivocal or unusual in character that they were 

 uncertain, and at first were misinterpreted. Some of the heavy 

 tracts of cobble and boulder delta stuff had been regarded as 

 moraine. The key to the history has been the determination of 

 the summit level of the sea-level water, but much time and travel 

 have been required to verify phenomena at critical points. Even 

 now there are stretches of the summit shore line, rather inacces- 

 sible, far from deltas and of weak development, which are inter- 

 polated on the map. Future study will verify the shore line. 



The position of the summit shore is determined by (i) wave- 

 built bars; (2) higher terraces on deltas; (3) lowest reach of the 

 ice-border drainage. The last is well displayed. Over large areas 

 the Potsdam sandstone has been stripped of its drift mantle, and 

 in the Altona region conspicuous channels have been cut (see 

 Woodworth's illustrations). These areas of glacial drainage make 

 the most conspicuous features of the map. 



The sandstone in this region has an eastward dip and formed 

 a hard floor, declining toward the receding ice front, thus favoring 

 the stripping. Four areas of the " stripped rocks " may be dis- 

 criminated on the map (plate 5). First, the Altona rocks, south 

 and southeast of Altona (81, page 18; 82, page 161). This area 

 is some 5 miles long by i or 2 miles wide. The upper margin on 

 the east slope of Big Hill must lie under iioo feet, and the lower 

 limit is at Pine ridge, at the marine plane. Earlier glacial stream 

 flow is indicated at higher levels south of Big hill. The Altona 

 rocks are famous for their production of huckleberries (plate 18). 



The other bare rock areas are partly on the adjacent Churu- 

 busco quadrangle. The second is the area southwest of Cannon 

 Corners, called the Blackman rocks. The third is the Stafford 



