718 ABSTRACTS OF PAPERS 



Pite and biotite after dolomite ("eozoon" b) ; antigorite after pyroxene 

 ("eozoon c) ; loganite after pyroxene, phlogopite, etcetera ("eozoon" d) ; alter- 

 nation of pyroxene and apatite ("eozoon" c) . The later form of silification was 

 effected by meteoric waters, resulting in antigorite after dolomite ("eozoon" f) 

 and antigorite after nemalite, chrysotite ("eozoon" g). 



A secondary result of the same processes appear in the calcite-pegmatite 

 veins, peculiar to the Grenville formation. These may be coarse granitic or 

 banded, and their constitution is shown by a large number of cross-sections, 

 and the source of the calcite deduced from reactions in the processes of silifi- 

 cation. On the derivation of the apatite in these veins and in the limestone 

 beds various hypotheses are considered, but it is attributed to a process of 

 concentration during the silification of the dolomite. 



NEW LIGHT ON THE KEWEENAW AN FAULT 

 BY A. C. LANE 



{Abstract) 



Recent exploration and drilling have shown that the strata on the east side 

 of tbe Copper Range were uplifted and the Eastern or Jacobsville sandstone 

 deposited on them, and that since then, by a great fault, the Trap Range has 

 overridden these sandstones in certain places several hundred feet. There 

 was a peneplanation (Cretaceous ?) subsequently, but the Keweenawan rocks 

 were not so peneplaned when the Eastern-Jacobsville sandstone was laid down 

 but that pebbles of the Keweenawan traps occur in it. 



GLACIAL EROSION IN THE GENESEE VALLEY SYSTEM AND ITS BEARING ON 

 THE TERTIARY DRAINAGE PROBLEM OF EASTERN NORTH AMERICA 



BY AMADEUS W. GRABAU 



(Abstract) 



The evidence for glacial overdeepening of the Warsaw, Genesee, and Dans- 

 ville valleys will be given, and from the pre-Glacial arrangement of the stream 

 valleys the question of northward or southward drainage in New York during 

 Tertiary time will be considered. 



Discussion 



Dr. J. W. Spencer: The drainage of the Canadian Highlands at an early 

 date was doubtless to the south, but the encroachment of the Saint Lawrence 

 River and tributaries lowered the northern country and robbed the heads of 

 the southbound streams. The apparent post-Glacial rise is everywhere north- 

 ward, so that the region of Ontario was relatively lower than now. When the 

 continent stood high, before the Glacial or during the Glacial period, the greater 

 northern elevation, as shown in the submerged channel of the Gulf of Saint 

 Lawrence and of the Hudson River, also obtained all the way to the Gulf of 

 Mexico, as found by the buried valleys. Accordingly, when the floor of Lake 

 Ontario is found to be 1,400 feet lower than the rock floor which crosses the 

 head of the Dundas Valley, there is no evidence whatever that the tilting was 



