Published nioiithlv by the 



New York State Education Department 



BULLETIN 419 • JANUARY IQ08 



New York, State Museum 



John M. Clarke, Director 



Bulletin ii8 

 PALEONTOLOGY 18 



GEOLOGIC MAP AND DESCRIPTIONS 



OF THE 



PORTAGE AND NUNDA QUADRANGLES 



INCLUDING A MAP OF LETCHWORTH PARK 



BY 



JOHN M. CLARKE & D. DANA LUTHER 



ACCOMPANIED BY A REPORT ON THE 



PLEISTOCENE HISTORY OF THE 

 GENESEE VALLEY 



BY 



HERMAN L. FAIRCHILD 



PAGE 



Geology of the Portage and 

 Nunda Quadrangles. J. M. 

 Clarke & D. D. Luther. 43 



Introduction 43 



Historical 44 



Bibliography 44 



Classification 46 



Description of formations.. 47 



Dip 68 



Pleistocene History of the 

 Genesee Valley in the 

 Portage District. H. L. 

 Fairciiild 70 



PAGE 



Evolution of western New- 

 York drainage 70 



Diversions of the river. 



Buried channels 71 



Glacial waters and canyon 



cutting 75 



Later stages 81 



Epitome of the history 81 



Canyons and cataracts 81 



Deformation of the lake 



planes 83 



Detrital filling of the valleys 84 



Index 85 



