GLACIAL LAKE SUCCESSION 157 



Susquehanna; (6) Mohawk-Hudson; (7) Champlain-Hudson ; (8) 

 ocean-level waters direct; (9) Lake Ontario-St. Lawrence. Some of 

 these systems received the Genesee Valley overflow more than once, or by 

 different immediate outflow, making the twenty stages in the drainage 

 history as now understood. It would seem unlikely that any other valley 

 in the world can approach the Genesee in the complexity of its drainage 

 history. 



The series of sixteen maps depict the waning Laurentian ice-sheet 

 with the glacial and marine waters that lay against its receding border. 

 The local lakes in the side valleys of the Hudson depression and about 

 the Adirondack highland are not indicated, and the ice border is more or 

 less generalized. The latter is located definitely along the lines of the 

 ice-border drainage. 



The chart (page 158) shows the time relationship of the waters in the 

 several basins of the State. The vertical spacing is only suggestive of 

 the succession of the waters and their geographic relations and has little 

 significance as to the duration of the episodes. 



Marine Waters 



During the waning of the latest ice-sheet the Hudson-Champlain Val- 

 ley and the St. Lawrence and Ontario basins were beneath the level of 

 the ocean. As the ice-front receded northward the sealevel waters fol- 

 lowed up the Hudson Valley, finally reaching the Champlain Basin and 

 eventually uniting with the oceanic waters of the St. Lawrence Gulf. 

 The Hudson Inlet thus became the Hudson-Champlain Inlet, and finally 

 the Hudson-Champlain Strait, connecting New York Bay with the Cham- 

 plain Sea. When the ice-front backed away from the Covey Hill prom- 

 ontory the glacial waters of the Ontario Basin, the Second Iroquois, fell 

 to and became confluent with the sealevel waters. The highest plane of 

 the sealevel waters in the Ontario Basin is relatively weak and has not 

 been fully determined, but an inferior level of long persistence, showing 

 heavy bar construction, has been mapped and named Gilbert Gulf. This 

 stage, which includes the series of strong bars at Covey Hill post-office, 

 is depicted in map number 16. 



On the parallel of New York city it appears that the land at the time 

 of the ice recession was at, or perhaps somewhat above, sealevel. North- 

 ward the land was increasingly below sealevel. The upraised and tilted 

 water plane, which indicates the amount of Pleistocene submergence or 

 of post-Pleistocene uplift, rises Bteadily from zero or present sealevel in 

 the district of New York city to over 700 rod on the Canadian boundary. 



