THE CHAMPLAIN SEA IN THE LAKE ONTARIO BASIN 545 



northern shore. The river heads in a chain of little lakes which 

 dot the surface of the pre-Cambrian rocks in the central part of 

 Frontenac County, 25 miles north of the east end of Lake Ontario. 

 The lowest of the small lakes is Lake Napanee, 446 feet above sea- 

 level. Thence the river flows across the nearly flat-lying Ordovi- 

 cian limestones which overlap the pre-Cambrian complex, past the 

 towns of Yarker and Napanee to the Bay of Quinte on Lake 

 Ontario (see Fig. 3). From Lake Napanee to Lake Ontario the 

 length of the river is about 24 miles, and its total fall is 200 feet. 

 Throughout this portion of its course Napanee River occupies a 

 pre-Wisconsin youthful valley cut in the limestone cuesta and con- 

 sequent upon its slope. The valley floor is 75-125 feet below the 

 intervalley upland surface and is bounded by abrupt limestone 

 scarps. Near Yarker the valley walls are scarcely a quarter of a 

 mile apart, but toward Napanee they diverge gradually to a dis- 

 tance of a mile and a half. 



The upland surface on either side of Napanee Valley displays 

 abundant evidence of wave and current action. Bedded clays in 

 many places provide a thin veneer of fertile soil over the barren 

 glaciated limestone surface. Elsewhere, bared rock surfaces are 

 studded with the larger bowlders from glacial drift; all the finer 

 products of the glacial mill have been washed away by currents 

 and waves. No distinctive shore features have as yet been 

 observed along the Napanee Valley to mark the upper limit 

 of wave action, but marine or lacustrine clays are present up 

 to altitudes of at least 450 feet in the vicinity of Yarker. At 

 Inverary, 15 miles due east from Yarker and 11 miles north from 

 Kingston, M. B. Baker and I have definitely located the limit 

 of wave action at elevations between 500 and 510 feet above sea- 

 level. 



The region is within the area covered by the ice barrier to which 

 Lake Iroquois owed its existence and could not have been freed 

 from its glacial burden until after the extinction of that lake. 

 The wave and current action is therefore that of Gilbert Gulf, 

 the portion of Champlain Sea which occupied the Ontario 

 basin after removal of the ice dam from the Thousand Island 

 region. 



