ABSTRACTS OF PAPERS 93 



pit exposures in tlie Hackensaclv Valley at Little Ferry, New Jersey ; in glacial 

 Lake Passaic at Mountain View and Morristown, New Jersey, and in the Hud- 

 son River valley at Beacon, Dunnings Point, Brockway, and Roseton, New York. 



These studies were undertaken with the object of securing material for a 

 museum exhibit on "Climates, Past and Present," and incidentally to see what 

 the possibilities were of applying De Geer's methods of clay geochronology to 

 the postglacial banded clays near New York City. 



The varve clay is present in all of the places mentioned above and there is 

 no question but that the De Geer method of geochronology is applicable. Sec- 

 tions were measured and considerable other data secured. The work of Antevs 

 in the Connecticut River valley, "The Recession of the Last Ice-sheet in New 

 England," published by the American Geographical Society, November, 1922, 

 shows what can be done in this direction in this section of the United States. 



Read by title. 



ORIGIN AND HISTORY OF EXTINCT LAKE CALVIN, IOWA 

 BY WALTER H. SCHOEWE ^ 



{Abstract) 



Lake Calvin is an extinct glacial lake which was formed by the displace- 

 ment of Mississippi River during the Illinoian stage of glaciation. The advanc- 

 ing glacier in crossing into Iowa blocked the valley of Mississippi River and 

 filled it with ice. This necessitated the finding of a new course to the west. 

 The stream found an opening by way of the Maquoketa River valley and 

 flowed first westward, then to the southward, through Goose Lake channel, to 

 the valley of Wapsipinicon River, and finally, over the low divide between 

 Mud and Elkhorn creeks, to the valley of the Cedar at Moscow ; thence, con- 

 tinuing southward to the junction of Iowa and Cedar rivers at Columbus 

 Junction, the combined waters of the Mississippi, Maquoketa, Wapsipinicoii, 

 Cedar, and Iowa rivers and those flowing from the edge of the ice, found their 

 pathway obstructed on the one side by the great ice-wall of the Illinoian ice- 

 sheet and on the other by the Kansan bluffs, which stand 120 to 140 feet high. 

 As the waters were unable to find an outlet, they rose and formed a vast and 

 deep expanse of water, to which Udden gave the name "Lake Calvin." During 

 the long existence of the lake the surplus water found its way to the unfilled 

 valley of the Mississippi below Fort Madison by way of an abandoned channel 

 south of Columbus Junction. 



Field evidence in the form of lacustrine silts and clays, wave-rounded shore- 

 lines, ice-rafted boulders, shingle or beach gravels, associated sandy shore de- 

 posits, lake terraces, an inlet and an outlet, and a comparison of the relative 

 widths of the Iowa and Cedar rivers within and without the lake basin — all 

 point to the former existence of Lake Calvin. 



Lake Calvin existed to the time of the lowan ice invasion. The long dura- 

 tion of the lake is in complete harmony with the present-day conception re- 

 garding the formation and origin of the gumbotils. It has been demonstrated 

 by Kay that the formation of gumbotil is an exceedingly slow process. The 



^ Introduced by Dr. George F. Kay. 



