688 



L. HUSSAKOF 



The specimen was collected from a clay bed at Menomonie, 

 Dunn County. Wisconsin. At this locality these beds are from 

 twenty to forty feet in thickness. The following notes regarding 

 them were kindly supplied by Dr. S. Weidman to whom I am also 

 indebted for the geological section here reproduced (Fig. 2). 



/otvan (lllinoisan) OuTwash 

 Gravel a nd coarse <sand 



*— Unconformity 



Lacustrine Clay* 

 v tfenomonie Beds 

 F/ne/u stratified s//t, fine sand 

 and calcareous c/a</ 



f/ne Sand 



Resting unconformably at Menomonie 

 '•;'•■/; on Upper Camhrian Sandstone. 



Fig. 2. — Section at Menomonie, showing relations of Pleistocene lacustrine clay 



beds. 



The clay beds are located in the valley of Red Cedar River and have 

 been utilized extensively for many years for the manufacture of brick. The 

 formation consists of finely stratified sand, silt, and clay, usually containing 

 from 5 to 10 per cent of calcium and magnesium carbonate. In other localities 

 the calcareous content is much higher and reaches 20 to 30 per cent. The 

 physical and chemical character of the deposit, as well as the occurrence of the 

 fish remains, indicate the lacustrine origin of the formation. Similar deposits 

 are widespread in Wisconsin and the adjoining states, and have very generally 

 been classed as lacustrine or estuarine 



The relations of the lacustrine clay (•'Menomonie beds") to the over- 

 lying Iowan (lllinoisan) glacial gravels indicate that the probable age of the 

 clay is the Interglacial stage between the Kansan and the Iowan (lllinoisan), 

 that is, between the second and third glacial stages of the Pleistocene. Xo 

 definite relations of the clay beds at Menomonie to the Kansan is exhibited, 

 the border of the Kansan being located 10 or 12 miles to the west, but, based 

 in part on other geologic data, the above inference as to the age seems war- 

 ranted. The stratigraphic position of the clay beds, in which the species of 

 fish, Cristh'omer namaycush, is found is therefore near the middle of the Pleis- 

 tocene series, and as variously estimated in years this particular deposit is 

 probably between 250,000 and 500,000 years old. 



