624: GEOLOGY OF CENTRAL WISCONSIN. 



evidently due largely to the difference in amount of lime and magne- 

 sium carbonates, but is not well understood. 



An attempt to study out the system of arrangement of the drift 

 materials meets with no little difficulty from the rarity of natural 

 or artificial sections. Enough information can, however, be obtained 

 from the few sections that do occur, and from records of well-boriners, 



' 2r> / 



to show plainly enough the existence of the two classes of material, 

 the unstratified and stratified. The unstratified condition character- 

 izes always the moraine-like heaps of limestone pebbles, and is in 

 general the condition of the materials occurring on high land, and ail 

 along the Kettle Range, where, however, there is often visible, in the 

 sand, a rude sort of bedding, not due to aqueous action, but indicat- 

 ing merely a gradual growth of the deposits. The knobby hills, 

 when not formed of limestone pebbles, are often made up of layers of 

 sand conforming roughly to the outlines of the hills. 



Stratified drift is to be seen in the valleys of streams, as also in 

 many not now occupied by streams. A few instances will serve to 

 give an idea of what is a general truth. About a mile east of the' 

 Wisconsin, on the side of the road from the village of Knowlton, 

 Marathon county, to the railroad bridge, finely stratified sand and 

 gravel may be seen, at an elevation of over 50 feet above the river. 

 The pebbles are all small, much rounded, and consist predominatingly 

 of granite, with some diorite, quartz, etc., and no limestone. At 

 Montello, Marquette county, in the immediate vicinity of the Fox 

 river, flowing wells are obtained from what appears to be strati- 

 fied drift. The wells are 50 to 90 feet deep, and pass through a 

 series of layers of sand, gravel, and clay, the gravel layers at differ- 

 ent horizons yielding waten A number of railroad cuttings in the 

 vicinity of Madison, and to the southward along the Catfish valley, 

 show finely stratified drift, one of the best points being at Stoughton 

 depot, where a bank 25 feet high shows very regular layers, three 

 to four inches thick, of alternating sand and gravel. On the opposite 

 Bide of the Catfish, at a lower level, the following alternation occurs: 



Feel.. Inches. 



Soil 1 



Fine gravel 4 



Cross-laminated sand 4 



Fine gravel 1 6 



Cross-laminated sand 3 



Horizontally laminated sand 2 2 



White brick clay to river level 15 



30 6 



