THE TOMAH AND SPARTA QUADRANGLES 625 



some layers so rich in greensand as to have a greenish-black color. 

 Sorting is extremely poor. Fossil fragments, of which every one 

 appears to have been washed about for a considerable time before 

 final deposition, are locally very abundant. The thickness varies 

 from I to 6 feet. 



The overlying calcareous layer varies from a calcareous sand- 

 stone to a nearly pure limestone. The rock has a brownish-pink 

 to red color and is generally cross-laminated with short fore-sets 

 to the laminations. These have no constant direction of inclina- 

 tion. Small articulate brachiopods are present locally in consider- 

 able abimdance. The thickness varies from nothing to about 4 feet. 



2. The micaceous shale is really a fine-grained, thin, laminated 

 sandstone. The colors vary from gray to yellow. The sandstone 

 is composed chiefly of quartz with some of the bedding and lamina- 

 tion planes containing an abundance of thin flakes of white and 

 colorless mica. Some beds are current-ripple marked and others 

 have the bedding planes abundantly covered with fucoidal mark- 

 ings. Fossils, all of which appear to have been washed about 

 before deposition, are quite abundant. The thickness varies 

 around 15 feet. 



3. The lower greensand is composed of thin laminated glau- 

 conitic and quartz sandstones. Greensand is present in essentially 

 every bed; the proportion varies widely. Some thin layers are 

 fully 75 per cent greensand, many beds have more than 20 per cent, 

 while in others its occurrence is limited to occasional grains. Some 

 of the strata are evenly bedded, but more commonly the bedding 

 is decidedly irregular and lenticular. Cross-lamination is present 

 throughout. The fore-sets are generally short and apparently 

 have no uniform direction of inclination. Near the middle are mud- 

 cracked layers which have been seen in nearly every exposure of the 

 member. Both wave and current ripple mark, the latter by far the 

 more abundant, are present in every exposure of any size. Fossils, 

 all of which appear to have been washed about before final deposi- 

 tion, are common in many beds. The thickness varies around 40 feet. 



4. The yellow sandstone member is composed of thick-bedded, 

 horizontal and cross-laminated yellow and gray sandstone. Green- 

 sand is present in some layers. Transverse worm tubes are the 



