THE TOM AH AND SPARTA QUADRANGLES 621 



E. St. Peter sandstone, Cashton, on the southwestern edge of the Sparta 

 quadrangle, estimated 30 feet above the base. 



Percentage 



1. 0,00. 



2. 1 .80, transparent quartz, high sphericity. 



3. 6.28, as No. 2. 



4. 19.21, as No. 3. 



5. 21 .42, transparent quartz with a few Hmonite grains and fragments 



of calcite, most well rounded, but numerous subangular grains. 



6. 40 . 00, transparent quartz with a few grains of limonite, well rounded, 



estimated 25 per cent subangular. 



7. 9.81, as No. 6, 50-60 per cent subangular, 10 per cent angular 



with no rounding. 



8. 1 . 13, transparent quartz, 75 per cent sharply angiilar, rest sub- 



angular. 



9. 0.352, transparent quartz, with rare garnet grains, essentially all 



angular. 

 The assortment, rounding, and cross-lamination of this sand suggest wind 

 deposition. 



Save for local and horizonal exceptions, the Cambrian sand- 

 stones are poorly cemented. Most of the beds crumble on slight 

 exposure and in numerous places fresh rock may be crushed to 

 sand with the hands. 



THE DRESBACH FORMATION 



The type locality for the Dresbach formation, first called the 

 ''Dresbach sand rock," is at Dresbach, Winona County, Minnesota, 

 18 miles west of this area. At Dresbach the character and 

 sequence of the strata appear to be quite similar to what they are 

 in these quadrangles, although lower shaley strata are present there 

 which have not been differentiated in this area.^ What is known 

 of the unexposed Cambrian strata of these two quadrangles is 

 included in the description of the Dresbach formation, although it 

 is quite possible that these strata contain the Eau Claire and 

 Mount Simon formations. 



The Dresbach strata immediately underlie the lower lands of 

 the two quadrangles. Where the formation has been completely 

 uncovered through the removal of the higher formations, there has 



' N. H. Winchell, Minn. Geol. and Nat. Hist. Snrv., Final Rcpt., II (1888), xxi. 



