552 GEOLOGY OF CENTRAL WISCONSIN. 



nearly pui-e limestone to a nearly non-calcareous sandstone being quite ^i- In« 

 abrupt (cut on Cliicago and Northwestern road, Sec. 35, Madison; also, 



out on same road at Mcndota Station, Westport). Thickness 15 . . 



II. White oolitic chert layer (Madison quanies) 6 



I. Greensand layer (Madison quarries) ^ _6 



Total "= ^ 



The bold bluff that rises from the mouth of Honey creek, Sauk 

 county, has already been cited as giving an unusually complete sec- 

 tion of the upper part of the Potsdam series. It shows, also, the 

 largest continuous exposure of the Lower Magnesian that I have ever 

 seen — a vertical cliff over 50 feet in height. The following is a de- 

 tailed section of this cliff, beginning above: 



J't. In. 



1. Heavy layer of brown-and-yeUow-mottled Hmestone, which leaves on solu- 



tion 2.2 per cent, of very fine clayey residue 1 ■ • 



2. No good exposure 5 ■ • 



3. Heavy layer of very close-textured, nearly vfhite, hmestone, with many 



dendritric markings; residue 9.09 per cent, and clayey 1 2 



4. Thin layers, 3 to 4 inches each, of hmestone hke the last; residue 5.8 per 



cent., clayey ■ 3 . . 



5. Thin layers of brown-and-gray-mottled limestone with minute crystal-hued 



cavities; residue 2.9 per cent., clayey 6 



6. Heavy layer of Ught gray, close-textured hmestone, with cavities hke No. 



5; residue 8.35 per cent., clayey 3 6 



7. Two heavy layers like No. 6; residue 6 per cent., clayey 5 2 



8. Shaly layers of porous, yellow-and-gray-mottled, crystalline hmestone; 



residue 7.2 per cent., clayey 2 3 



9. Thi-ee layers of yeUow-and-gray- mottled, close-textured hmestone; residue 



18.85 per cent., clayey 3 .. 



10. Heavy layer of yellowish, sandy hmestone; residue 40.17 per cent., fine, 



gray sand , ■.-. 2 .. 



11. Heavy non-arenaceous layer, with very indistinct subordinate bedding 3 6 



12. Very irregular, brownish, close-textured limestone, occurring in thin broken 



layers, the cracks being lined with white stalactitic lime carbonate; resi- 

 due 4. 38 per cent., clayey 1 6 



13. Two heavy layers of brownish-gray, close- textured limestone; residue 3.42 



per cent., clayey 2 6 



14. Irregularly thin bedded, very close-textured chonchoidal-fracturing gray 



limestone; residue 9.3 percent., clayey 1 4 



15. Very indistinctly bedded, nodular- weathering, close-textured, mottled hme- 



stone; residue 7.17 per cent., clayey 8 8 



16. Very irregularly bedded, rough-surfaced, close-textured, gray limestone; 



residue 28.97 per cent., fine sand and clay 3 6 



17. Thick layer of porous, brecciated, highly-crystalline hmestone; residue 



13.67 per cent. , fine sand and white clay 1 9 



18. Thick layer of compact, yellowish brown, granular, smooth-fracturing 



hmestone, with much dendritic manganese oxide; residue 16.65 per 



cent., clayey 1 7 



Total 52 5 



