678 



GEOLOGY AND TOPOGRAPHY OF THE LEAD REGION. 



(4) In the S. E. qr. of Sec. 8, T. 7, R. 2 W., the Lower Magnesian 

 is 200 feet, and the St. Peters 100 feet thick, its upper surface being 

 nearly horizontal; both formations appear to have about their average 

 thickness. 



(5) In the S. E. qr. of Sec. 2, T. 6, R. 3 W., the sandstone is about 

 70 feet thick, and the Trenton limestones about 50. 



There are several new localities which were examined in 1874, 

 where slight upheavals of the formation appear to have taken place. 

 The most marked example of this, known as Red Rock, is situated in 

 the valley of the Pecatonica, in T. 2, R. 4 E. The sandstone emerges 

 from the river near the center of Sec. 20. It reaches it greatest ele- 

 vation near the quarter-post of Sees. 17 and 18, where- it has a thickness 

 of over 100 feet, and disappears again below the river in the S. E. qr. 

 of Sec. 7. The average width of the exposure is about half a mile. 

 It also extends up the valley of a small creek as far as the center of 

 Sec. 8. This exposure covers about one and a half square miles. The 

 following section (Fig. 9) through the railroad cut at this place 

 illustrates the upheaval: 



FIG. 9. 



UPHEAVAL OP ST. PETERS SANDSTONE AT RED EOCK. 



In the northeast part of T. 3, R. 5 E., there is an upheaval of sand- 

 stone, beginning at the creek which flow r s nearly due west, south of 

 Sees. 11 and 12. The disturbance continues north for some distance, 

 as the whole ridge between this creek and the one next north of it 

 lies in the sandstone as far north as the Pecatonica river, in T. 4, R. 5 

 E. The thickness of the sandstone is here so great that it is hardly 

 probable that it has its normal position. A third disturbance, and the 

 last which w r ill be cited, is in T. 2, R. 6 E. The sandstone on the 

 small branch in Sees. 35 and 36 slopes gently toward Skinner creek, 

 which appears to lie in a slight depression or synclinal valley. Pas- 

 sing over the ridge between Skinner and Jordan creeks, a slight an- 

 ticlinal ridge was discovered, by means of observations on the top of 



