Geology of the Region about BeloiL 197 



in the region as well as at Janesville. Above these are eighteen 

 feet of Lower Blue limestone with two layers of a few inches 

 each in thickness, one highly crystalline, the other very fossilifer- 

 ous, easily recognizable in the three quarries which include this 

 horizon. The Upper Buff limestone has been divided by Prof.- 

 Chamberlin into five subdivisions, known by U3 at Beloit as the 

 Carpenter, Lower Fucoidal, Pseudo-birdseye, Upper Fucoidal and 

 Cherty beds respectively ; the lower and upper of these are still 

 further divisible, as shown on the chart, and their divisions recog- 

 nizable throughout the region and questionably as far away as 

 Janesville. The Upper Blue limestone which completes the 

 Trenton section is estimated at twenty feet in thickness, although 

 as we shall see, this cannot be certainly determined. 



Beginning with Scott's quarry, we have the transitional layers 

 or nearly all of them, and just below, separated by a few feet 

 unexposed, the characteristic St. Peters sandstone; in the Second 

 railroad quarry, a mile and a quarter to the south, we have a por- 

 tion of these layers exposed, and above them the entire thickness 

 of Lower Buff and Lower Blue, and, in the broken and nearly in- 

 accessible upper layers, probably the lower part of the Upper Buff 

 layers ; in two other quarries less than a mile from this, we find 

 the same horizon, including the crystalline and fossiliferous 

 layers before mentioned. In a ravine below Carpenter's quarry 

 also, the Lower Blue layers are exposed. Carpenter's quarry forms 

 the next step in the ladder, and here the exact matching becomes 

 difficult owing to the broken and weathered condition of the top 

 of the second quarry, and so we are obliged to call in the aid of 

 the large quarry west of Janesville, which includes both of these 

 horizons. There is in the very bottom of Carpenter's quarry a 

 well marked shaly seam ; a similar seam is found near the top of 

 the second quarry, eighteen feet above the junction of lower buff 

 and lower blue. At Janesville a seam is found seventeen feet 

 above this junction, and at about this horizon the shaly fossilifer- 

 ous Lower Blue layers pass by insensible gradations into the com- 

 pact, unfossiliferous Carpenter beds. The fact that nearly all the 

 subdivisions are a little thicker at Beloit than at Janesville, makes 

 the difference of a foot in the height of this seam above the junc- 



