378 J. S, DILLER — G1C0L0GY OF THE TAYLORVILLK REGION. 



with rare exceptions in the Shoo Fly and Foreman beds, is toward the 

 southwest at angles varying from 39° to 75°. 



It is evident that one of the first problems to solve in analyzing the 

 Taylorville general section concerns the position of each formation in rela- 

 tion to those immediately above and below; or, in other words, to deter- 

 mine the original conformities and unconformities among the sedimentary 

 rocks involved. This is a difficult task in the Taylorville region, where 

 the stratified rocks arc frequently penetrated and otherwise associated 

 with eruptive masses, and all of them save the auriferous gravels and 

 later formations have been involved in profound foldings and disloca- 

 tions. 



Among the rocks extending from well down in the Silurian to the late 

 Pleistocene there are four breaks in the conformable superposition of the 

 strata. These unconformities may be designated respectively by the 

 horizons between which they occur, as the Neocene-Jura, Jura-Trias, 

 Trias-Carl >oniferous and Pleistocene-Neocene. 



Unconformities. 



Trias-Carboniferous Unconformity. — The relation of the Trias to the Car- 

 boniferous is best exposed on the northern slope of Genesee valley oppo- 

 site Robinson's, where the accompanying section (figure 2) was measured. 



S.W. N. E. 



V4 



Figure 2.— Section of Genesee Valley near Robinson's. 

 9 = Foreman beds; 11 = Hosselkus limestone; 12 = Swearinger slates: 13= Robinson beds; 

 E = Eruptive rocks. 



Beginning with the limestone on the left-hand spur where it has been 

 burned for lime, we find it contains fossils that identify it with the 

 Hosselkus limestone of the next two spurs to the eastward. This spin- 

 is made up chiefly of slates in which no fossils have been found. The 

 first ravine toward the right is cut in the porphyrite, the eastern side of 

 which is tufaceous and belongs to the Robinson beds. The tuff and cal- 

 careous sandstone both contain an abundance of Carboniferous fossils, 

 and in connection with the tufaceous conglomerate which underlies the 

 sandstone they form the second spur of the section up to an elevation of 

 4,500 feet. Above that point the spur is composed of Halobia slates 

 and the Hosselkus limestone as represented in figure 2, and both of these 



