366 ])RAKE — THE GEOLOGY OF IXDIAX TERRITORY. [Sept. '.i, 



The sandstones vary from massive to flaggy and shaly, and in places 

 near and at the top they grade into a grit. This grit appears to be 

 the equivalent of the so-called Millstone grit of the Geological Sur- 

 vey of Arkansas, since it has the same lithological characteristics and 

 apparently has the same stratigraphic position. It is probable, 

 therefore, that not over one hundred feet of the shales and sand- 

 stones overlying the limestones at this place should be referred to 

 the Boston group. The above section (Sec. c, PL V), with slight 

 modifications, represents the group as it is shown in outcrops 

 between Bunch and Marble. 



The Boston group is well exposed along the west side of Big 

 Vian creek, northwest of Vian, where Sec. d, PI. V, was made. 

 The section at that place is as follows : 



FEET. 



Massive sandstones (Coal Measures ?) loo-f- 



Arenaceous black clay shale , 75 



Brownish, weathering, hard limestone }4 



Shaly sandstone 5 



Gray, massive, hard limestone 5 



Black clay shale. 10 



Massive, hard, gray limestone at the base which 

 grades into shaly brownish weathered lime- 

 stone at the top 15 



Clay shale (?) 10 



Massive, gray, firm, fossiliferous limestone 35 



The following is a section on the east side of Illinois river, 

 about west-northwest of Marble : 



FEET. 



Sandstone and grit (Coal Measures?) 30-]- 



Blue clay shale 5 



Uniformly textured, smooth, gray limestone in 



strata i to 2 feet thick 10 



Nodular friable limestone in thin, irregular, rough- 

 surfaced strata with clay partings and fillings 

 of lenticular places through the strata 10 



Rather uniformly textured, massive, gray, fossili- 

 ferous limestone 50 



Blue clay shale 20 



