A Geological Reconnoisance. 187 



is made up of a non-fossiliferous, light-colored, fine-grained 

 limestone that breaks with a conchoidal fracture and possesses 

 characteristics of lithographic limestone. 



It is quite possible that the Niagara uplift is in some way- 

 connected with the agency that produced such extensive 

 brecciation in the lower beds of our Iowa Devonian. 



Attention was next directed to the exposures in the south- 

 eastern part of Buchanan county. At Pine Creek mill, 

 between Independence and Quasqueton, the exposure in the 

 south bank of the stream embraces the Barren beds observed 

 near Independence, overlaid with the lower part of the S. 

 pennata beds Atry-pa reticularis of the Independence type, 

 A. aspcra^ var., occidentalism and casts of Paracyclas eUiptica? 

 constitute the observed fauna. 



Below the mill dam at Quasqueton the Brecciated beds 

 are well exposed on both sides of the river. On the east 

 bank the Independence shales crop out from beneath the 

 breccia, the line of junction being marked by a series of small 

 springs. At Gemmel's quarr}-, up on the high land a mile 

 and a half east of the river the strata belong to the Acervu- 

 laria davidsoni beds. S fir if era far ry ana H., which varies 

 considerably in different localities, is present with the rest and 

 coincides in external appearance and expression with the forms 

 found at Hanson's and other t3'pical locaHties in Muscatine 

 county. 



At Tro}' mills, just beyond the southern edge of Buchanan 

 county, the strata are brecciated beds in the channel of the 

 river with Gyroceras, GyfiduJa^ and the forms usually found 

 in such association; the breccia is followed by barren beds 

 that break up into angular fragments on exposure to the 

 weather; then come the S. pennata beds, but not very well 

 developed; above the last lie beds with PhiUifsastrea gigas 

 Owen, in place; and the section here is terminated by beds 

 containing Acerviilaria davidsoni and Sfirifcra farryana. 



At Troy mills, Acervtdaria frofunda H., appears to be 

 absent. Careful search at its usual horizon and in the weath- 



