58 IOWA ACADEMY OP SCIENCES. 



fauna, and its record of anomalous conditions of deposition. 

 In the field the distinction between the Le Claire and the Ana- 

 mosa stages are even more easily recognized, though faunally 

 the two stages are intimately related. In the Anamosa stage 

 oblique bedding is unknown; libhologically the rock is an 

 earthy, finely and perfectly laminated dolomite, not highly 

 crystalline in its typical aspect, and too impure for the manu- 

 facture of lime. It may be quarried in symmetrical blocks of 

 any desired dimensions, while the Le Claire limestone breaks 

 into shapeless masses wholly unfit for building purposes. The 

 quarry beds of the Anamosa stage are quite free from fossils, 

 but along the Cedar river in Cedar county the brachiopod fauna 

 of the upper part of the Le Claire reappears in great force in a 

 stratum four feet in thickness, up near the top of the forma- 

 tion. The beds of the Anamosa stage are very undulating, and 

 dip in long, graceful, sweeping curves in every possible direc- 

 tion. The knobs and bosses and irregular undulation devel- 

 oped on the sea bottom as a result of the peculiar condition 

 prevailing during the Le Claire age, persisted to a greater or 

 less extent after the age came to an end, and it was upon this 

 uneven floor that the Anamosa limestone was laid down. The 

 puzzling flexures of the Anamosa limestone, and the puzzling 

 variations in altitude at which it occurs, were largely deter- 

 mined by irregularities in the upper surface of the Le Claire 

 formation. 



THE BUCHANAN GRAVELS: AN INTERGLACIAL 

 DEPOSIT IN BUCHANAN COUNTY, IOWA. 



BY SAMUEL CALVIN. 



About three miles east of Independence, Iowa, there are 

 cross-bedded, water-laid deposits of sand and gravel of more 

 than usual interest. The beds in question occur near the line 

 of the Illinois Central railway. The railway company indeed 

 has opened up the beds and developed a great gravel pit from 

 which many thousands of carloads have been taken and used as 

 ballast along the line. 



Overlying the gravel is a thin layer of lowan drift, not more 

 than two or three feet in thickness, but charged with gray 



