THE LE CLAIRE LIMESTONE. 



187 



the horizon. McGee in discussing the Rcoidar Dcfonnatioiis 

 of Nortlicastern lozva'^ quotes Dr. White on the Wapsipinicon 

 Hne of disturbance and accepts the observations on which the 

 statement is based as evidence of a syncHnal fold extending 

 from Le Claire to Anamosa. White's observations appear to 

 have been made only at the two points mentioned. At both 

 places the strata seem to be inclined at a high angle. On the 

 assumption that the inclination of the strata indicates orogenic 

 disturbance, the conclusion that the disturbed beds were parts 

 of the same fold was very natural. There is, however, no 

 fold, nor is there any line of disturbance. In the whole 

 Niagara area southwest of the line which marks the limit of 

 the Le Claire limestone, the phenomena seen at Le Claire 

 and west of Anamosa are repeated scores of times and in 

 ways that defy systematic arrangement. The beds incline at 

 all angles from zero to thirty degrees, and even within short 

 distances they may be found dipping in every possible direc- 

 tion. Twenty miles southwest of the line supposed to be 

 traversed b}^ the synclinal fold, for example at the lime kilns 

 on Sugar creek, along the Cedar river above Rochester, at 

 Cedar Valley, as well as at many intermediate points distri- 

 buted promiscuously throughout the area of the Le Claire 

 limestone, the beds stand at a high angle, and the multiplicity 

 of directions in which they are inclined, even in exposures that 

 are relatively near together, is wholly inconsistent with the 

 idea of orogenic deformation. The beds are now practically in 

 the position in which thev were laid down in the tumultuous 

 Niagara sea. The principal disturbances they have suffered 

 have been the results of epeirogenic movements which affected 

 equally the whole region over which these limestones are distri- 

 buted, as well as the adjacent regions of the Mississippi valley. 

 The exposures at Port Byron and Le Claire present some 

 interesting features that are not seen so well at any of the 

 exposures farther west. In the first place the lime quarries 

 at Port Byron show the characteristic oblique position of the 

 strata and at the same time they demonstrate that the oblique 



1 Pleistocene History of Northeastern Iowa, p. 340. 1891. 



