56 IOWA ACADEMY OF SCIENCES. 



and accepts the observations on which the statement is based 

 as evidence of a synclinal fold extending frooa Le Claire to Ana- 

 mosa. 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 incli- 

 nation of the strata indicates orogenic disturbance, the con- 

 clusion 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 phe- 

 nomena 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 direction. Twenty miles southwest of the line sup- 

 posed to be traversed by the synclinal fold, for example at the 

 lime kiln on Sugar creek, along the Cedar river above Roches- 

 ter, at Cedar Valley, as well as at many intermediate points 

 distributed 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, eve a in exposures that 

 are relatively near together, is wholly inconsistent with the 

 idea of orogenic deformation. The beds are now praciically in 

 the position in which they 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 dis- 

 tributed, as well as all the adjacent regions of the Mississippi 

 valley. 



The exposures at Port Byron and Le Claire present some 

 interesting features that are not saen 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 

 bedding is real and not a mere deceptive appearance due to 

 cleavage of a mass of sediment that was originally built up 

 regularly and evenly on a horizontal base. As in other groups 

 of strata, there are faunal and lithological variations when the 

 beds are compared one with another. These varying charac- 

 teristics do not intersect the beds in horizontal planes as they 

 would if the present bedding were due to cleavage of a mass 

 that had risen vertically at a uniform rate, but they follow the 



