54 IOWA ACADEMY O^ SCIENCES. 



With respect to their distribution the strata of this stage are 

 well developed at Le Claire in Scott county. They are seen 

 in the same stratigraphic relation at the lime kilns on Sugar 

 creek and at Cedar Valley in Cedar county. They occur beneath 

 the quarry stone at and near Stone City, Oiin, and Hale in Jones 

 county. They are again seen at numerous points west of the 

 Jones county line in Linn. Indeed they are somewhat gen- 

 erally, though by no means universally, distributed in the east 

 central part of Scott, southwestern parts of Clinton, western 

 Cedar, and the southern parts of Jones and Linn. They seem 

 to be limited to the southwestern corner of the Niagara area. 

 A line drawn from the mouth of the Wapsipinicon through 

 Anamosa would mark approximately their northeastern limits. 



The Le Claire limestone is in some respects unique among 

 the geological formations of Iowa. In the first place it varies 

 locally in thickness, so much so that its upper surface is exceed- 

 ingly undulating, the curves in some places being very sharp 

 and abrupt. In the second place it differs from every other 

 limestone of Iowa in frequently exhibiting the peculiarity of 

 being obliquely bedded on a large scale, the oblique bedding 

 often affecting a thickness of fifteen or twenty feet. The phe- 

 nomena suggests that during the deposition of the Le Claire 

 limestone the sea covered only the southwestern part of the 

 Niagara area, that at times the waters were comparatively 

 shallow, and that strong currents, acting sometimes in one 

 direction and sometimes in another, swept the calcareous mud 

 back and forth , piling it up in the eddies in lenticular heaps or 

 building it up in obliqely bedded masses over areas of consid- 

 erable extent. The oblique beds observe no regularity with 

 respect to either the angle or direction of dip. Within com- 

 paratively short distances they may be found inclining to all 

 points of the compass. Again the waters at times were quiet, 

 and ordinary processes of deposition went on over the irregular 

 sea bottom, the beds produced under such circumstances con- 

 forming to the undulating surface on which they were laid 

 down. In some cases these beds were horizontal as in the 

 upper part of the section illstrated in plate 1, while in other 

 cases they were more or less fiexuous and tilted as seen in the 

 left bank of the Wapsipinicon above Newport. (Figure 2.) 



Professor Hall accurately describes some of the variations in 

 the inclmaiion and direction of dip in the Le Claire limestone 



