54 
IOWA ACADEMY OE 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 Cit^^^, OliD, 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 flexuous 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 inclination and direction of dip in the Le Claire limestone 
