IOWA ACADEMY OP SCIENCES. 
53 
The succession of strata in the Winterset limestone is as 
follows, with uniform general characteristics throughout the 
county: 
13 ft. Limestone, very shaly above, lower part heavier but with vary- 
ing- thickness of marly partings. This forms the base of the 
Missourian limestone. 
2 ft. 8 in. Shale, clayey, gray above, black below, 
4 in. Limestone; dense, jointed. 
9 in. Shale, clayey, gray. 
6 in. Limestone, irregular, gray, fossiliferous. 
2 ft. 6 in. Shale, clayey, gray. 
1 ft. 9 in. Limestone, irregularly concretionary. 
9 ft. 6 in. Sandstone, shaly, gray. 
In section 22 of Lincoln township the shales that are clayey 
in outcrops found in the northern part of Scott township, are 
calcareous shales, giving evidence clearly visible that the 
uppermost part of the Des Moines shales gradually changes 
into limestone toward the southwest. This necessary condition 
has been generally recognized concerning the Des Moines 
shales as a whole, but no transition now visible has to my 
knowledge been pointed out, unless it be in the deep well rec- 
ords of Montgomery county. 
While there may be a marked difference in fauna between 
that of the Des Moines stage and that of the Missourian,* such 
distinctions as exist in the fossils seem satisfactorily referred 
to oscillation causing varying conditions of depth in the water 
with no very marked break. When the bottom of the sea was 
depressed, the deeper water fauna migrated into this deepening 
water. When the bottom was elevated, the deeper water fauna 
moved farther out to conditions more favorable, while their 
place was taken by a shallow water fauna. Of course if the 
Winterset limestone, and its shore equivalent, were laid down 
in an advancing sea, there must have been unconformity beneath 
the deposits somewhere, but not where the strata are still exist- 
ing in Madison county. The changes in depth of water are 
accompanied by changes in the character of the strata. These 
♦University Geological Survey of Kansas, vol. I, p. 181. 
