Deposition of the Burlington Limestones. — Fultz. 247 
uninterrupted. I quote from White, Geology of Iowa, 1870, 
Vol. I, page 202 : "The accumulation of the strata of the sub- 
( Carboniferous group in southeastern Iowa, from the Lower 
Burlington limestone to the St. Louis limestone inclusive, was 
evidently uninterrupted." And this seems to have been the 
generally accepted belief. I question the truth of the state- 
ment and think evidence can be furnished to show that there 
were disturbances and cessations of deposit within the pe- 
riod indicated. It is quite probable that there was some dis- 
turbance at the close of each of the subdivisions; but the 
instance I shall bring forward occurs well within the limits 
of one of them. 
Evidence of disturbance and cessation of deposit is three- 
fold, viz. : more or less abrupt changes in fossil forms, change 
in lithological characters, and erosion with consequent uncon- 
formity. At present I shall confine myself exclusively to the 
.last mentioned evidence, although elsewhere* I have given my 
views on each of the three and discussed their bearing on 
each other. 
Almost everywhere in the vicinity of Burlington, where the 
upper division of the Burlington limestone is exposed, there 
occurs, somewhat below the middle, a stratum of heavy bed- 
ded white limestone about 6 ft. in thickness. Generally un- 
derlying this there is either a thin stratum of blue clay or 
a yellow sandy limerock. Immediately overlying there is 
uniformly found a bed of tough blue shale. The abrupt 
change in the lithological character of the deposit, coupled 
with a somewhat marked change in fossil forms, led me to 
believe that there must have been some disturbance and possi- 
bly a cessation of deposit. This belief was strengthened by 
the fact that the surface of the limestone ;it various places 
exhibited a somewhat water-worn appearance. 
In the southern part of the city limits of Burlington. al ;i 
locality known as "The Cascade," there are several quarries 
in which nearly the whole depth of the Upper Burlington 
limestone-is worked. The massive white layer spoken of fur- 
nishes a goodly part of the rock taken out. It was in one of 
*Paper read al the meeting of the Iowa Academy of Science, Decem- 
ber 26 ;iik1 •-';. 1893. 
