786 LHE JOORNAL OLNGEOLOGN, 
limestone to the top of the impure limestone at the summit of 
the section— No. 14—varies from 213 to 238 feet. However, 
the Professor underestimated the thickness of the rocks from the 
base of the Wreford limestone to the base of the upper flint at 
Fort Riley by about 27 feet,‘ and if this be added to the 238 
feet it will give a thickness of 265 feet, which is exactly the 
thickness which we have assigned to the Chase formation. 
THE MARION FORMATION. 
Succeeding the Chase formation are thin, buff limestones and 
shales; higher, marls and shales with gypsum; and lastly, col- 
ored shales and marls which continue to the base of the brown 
Dakota sandstones of the Cretaceous. These rocks cover the 
greater part of Marion county and are exposed in many places 
so it is proposed to call them the Marion formation. ‘The natural 
opportunities are not as favorable for constructing an accurate 
section here as in the Chase formation, on account of the com- 
paratively level character of the region, presenting few steep 
bluffs and strata that may be readily traced across the country. 
The rocks composing the formation are estimated to have a thick- 
ness of 400 feet. 
Some 50 to 60 feet above the Marion and concretionary lime- 
stone is a buff limestone which contains large numbers of small 
Lamellibranchia and twenty feet higher is a buff limestone contain- 
ing large Lamellibranchia. In some localities near this horizon is 
a limestone containing Pleurophorus in which are large concre- 
tions ; these are well shown on sections 34 and 27, north of Won- 
sevu. On Turkey Creek, south of the Smoky Hill Valley and 
Abilene, is a conglomerate rock from 15 to 20 feet thick, which 
is some 150 feet above the base of the formation. On the south 
bank of the river opposite Abilene is a buff limestone containing 
Lamellibranchia, which is probably a little below the conglom- 
erate. 
Paleontology —In the Marion formation but few Brachiopods. 
t Professor Hay gave 77 feet as the thickness of the rocks from the base of the 
lower flint (Wreford limestone) to the base of the upper flint beds; while I found the 
thickness of the same rocks to be near 104 feet on the hill at Fort Riley. 
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