SILURIC FORMATIONS IN MISSOURI 
133 
name, referred to the white, massive oolite,^ well exposed in many 
places in the eastern parts of Pike county. At the same time it 
was stated that the terrane appeared to be represented elsewhere 
in the county by a yellow limestone that was not oolitic in its 
lithologic character. Afterwards E. O. Ulrich ^ extended the 
term to cover its normal equivalent rather than the local oolitic 
phase alone, to which T. E. Savage ^ had given the name Gyrene 
member. 
In Pike county the white oolite in one or two massive layers 
has a thickness of four to ten feet. It contrasts strongly with the 
soft blue Ordovicic shales beneath; and with the equally striking 
brown, earthy dolomites above. 
The oolitic phase of the terrane occupies an area of about 100 
square miles, chiefly in Pike county, between the line of the St. 
Louis and Hannibal railroad and the Mississippi river. The 
formation is best exposed in the valley of Noix creek west of 
Louisana, and along the bluffs of the Mississippi river. Out¬ 
crops occur in northeastern Lincoln county where they occupy 
small isolated areas in the tops of the hills. 
On the east side of the Mississippi river this oolite is well 
displayed in the cliffs bordering the great stream. It is especially 
well shown near Hamburg, in Calhoun county, Illinois. 
West and south of the line of the St. Louis and Hannibal 
railroad the oolite is replaced by normal yellow limestone. 
The Bowling Green dolomite is a massive, brown, earthy mag¬ 
nesian limestone. It is well displayed to a thickness of 30 feet 
around the town of Bowling Green, in Pike county, Missouri. 
Farther to the east, near the Mississippi river, it is only four to 
five feet thick. Southward in Calhoun county, Illinois, it also 
attains a thickness of more than twenty-five feet. Northward, it 
increases rapidly in vertical measurement, as is indicated in numer¬ 
ous deep-well records. 
As displayed in Pike county the Bowling Green dolomite ap¬ 
pears to contain a very few organic remains. According to 
Savage ® it constitutes the upper portion of a formation which is 
very much thicker to the southward, in southeast Missouri, to 
which the name Edgewood formation is applied. On the other 
2 Proc. Iowa Acad. Sci., Vol. V, p. 62, 1898. 
3 Bull. Geol. Soc. America, Vol. XXII, p. 608, pi. xxxiii, 1911. 
4Amer. Jour. Sci., (4), Vol. XXVIII, p. 509, 1909. 
5 Illinois Geol. Surv., Bull. 23, p. 19, 1913. 
