222 CEMENT MATERIALS AND INDUSTRY. [bull. 243. 
LA TE ORDO VIC J AN SHA LE. 
This formation is composed largel} 7 of bluish to greenish shales, 
often containing a large precentage of lime. North of Lincoln County | 
thin bands of pure limestone, varying from a few inches to a few feet 
in thickness, are usually interbedded with the shales. These limestone 
bands become more numerous and thicker as the base of the formation ' 
is approached. The formation varies from- to over 100 feet in thick- 
ness, and immediately overlies the Trenton limestones. In its expo- 
sures near Mississippi River, in Ralls, Pike, and Lincoln counties, it 
is usually overlain either by Devonian shales or by the great series of 
Mississippian limestones described on a later page. The following 
analysis is of a specimen of this shale from near the base of the river 
bluff at Louisiana, Pike County: 
Analysis of Hudson shales from Louisiana, Pike County, Mo. a 
Silica (Si0 2 ) '.- - 57.01] 
Alumina (A1 2 3 ) 24.431 
Iron oxide (Fe 2 3 ) 5. 77 
Lime (CaO) 1.40 
Magnesia (MgO) 49 
Alkalies (K 2 0, Na 2 0) 3.81 
Combined water 7. 20 
Moisture 43 ! 
DEVONIAN FORMATIONS. 
In the northeastern portion of Missouri (see PL IX) a series of 
dark-colored shales of Devonian age appears in places above the] 
Hudson shales and below the Mississippian limestones. These Devo- 
nian shales vary from 10 feet or less to 50 feet in thickness. At 
Louisiana, Pike County, 8 feet of Devonian shales appear in the river 
bluffs, overlying the Hudson shale, whose analysis is given in the 
preceding table. In Jefferson County, as at Sulphur Springs, similar 
shales occur resting on the Trenton limestone, but their distribution 
is very irregular. 
MISSISSIPPIAN ("LOWER CARBONIFEROUS") LIMESTONES AND SHALES. 
DISTRIBUTION. 
The Mississippian limestones are the surface formations over almost 
one-fourth of the entire area of Missouri. Their three most promi- 
nent areas of outcrop are along the Mississippi and Missouri rivers 
and in southwestern Missouri. These three areas are connected by 
narrow bands of outcrop so as to realty form portions of one large 
area, but, for convenience, they will be discussed separately. The 
a Missouri Geol. Survey, vol. 11, p. 404. 
