91 
THE MAGNESIAN SERIES OF THE OZARK UPLIFT. 
FuANK L. Nason, Geological Survey of Missouri, Jefferson City, Mo. 
During the writer's stud}- of the iron ores of Missouri, tiie 
question as to the position of the iron ores relative to the Magne- 
sian or Ozark series became one of prime importance. Dr. A. 
Schmidt, in his report on the iron ores (Geological Survey of 
Missouri, 1872), definitely refers to the specular ores in the -'Sec- 
ond Sandstone,"' and to the limonites generally o» the "Third 
Magnesian. ' The same views were retained in the report of Prof. 
Broadhead in 1873. In the earlier survey's whenever mention is 
made of the specular iron ores of the above series of rocks, they 
are also placed in the "Second Sandstone.'" 
"Without going into the minute history- of the origin of the terms 
"First, Second and Third Magnesian limestone, "' "First, Second 
and Third sandstone,"' etc., it will be sufficient for the present to 
state that the position of the specular ores was found to be in 
cave-like excavations in the so-called Third Magnesian limestone 
and under instead of in the so-called second sandstone. 
The next point to be settled, as far as possible, was to deter- 
mine the source of these extensive and numerous deposits. Their 
existence in caves showed conclusively that the iron was of sec- 
ondary origin, probably derived from the leaching of superincum- 
bent rocks. The leached rocks, according to the earlier geologists, 
must have been. Second Magnesian limestone; First sandstone and 
First magnesian limestone. Farther, if the Lower Carboniferous 
and Coal Measures rocks extended over the "Ozark uplift, "" these 
also would contribute their quota of iron to the specular deposits. 
"With the view of settling the point as to the existence of even 
traces of the Lower Carboniferous rocks, and also of determining the 
approximate thickness of the First sandstone, it was determined to 
study a section across the entire Ozark uplift from north to south. 
As has been explained very carefully by Pumpelly and by Broad- 
head, the Ozark mountains are really no mountains at all. There 
is a great anti-clinal fold running southwest from St. Louis. The 
drainage from this great area which Prof. Broadhead has very 
happily called the Ozark uplift, has resulted in the formation of 
great streams. These streams, flowing to the great drainage val- 
leys of the Missouri and of the Mississippi rivers, have, near 
their mouths, cut deeply into the strata of rocks which form the 
uplift. On this account it was inferred that l>v followino- two or 
