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GEOLOGY. 107 
GEOLOGY. 
By Hon. G. C. SWALLOW, A. M., M. D., 
Professor of Geology, Agriculture and Botany, in the University 
of the State of Missouri, and late State Geologist. ~ 
ROCK FORMATIONS OF MISSOURL 
The stratified rocks of Missouri belong to the following divis- 
ions : 
System I —Quaternary; System Il —.Zerfiary* System III — 
Cretaceous (?) ; System 1V—Carboniferous ; SystEM V—Devonian ; 
System VI—Stlurian ? ; System VIU—Azoic. 
The rocks of these divisions will be examined in their order 
from the top, down. 
SYSTEM I— QUATERNARY. 
When it is remembered that these formations contain the entire 
geological record of all the cycles from the end of the Tertiary 
period to the present time, and that their economical value is 
greater than that of all the other formations combined, I shall 
need no apology for entering somewhat into details in recording 
the phenomena they present. 
The Quaternary or Post Tertiary system comprises the Drift and 
all the deposits above it—all the strata included in the Alluvium and 
Diluvium of former authors. There are, within this period, four 
distinct and well marked formations in this State, which we have 
thus named in the order of their stratigraphical position :* 
ALLuviuM, 30 feet thick ; Borrom Prarrig, 35 feet thick; Burr, 
200 feet thick; Drirt, 155 feet thick. 
All of the latest deposits—all that have been formed since the 
present order of things commenced upon our continent—are inclu- 
ded in the - 
ALLUVIUM, 
All the deposits observed in the State, belonging to this forma- 
tion, are : 
~ ist, Soils; 2d, Pebbles and Sand; 3d, Clays; 4th, Vegetable 
Mold or Humus ; 5th, Bog Iron Ore; 6th, Calcareous Tufa ; 7th, 
Stalactites and Stalagmites. 
ist. Soz/s are a well known mixture of various comminuted and 
decomposed mineral substances, combined and mingled with 
decayed vegetable and animal remains, all comprising those ingre- 
dients peculiarly adapted to the nourishment of the vegetable king- 
dom. They are formed by the action of water, particularly in the 
form of rain and dews, cold, heat, and other atmospheric influences, 
together with the codperation of the vegetable and animal king- 
doms. 
But the soils of Missouri are made up by the mingling of organic 
matter with the comminuted marls, clays and sands of the Qua- 
ternary Deposits, which cover all parts of the State with a vast 
abundance of the very best materials for their rapid formation. 
* See the Section of the Rocks of Missouri on opposite page. 
, 
Hence the soils of the State, are very deep and wonderfully produc- 
~= 
tive; save in those limited localities where the materials of the 
Quaternary Strata are unusually coarse, or entirely wanting. 
2d. Pebbles and Sand. Many of our streams abound in water- 
worn pebbles, which constitute their beds, and form bars along 
their margins and across their channels. These pebbles were 
derived from the drift and the harder portions of the adjacent 
rocks. ‘They vary in size according to the transporting power of 
the streams in which they are found. 
The economical value of these pebbles for roads and streets, and 
the obstruction they often present to navigation, as in the Osage, 
give them unusual importance in our geology. The Osage, Gascon-, 
ade, Niangua, Marais Des Cygnes, Sac and Spring Rivers of the 
South, and the Salt, South, North, Fabius and Chariton of the North, 
all furnish good and abundant examples of those deposits which have 
been formed by the action of those streams. 
Sand is the most abundant material in the alluvial bottoms of 
the great rivers in the State. Vast quantities of it are constantly 
borne along by the irresistible current of the Missouri. Its whirl- 
ing, rolling, turbulent waters form of it extensive bars in incredi- 
bly short periods, which they again wear away, often still more 
rapidly than they were formed 
These sand-bars so common in this stream, frequently extend 
along its bed several miles, with a breadth varying from one to five 
or six furlongs, and limited in thickness only by the depth of the 
water. A slight fall in the river leaves these vast sand-beds dry, 
when their surfaces are soon covered by a growth of weeds, inter- 
spersed with young willows, cottonwood, and sycamores. The 
fickle stream, however, seldom leaves these sand-beds to a long 
repose, but returns to its old channel by a rapid removal of their 
loose materials. 
At high stages of water, both the Missouri and Mississippi over- 
flow their low bottoms, and leave deposits of a grayish-brown, or a 
grayish-yellow sand, similar to that in the sand-bars mentioned 
above. The thickness of these beds depends upon the height and 
continuance of the overflowing waters, varying from a mere per- 
ceptible stratum to several feet. 
That from the flood of 1844 is very conspicuous throughout the 
length of the Missouri bottom. It is sometimes six or eight feet 
thick, particularly in low bottoms so heavily timbered as to obstruct 
the current. 
At the lower end of the Waconda Prairie, this deposit is very 
evenly distributed over its surface ; but it increases in thickness as 
the prairie descends to the low timbered bottoms, lower down the 
stream, where it is six or seven feet, and its surface becomes very 
irregular, like the surface of a lake, when disturbed by a high wind, 
or a chopped sea. 
These sands were doubtless derived from those extensive sand- 
stone formations on the Platte. 
3d, Clays. These are dark bluish-gray, argillaceous strata, ren- 
dered more or less impure by fine silicious, calcareous and 
decomposed organic matter. When the floods of the Mississippi 
and the Missouri subside, the lagoons, sloughs, and lakes are left 
full of turbid water. The coarser materials soon settle into a 
stratum of sand, but the finer particles more gradually subside, and 
form the silico-calcareous clays of their alluvial bottoms. Thus, 
