GEOLOGY. 109 
These “‘ Bottom Prairies ’’ extended from the mouth of the Yel- 
lowstone to the Mississippi, and probably from the St. Peter’s to 
the Arkansas. Since they were formed, the rivers have been ever 
busy wearing away the bottom prairie and depositing the alluvial 
bottoms above described, until we have but few remnants, such as 
the Waconda and Hupan-Kuty, of the vast bottom prairie which 
once occupied these great valleys. These beautiful savannas are 
almost universally called ‘‘ Bottom Prairie,’ and I have proposed 
that as the geological name of the interesting formation on which 
they rest. The scenery of the alluvial bottom and the bottom 
prairie is well represented in Section 2 and Plate 12 of my Geo- 
logical Report. 
BLurFrF. 
This formation rests upon the drift, as is obvious whenever the 
two formations are well developed. In many places, as at St. 
Joseph and at the mouth of the Big Nemeha, it is seen dipping 
beneath the beds of the bottom prairie. The bluff formation rests 
upon the ridges and river bluffs, and descends along their slopes to 
the lowest valleys. The bottom prairie is confined to the river 
bottoms, and was deposited in horizontal beds between the bluffs. 
Thus, while the bottom prairie occupies a higher geological horizon, 
the bluff is usually several hundred feet above it in the topograph- 
ical. 
This formation, when well developed, usually presents a fine 
pulverulent, obsoletely stratified mass of light-grayish buff, silicious 
and slightly indurated marl. Its color is usually variegated with 
deeper brown stains of oxide of iron. The bluff above St. Joseph 
exhibits an exposure of it 140 feet thick, presenting its usual char- 
acteristic features. When but sparingly developed, it generally 
becomes more argillaceous, and assumes a deeper brown or red 
color, as on the railroad south of Palmyra, where it is a dark brick - 
red tinged with purple. In some places, the ferruginous and cal- 
careous matter increases, and we find concretions of marl and 
iron-stone, either disseminated through or arranged in horizontal 
belts. At other places, it has made more arenaceous matter, and 
is much more decidedly stratified, as at a point one mile above 
Wellington, and in the bluff at St. Joseph. 
Range and Thickness. So far as my own observations extend, 
this formation caps all the bluffs of the Missouri, from Fort Union 
to its mouth, and those of the Mississippi from Dubuque to the 
mouth of the Ohio. It forms the upper stratum beneath the soil 
of all the high lands, both timber and prairie, of all the counties 
north of the Osage and Missouri, and also St. Louis, and the other 
Mississippi counties on the South. 
Its greatest development in this State, is in the counties on the 
Missouri, from the Iowa line to Booneville ; but thence to St. Louis 
it is not so thick. In some places it is two hundred feet thick. At 
St. Joseph it is one hundred and forty; at Booneville, one hun- 
dred ; and at St. Louis in St. George’s Quarry, and the Big Mound, 
it is almost fifty feet; while its greatest observed thickness in 
Marion County was only thirty feet. 
Organic Remains. The fossils of the bluff are very numerous 
and interesting. 
I have collected from it, of the Mammalia, two teeth of the Z/e- 
phas primigenius, the jaw bone of the Castor fiber Americana, the 
molar of a Ruminant, and the incisor of a Rodent; of the Mol- 
/usca, seventeen species of the genus //edix, eight Zimnea, eight 
Physa, three Pupa, four Planorbis, six Succinnea, and one each of 
the genera Va/vata, Amnicola, Helicina, and Cyclas, besides some 
others not determined. 
These /acustrine, filuviatile, amphibious and land species indicate 
a deposit formed in a fresh-water lake, surrounded by land and fed 
by rivers. These facts carry back the mind to a time when a large 
portion of this great valley was covered by a vast lake, into which, 
from the surrounding land, flowed various rivers and smaller 
streams. We see the waters peopled with numerous mollusks, the 
industrious beaver building his habitation, the nimble squirrel, the 
fleet deer, the sedate elephant and huge mastodon, lords of the 
soil. There must have been land to sustain the elephant and mas- 
todon and helices, fresh water and land for the beaver, and fresh 
water for the cyclas and limnea. 
I have been thus minute in my examinations of the bluff, the 
bottom prairie, and the alluvial formations, both on account of 
their vast importance to our agricultural interests, and the compar- 
atively little attention geologists have given to them. It is to this 
formation that the central Mississippi and southern Missouri valleys 
owe their preéminence in agriculture. The most desirable lands of 
Iowa, Missouri, western Illinois, Kansas, and Nebraska, all rest 
upon the fine silicious marls of the bluff formation. Where it is 
best developed in western Missouri, the soil is inferior to none in 
the country, 
The scenery presented by the bluff formation is at once unique 
and beautiful and gives character to nearly all the best landscapes 
on the Lower Missouri. Plates I and II of the Missouri Reports 
give characteristic views of the scenery where this formation is 
well developed. 
DriFT. 
This formation lies directly beneath the bluff, and rests upon the 
various members of the Palzozoic series, as they successively come 
to the surface. In this formation there appear to be three distinct 
deposits :— 
1st. What might be called an A/tered Drift frequently appears 
in the banks of the Missouri River. 
These strata of sand and pebbles appear to be the finer materials 
of the drift, removed and rearranged by aqueous agencies subse- 
quent to the Drift period, and prior to the formation of the bluff. 
The pebbles are from all the yarieties of rocks found in the true 
drift, but are comparatively small. 
2d. The Boulder formation, as it was left distributed by those 
powerful and widely extended agencies, which formed that deposit 
of the northern hemisphere. It is a heterogeneous stratum of sand, 
gravel, and boulders, all water-worn fragments of the older rocks. 
The larger part are from the Igneous and Metamorphic rocks, in 
place at the north, and the remainder from the Palzozoic strata, 
upon which they rest. The Metamorphic and Igneous rocks must 
have come from the northern localities of those strata, the nearest 
of which, is on the St. Peter’s River, about three hundred miles 
north of St. Joseph. But the Palzozoic fragments are usually from 
localities near where they rest, as shown by the fossils they contain, 
and are as completely rounded as those from the more distant points. 
