CHAPTER II. 
OBSERVATIONS ON THE GEOLOGY OF THE ROUTE. 
FROM THE MISSISSIPPI RIVER TO THE BASE OF THE SANTA FE AND AL- 
BUQUERQUE MOUNTAINS. 
ALLUVIAL FORMATION OF THE MISSISSIPPI AND ARKANSAS. —BLUFFS. itas AMORPHIC ROCKS AT LITTLE ROCK.—TERTIARY FOSSILS.— 
CARBONIFEROUS STRATA.—PETIT JEAN NUN —DARDANELLE ROCK.— TRAP DIKES. —BITUMINOUS COAL.-—FonT SMITH —POTEAU 
MOUNTAINS AND SUGAR-LOAF.— COAL. ND FORT SMITH.—COAL IN/ARKANSAS.— VIEW NEAR FORT COFFEE. —D18- 
TURBANCES OF THE CARBONIFEROUS STRATA.—SANS BOIS RANGE. —(OAL AT RING'S PLANTATION.—COAL-PLANTS FOSSIL. —DELAWARE 
MOUNTAIN.—- CARBONIFEROUS LIMESTONE IN RIDGES.—PROXIMITY OF OUTCROPS OF GRANITE.— DELAWARE MOUNTA:N TO ANTELOPE 
HILIS.—GYPSUM FORMATION —LITHOLOGICAL CHARACTERS.—DENUDATION MOUNTAIN.—ROCK MARY AND OTHER MOUNDS.—THEIR 
ORIGIN EXPLAINED —GYPSUM IN THICK BEDS.— DorLoMrTE.— DISTURBED STRATA.—CRETACEOUS FORMATIONS AND FOSSILS. —ÁCCUM 
LATIONS OF PEBBLES; ALLUVIUM.—ANTELOPE HILLS. — WHITE SANDSTONE IN BLUFFS ALONG THE ROUTE.—TABLE melee udi 
SANDSTONE NEAR THE LINE.— BLUFF FORMATION OR LOESS.—LLANO ESTACADO.— [TS VERTICAL BLUFFS.—ENCAMPMENT CREEK.—SEC- 
TIONS. — TUCUMCARI HILL.— PYRAMID MOUND.—COLORED SECTION, —F 0s8ILs. —PLAZA LARGA.— DEGRADATION OF THE STRATA.—CRE- 
TACEOUS FOSSILS.—ANTON CHICO.— CAÑON BLANCO AND CUESTA. —(GALISTEO.—TRAP DIKE AND VOLCANOES.—GRANIT 
I. MISSISSIPPI RIVER TO DELAWARE MOUNTAIN. 
As the operations of the survey did not commence until the arrival at Fort Smith, there are 
comparatively few observations upon the topography or formation of the country along the valley 
of the Arkansas up to that point. The geology, however, of the starting point of our Cescrip- 
tions is very simple. We find along the Mississippi a broad area of alluvium, the surface of 
which is but little elevated above the stream. It is a broad ailuvial plain, with nothing to 
break its monotony, if we except the numerous ereeks with tortuous courses, bayous ard elon- 
gated and curved lakes, horse-shoe like, which mark the former channel of the river, and testify 
to the ceaseless changes which are progressing from day to day along its whole course. A 
great portion of the plain consists of low swamps, which become flooded when the rivers are 
swollen, and then receive a fresh deposite of fine earth or clay. "This alluvial formation borders 
the Arkansas on both sides up to Little Rock, where the first exposure of older and harder 
formations was found. A portion of the alluvial formation, however, is undoubtedly of mwh 
greater antiquity than the rest, and was formed when the general surface of the country was 
less elevated than it now is. "This older alluvium forms high banks or bluffs which sometimes 
abut upon the stream, but more frequently rise above the level of the plain several miles back 
from the river. They are familiarly known as the Bluffs, and have been recognised by Sir 
Charles Lyell as the probable equivalent of the formation known as Loess along the Rhine. 
According to Mr. Marcou, the alluvium along the Arkansas resembles that of the Mississippi. 
Its color is reddish-yellow, and it is partly formed of a layer of yellowish sand which is easily 
washed away by the river from the more clayey portions above, and the course of the stream is 
thus rendered very crooked. These deposites are very fine, and no pebbles were seen until within 
one mile of Little 
Little Rock.—The outerop of rocks at this place forms a ridge raised about fifty fect 
above the stream. According to Mr. Marcou, the rock is of a black color, schistose, metamor- 
dec and much contorted. He also mentions sandstone and quartz veins, having a direc- 
on EEN. and W.W.S. (See notes.) This is, probably, the trend of the ridge. Similar 
