50 GUIDEBOOK OF THE WESTERN UNITED STATES 
The geology of eastern Texas is not very impressive to the observer 
traveling by train until the Colorado River is crossed and the regular 
succession of Tertiary and Cretaceous strata comes to the surface. 
oemer, the pioneer geologist of Texas, writing in 1846, when San 
ntonio was the frontier, said, ‘‘It is only where civilization ceases 
and the wilderness commences that the  ooknd relations of the 
country begin to be interesting.’’ Of the region around Columbus, 
Gonzales and Seguin, he remarked, ‘‘ You see no solid rock in place 
excepting irregular layers of a coarse calcareous ence: . 
on the steep banks of some of the river; * * the sur- 
face is covered with loose materials.”’ Hage, a studies have 
brought to light in this region the following very interesting succession : 
Formations of east-central Tevas BRI near the Southern Pacific lines 
fikret af th rg ree S 7 
PP ¥ duilea Craraner) 
Age Group Formation Principal materials 
Quaternary. Alluvium and terrace deposits. | Gravel, sand, and loam. Nonmarine. 
she paisa a Lissie and Reynosa formations. | Gravel, sand, and clay. Nonmarine. 
sagem ant tain gray, and dg clays 
stained purple and red toward the to 
Pliocene. Lagarto clay. with abundant calcareous nodules and 
a few thin sandstones. Nonmarine. 
Massive, in part cross-bedded yellowish 
Oakville sandstone. or coavih indurated sandstones and 
brown calcareous clays. Nonmarine. 
Light-colored sands and loosely indurated 
Catahoula sandstone. sandstones and clays, many of them 
ashy. Mostly nonmarine. 
[eneiniagn . wil Weemaeestibed | deol 
ne wit Tai - 
Juin: | Payette selene. bearing clays and thin beds of 
olecanic ash. Mostly nonmarine. 
Miocene. 
Dark-brownish, gray, and greenish- 
Yegua (“‘Cockfield”) formation.| clays and clayey sands, many of the 
carbonaceous. Mostly nonmarine. 
———— ee te sands es 
Fs clays. The 
Cook Mountain formation. basal member (Sparta sand) a loose 
or loosely indurated nonmarine sand. 
_ | Glauconitie and oolitie sandstones in- 
shown atta = — an iron cutneint; glau- 
conitic clays; marine and sparse! 
Claiborne. ber. fossiliferous. eons 
a Mount Selman . Rather fine light-gray or iron-stained 
Eocene. formation. — City | "sands w Riry thin interst interstratified light- 
‘ gray ©. 
clays, in Sooo ap sew ne and in- 
Reklaw mem- Glauconiti ic sands and 
ber. durated with iron oxide. 
Very coarse and pure quartz sand, loose 
Carrizo sand. or oe with little or no cementing 
: terial. Nonmarine, 
Bedded yellowish-brown and red sands 
dstones 
ane eobvatog a few marine fossils. 
Midway formation. a rarely a thin festierous 
sandstone near the top. 
