Geologic Story of the Colorado River. — Hill. 289 
1. Quaternary. Thickness. 
1. Older Terrace deposits of Colorado river at Austin, superficial. 
1 a. Upland gravel as seen at McDade, superficial. 
2. Tertiary. 
Eo-Lignitic (“Laramie”) or basal Eocene, Bastrop 
county probably..1,000 
3. Upper Cretaceous. 
a. Upper arenaceous beds, eastern edge Travis 
county... . 300 
b. Middle (Exogyra ponderosa) marls, east half of 
Travis county.1,000 
c. Austin or Niobrara chalk, city of Austin. .600 
d. Eagle Ford or Benton shales, city of Austin.300 
The Lower Cross-Timber or Dakota sands are missing 
here; present in North Texas .200 
4. Lower Cretaceous. 
a. Yola limestone, or Shoal Creek horizon, Austin.50 
b. Exogyra arietina clays, west of Austin.100 
c. Washita limestone (metamorphosed chalk) west 
of Austin.160 
d. Medial or Hippurites limestone (metamorphosed 
chalk) West of Austin.900 
e. Basal or Fredrickburg limestone, (metamorphosed 
chalk) Burnet .300 
f. Trinity, basal littoral beds, Burnet.300 
5. Carboniferous. 
a. Bituminous shales and sandstones, Marble Falls 
and Smith wick.300 
b. Encrinital, or Marble Falls limestone...500 
6. Silurian 
Barren white limestone beds, Lower Marble Falls. 
7. Cambrian. 
(Indeterminate limestone flags.1,150 
a. Upper ■< Potsdam sandstones ; western Burnet 
( county.625 
b. Lower.—The Llano group of Walcott, Sand mountain. .2,000 
Total 9,520 
It is impossible to give the details of each of these forma¬ 
tions. The general character of the paleozoic section has 
been defined by Walcott,* except the Carboniferous. The 
writer has previously defined the Cretaceous with the excep¬ 
tion of the horizon here mentioned as the Yola limestone, 
which is new. The basal Tertiary or Eo-lignitic beds have 
been studied by the writer and others during the past year 
from the Rio Grande to the Alabama. The Quaternary beds 
will be more fully defined later. 
UNCONFORMITIES AND DISTURBANCE. 
This section presents an extensive perspective of the strati¬ 
graphic history of the region from earliest Cambrian to the 
present. As previously shown by Walcott, the Llano beds are 
Notes on the Paleozoic rocks of Central Texas. Am. Jour., Sci. Dec, 1884. 
