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SOIL SURVEY OF SAN SABA COUNTY, TEXAS. 25
color and stiff structure of the subsoil. In this county they are derived
from the Cambro-Ordovician, Carboniferous, and Cretaceous
limestones. The rocks differ in lithologic character, and there may
be corresponding soil differences, but the soil color is the same and
this was used as the chief basis of differentiation.
The San Saba series also comprises soils residual from limestone.
The types in this series are characterized by black or dark brownish
soils, and brownish or very dark gray subsoils. These soils typically
are calcareous. They are derived from the same limestone formations
as the Crawford, but differ from the latter in having a darker
color and in containing higher percentages of calcium carbonate.
Locally, as the soil becomes more cherty a reddish cast appears in the
subsoil, and in the mapping sharp distinctions can not be made
from the Crawford. The San Saba series is important in this county.
It occupies nearly as large an area as the Crawford and constitutes
a large part of the most valuable pasture land.
In the Darnoc series are included types with brown or dark olive
brown to black soils and greenish-yellow, greenish-brown, or olivecolored
subsoils. These soils are calcareous, and stiff and compact in
structure. The material is residual from soft, somewhat calcareous,
black, carbonaceous shale, with only a minor influence from limestone
and sandstone. The topography is steeply sloping to nearly
level. The drainage is good.
The Pontotoc series includes residual soils derived from calcareous
rocks consisting of sandy limestones and calcareous, ferruginous
sandstones, both of which contain notable percentages of glauconite.
The parent rocks in this county belong to Cambrian formations,
mapped in the Llano-Burnet folio of the United States Geological
Survey as the Wilberns, Cap Mountain, and Hickory sandstone formnations.
The characteristic soil color is reddish brown or brown.
The subsoil is dark red or brownish red. The surface drainage generally
is good.
The types in the Harley series are characterized by the lightbrown
to brown color of the surface soils and the yellow, greenishyellow,
or yellowish-brown color of the subsoil. Where a clay subsoil
is present it is typically stiff or only moderately friable. The
soils are derived mainly from sandstones, and are less calcareous than
the associated Pontotoc soils. Black concretions are commonly
present in both surface soil and subsoil. These soils occur in relatively
low situations and oxidation apparently has not advanced so
far as in the Pontotoc soils.
The types in the Tishomingo series are characterized by a reddishbrown
or brownish-red color of the surface soil and a red or darkred
color of the subsoil. The subsoil, where the soil material is
deep, is a moderately stiff, gritty clay, which in this county assumes
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