This area (Pl. 9), often called “the caprock,” is an elevated plateau
which rises above the rolling plains which surround it. The High Plains
are bounded by the Pecos River valley on the south, southeast, and west
and by the North-Central Plains on the east.
The surface of the High Plains is very flat and characterized by a
sparse cover of grasses and few trees. The surface strata consist
largely of unconsolidated deposits of sands and gravels of Quaternary
and Tertiary age, with remnants of Lower Cretaceous limestones along the
southern margin. The rocks of the High Plains are mostly
unfossiliferous, but mammalian remains have been found at several
localities.
[Illustration: Plate 9
Physiographic map of Texas.]
HIGH PLAINS
NORTH-CENTRAL PLAINS
GRAND PRAIRIE
TRANS-PECOS TEXAS
VAN HORN UPLIFT
THE BIG BEND AREA
SOLITARIO UPLIFT
MARATHON UPLIFT
EDWARDS PLATEAU
LLANO UPLIFT
BALCONES FAULT ZONE
GULF COASTAL PLAIN