STRATIGRAPHY OF PERMIAN ROCKS (continued) BONE SPRING LIMESTONE
The Bone Spring limestone is the oldest formation exposed in the
Guadalupe and Delaware Mountains. it forms a bench of varying
height along the west-facing escarpment of the mountains, which
is fringed on the west by alluvial deposits or outcrops of down-
faulted rocks. (For views of typical exposures see pl. 5; for
map relations, pl. 3.) The formation passes beneath the surface
in the southern Delaware Mountains, south of the area described,
but across the Salt Basin to the southwest is extensively
exposed and forms the upper three-fourths of the east-facing
escarpment of the Sierra Diablo.46 The formation was named by
Blanchard and Davis,47 but it had previously been recognized by
both Shumard48 and Girty49 as the "basal black limestone"
(member 4 of Shumard's section). The type locality is in the
lower course of Bone Canyon below Bone Spring, on the west side
of the Guadalupe Mountains 1 mile northwest of El Capitan, where
there are characteris