H kexnkdy D ] GEOLOGY OF WESTERN DIVISION. 17 
the bluff in the neighborhood of Corpus Christi, and possibly should 
be correlated with the blue clays of the east and form a portion of 
Hilgard's Port Hudson or McGee's Columbia. 
Probably underlying these clays is the Reynosa limestone, typically 
a tufaceous lime rock, but frequently so mixed with clays and sands 
as to almost lose its identity, included with the Reynosa division 
are several beds of conglomerate, consisting of pebbles and gravel 
cemented together by a limy matrix, together with gravels and limy 
clays. 
The Reynosa limestone is by far the most important member of 
the Coastal Plain group as Seen in the southwestern end. It is exposed 
high up on the northern side of the range of hills bordering the south- 
ern margin of the Nueces River Valle}^ in McMullen County. Where 
the Nueces has broken through this range the Reynosa limestones 
can be traced like an old shore around the end of the range and along 
its southern side, where the limestone is found high up on the flank 
and caps the lower levels of the hills south of San Diego. It occurs 
at Rogers, a few miles west of Corpus Christi, and at several points 
on the prairie in upper Hidalgo and Starr counties, and may possibly 
be found in other areas. 
In connection with the apparent trend of the Reynosa beds in a 
general north-south direction, it is noticeable that these limestones 
are directly associated with gypsum deposits in the upper end of 
Hidalgo and Cameron counties, and with the heavy salt deposits of 
the Sal del Rey region in southern Texas. Disagreeable-smelling 
sulphur water flows from a deep well at Corpus Christi, and small out- 
crops of sulphur clays appear in the Rio Grande country near Rio 
Grande City. 
The Reynosa limestone with its associated clays, conglomerates, and 
marls has been considered of Pliocene age. 
Pleistocene deposits containing vertebrate fossils have been recog- 
nized in the Eqtius beds in the neighborhood of San Diego, although 
some doubt has been thrown on the age of these deposits, Cope con- 
sidering them to be Upper Pliocene. As in the case of the underl- 
ing Miocene deposits of the Bordas district, not enough work has yet 
been done to determine their areal extent or even to absolutely prove 
their existence. The beds here considered as Miocene, unlike any 
other deposits of Tertiary age in Texas, are all standing up at very 
high angles, in many places showing dips of 75° or 80°. This is the 
more noticeable in the southwest corner of Live Oak, northeast cor- 
ner of Duval, and southeast corner of McMullen counties. Man}^ of 
the smaller dome-shaped hills have the appearance of having been 
formed by a thrust from below, the sandstones forming them dipping 
in every direction. 
Bull. 212—03 2 
