52 OIL FIELDS OF TEXAS-LOUISIANA COASTAL PLAIN, [bull. 212. 
but the sands nowhere seem continuous, appearing to form lenses. 
Occasionally the sands are indurated, and in places the}' occur in the 
form of bowlders scattered through the clay beds. The clays are 
sometimes thinly laminated or partially stratified, but are more fre- 
quently massive, and have a tendency to break into cuboidal blocks. 
The most important bed of clay in this group is a heavy bed of blue 
clay containing numerous concretions of carbonate of lime. The 
arrangement of the lime concretions gives to this clay the appearance 
of being partially stratified, as in most exposures seen these concre- 
tions lie in regular planes, and while for the greater part rounded and 
nodular in form, in several sections they appear as flat concretions, 
sometimes being over a foot in length while not more than 2 or 3 
inches in thickness. 
( )wing to the nature of the country underlain by these beds very few 
sections of any value are to be seen. Near Oorrigan, on the Missouri, 
Kansas and Texas Railroad, in Polk County, laminated gypseous 
cla} 7 s of this series occur, the thickness being a little over G feet. 
The}' also appear at Fleming, Chester, and other localities along this 
railroad. Near Fleming, in the eastern edge of Polk County, the fol- 
lowing section appears in a railroad cutting: 
Section near Fleming, Polk County. 
Feet. 
1 . Surface gray sand ... .} 
2. Brown mottled sand . 2 to 4 
3. Gray stratified sand containing fossil palm wood in great abundance, 
with numerous quartz, jasper, and other pebbles; gravelly in some 
localities . . ... . _ 20 
4. Blue clay partially stratified, hut showing a tendency to break up into 
conchoidal blocks, and containing numerous nodules of calcareous 
matter . . 50 
5. Red clay having practically the same structure as No. 4, but without 
limy concretions 10 
(5. Yellow sand, visible 4 
Five miles farther east the same clays appear underlying the gray 
sands, but in this place they appear as a partially stratified mottled 
clay containing nodules of lime. This mottled condition may be due 
to a mixture of the red and blue clays, as in none of the localities 
observed does there appear to be any real parting or line of division 
between the red and blue clays, except that the red does not contain 
calcareous nodules, which appear to be altogether confined to the blue 
clays. In the Rockland section the blue clays have a thickness of 20 
feet, while the other Frio deposits in the same section consist of 
green, brown, and pale-blue clays having a thickness of 60 feet. 
In this locality the blue clays contain a small quantity of gypsum 
crystals in close association with the calcareous nodules. 
