GRAND GULF GROUP. 43 
Section of Grand Gulf beds near Star. 
Feet. 
3. Heavy-bedded sandstone, in places barely cemented together so that great cares have been 
made in the hill by the action of weathering agencies Thickness undetermined. 
2. G ray clay 10 
1. Hard white sandstone with bluish streaks through it. In places the stone is very compact 
and will take a slight polish. The larger part of it. however, is a loosely cemented, coarse- 
grained sandstone containing a small amount of mica and small irregular particles of clay 
which were washed into the matrix before it was hardened. The clay particles seem to have 
shrunk, leaving small irregular openings in the clay mass 15 
Two specimens of this sandstone were tested in the engineering laboratorj- of Purdue 
University with the following result: 
Crushing strength of Grand Gulf sandstone from Star. 
Pounds per square inch. 
Sample Xo. 1. 4 by 4 inches 2, 740 
Samj)le Xo. 2, 4 bv4 inches 3, 260 
South and east of the line above mentioned the sandstones are wanting and the forma- 
tion is essentially a series of indurated, laminated clays and sands of various characters, 
from the white plastic pottery clays to the less pure lignitic and gypsiferous ones containing 
lignitized tree trunks and in places beds of pure lignite. 
Four outcrops of Grand Gulf clays on Chickasawhay and Pascagoula rivers are mentioned 
by Doctor Hilgard. The northernmost of these is on Col. Sam Powe's place, 2 miles south of 
Winchester. Wayne County. At this locality are well-preserved lignitized trunks of trees 
and old stumps which have been covered with the "ancient soil'* absolutely on the spot 
where they grew. Above the old trunks and stumps are thin seams of sandy clay, between 
which are successive layers of leaves. The whole is covered with 20 feet or more of Lafayette 
sand. Most of the submerged trees, according to Hi Igard, are dicotyledons; some are coni 
fers and some palms. 
To the west from Chickasawhay River a very plastic clay immediately underlies the 
Lafayette sands and overlies the darker lignitic clays as found along the river. This plastic 
clay is found in numerous wells beneath the Lafayette and likewise outcrops along the 
streams where the Lafayette has been removed. Deposits of leaves and vegetable matter 
similar to those mentioned above were observed by L. C. Johnson along Leaf River near 
Augusta, at Rawles Springs in the northwestern part of Perry County, and at Carpenter Bluff, 
Perry County. At the last place the Lafayette, according to Johnson, overlies about 50 feet 
of gray sandy clays, below which are 14 or 15 feet of blue mud filled with leaves and rotten 
logs. 
One and a half miles north of Hattiesburg, on the Gulf and Ship Island Railroad, the 
clay is characteristically developed. It is here very plastic, free from sand, and varies in 
color from white to blue, gray, and cream. It is nonfossiliferous and free from any lime 
concretions. It is very similar to the clay farther west along Pearl River, except that the 
latter clay has numerous lime concretions through it. 
Below the variegated plastic clay so common at the surface at Hattiesburg the strata con- 
tain more or less sand, lignitic material, and plant remains. Ferruginous nodules and in 
places more or less iron pyrites and numerous salts are present, which give rise to a great 
variety of mineral springs and inferior well waters. 
The plastic Hattiesburg clay passes underneath the younger formations to the south. In 
some of the deep wells along the coast a bluish-green plastic clay, with a maximum thickness 
of 1.50 feet', is reported to be struck from 450 to 5.50 feet. Whether this is the same clay as 
that coming to the surface at Hattiesburg it is impossible to say. With a southward dip of 
the strata of 6 to 8 feet per mile the base of the Hattiesburg clays would be penetrated at 
Mississippi City at a depth of about 600 feet. It has not been possible with the present 
data to ascertain the southward dip of the Grand Gulf, but it is very probable that 7 to 10 feet 
per mile is an average estimate. Regarding the dip of the Grand Gulf Hilgard« said that " the 
aAm. Jour. Sci., 3d ser., vol. 22, July, 1881. 
