EOCENE CLAYS. 55 
Soda (Na 2 0) 106 
Brown oxide of Manganese • .167 
Phosphoric acid 052 
Sulphuric acid 032 
Organic matter and water 3. 689 
99. 863 
The Porters Creek clay comes to the surface along the Mobile, Jackson and Kansas City 
Railroad and on the hillsides and streams in Tippah County. At almost every place where 
it is seen it has a strikingly similar appearance, so that it can readily be distinguished from 
the Lafayette or Wilcox, lying farther to the west. It outcrops on the railroad one-half 
mile north of Walnut, Tippah County, at the water tank, and again one-half mile nortli of 
the tank. At each of these places it occurs in horizontal strata. It is very plastic, of a 
leaden-gray color, with a slight pink tinge. It is free from sand and does not effervesce 
with acid. Farther west it is reported to have a slight amount of calcareous matter through 
it. The same clay occurs in the hills 2h, to 3 miles southwest of Walnut, with a coarse- 
grained fossiliferous sandstone capping the tops of the hills. 
The relation of the Porters Creek clay to the other strata in the vicinity of Walnut is given 
in the generalized section below: 
Generalized section near Walnut. 
Ft. In. 
6. Gray fossiliferous sandstone capping tops of hills 50-75 
5. Leaden-gray nonfossiliferous joint clay, as seen along railroad north of Walnut and in 
hills 2% miles southwest 50-75 
4. Greenish band of calcareous sandstone, as seen at Chalybeate 8-26 
3. Yellowish calcareous sand, with slight amount of greensand present at Chalybeate and 
on Bobo place, east of Walnut 30-40 
2. Turritella limestone rock, as seen at Chalybeate and vicinity 5-15 
1. " Owl Creek" marl, as seen at Chalybeate and farther south 10 
The "Owl Creek" marl bed belongs to the uppermost horizon of the Cretaceous. All the 
strata above belong to the Tertiary. The same order of strata is present at Ripley. 
As above stated, the Turritella limestone lying below and the fossiliferous sandstone above 
the Porters Creek clays have not been found in southern Mississippi. At Scooba, Kemper 
County, the heavy Flatwoods or Porters Creek clays are very common. The " Flatwoods " 
belt here is about 10 miles wide and the entire area is underlain by gray plastic clay. The 
following analysis of a sample of the clay from Scooba was made in the laboratory of the 
United States Geological Survey : 
Analysis of Porters Creek clay from Scooba, Kemper County. 
[By W. S. McNeil.] 
Silica (Si0 2 ) 61. 92 
Alumina (A1 2 3 ) 19-47 
Ferric oxide (Fe 2 3 ) 2.81 
Magnesia (MgO) 1-98 
Soda (Na 2 0) 50 
Loss on ignition 12. 29 
98.97 
WILCOX CLAYS (EOCENE). 
The clays of the Wilcox formation comprise a large assortment, from the coarse sandy clays, 
well adapted for making lime-sand brick, to the white pottery clays as found at Holly 
Springs and Oxford. They occur more or less generally throughout the formation, but those 
which have so far been developed and used to any extent are found outcropping in a com- 
paratively narrow belt that extends in a general north-south direction near the center of the 
Wilcox area. The outcrop of the clays is marked by a series of stoneware factories. This 
belt, from 3 to 10 miles wide, can be traced into Tennessee, and from the Tennessee line 
southward it passes through northwestern Benton, eastern Marshall, central Lafayette, 
western Calhoun, central Webster, eastern Choctaw, and central Winston counties. Farther 
south there has been no detailed work to determine whether or not the clays are present. 
