18 GEOLOGY AND MINERAL RESOURCES OF MISSISSIPPI. 
At the big oxbow bend in Oaknoxubee River, one-fourth mile below the wagon bridge at 
Macon, the river has formed on its south side a bluff 75 feet high (PI. Ill, yl). This bluff 
shows a solid mass of white or slightly yellow limestone, nonfossiliferous and apparently 
without bedding planes, but in a view from a distance the stratification of the material is 
apparent from the fact that the unequal hardness of the strata has caused some to weather 
more rapidly than others. There is a marked dip to the south. This same limestone out- 
crops in all the smaller streams flowing into the Oaknoxubee from Macon to the Alabama 
border. It is a part of the upper subdivision of the Selma. Still farther west the prairies 
and hillsides from which the soil has been removed are covered with large oyster shells 
which have given rise to the term "shell land." 
There is a striking difference in the character of the general topography and vegetation 
of the Selma chalk and the overlying Porters Creek clays. The cold, gray, and apparently 
lifeless soils of the Porters Creek produce a growth of short leaf pine which does not appear 
on the black calcareous soils of the Selma. In some of the abandoned fields of the Selma, 
where there is a thin veneering of Lafayette, there is more or less pine, particularly along 
the edges of the Selma, but pine is not native to these soils. Black, white, and post oak, 
with some hickory, poplar, gum. and walnut, are the principal limbers of this formation. 
On the wesl side of Quilby Creek, where it runs south along the State line between Ala- 
bama and Mississippi, 7 miles east of Sucarnochee, Miss., the Selma chalk forms a small 
bluff. The prairie soil extends back 2 miles farther west and is overlain by the Porters 
Creek clay. On the east side of the creek, about 100 yards east of the Alabama line, the 
Selma forms a bluff somewhal higher than on the opposite side in Mississippi. The top of 
the bin If is -apped by a coarse-grained sandstone, cemented by lime carbonate, and this 
doubtless represents the lowest member of the Ripley, which is present in Alabama but 
wedges out in southeastern Mississippi. The sandstone contains huge, round lime con- 
cretions the size of the closed hand. 
Three miles north of Scooba the western border of the Selma chalk outcrop is seen in a 
series of hills forming the south bank of Wahalak Creek. The bottom of the creek here is 
about 1', miles wide, with the steeper slope on the south side. The creek has channeled 
its bed into the white Selma chalk, which outcrops continuously throughout its course. 
The limestone occurs in the bed of the creek to a point 6$ or 7 miles northwest of Wahalak, 
but the overlying Porters Creek clay is present on the higher land on both sides of the 
creek 
On the low range of hills south of Wahalak Creek, beginning near the Mobile and Ohio 
Railroad track and extending eastward, is a bed of sand rock 10 feet thick capping the tops 
of the hills. It is a coarse grained sandstone cemented with lime carbonate and contains 
numerous little bivalve shells. It is similar to sandstone found 7 miles east of Sucar- 
nochee and doubtless represents the lowest beds of the Ripley formation. 
In the \ icinity of Prairie Rock there is a hard crystalline limestone, or "flint rock," very 
different from the soft chalk-like limestone along the river at Macon. This so-called "flint 
rock" has been used for road metal and foundations for houses, but the readiness with 
which it bieaks down under the action of weathering agents renders it unsuitable for such 
purposes. 
Men familiar with the districts say that the hard flinty limestone is rarely more than 4 feet 
thick, and always occurs near the surface. Below this hard stratum comes the soft, whiter 
"rotten limestone," which is, on an average, 20 feet thick and is underlain by the "blue 
rock." Cisterns are always dug to the " blue rock," which requires no curbing. 
There are two distinct soils in the Selma area, giving rise respect i vely t o " t he post -oak " land 
and the "prairie" proper. The former is the highest land between the stream divides, 
which has suffered but little erosion. It is a very level table-land, sloping gently to the 
streams. This post-oak land is covered with a thin veneering of Lafayette loam, rarely 
more than 10 feet thick. It has a growth of post oak and some scrubby black-oak timber. 
The "prairie" land is that from which the Lafayette has been removed, so that the rich 
