Pontotoc County, in the north central part of the state, is in parts of four physiographic regions, namely; the BLACK PRAIRIE BELT, the PONTOTOC RIDGE, the FLATWOODS, and the NORTH CENTRAL PLATEAU.
Characteristics respectively of the four physiographic regions are four terranes: the Selma chalk and the Ripley formation of the (upper) Cretaceous, and the Midway and the basal Wilcox series of the lower Eocene. In the extreme eastern part, the out-crop of Selma chalk forms a belt about three miles wide, extending from the north to the south side of the county. Just west of the Selma chalk the Ripley formation covers a belt four to nine miles wide. In order, in the western half of the county, the midway and Wilcox series constitute belts, respectively six to eight miles wide, and three to six miles wide.
The oldest formation, the Selma chalk, and the next oldest, the Ripley, of the eastern part of the county, contain no bauxite deposits. Neither does the next succeeding terrane, the Midway series; but some of its divisions are so closely related to the bauxite bearing Wilcox series, as to make a discussion of both series essential.
The Holly Springs, having a thickness of 700 to 750 feet, is a highly cross bedded, more or less micaceous sand containing lenses of clay. The Bashi (Woods Bluff) formation is a glauconitic calcareous sandy marl, containing large calcareous concretions and is found only near Meridian in Lauderdale County. The Hatchetigbee (Grenada) formation consists of 250 feet of lignitic clay, lignite and sand.
All these formations are typically unconsolidated beds, showing no evidence of folding or faulting in the area under consideration. The normal dip is a little south of west, at an average of twenty five to thirty feet to the mile.
The bauxite deposits of Pontotoc County are confined to the western tier of townships, range 1, east, which makes up the western quarter of the county. They constitute the largest deposits and are the best grad of ore in Mississippi.
There are two main groups: "Smoky Top" and vicinity, ten miles west of Ecru, and "Big Hill" and environs, eight to nine miles due west of Pontotoc. The Pontotoc - Toccopola concrete road, completed to a point within two miles of the Big Hill deposits, will permit immediate development in a small way. The known deposits of bauxite and bauxitic clay and the prospective ones under cover have a total area in the county of more than a thousand acres. The largest single deposit is Smoky Top, which has an area of 263 acres. The deposits at Big Hill and environs, about ten miles south of Smoky Top, have a total area of 456 acres. The ore lies near the tops of the hills, ridges, and spur-ridges of the region, at an elevation approximately five hundred feet above sea level (B. M. assumed), except where the monoclinal dip brings it to a lower level. The spurs and spur ridges containing ore have a relief ranging from thirty to nearly one hundred feet and many of them seem to have been held up by the hard resistant cap of bauxite ore. Consequently the overburden is in general less than ten feet and in many places less than five feet.
The bauxite in Pontotoc County, like that at other places in the state, is in the basal Wilcox (Eocene), probably in the Ackerman formation, near its contact with the Porter's Creek clay, of the Midway. The ore is in beds which extend over considerable areas and which vary in thickness from one foot to sixteen feet.