GEOLOGY AND MINERAL RESOURCES OF MISSISSIPPI. 7 
GEOLOGY. 
Though the general geologic structure of Mississippi is very simple, the details of the 
stratigraphy are hard to make out, owing largely to the extent to which the underlying 
rocks are covered by the more recent deposits, such as the alluvial deposits and the "Orange 
sand," or Lafayette formation. 
The oldest rocks in the State are a series of limestones and shales of Devonian and Car- 
boniferous age, which outcrop in northeastern Mississippi, covering much of Tishomingo 
County and a small portion of Itawamba County. 
The newer rocks outcrop south and west of this older mass, occupying successive roughly 
parallel bands, and all of these rocks dip slightly to the southwest, so that if the observer 
should start in Tishomingo County and travel through the State either to the south or west 
he would find himself continually passing over newer and newer series of rocks, until he 
finally reached the very recent alluvial deposits which fringe the Gulf and Mississippi River. 
The above conditions are shown in the cross sections (figs. 1 to 5). 
Fig. 
1. — Cross section from mouth of Yellow Creek to Mingo. A, Cretaceous; B, Chester; C, St. Louis; 
D, Tullahoma; E, Devonian. 
The following table shows the geologic groups which are exposed in Mississippi, the newest 
formations being at the top of the table and the oldest at the bottom: 
Geologic formations of Mississippi. 
River alluvium — Sands, silts, and loam. 
T oe-s I Yellow loam— Surface loam or brick clays of northwestern Mississippi. 
(Loess— Gray to buff -colored calcareous silt containing land shells. 
Quaternary -, Port Hudson — Greenish to bluish c!avs with interbedded sands; calcareous con- 
cretions in lowest members. 
Lafayette— Red to yellow sands and iron-stained pebbles; sands in places con- 
l tabling large amount of clay. 
Miocene(?) .Grand Gulf — Gray aluminous sandstones, interbedded with white to gray plastic 
clays in northwest; darker colored clays containing lignitized 
wood and vegetable matter southeast. 
Miocene Pascagoula— Calcareous clays containing numerous fossils. 
Oligocene. . . Vicksburg— White, yellow, and blue crystalline limestone, interbedded with thin 
Tertiary. \ layers of indurated marl and clay. 
Jackson — Gray calcareous clays, lignitic clays with gray siliceous sands and 
some green sand. 
[Lisbon— Calcareous clays and greensands. 
Claiborne. <Tallahatta buhrstone— Aluminous and quartzitic sandstones, 
Eocene 1 | greensands, and clay stones. 
Wilcox— Highly stratified sands and clays of various colors, with some green- 
sand-marl beds. 
\fiHw (Porters Creek— Gray aluminous clays. 
I awaj "'(Clayton— Limestone, sands, and clays. 
| Ripley^ Limestones, sandstones, and marls. 
r t |Selma Chalk— White chalkv limestone and blue calcareous clays. 
dce u ) Eutaw— Siliceous sands and ciays, with some greensand. 
I Tuscaloosa— Variegated sands and clays. 
[Chester— Sandstone, limestone, and clays. 
Carboniferous <St. Louis— Limestone and chert. 
|Tul!ahoma— Siliceous chert. 
Devonian New Scotland— Dark limestone and shale. 
DEVONIAN. 
Until recently the oldest rocks of Mississippi have been referred to the Lower Carbonif- 
erous, but a more thorough investigation has proved the presence of a fauna referred, by 
Charles Schuchert, now of Yale University, and E. M. Kindle, of the United States Geo- 
