LOWER CARBONIFEROUS ROCKS. 11 
The Tullahoma chert is thinnest in the north. At the old McMaster mill it is represented 
by a thickness of 30 feet. Near the mouth of Whetstone Creek the formation has thickened 
to 100 feet, and at the mouth of Bear Creek, on the Alabama border, it has a thickness of 
150 feet. 
Along the headwaters of the small streams flowing into these larger streams the chert is 
always present and extends westward until it is covered by the later Cretaceous deposits. 
The southward extension is limited by the St. Louis limestone, which overlies the chert. 
ST. LOUIS LIMESTONE. 
Across the line in Alabama the St. Louis limestone has been recognized by McCalley « 
along Tennessee River, where it is about 150 feet thick. The characteristic fossil Lithostro- 
tion canadense has never been found in Mississippi, though a more thorough search may 
show its presence. 
This formation in Mississippi consists of a series of dark-blue to gray limestones with more 
or less chert through it. In places the limestone is quite fossiliferous. Many of the fossils 
were determined by Hilgard, but many of the names he used have now become antiquated. 
The St. Louis is distinguished from the Tullahoma by the fact that it has less chert and a 
greater amount of pure gray limestone. 
In the upper part of the St. Louis there is a still lighter colored oolitic limestone contain- 
ing Platycrinus huntsvittei. This no doubt is the equivalent of the Ste. Genevieve lime- 
stone of Missouri, southern Illinois, and western Kentucky. The area of the Platycrinus 
limestone in Mississippi is limited, being confined to sees. 22, 26, and 27, T. 4 N., R. 11 E. 
On John Trammel's land, in sec. 22, T. 4 N., R. 11 E., the limestone is overlain by the heavy- 
bedded sandstone belonging to the Chester formation. The Carboniferous west of this 
locality is covered with the Cretaceous and Lafayette formations. 
CHESTER FORMATION. 
The upper division of the Carboniferous in Mississippi is represented by a series of sand- 
stones, limestones, and shales belonging to the Chester group. The lowest member of the 
Chester is a compact, coarse-grained sandstone which rests on the oolitic St. Louis limestone. 
The thicknesses of the various beds are not known, owing to the scarcity of exposures, 
which occur along the larger streams where the overlying Cretaceous has been removed. 
The changeable character of the lower part of the formation is clearly shown at the steel 
bridge across Bear Creek near Mingo, where the following section may be seen: 
Section at bridge across Bear Creek, near Mingo. 
6. Top of hill covered with Lafayette. Ft. In. 
5. Heavy-bedded, coarse-grained sandstone 20 
4. Fine-grained, dark-colored limestone giving rise to springs, with thin bands bearing Spirifer 
i7icrebesccns( ?) 4 
3. Highly fossiliferous shale 22 
2. Coarse-grained limestone containing a large amount of iron oxide 6-8 
1. Dark-colored compact shale 10 
The sandstone continues along the creek to the south and becomes coarser in texture. 
This sandstone represents the uppermost member of the Chester formation in Mississippi. 
Along Bear Creek it attains a thickness of at least 100 feet and perhaps much more. This 
creek along its middle course has channeled its bed deep into the sandstone, leaving high 
perpendicular cliffs standing on either side. 
The area of outcrop of the Chester formation is confined chiefly to the stream valleys 
along Bear Creek and its tributaries in eastern Tishomingo County, along the headwaters of 
Tombigbee River in southeastern Prentiss County, and along Bull Mountain Creek in east- 
ern Itawamba County. The southernmost outcrop in the State occurs along Bull Mountain 
Creek near the northern edge of Monroe County. The area between these streams is covered 
a Op. cit., , p. 36. 
