12 Geological Survey of Alabama. 



3. The Bell's Landing Section. This is 140 feet in thickness, and in- 

 cludes two important marine beds, and a third quite small and apparently 

 unimportant. These fossiliferous beds are interstratified with yellowish 

 sands in the upper, and rather heavy-bedded sandy clays in the lower, 

 part of the section. The upper marine bed, called the Bell's Landing 

 Marl, is about 10 feet in thickness, and has 40 feet of sandy strata above 

 it. The middle bed is called the Gregg's Landing Marl, and it lies 20 

 to 25 feet below the preceding, from which it is separated by dark-gray, 

 sandy clays. This bed is some five or six feet in thickness, and the upper 

 part of it is seen near the water level at Bell's Landing, while the whole 

 bed is well shown at several points higher up the river, notably at Gregg's 

 Landing, Peebles' Landing and Lower Peach Tree. The lowermost of the 

 fossiliferous beds of this section is only about one foot in thickness, and 

 it lies about 50 feet below the Gregg's Landing bed, being separated from 

 it by sandy clays. It is highly glauconitic, but does not contain any great 

 variety of fossils. It has been observed only at Lower Peach Tree. The 

 Bell's Landing Marl is distinguished from all others in Alabama by the 

 great size of the shells which it holds. This bed is seen at the typical 

 locality, Bell's Landing; at Peebles' Landing, at Gregg's Landing, at 

 Lower Peach Tree and at Yellow Bluff on the Alabama, and at Tusca- 

 homa, Turner's Ferry and Barney's Upper Landing on the Tombigbee 

 River. 



4. The Nanafalia and Coal Bluff Section The. strata of this section 

 are 200 feet in thickness, and consist of about 50 feet of gray, sandy 

 clays at top, which show a great tendency to indurate into tolerably 

 firm rocks, resembling very closely some of the strata of the Buhrstone. 

 Below this, about 80 feet of sandy beds, often strongly glauconitic, 

 characterized throughout by the presence of small oysters, Gryphcea thirsce. 



Near the base of this sandy division there is a bed about 20 feet thick, 

 literally packed with these shells. 



Below the Gryphcea thirsce beds follow some 70 feet of cross-bedded 

 sands, glauconitic, and apparently devoid of fossils, including, about 10 

 feet from the base of the section, a bed of lignite which varies in thick- 

 ness from four to seven feet. 



The greatest variety in the shells of this group is seen in the strata 

 which immediately underlie the lowest of the beds containing Gryphcea 

 thirsce, and the following section of the type locality is therefore given : 



