DESCRIPTION OF BENTONITE OUTCROPS 607 



and have a light red, purplish color m a number of layers. Six miles to 

 the east of Dayton the bentonite was not found, but the limestone lying 

 on top of the Lowville rocks is a very dark red limy shale, containing 

 fossil sun cracks, being either a near-shore phase of the Hermitage forma- 

 tion or the Le Eay part of the Lowville. At High Bridge, Kentucky, the 

 section has been described by Ulrich, 4 who has the following to say about 

 the bentonite layer : 



"Near the middle of the beds there is a very soft clay layer, about two feet 

 in thickness, nearly white, with often a greenish tinge. Some fragments 

 were seen in which the green color is decided. It has a peculiar unctuous 

 feel, is readily cut with a knife, and when exposed a short time to the atmos- 

 phere breaks up into small flakes." 



At this place the bentonite (which is about 5 feet thick) rests on Low- 

 ville rocks, locally known as Tyrone limestone, while just above the ben- 

 tonite is 18 feet of thin-bedded, dove limestone with some shaly layers, 

 being upper Lowville, known locally as Le Eay limestone. On top of the 

 Le Ray is 26 inches' of the Curdsville formation, which here occurs be- 

 tween the Lowville and the Hermitage. At the base of the Curdsville 

 there occurs an impure layer of the clay, representing reworked volcanic 

 ash. As the locality at Bessemer, Alabama, is in the Woodward Iron 

 Company's mine shaft, the sides of which are now cemented, it is imprac- 

 ticable to get any section, but it is stated by the geologist of the Tennessee 

 Coal, Iron and Railroad Company 5 that the "green clayey material" (the 

 bentonite as now known) occurred about 75 feet below the big seam of 

 red ore, and apparently just on top of the Chickamauga limestone. ' As 

 the bentonite was known to occur in the Birmingham district, a day was 

 spent on Red Mountain, just east of the Woodward Iron Company's shaft, 

 and the bentonite was found to outcrop at two places. The first exposure 

 was seen in the edge of Birmingham, on the Twentieth Street cut, on the 

 west side of Red Mountain, about 100 yards from the crest of the road. 

 The second exposure was seen on the Altamont-Mount Terrace road, near 

 the crest of Red Mountain, which at this point is built up as a suburb of 

 Birmingham. The bentonite occurs 32% feet below the Silurian-Ordo- 

 vician contact and rests on a ripple-marked chert layer at the top of the 

 Lowville formation. It is overlain by between 3 and 4 feet of grayish 

 blue, thick-bedded limestone containing a number of thin chert layers. 

 Limestone beds which vary in lithology extend from the bentonite bed to 

 the Silurian contact. 



* E. O. Ulrich : Correlation of the Lower Silurian horizons of Tennessee and the Ohio 

 and Mississippi valleys with those of New York and Canada. American Geologist, vol. i, 

 1888, p. 107. 



8 Letter of A. S. Blair. Geologist of the Tennessee Coal, Iron and Railroad Company, 



