8 Geological Survey of Alabama. 



minimum thickness is 350 feet, of which the uppermost 150 feet con- 

 sist of a tolerably pure but somewhat silicious Limestone, filled with 

 masses of coral. 



The next succeeding 150 feet are made up of a soft white Limestone, 

 often quite pure and filled with Orbitoides Mantelli. The lowermost 60 

 feet are of impure argillaceous Limestone, which, in disintegrating, yields 

 a black calcareous soil similar to that derived from the rotten Limestone 

 of the Cretaceous. This lower portion of the White Limestone surpasses 

 the others in the variety of its fossils, and most of the forms described 

 in this bulletin from the White Limestone come from this horizon. 



2. The Claiborne. The thickness is 140 to 145 feet, and the materials, 

 sands and clays, which are generally calcareous and often glauconitic. 

 Near the top of the subdivision is a bed of glauconitic sand 15 to 17 feet 

 in thickness, filled with shells in perfect state of preservation. The 

 sandy clays forming the lowermost 50 feet are likewise filled with a great 

 variety of shells in good state of preservation. The intervening calcare- 

 ous clays and calcareous sands are distinguished by the great numbers of 

 shells of Ostrea sellceformis which they hold, as well as by the compara- 

 tive rarity of other forms. 



In view of the importance of this subdivision, I give below a more 

 detailed section of the Claiborne Bluff and of the Lisbon Bluff, which is 

 stratigraphically the continuation of the Claiborne Bluff. 



This section, which was made jointly by Mr. Aldrich and myself, was 

 first published by Mr. Aldrich in the American Journal of Science, 

 October, 1885. In the Geological Keport for 1883-4 substantially the 

 same section is given, but I shall here retain the numbers and letters by 

 which the several beds are distinguished in the section published by Mr. 

 Aldrich, as the references given in this Bulletin are generally to this 

 particular section. 



Section of the Bluff at Claiborne. 



Drift \ 40ft. 



D. White Limestone bed containing Scutella and casts of shells. 

 Zeuglodon bones found in this bed. Hale, American Journal of Science > 

 1848, p. 361 45ft. 



C. Scutella bed. S. Lyelli in great numbers - 3 ft. 



B. Coarse ferruginous sands, indurated at bottom 6ft. 



A. Claiborne fossiliferous sand ; source of most of the Claiborne shells ; 

 thin layers of lignite about 10 feet down from top 17 ft. 



1. Indurated glauconitic sandy ledge 4 ft. 



2. Calcareous clayey strata, becoming sandy in lower part-... . 18 ft. 



