VARIOUS STAGES 411 



Feet 



3. Dark, crystalline limestones frequently brecciated, alternating with 



thick bedded gray limestones; thin sheets of calcite in the bedding 

 planes or in masses and veins ; containing Ophileta complanata. 

 Horizon A-1 215 



4. Gray, crystalline limestone 48 



5. Compact dolomitic gray limestone mottled with dark blotches 36 



6. Soft, porous w^hite limestone 18 



7. Thin, laminated dark limestones containing brecciated fragments of 



black limestone 220 



8. Compact, splintery black limestones alternating with light gray oolitic 



limestones and drab colored dolomitic limestones, containing 

 Riheiria calcifera and Asaphus marginalis. Horizon A-2 322 



9. Thick bedded crystalline and compact dark limestones 624 



10. Gray crystalline limestone 132 



11. Gray crystalline limestone alternating with bands of dark crystalline 



limestone. . , 313 



12. Massive beds of light gray crystalline limestone 198 



13. Thick bedded crystalline limestones of dark color, stained with iron 



oxide, containing Bathyurus amplimarginatus. Horizon A-3 157 



14. Compact yellowish gray and drab dolomitic limestone, frequently thin 



bedded and laminated, alternating with numerous thin beds of 

 dark limestone, weathering to a light gray color. Nodules of chert 

 occur frequently, and in such occurrences the rock tends to be 

 arenaceous .. 2,335 



Total thickness of the Beekmantown 4,803 



GROUP II.-STONES RIVER STAGE 



1. Carbonaceous crystalline black limestone alternating with light gray lime- 

 stone, containing Leperditiafabulites, Protorhyncha ridleyana, etcetera. 

 Horizons A-4, A-5, A-6 253 



Total thickness of the Stones River group 253 



GRO UP III.—BLA CK RI VER STA GE 



1. Black, fetid, shaly limestone alternating with thick beds of gray lime- 

 stone, the latter containing veins of calcite ; contains Stropliomena 

 filltexta, Maclurea bigsbyi, Keceptaculites occidentalis, Bhinidictya mu- 

 tabilis, etcetera. Horizon A-7 93 



Total thickness of the Black River formation. 93 



GROUP IV.-TRENTON STAGE 



1. Compact lusterless shaly black limestone, rarely crystalline, containing 



Rafinesquina alternata. Horizons A-8, A-9 187 



2. Thick bedded gray limestones, usually unfossiliferous. Horizon A-10. . 124 



3. Thin bed of fissile black shale, containing lenses of fossiliferous limestone. 



• Horizon A-1 1 2. 5 



4. Crystalline gray limestone, containing lllxnus crasdcauda, Isoteliis platy- 



cephalus, etcetera. Horizon iV-12 43. 



