836 



SCIENCE. 



[N. S. Vol. XVI. No. 412. 



the northern border of its outcrop overlies the 

 Vicksburg Limestone, in Covington County 

 ■we see it lapping up over both upper and lower 

 Claiborne. 



4. At Chattahoochee landing on the Georgia 

 side of the river there is a well-known ex- 

 posure of Tertiary (Chattahoochee) fossilifer- 

 ous beds, overlain by the eross-bedded sands 

 and purplish clays of the Grand Gulf, which 

 in turn are capped by the sands, etc., of the 

 Lafayette. 



5. In Escambia County, at Coal Bluff and 

 at the mouth of Silas Creek on Escambia 

 Eiver, and at Lovelace's old mill near Roberts, 

 the Grand Gulf beds are seen overlying strata 

 holding casts of Cardium Chipolanum and 

 other fossils, which led Dr. Dall to correlate 

 them with the lower Miocene (more recently 

 Oligocene). In our 'Coastal Plain Eeport,' 

 we considered the fossiliferous beds to be a 

 part of the Grand Gulf strata, and the lower 

 Miocene age of the latter was thus thought 

 to be definitely fixed. Our recent observa- 

 tions, however, of the unconformity existing 

 between the Grand Gulf and the fossiliferous 

 Tertiary beds in these localities, and of the 

 occurrence of the former as surface beds, 

 southward to the very shores of the Gulf, com- 

 pel us to change our views and to assign to the 

 Grand Gulf a place in the stratigraphieal 

 column not only far above the Tertiaries ex- 

 posed on the Chattahoochee and Escambia 

 rivei-s, but also above any unquestioned 

 Tertiary existing in Alabama. 



6. The evidence of the comparatively recent 

 age of the Grand Gulf formation thus fur- 

 nished by its surface distribution, is eon- 

 firmed and extended by the materials brought 

 up from three deep wells bored in Mobile 

 Cotmty, viz., one at the brewery in the city, 

 one about three miles southwest of the city, 

 (the Bascom Well) and one at Alabama Port 

 on Mon Louis Island near the southeastern 

 end of the county. 



The boring at Alabama Port had last sum- 

 mer gone down to a depth of 900 feet, and 

 from near the bottom shells were brought up 

 which have been identified, viz., Rangia John- 

 soni, Dall; Mactra lateralis. Say; Hydrohia 

 Moliliana, Dall, and about ten other species, 



mostly new and brackish water forms. Above 

 the shell horizon the boring penetrated mainly 

 sands and clays and sandstones, the latter re- 

 ported as being altogether 400 feet thick and 

 in places exceedingly hard. These beds can 

 not well be anything else than Grand Gulf, 

 and the shells come from below them and 

 represent the Pascagoula horizon of Johnson, 

 regarded by Dr. Dall as of Chesapeake Mio- 

 cene age. The boring at the brewery in Mo- 

 bile brought up the same shells from a depth 

 of 735 feet, and the boring at Biloxi, Miss., 

 reached the same Pascagoula formation at 

 the depth of 700 feet. 



The boring at the Bascom Well near Mobile 

 pierced the same formation and furnished the 

 same fossils, but this boring went deeper, and 

 between the depths of 1,500 and 1,556 feet 

 brought up shells which are identical with 

 forms occurring at Oak Grove in Florida, now 

 considered as Oligocene by Dr. Dall. 

 List of Shells from Bascom Well, Mohile, 

 Ala. (from 1,500 to 1,556 feet depth). 



Mitra cf. Hanleyi, Dohrn. 



Litiopa sp. fragments (probably young). 



Nassa sp. fragments (probably yoving). 



Tornatina incisula, Dall. 



Tereira indenta. Con. 



Neverita dtipUcata, Say. 



Bittium priscum, Dall. 



Oliva sp. young. 



Turritella terehriformis, Dall (Alum BluS 

 horizon). 



Micromeris sp. very young. 



Leda acuta ( ?) Con. young. 



Leda sp.? 



Nuciila sinaria, Dall. 



Phacoides piluJiformis, Dall. 



Hemicardium apatelicum, Dall. 



Corliila Whitfieldil Dall. (young). 



Orhitoliies duplex. Carp. 



Orhiculiva adunca, F. & M. 



Lucina Pennsylvanica, Lirm. 



Lucina dentata. Lam. 



Yenus Burnsii, Dall. 



To sum up the evidence thus adduced : The 

 Grand Gulf is not Eocene, it is not Oligocene, 

 it is not Miocene, since it overlies in turn each 

 of these formations. By its position it must, 

 therefore, be either Pliocene or more recent. 



