604 D. W. LANGDON, JR. CRETACEOUS AND TERTIARY STRATA. 



Feet. 

 59— Buhrstone 55 



60 — Greenish-yellow calcareous clay, with a few decomposed fossils and an occa- 

 sional large shell of Ost?'cea selloeformis 12 



61 — "White sandy limestone, with small shells of Ostrcea sellcBfoi^mis in abun- 

 dance and pockets of larger sized shells. Makes capping ledge to island 

 at mouth of Omussie creek, where the bluff is about twenty feet high. 

 This stratum is made up of alternate beds of hard and soft strata, all 

 containing more or less abundant remains of Ostrcea sellce/ormis. The 

 harder strata weather out into root-like shapes, and are sometimes rather 

 argillaceous. Many return dips occur in this stratum, stringing it along 

 the banks for many miles further than it would extend normally. The dips 

 are all steep both ways, and many gaps in the succession are caused by 

 the washing out of the softer strata. Owing to these gaps and return 

 dips, it is rather difficult to estimate the thickness of this stratum with 

 much accuracy. It dips below the surface of the river two miles below 

 Gordon, Alabama, and is last seen on the Georgia bank. At Gordon 

 there is a very pronounced return dip. Estimated at (and not exceed- 

 ing) 60 



62 — The " Scutella bed ; " weathers so as to make it not possible to " count up " 

 its thickness. It is literally full of fossils, mainly Scutella lyelli (?) and 

 Pecten nuperus^ with a few smaller and thicker shells of Scutella. A 

 bluff about 20 feet high occurs opposite the mouth of Cowhatchee creek, , 



Georgia -96=8^ ^7-1 



63 — White orbitoidal limestone, seen first at Dougherty's wood-yard (Georgia), 

 on the Alabama bank, 9 miles by river from Neal's landing, Alabama. 

 This limestone contains numbers of echinoids about 5 miles above Neal's. 

 The limestone continues as far as Miriam's landing, at which place the 

 thickness is 200 



64 — Argillaceous and sandy limestone, alternating with strata of purer charac- 

 ter. Contains a pecten and an Ostrcea very close to our recent virginica. 

 This may be termed the Chattahoochee limestone. It is well' developed 

 there and in the eastern river bank for the succeeding 10 miles 2^ 



65 — Light yellow sand, containing pockets of fossils. Where there are no 

 shells the sand is very calcareous. Fossils resemble those described by 

 Conrad as Miocene from York county, Virginia, and Maryland 35 



66— Gray sand, slightly calcareous 5 



67 — Gray calcareous sand filled with shells. The leading fossil is a Mactra ^0=15- 



68 — Black lignitic sand. This contains much pyrite, and from the efflorescence 



of ferrous sulphate arises the name Alum bluflf; varies with preceding-- 10=1^ 



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