138 GEOLOGICAL SURVEY 
known in the State, of this formation, before Mr. Ruffin’s discoveries. It is known to Geologists as 
Effingham’s Mills, and was first made known by Dr. Blanding. It forms the banks of the stream, 
to the height of four or five feet, and extends across the swamp at the mill. ‘The bed is composed 
principally of a poor, silicious marl, with irregular bands of marl stone running through it. ‘The 
most common of all Cretaceous fossils, Hxogyra costata, abounds here. I also found Trigonia tho- 
racica, and another undescribed species. 
It is highly probable that the channel of the creek, like that of the Peedee, is cut in this forma- 
tion, for it may be traced some miles lower down. It appears again as the creek approaches the 
river, and at its mouth it rises into beds of considerable thickness. 
West of this, on Lynch’s Lake, it also occurs; and I received, from the Hon. G. C .Cooper, speci- 
mens from the Black Mingo, near Indian Town, which prove the existence of the fossilliferous 
marl stone at that place. Among them were Ammonites placenta, with the nacreous portion of the 
shell beautifully preserved ; and a fragment of a shark’s tooth, of the genus Carcharodon. 
My. Ruffin examined other localities on Black River, below King’s Tree, that I did not, for want 
of time, visit. 
The same inequality of surface is presented on Lynch’s Creek that was observed on the Peedee, 
and the depressions are, in like manner, filled with beds of Tertiary marl—showing that the Creta- 
ceous formation formed the bottom of the Tertiary sea, during the deposition of these beds. 
The unequal distribution of carbonate of lime in the softer marl and marl stone, is not an un- 
common circumstance; for when beds are porous, and consequently permeable to water, they are 
subject to lose a portion of their lime, which is dissolved and carried away. The water holding 
the lime in solution is, however, often arrested by meeting with less porous strata, and the result is, 
frequently, the formation of a hard, caleareous bed; so that marl stone is often formed at the 
expense of the lime of the superincumbent strata. 
Ten specimens of marl, analysed by Mr. Ruffin, from various sections of the Peedee beds, gave 
an average of 34 per cent. of carbonate of lime; and eight specimens of marl stone presented 
an average of 75 per cent. Near the upper surface of the beds it is often observed that very little 
lime is present, and that hollow moulds of the exterior of the shells remain, which are coated with 
oxide of iron. This generally happens where sulphuret of iron is present: it generates sulphuric 
acid, which acts as a solvent of the lime; or else it forms sulphate of iron, which is decomposed 
by the lime, leaving behind incrustations of oxide of iron. 
The cretaceous fossils of the State, so far as they are known, are comprised in the following very 
short list. 
Carcharodon, sp? near megalodon. 
Lamna, sp? 
Belemnites Americanus, Mor. 
Ammonites placenta Dekay. 
Turritella vertebroides, Mor. 
Natica petrosa, aS 
Ostrea cretacea, 44 
Exogyra costota, Say. 
Plagiostoma dumosum? Mor. 
