140 GEOLOGICAL SURVEY 
formations deposited on the same spot, and superimposed, the one upon the other, as are the Cre- 
taceous and Tertiary rocks, must have been very great, to say nothing of the almost total extinction 
of animal life, which took place at the close of the Cretaceous period. 
The Tertiary rocks of South Carolina are composed of beds of loose sand, clay, gravel, and sand- 
stone, together with strata of limestone of great thickness, and beds of soft or pulverulent mart. 
A line drawn from the mouth of Stevens’s Creek, on the Savannah, north of Hamburg, crossing 
the Saluda and Broad rivers, near their junction; the Wateree, at the Canal; Lynch’s Creek, at 
Evans’s Ferry, and Thompson’s Creek, at the point where it enters the State, in Chesterfield Dis- 
trict, will mark, with sufficient accuracy, their upper boundary. Wherever the rivers, in their 
downward course, enter this boundary, they wash away the more yielding Tertiary rocks, and 
expose the metamorphic, and very frequently the granitic rocks; and hence it is that at these 
points, in ascending the rivers, we meet with the first falls. And this is true along the whole 
Atlantic slope—the boundary of the Tertiary, coinciding with the first, or lowermost, falls on the 
rivers; and for the obvious reason that the Tertiary rocks do not offer sufficient resistance to the 
force of the streams to produce obstructions. 
Nothing can be better marked than this boundary: a line of outcropping, sandy strata extends 
along the entire distance, overlapping the clay slates, or grauite, and producing a striking change in 
the topography, and even in the botanical character of the country. 'The long-leaved pine, (Pinus 
palustris,) finds here the line that limits its distance from the coast; nor does it venture beyond it, 
excepting where a sandy, granitic ridge meets this line, and iempis it to proceed a few miles beyond. 
It is interesting to find so conspicuous a plant as this noble pine marking, throughout its entire 
range, with such accwacy, the boundary of a geological formation. 
Among the under-growth characteristic of this region, the scrub oak, (Quercus catesbei,) is promi- 
nent. The rare Ceratiola is confined toa very narrow belt here, together with several showy 
species of Baptisia. The brown grass, (Andropogon,) which takes possession of barren wastes 
higher up, is here replaced by the genus Aristida, which is the natural grass of the open pine woods. 
In short the Flora of the upper verge of the Tertiary is as distinct from that of the rest of the State 
as are the two geological systems that meet there, from each other. 
_ Eocene. 
We have seen that the Cretaceous formation sinks under the Santee River, forming a depression 
of great depth, which is filled with calcareous and other rocks, and which I have named the 
Charleston Basin. The calcareous rocks are those which Mr. Ruffin called the Carolina Bed, on 
account of their great development in the State. They are seen outcropping, at intervals, along 
the right bank of the Santee, as high up as Stout’s Creek, about ten miles below the junction of the 
Congaree and Wateree rivers; again, in the vicinity of Orangeburg Court House; on Rocky 
Swamp, 8. Edisto; on the head waters of the Salketchie; on 'Tinker’s, and down the Savannah, 
below the Lower Three Runs. The marl of these beds is also said to exist on Ashepoo River, and 
if so, this is the most western point in the State where it occurs. Underlying these vast deposits of 
calcareous matter, are beds of clay, sand, gravel, &c. which, together with the Carolina Bed, con- 
stitute the Eocene formation of the State. 
