16 GEOLOGY. 



yellow. It frequently contains beds of marl and calcareous 

 gravel, and is generally highly impregnated with iron. In 

 some localities it has the appearance of green marl, and con- 

 tains grains of sillicate of iron. Like the salt-marsh it rests 

 at no great depth on a sandy post-pliocene formation. This 

 older recent alluvium derives much interest from the circum- 

 stance of its presenting in many parts of the salt-marsh and 

 tide-swamps where it occurs, indubitable proof of the subsi- 

 dence, at a recent geological period, of the sea-coast from 

 Florida to South Carolina. Stumps of cypress, pine, and other 

 fresh- water trees, in an erect position and worn away to a 

 horizontal line, are found in it, both in the tide-swamps and 

 salt-marsh, with their tops buried three or four feet below the 

 surface of the land, and at the same depth below the ordinary 

 height of the tides. In the salt-marsh these remains occur 

 several miles from the present forests, and where the water is 

 now salt at every stage of the tide and at all seasons of the 

 year. The kind of trees, their erect position, the horizontal 

 line of erosion, the accumulation of soil above them, and the 

 flowing of the salt water, three or four feet above and several 

 miles beyond them, all indicate a sinking of the land posterior 

 to the inland swamp formation. 



A still higher interest is connected with this formation 

 from its being the depository of all the fossil bones of the ter- 

 restrial mammalia, which have been discovered on the coast 

 of Georgia. 



These remains having been very abundant, and embracing 

 several genera and species of great interest, and their position 

 having been ascertained with much exactness, a somewhat 

 minute account of the circumstances under which they were 

 found may be useful. 



The four localities at which they have been discovered are 

 Skidaway Island and Heiner's Bridge, in Chatham county, and 

 the Brunswick canal and Turtle river in Glynn county. The 

 features which characterize these deposits being in all essen- 

 tial particulars the same, one description will answer for them 

 all. In every instance the fossil bones have been found im- 

 bedded in the inland swamp alluvium, near its bottom, and 

 resting on a yellow or white sand of a post-pliocene formation. 



