262 GREEN SAND AND CRETACEOUS. 
ter, appear at Ashwood and Wilmington, on the 
Cape Fear River, in North Carolina ; and in South 
Carolina they are again seen on Lynch's Creek, 
and on the Pedee and Santee Rivers, as well as in 
the region west of the city of Charleston. Farther 
south, "they occur in Sandersville, in Georgia ; and 
they occupy a large extent of country in Alabama. 
The same strata cover nearly the whole state of 
Mississippi, and also abound in the southwestern 
portion of Tennessee, Louisiana, between the Alex- 
andria and Natchitoches, and on the Washita Riv- 
er, and in Arkansas on the calcareous platforms of 
Red River. But, though these cretaceous forma- 
tions belong to the same period, yet the northern 
and southern sections present very marked differ- 
ences of mineral and fossil constituents. The 
northern, or green sand formation, may be said 
to extend through New-Jersey and Delaware, to 
the eastern shore of Maryland, over a nearly hor- 
izontal plain, the mean elevation of which above 
the sea is not more than from 40 to 60 feet, 
though in the northeast of Monmouth it rises 300 
feet above the sea. It consists of strata of a 
friable material, more or less arenaceous or ar- 
gillaceous in its texture, of a dark greenish or blu- 
ish colour, including bands or layers rich in a pe- 
culiar fossil, and characterized by a thick bed of 
green sand, or, as the inhabitants term it, marl. 
The northern and western portions of the newer 
secondary or cretaceous formations consist of lime- 
stone of various degrees of hardness, more or less 
abundant in fossils, and having the particles of 
green sand only sparsely disseminated through the 
mass. These limestone strata, which thus compose 
nearly the whole of the cretaceous group in the 
Southern States, exist on a scale of vast extent and 
thickness, rising into bold, undulating hills, resem- 
bling the surface of the chalk in Europe. 
The " marl" or green sand stratum contains, often 
as its sole ingredient, a peculiar mineral, in the 
