LONG-ISLAND DIVISION. 
273 
4. That these strata, like those of New-Jersey, Maryland, Delaware and Virginia, overlie 
the mass of strata containing the white, mottled, red, and brown pyritous clays, and the 
sands containing lignite ; and underlie the drift and quaternary deposits. 
5. That the fossil shells found on Long island, as nearly as can be ascertained from published 
sections, and from the testimony of those that have found them in excavations, seem to be 
located beneath the drift deposits, and above the white, variegated and pyritous clays, and 
sands containing lignite. 
It follows from these facts, that the lower part of the Long-island division, embracing the 
white, mottled, red and pyritous clays, with their associated beds of gravel, conglomerate, 
and sand containing lignite, are geologically equivalent to the beds in New-Jersey called by 
Prof. Rodgers the Potter's clay formation* and to the lower division called by others the 
Greensand formation, Ferruginous sand formation, Cretaceous formation, etc.; and that 
the overlying loams, and clays containing the green earth, with associated sands, gravel, etc. 
are equivalent to the green marl deposits, or to the tertiary, or perhaps to both these periods. 
The facts now known and published are not sufficient to decide their exact equivalency, 
but it is probable that these deposits, and those containing the shells, belong to both the green 
marl and tertiary epochs. 
Fig. 7, Plate 4, and some others that have already been mentioned, show two distinct 
epochs of deposition in these strata below the drift deposits. 
2. Physical causes of this formation. 
Origin of the materials. It is universally admitted that the materials of the sedimentary 
strata, among which those of the formation under consideration may be classed, are derived 
from the disintegration, decomposition and abrasion of older rocks, and from animal and 
vegetable secretion. 
It is also well known to those who have investigated the geology of the Southern and Middle 
Atlantic States, that there is a long and broad belt of primary rocks, extending nearly parallel 
to the primary Atlantic chain of mountains, but some distance from it, that are remarkably 
prone to disintegration and decomposition, from Georgia to Maryland. They reappear; or 
rocks somewhat similar, and also prone to rapid disintegration, emerge in the southeast part 
of Connecticut, extend across Rhode-Island, and probably across Massachusetts under more 
recent rocks. These rocks are various in character, composed of granite, gneiss, hornblendic 
and talcose rocks. The materials resulting from their decomposition and disintegration are 
extremely various in their aspect and composition. Red, green and yellow are common colors 
of the sands, loams and clays. I have seen decomposing and disintegrating rocks in North- 
Carolina, between Hillsborough and Charlotte, producing a material which bears a striking 
* Geological Report of New-Jersey, 1840, p. 170. 
35 
Geol. 1st Dist. 
