tfOETH-CAROLINA GEOLOGICAL SURVEY. 83 



of the marl is better towards the bottom, or lower in the bank, 

 than where it is exposed. At certain points in New Jersey 

 it has a sandy base, but several feet above it becomes a rich 

 marl. 



The color of this kind of marl is green or dark green. It 

 is always rather sandy, but still it is rich even then in fertiliz- 

 ing matter. The Blackrock beds here have a dark green, or 

 greenish gray, and may be divided into two parts : the upper 

 which has a darker color, and is much like clay to the feel ; 

 and the lower, which is consolidated and of a greenish gray, 

 and rather gritty to the touch. There is no dividing line 

 which is so clearly marked that we can fix upon the termina- 

 tion of the lower, and the beginning of the upper division, 

 but still the difference observable is sufficiently strong to 

 admit of the division I have proposed ; though, geologically, 

 it may be regarded as one mass. The division is more im- 

 portant in an economical point of view, inasmuch as the 

 composition of the upper is quite dissimilar to the lower 

 bed. 



54. In New Jersey the green sand formation is composed 

 of six distinct beds ; three of which are known as green sand 

 proper, in consequence of the peculiar composition ; and three 

 which are composed of a common marine sand, and which 

 separates each of the respective beds from the other. In 

 North- Carolina it is probable that equivalent beds exist, but 

 it has been impossible up to this time to recognize but two. 

 At Blackrock the lowest is known by its fossils : the Exogyra 

 costata, Ostrea falcata, Belemintes Americana, and casts of 

 the cucullea vulgaris. This mass terminates in one which is 

 quite argilaceous, and in this part of it no fossils have been 

 observed. 



The third or upper bed may be probably recognized at 

 Tawboro', on the Tar river, at the marl beds of Col. Clark. 

 It is only about four feet thick, but is underlaid by sand, in 

 which much sulphuret of iron is disseminated. 



The annexed section, fig. 2, shows the relations of the beds 

 referred to upon the Tar river: 



