356 W. B. CLARK — UPPER CRETACEOUS FORMATIONS OF NEW JERSEY. 



and at Woodbury, in Gloucester county. Many millions of bricks are 

 annually produced at these places. 



The Matawan formation in New Jersey has also been worked in its 

 more glauconitic layers, both in the Crosswicks clays and Hazlet sands, 

 for greensand marl, but very little is being done at the present time. 



The workable marls come chiefly from the succeeding formations, all 

 of which, from the Monmouth to the Shark river, have produced valu- 

 able fertilizers throughout the area of their occurrence. The Monmouth 

 formation was the earliest worked, and extensive pits were opened in 

 Monmouth county. New Jersey, where it is most highly glauconitic. 

 Throughout central and southern New Jersey little digging has been 

 done at this horizon, as the deposits become too argillaceous ; but in 

 Delaware, especially in the vicinity of the Chesapeake and Delaware 

 canal, the thin but very marly layers have yielded thousands of tons in 

 quite recent years. 



The Rancoeas formation, more particularly in its lower division, has 

 been worked for marl at several points in Monmouth county, especially 

 in the southwestern part, at and near Hornerstown. It has been most 

 largely developed for this purpose in recent years, however, in the more 

 southern counties' of the state, at Blackwood, in Camden county; at 

 Sewell and Mullica Hill, in Gloucester county, and about Woodstown, in 

 Salem county. The same beds have been worked to some extent in 

 Delaware and on the eastern shore of Maryland, particularly in the val- 

 ley of the Sassafras river. 



The marl richest in fertilizing ingredients belongs to the Manasquan 

 formation, which, with the Shark River formation, which overlies it, has 

 been worked largely in eastern Monmouth county (plate 49, figure 1). 

 The Squankum marl, so called, obtained near Farmingdale, has been 

 extensively exported and is in high repute. Very large pits were also 

 opened at Vincentown, Burlington county, and are still worked to some 

 extent. 



The greensand marls were first used as fertilizers in 1768, the first re- 

 corded pit being opened near Marlboro, Monmouth county, New Jersey. 

 It was not, however, until 1820 that the marl came into general use, and 

 for the next half century millions of tons of it were employed for agri- 

 cultural purposes. Much of it was dug from small openings for local 

 consumption by the land-owners whose farms were in the marl district, 

 or was hauled by wagons into the neighboring county. A great number 

 of larger pits were opened by companies engaged in the marl trade, the 

 railroads oftentimes building branch tracks into the excavations. Thou- 

 sands of carloads were thus removed directly from the pits and shipped 

 to distant points. During the last 25 or 30 years, since the commercial 



