REDBANK SANDS OF MONMOUTH FORMATION. 



335 



mouth county the Redbank sands have a thickness of about 100 feet, 

 which declines gradually to the southward until in the Pine Hill region 

 it has dropped to about 60 feet, from which point it still further declines 

 to the region of Red hill, in Burlington county, beyond which it entirely 

 disappears unless replaced by the argillaceous deposits which have been 

 above described. 



The Redbank sands, as developed in the north, do not occur through- 

 out southern New Jerse}', but reappear in Delaware and the eastern coun- 

 ties of Maryland, where their characteristic features are again developed 

 and where they have a thickness in the Sassafras river basin of about 60 

 feet. They decline somewhat in thickness toward the Chesapeake bay, 

 and upon the western shore of the Chesapeake cannot be distinguished 

 from the other members of the Monmouth formation. The deposits, in 

 the two areas where all the members are characteristically developed, 

 consist typically of very red sands which in their more unweathered por- 

 tions carry grains of glauconite. Beds of dark sandy marl and black 

 micaceous clay are at times interbedded with the sands, the former fre- 

 quently occurring at the base while the latter is more common higher in 

 the series. A greenish gray or reddish clay, more or less indurated, occurs 

 at the very top of the formation in Monmouth county and forms a firm 

 unyielding capping for the Monmouth formation (plate 47). 



Fossils. — The fossils of the Monmouth formation are very numerous 

 and well preserved, at times forming solid shelly layers. Many of the 

 species are identical with those found in the Matawan formation, while 

 a few are found ranging upward into the Rancocas formation. A con- 

 siderable number of forms are restricted, however, to the Monmouth 

 itself. Among the characteristic and common species found in this for- 

 mation and determined bv the authors are the following : 



t Bolivina punctata, D'Orbigny. 



Marginulina trilobate, D'Orbigny. 

 • Vaginulina strigillata, Reuss. 



Cristellaria cultrata, Montfort. 



, Oslrea larva, Lamarck. 



Ostrea tecticosta, Gabb. 

 v Ostrea crenulima rginata, Gabb. 



Gryphea convexa, Morton. 



Gryphea vesicularis, Lamarck. 



Exogyra costata, Say. 



Anomia argentaria, Morton. 

 ^Camptonectes parvus, Whit. 



Xelthea qubiquecostata, Sowerby. 

 "■ Spondyhis gregaiis, Morton. 

 ? flicatvla urticosa, Morton. 



Catopygus pusillus, Clark. 

 3 Cassidulus florealis, Morton. 

 v Terebratella vanuxemi, Lyell and Forbes. 



A.rinea mortoni, Conrad. 



Nulcalana protexta, Gabb. 



\Trigonia mortoni, Whit. 

 . Trigonia cerulea, Whit. 

 \ Crassatella vadosa, Morton. 

 " Crassatella subplana, Conrad. 

 • Diceras dactyloides, Whit. 



Cardium eufaulensis, Conrad. 



Cardium dumosum, Conrad. 

 - Cardium multiradiatum, Whit. 

 v Leiopistha protexta, Conrad. 



