MARYLAND GEOLOGICAL SURVEY 9i> 



the Matawan and Monmouth is made chiefly on the basis of change 

 in lithologic character, but in part on that of the fossil contents. 

 Although some organic forms range through both the Matawan and 

 Monmouth, yet each formation has a few characteristic forms, the 

 assemblage in each being on the whole fairly distinctive. 



The Monmouth Formation. 



The name Monmouth was first proposed for this formation in 1897 

 by W. B. Clark^ when it was decided to combine in a single unit the 

 deposits formerly included in the Navesink and Eedbank formations. 

 It was suggested by Monmouth County, ISTew Jersey, where the de- 

 posits of this horizon are characteristically developed, and replaces 

 the term Lower Marl bed of the earlier workers in N"ew Jersey. On 

 the basis of its marine fauna it is correlated with the Senonian of 

 Europe. 



Areal Distribution. — Within this county the Monmouth formation 

 lias only a slight development. It outcrops in the vicinity of Colling- 

 ton and eastward from that place to Patuxent Kiver and thence 

 southward along the banks of the stream to the vicinity of Governor 

 Bridge. The Monmouth dips to the southeast and is believed to 

 underlie the Eocene and Miocene deposits to the southeast of its ont- 

 crop. In its wider distribution the formation has been recognized 

 by outcrops in a zone extending from the northeastern portion of this 

 county to Earitan Bay in New Jersey. 



Character of Materials. — The formation is prevailingly arenaceous 

 in character and nnconsolidated except where locally indurated by 

 the segregation of ferruginous material derived from tlie glauconite. 

 The sands composing the Monmonth deposits vary in color from red- 

 dish brown to dark green or nearly black. The fresh material always 

 contains considerable glauconite and this gives to the deposits their 

 dark color. In their more weathered portions the sands generally 

 range in color from rich brown to reddish brown, but at some places 

 they are dark gray. 

 iClark, Bull. Geol. Soc. Amer., vol. VIII, 1897, pp. 315-358. 



