60 THE PLIOCENE AND PLEISTOCENE DEPOSITS OP MAEYLAND 



The most northerly outcrop of the Chesapeake beds is in the cliffs at 

 Gay Head on Marthas Vineyard, but material which has been provision- 

 ally referred to the Miocene has been dredged on Georges Bank and the 

 Banks of Newfoundland, indicating, if the reference is correct, the exten- 

 sion of the Chesapeake group indefinitely northward beneath the sea. 



Immediately south of Marthas Vineyard, the Chesapeake beds dis- 

 appear, but come to the surface again in New Jersey where they are well- 

 developed in the hills south of Matawan, as well as along the coast near 

 Asbury Park. From here, the Chesapeake beds extend southwest across 

 New Jersey to Delaware. In this region, two well denned formations are 

 recognized. The lower one is a greenish-blue sandy clay abundantly sup- 

 plied with fossils and is seen only in the southern portion of the State, 

 near Shiloh and Salem. The upper formation consists of a fine quartz 

 sand and clay grading upward into gravel. This member covers the 

 greater portion of the district. In deep well borings at Atlantic City, a 

 third and higher formation has been discovered. In Delaware the surface 

 of the country is covered with sands and gravels to such an extent as to 

 effectually obscure the underlying formations. The meager information 

 which has been secured from artesian wells and natural sections leaves 

 little room to doubt, however, that the central and southern portions of 

 the State are underlain by the Miocene. 



The Chesapeake beds enter Maryland from Delaware a few miles south 

 of Galena, and after crossing the State from northeast to southwest con- 

 tinue on into Virginia. Of all the districts of the Middle Atlantic slope, 

 southern Maryland is most favorably situated for the study of the 

 Chesapeake group. Within the borders of this district many of the 

 features which are wanting in other regions find their full development. 

 The materials composing the various formations, which are sandy or ob- 

 scured in other regions, here differentiate into three well defined forma- 

 tions, and the organic remains, so helpful to the geologist, while seldom 

 seen to the north and only occasionally met with to the south, are in 

 Maryland found in great beds many feet in thickness and miles in extent. 

 In other localities, the exploration of these deposits is greatly retarded 

 through lack of exposures, but in this State we have, in the famous Calvert 



