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



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as is shown in the wells at Asbury Park, where it has a thickness of about 

 400 feet. Along the strike toward the south it is already less than 200 

 feet in thickness in northern Burlington county, while in the region 

 directly to the east of Philadelphia and Camden it has further declined 

 to 125 feet. In Gloucester county it thickens again, having been found 

 in well-borings to exceed 175 feet in places. Farther to the south it thins 

 and in the vicinity of Salem has declined to 80 feet. In the state of 

 Delaware it is not over 60 feet, but it gradually thickens through the 

 eastern counties of Maryland until, near the mouth of Sassafras river, 

 it again exceeds 100 feet in thickness. In eastern Anne Arundel, upon 

 the western shore of Chesapeake bay, its thickness has already declined 

 to 60 feet, while in the region farther south, in western Anne Arundel 

 and Prince George's counties, it has still further diminished, until at the 

 Fort Washington bluffs it is but little more than 15 feet thick. Its last 

 appearance to the southward, so far as observed, is in the valley of Piscat- 

 away creek. Upon the opposite side of the Potomac the Eocene is 

 found resting directly upon the Potomac. 



Stratigraphlc relations. — The Matawan formation rests un conformably 

 upon Lower Cretaceous strata throughout the northern Atlantic Coastal 

 plain. Locally the line is at times not readily discernible, especially 

 when the upper portion of the Lower Cretaceous contains beds of dark 

 colored clay, such as characterize the strata to some extent in the north- 

 ern portion of the region. Commonly, however, the line of contact is 

 sharply defined, since the upper portion of the Lower Cretaceous con- 

 sists generally of white sands or fine gravel, which can be readily distin- 

 guished from the overlying Matawan. Not infrequently, however, in the 

 interstream portions of the country, the line of contact is obscured by 

 late Tertiary or Quaternary deposits, so that its location has to be hypo- 

 thetically determined for cartographic purposes, unless, well-borings can 

 be found or the beds reached by the geologist's auger. 



The Matawan formation is conformably overlain by the succeeding 

 formation, but the lithologic differences are so clearly marked through- 

 out the whole area of occurrence of the two formations that the line of 

 contact can be readily determined. 



Divisions — General characteristics. — The Matawan formation can be 

 readily subdivided upon lithologic grounds throughout the northern 

 portions of the area, while to the south these differences become gradually 

 obscured, until in the southern portion of New Jersey, in Delaware, and 

 in Maryland the divisions observed in the north can be no longer recog- 

 nized. 



The northern series will be considered under the head of the Cross- 

 wicks Clays and the Hazlet Sands, so called from localities where they 



