66 The Upper Cretaceous Deposits of Maryland 



about two miles. In the interstream portions of Anne Arundel County 

 it extends from water level to the higher points of the region, and 

 although of less thickness it covers a wider area from northwest to south- 

 east on account of the more elevated character of the country. Beyond 

 the Patuxent River the outcrop gradually narrows until it disappears 

 entirely before the center of Prince George's County is reached. A few 

 outliers are found on Elk Neck in Cecil County and at a few points in 

 Anne Arundel County. 



Lithologic Characters. — The Matawan formation consists largely 

 of dark-colored micaceous sandy clays, often glauconitic. At times the 

 deposits become very sandy and lighter-colored, while at other times they 

 form a black clay. The upper part of the formation is generally pre- 

 dominantly arenaceous, the sands varying in color from almost white to 

 a dark greenish black. The beds in general are very persistent in char- 

 acter, and the rapid change of materials so common in the Raritan and 

 Magothy formations dot's not occur. A thin pebble bed at times marks 

 the base of the formation. Iron pyrites has been found at times in the 

 darker and more carbonaceous beds. 



The glauconitic constituent of the beds is much less pronounced thau 

 in the overlying Monmouth formation, although glauconite grains are 

 not uncommon. The decomposition of the glauconite in the weathered 

 beds produces reddish-brown materials that are at times indurated by the 

 hydrous iron oxide, producing thin ledges or crusts on exposed surfaces. 

 The deposits of the Matawan formation are quite unlike those of the 

 underlying Magothy and show by their pronounced stratification the dis- 

 tinctly marine conditions which prevailed during their deposition. The 

 homogeneous nature of the material over extended areas is in marked 

 contrast to the alternating sands and clays that are found so extensively 

 in the Magothy. The materials of the Matawan are on the whole much 

 more like the succeeding Monmouth formation, but the latter is more 

 arenaceous and glauconitic. and the dark-colored micaceous sandy clays 

 and black clays of the Matawan are rarely found. The Matawan deposits, 

 especially in Anne Arundel County, frequently contain large oval con- 

 cretions of clay ironstone which are very characteristic. 



