DISTRIBUTION AND CHARACTER OF MATAWAN FORMATION. 327 



2 or 3 miles. Farther to the south, upon the eastern shore of Maryland, 

 it again slightly broadens, and below the mouth of the Sassafras river 

 has a width of some 5 miles. Upon the western shore of Maryland, in 

 Anne Arundel county, its areal distribution is very variable on account 

 of the extremely broken character of the country, but upon the whole 

 has narrowed in extent as compared with the eastern side of the Chesa- 

 peake. In places it reaches 3 or 4 miles in width, but more often is less 

 than 1 mile. Farther to the south, in Prince George's county, it is found 

 simply as a narrow strip, at no point reaching a mile in width, and con- 

 tinues in and out along the slopes of the hills, following the contours of 

 the valleys. 



Character of materials. — The deposits of the Matawan formation are very 

 variable. Sands and clays predominate. The sands are at times white 

 and coarse, but are more commonly fine grained and deeply colored by 

 iron, which may even cause local induration, or they are mixed with 

 argillaceous materials, forming either a silvery micaceous sand or a choco- 

 late colored marl, in the latter case grains of glauconite being present in 

 greater or less amounts. 



The clays are generally black or drab in color, but may locally carry 

 seams and pockets of glauconite, which give it a greenish tinge. At a 

 few points the deposits are somewhat calcareous as the result of their 

 molluscan contents, but in general the beds are not highly fossiliferous. 



Strike, dip, thickness — The strike of the beds is north-northeast to south- 

 southwest, with apparent local variations where the overlying Cretaceous 

 and Tertiary deposits have been either more largely eroded or more fully 

 preserved, causing the line of outcrop to be at times diverted at a con- 

 siderable angle from the normal strike. This is seen in northern Mon- 

 mouth county where the stripping off of the cover of the later Cretaceous 

 formations has caused the widening out of the belt of the underlying 

 Matawan and has turned the line of contact very nearly at right angles 

 to the strike. Such variations may be easily detected when the normal 

 dip is present, but may lead to considerable complication when it is not. 



The dip of the formation is upon the average about 25 feet in the mile, 

 but locally it may be either slightly increased above or slightly de- 

 creased below this amount. The determination of the dip depends for 

 the most part upon records afforded by well-borings, although some of 

 the natural section lines, especially in the Mount Pleasant hills, New 

 Jersey, and along the Severn river, Maryland, afford valuable data. 



The thickness of the Matawan formation is very variable, but in general 

 becomes gradually reduced in passing from the northern to the southern 

 portions of its area of outcrop. In Monmouth county it has been found 

 to be about 275 feet, with a gradual thickening toward the southeastward, 



