296 THE STRUCTURE AND SUCCESSION AT 



easily. It is possible that these strata alternate with concealed 

 limestones and marls, as farther east. 



Eastward toward the top of the series the cliffs become higher 

 and more continuous. Beds of calcareous sandstone, calcareous 

 red and green marl, and gray compact limestone alternate 

 rapidly. The sandstone varies in compactness and texture, some 

 breaking into slabs of several square feet, but scarcely one-fourth 

 to one-half inch thick, while others form large cubical or 

 rhombohedral blocks. The last varieti.es are especially 

 well mottleid with streaks and lenses of carbonaceous matter, so 

 regularly arranged as to give considerable relief to the usual 

 monotony of color in the cliffs. All the sandstones are red or 

 brown, except a six-inch bed of hard gray rock, almost a 

 quartzite, which overlies one of the gray limestone strata. Some 

 of the flagstones are well ripple-marked, the wind having come 

 from the east, and contain fine worm-like trails, too indistinct 

 to ascribe to any particular origin. Rain-prints are also exposed 

 on these beds. The weathering is often irregular, in one 

 instance the softer black carbonaceous matter having entirelv 

 disappeared, leaving a skeleton reck. 



The calcareous marl exhibits all degrees of cohesion between 

 clay and shale. A bed of gypsum lies between two of marl; 

 and the overlying stratum of the three is practically all clay, 

 and contains a few small bedded stringers of fibrous gypsum, 

 each about cin,e-fourth inch thick. The limestone is of a slate- 

 gray color, com])act in texture, but not gritty. 



Succession. — A section of this formation is more difficult 

 to get than of either of the others. The lower part consists of 

 about 200 feet of laminated, shaly, micaceous sandstone, with a 

 considerable proportion of lime. In some parts the rock may 

 fairly be called a limestone. Above this a nearly continuous 



