66 The Lower Cretaceous Deposits op Maryland 



The dip of the beds is to the southeast, and is in general at the rate 

 of about 50 feet in the mile. It is greater in the Fall-line zone, as shown 

 in the Putty Hill, Carney, and Camp Chapel areas, and is less to the 

 eastward. 



The observed thickness of the Arundel formation varies from a few 

 feet to about 100 feet or perhaps 125 feet in the middle of the belt in 

 central Maryland. It apparently thins seaward, as shown by the well 

 ■ boring at Sparrows Point. 



Stratigraphic and Structural Kelations. — The Arundel forma- 

 tion overlies the Patuxent formation unconformably, occupying what 

 appear to be old drainage lines therein, but extending beyond these to 

 the seaward where it spreads into a more or less continuous sheet. The 

 formation rarely comes in contact with the crystalline rocks, but a few 

 instances are known, as at one locality north of Eelay and in the Camp 

 Chapel area. 



The deposits are unconformably overlain by the Patapsco formation, 

 or in the absence of the latter by the later Tertiary and Quaternary 

 formations. 



The internal stratigraphic and structural features are relatively simple, 

 the strata consisting for the most part of widely extended beds or lenses 

 of clay with included beds of lignite and iron ore. Some cross-bedding 

 is found in the basal beds landward but it is unusual. The strata give 

 evidence of deformation similar to the Patuxent beds in the Fall-line 

 zone, and are likewise affected by the general warping of the underlying 

 Patuxent previously described. 



Organic Eemains. — Both animal 'and plant remains occur in the 

 Arundel, its manner of deposition favoring the preservation of both. 



The Arundel fauna represents, so far as known, three orders : Dino- 

 sauria, Crocodilia, and Testudinata. 



The dinosaurs represent all of the sub-orders, including two of the 

 heavier, megalosaurian carnivores, Allosaurus and Creosaurus, and one 

 of the lighter, compsognathus type, Ccelurus. The quadrupedal Sau- 

 ropoda are represented by at least one genus, possibly two, Pleuroccelus 

 and Astrodon, including two or three species in all, while of the Orthop- 



