632 PRINCIPLES OF STRATIGRAPHY 



to those of the Huang-ho and the Indo-Gangetic plain. Extensive 

 torrential deposits are absent here, the series being composed mainly 

 of sands and clays. The series goes back to late Jurassic or early 

 Comanchic time, and comprises four main divisions, the Patuxent, 

 Arundel, Patapsco, and Raritan. The organic remains in these 

 deposits are chiefly land plants, while the remains of a land fauna 

 have also been found. No marine organisms are known except in 

 the upper part of the series, the Magothy formation of New Jer- 

 sey, which, however, also contains land plants. Above this series 

 lie sands and clays with an Upper Cretacic marine fauna. These 

 deposits were spread upon a broad coastal belt by rivers coming 

 from the region of Pakeozoic and older strata on the northwest, 

 where peneplanation was in progress. The sea margin at this time 

 must have been some distance farther to the east than the present 

 coast. The rivers were numerous and more or less evenly spaced, 

 so as to produce a continuous series of confluent deltas which ex- 

 tended from Massachusetts to the Gulf of Mexico. Lan.dward the 

 subdivisions of this series are separated by erosion disconformities, 

 marking periodic upwarpings, but seaward they become thicker, 

 and the disconformities probably disappear. Somewhere east of 

 the present coast line these deposits probably pass into a continu- 

 ous marine series, now submerged. 



The fluviatile origin of these deposits is suggested by the dis- 

 continuity of the strata, beds and lenses of clay and gravel occurring 

 in sand and vice versa. Many of the clays are strongly variegated 

 in color, the state of oxidation of the iron varying both horizontally 

 and vertically, while concentrated segregations of the iron also oc- 

 cur. Such variable conditions for oxidation exist on river flood 

 plains, but not in lakes or on the sea bottom. The abundant plant 

 remains, which by their character show little transportation, as 

 well as the absence of marine, brackish or even lacustrine organ- 

 isms, strongly indicate fluviatile conditions, as do also the bones 

 of dinosaurs, turtles, and crocodiles. 



The Arundel formation appears to have been deposited within 

 stream valleys eroded in the Patuxent, and in this formation gyp- 

 sum has been found. This suggests greater aridity during the 

 period of deposition of this formation than during the time the 

 more widely spread sands and clays of the other divisions accumu- 

 lated. In the Raritan formation feldspathic sands occur, further 

 suggesting an increase in aridity, while lignitic quartz sands alter- 

 nating with highly oxidized sands testify to a variety of conditions. 

 Some of the quartz sands show the characteristics of dune deposits. 

 Upward the occurrence of lignites with Teredo borings marks the 



