MESOZOIC ERA: THE AGE OF REPTILES 



509 



tinuous water bodies 

 but in river basins 

 analogous to the 

 Great Valley of Cali- 

 fornia. These conti- 

 nental deposits were 

 formed by the con- 

 fluence of alluvial 

 fans (p. 124) made 

 by streams flowing 

 from higher land at 

 the margin of the 

 area ; deposits formed 

 by rivers meandering 

 over the lowland ; 

 lake deposits in places 

 where the drainage 

 was obstructed, as in 

 Tulare Lake, Cali- 

 fornia ; and it is pos- 

 sible that parts of the 

 area were covered by 

 tidal waters and that 

 in such places estua- Fig. 480. — Map showing the probable outline of North 

 , . . .. America during a portion of the Upper Triassic. The 



nne deposits were laid continen tal deposits are shown in solid black. (Modified 

 down. Since the re- after Schuchert.) 

 gion was in an arid or 



semiarid condition, deposits of wind-blown sand were doubtless laid 

 down on land, some of which probably constitute a part of the 

 Triassic sandstone. 



These basins were separated from the Appalachian Mountains on 

 the west by ridges of crystalline rocks (Fig. 481). The presence of 



Fig. 481. — Section through the Connecticut valley and adjacent region in 

 Massachusetts. Js is Triassic sandstone. (After Emerson.) 



high land between the basins and the Appalachians is shown by the 

 composition of the sediments laid down in the depressions, which were 



