Maryland Geological Survey 87 



With the opening of the Magothy epoch a considerable change was 

 already manifest, although the lagoons must still have existed over much 

 of the area in which the rapidly alternating arenaceous and argillaceous 

 sediments were deposited. Somewhat varying deposits are found, but in 

 general the strata become persistent over wider areas and marine fossils, 

 such as characterize the Magothy areas in southern Maryland, as well as 

 farther north on the shores of Earitan Bay in New Jersey, indicate the 

 entrance of the sea in places. The area of sedimentation must, however, 

 have been near the shore, for land plants are splendidly preserved at many 

 points and doubtless lived at no great distance from the sea along the 

 coastal border. 



The rapidly alternating deposits of sand and clay over considerable 

 areas suggest current changes that may find their explanation in pro- 

 nounced seasonal differences. In other localities, however, homogeneous 

 deposits of considerable thickness give no such indications. 



There is little to suggest any great depth of water in the present known 

 area of Magothy deposition beyond the finding of traces of glauconite in 

 the more marine sediments at one or two localities. Although little is 

 known regarding the actual origin of glauconite, except through the 

 medium of foraminiferal disintegration, yet it is quite conceivable that 

 these slightly glauconitic beds may have been at inconsiderable depths 

 under conditions of slow deposition of terrigenous materials, since so 

 much of the Magothy lithology is littoral in character, as are also the 

 marine faunas. 



The close of Magothy time witnessed a further oscillation of the sea 

 floor with probable erosion along the coastal margin but with the early 

 renewal of seaward tilting which for the first time during the Cretaceous 

 period brought the sea widely over this portion of the Coastal Plain. The 

 very marked changes in sediments and the widespread uniformity of 

 materials suggest that the old barriers were broken down as the result of 

 a greater seaward tilting. To the north of Maryland there seems to be 

 some evidence of oscillation during Matawan time in the slight faunal 

 changes recorded, but in Maryland the marine faunas show but slight 



