MARYLAND GEOLOGICAL SURVEY 131 



elevation was probably proceeding slowly, as the Matawan and Mon- 

 mouth formations are found outcropping farther and farther to the 

 southeast. 



After the deposition of the Monmouth formation land movements 

 again caused the shore line to retreat eastw^ard, but to what point is 

 not definitely known. Farther north, in I^ew Jersey, deposition 

 still continued in some places, for the Rancocas formation, which 

 overlies the Monmouth formation and is not recognizable in the 

 Maryland area, is there overlain by another and later deposit of 

 Cretaceous age, the Manasquan formation. 



SEDIMENTARY RECORD OF THE EOCENE. 



At the close of the Cretaceous period the recently deposited sedi- 

 ments were uplifted to form a land mass and sedimentation was suc- 

 ceeded by erosion. In early Tertiary time a depression carried 

 most of the region again beneath the waters of the ocean and the 

 Eocene deiwsits were formed. The great amount of glauconite 

 present in these formations indicates that the adjacent land mass 

 must have been low and flat, so that the streams carried only small 

 amounts of terrigenous material. The water in which this was 

 dropped was doubtless only a few hundred fathoms deep, as glau- 

 conite is not produced at great depths. The land-derived materials 

 at the beginning of the Eocene consisted of small, well-rounded peb- 

 bles which were deposited in several places in the region ; but later 

 the materials carried consisted of fine sand or clay. Many forms 

 of animal life existed in these waters and their remains now com- 

 pose layers of marl several feet in thickness. 



Studies of the fossils found in the Eocene deposits indicate that 

 there were many changes in the fauna during this time. These 

 changes were probably influenced to a greater or less extent by varia- 

 tions in physical environment, yet the character of the deposits them- 

 selves gives little evidence of such changes. Instead it seems that 

 the conditions under which the Eocene deposits were jiroduced were 

 remarkably uniform, considering the great length of time which 

 elapsed from the beginning to the close of the period. 



