142 PHYSIOGRAPHY AND GEOLOGY OF THE COASTAL PLAIN PROVINCE. 



rence in a letter to the editor of the Farmer's Eegister dated June 26, 1834, 

 and expressed himself as hopeful that other localities might be found in 

 that region which would furnish as good greensand for fertilizing purposes 

 as that of the New Jersey Cretaceous deposits. 



Strike, dip, and thickness. — The strike of the St. Mary's formation is 

 almost due north and south throughout Virginia but north of the Potomac 

 Eiver in Maryland the strike gradually changes to a northeast-southwest 

 direction. The dip of the strata is to the east at about 10 feet to the mile. 

 The maximum thickness of the formation is about 150 feet although this 

 is attained only after the formation disappears beneath the tide, the out- 

 cropping portion of the formation being somewhat thinner. 



Paleontologic character. — The St. Mary's formation is very rich in fos- 

 sil remains as in the case of the other Miocene formations, the forms con- 

 stituting an extremely varied marine fauna, essentially molluscan in char- 

 acter, although containing representatives of nearly all the leading groups 

 of animals from the Protozoa to the Mammalia. The only plants thus far 

 recognized are a few diatoms although there is no doubt but that a careful 

 examination of the sands and clays would show the presence of a large 

 number of diatom species. The St. Mary's formation is found in "West- 

 moreland, Eichmond, jSTorthumberland, Lancaster, Middlesex, Gloucester, 

 James City, York, Surrey, Isle of Wight, Nansemond, Sussex, and South- 

 ampton counties. Along the Potomac Eiver it appears first in the lower 

 part of "Westmoreland County ; along the Eappahannock Eiver in the vicinity 

 of Bayport; between the York and James rivers in several stream cut- 

 tings west of "Williamsburg, and along the James Eiver in many excellent 

 exposures at Dillards Wharf, Claremont, Schmidt's Bluff, etc. : in numerous 

 exposures along the Blackwater and Nottoway rivers in Isle of Wight, 

 Southampton, and Nansemond counties; and in frequent exposures along 

 the Meherrin Eiver both in A' irginia and North Carolina. 



DETAILED SECTIONS. 



SI'X'TIONS EXPOSED IN SMALL STREAMS ON '^NORTHERN NECK." 



The St. Mary's formation is exposed in numerous places on the penin- 

 sula between the Potomac and Eappahannock rivers. The exposures sel- 

 dom show more than a few feet of Miocene blue sand outcropping beneath 

 the Pleistocene cover. 



One-half mile north of Litwalton where the road crosses the stream 

 there is a very good exposure of Pleistocene brown sand about 25 feet in 



