MARYT^A^^D GEOLOGICAL SURVEY 31 



articles describing Eocene fossils from this County. He also made 

 some valuable correlations as a result of his paleontological investi- 

 gations. 



Finch and Lea in 1833, described the Eocene exposures at Fort 

 Washington. Ducatel studied the Eocene formations purely from 

 an economic standpoint in his attempts to determine the value of 

 greensand as a fertilizer. In his reports he makes frequent refer- 

 ences to the greensand deposits of this region and gives some sec- 

 tions of the strata exposed at certain localities. 



In 1845 and again in 1856 Bailey published descriptions of 

 microscopic fossils found in the marls at Fort Washington. How- 

 ever, we cannot be positive as to the age gf the strata from which 

 they were obtained as the Eocene and Cretaceous had not then been 

 differentiated in that region. 



Tyson in his geologic reports discussed the economic value of the 

 greensand marl deposits of the County. Heilprin, in 1881-2 and 

 in 1884, published articles dealing almost entirely with the correla- 

 tion of the Eocene deposits of the Atlantic Coastal Plain. He con- 

 sidered the deposits at Upper Marlboro, Piscataway, and Fort Wash- 

 ington, the oldest representatives of the Eocene and referred them 

 to the Eo-Lignitic member, which forms the base of his Eocene series. 

 Since 1888 Clark has been the principal investigator of the Eocene 

 deposits of Maryland and in several of his published articles he 

 has referred to the Eocene strata of Prince George's County. He 

 proposed the classification of the Eocene adopted in this report. 

 The most complete article is by Clark and Martin in the Eocene 

 volume of the Maryland Geological Survey published in 1901. In 

 this volume the fossils of the region are fully described by specialists 

 and each recognized species is illustrated. 



The Miocene. — The Miocene strata, although extremely fossili- 

 ferous elsewhere in Maryland, are almost devoid of megascopic 

 fossils in Prince George's County, consequently there are few refer- 

 ences in the literature to the Miocene deposits of the region. In 

 1838, Conrad, who called the Miocene the Medial Tertiary, referred 

 to these deposits as overlying the Eocene in the vicinity of Upper 

 Marlboro and Fort Washington. 



