44 THE PHYSICAL FEATURE'S OF CECIL COUNTY 



The Upper Cretaceous Formations. 



To Professor George H. Cook is due the credit for first differentiat- 

 ing the Upper Cretaceous beds of the Atlantic Coastal Plain. In 

 1854, Cook announced that the Coastal Plain deposits contained three 

 distinct beds of marl, a discovery which he elaborated considerably at 

 a later period, for in 1868 he announced that the Coastal Plain of 

 New Jersey carried the following beds: Clay Marl, Lower Marl, 

 Ked Sand, Middle Marl, Yellow Sand and Upper Marl. Before this 

 announcement had been made, however, Philip T. Tyson had dis- 

 covered the presence of Cretaceous beds in Maryland and had mapped 

 them in Cecil county, although he did not determine their sub- 

 divisions. 



Uhler and Darton later also took part in the discussion, but con- 

 fined their work mostly to the Cretaceous as developed on the western 

 shore of Maryland. Darton named it in part the " Severn formation/' 

 and noted its presence on Elk Neck in Cecil county. 



In 1891, Professor Clark took up the investigation of the Upper 

 Cretaceous formations of New Jersey where Professor Cook had 

 left it. He prepared, in 1892, a map of Monmouth county, New 

 Jersey, in which Cook's terms were used, but in 1893 he abandoned 

 Cook's nomenclature and substituted the following: Matawan forma- 

 tion = Clay Marl; Navesink formation = Lower Marl; Red Bank 

 formation = Red sand; Rancocas formation = Middle Marl; Manas- 

 quan formation = Upper Marl. In 1894, he announced the continu- 

 ation of many of these formations southward through New Jersey into 

 Maryland, and in 1897 published, with R. M. Bagg and G. B. Shat- 

 tuck as collaborators, a summary of the investigations which had been 

 carried from Atlantic Highlands to the Potomac river. This paper 

 was accompanied by two maps which showed the distribution of the 

 Cretaceous over the entire area, As the work was extended south- 

 ward, it seemed necessary to unite the Navesink and Red Bank forma- 

 tions into one member, which was known as the Monmouth formation. 

 The Matawan, Monmouth and Rancocas formations were all repre- 

 sented on the map as present in Cecil county. 



