150 THE COASTAL PLAIN FORMATIONS OF CECIL COUNTY 



The oldest rocks of the Coastal Plain in Cecil county belong to the 

 Potomac group and represent the Lower Cretaceous or the Lower 

 Cretaceous and Upper Jurassic. They are separable into three well- 

 defined formations, which are known, beginning with the oldest, 

 as the Patuxent, Patapsco and the Earitan. These deposits consist 

 of clays, sands and gravels, and bear great numbers of fossil plants. 

 They were laid down in an estuary and are separated by a great 

 unconformity from the rocks of the Piedmont Plateau on which 

 they rest. The Upper Cretaceous rocks follow next in the series 

 and consist of the Matawan and Monmouth formations. These beds 

 are composed of clays, sands and greensands, yield a few animal 

 remains and point to marine conditions of deposition. They lie un- 

 conformably on the Potomac beds. The Aquia formation, the only 

 representative of the Eocene, is the next member of the Coastal Plain 

 series. It lies unconformably on the Upper Cretaceous beds and like 

 them is composed of sand and greensand and points to the existence 

 of an ocean over the region which it now occupies. Above the 

 Eocene deposits and lying unconformably on them is the Lafayette 

 formation, which has been questionably referred to the Pliocene divi- 

 sion of the Neocene. It consists of clays, sands and gravels. It was 

 deposited in shallow water near shore but since its elevation above 

 ocean-level has been so vigorously attacked by erosion that only a 

 few outliers now remain along the western edge of the Coastal Plain 

 and the eastern border of the Piedmont Plateau. The deposits now 

 occupying the greatest surface area of the county belong to the Pleis- 

 tocene. They are known collectively as the Columbia Group and are 

 separated into the Sunderland, Wicomico and Talbot formations. 

 They record many of the events which took place along the shore of 

 the Pleistocene ocean when glaciers covered the surface of North 

 America only a little way toward the north. They lie unconform- 

 ably upon all formations which precede them and record an oscillating 

 shore-line which constantly changed its position. 



In prosecuting the geological work of Cecil county, the author has 

 been assisted in the field by Messrs. F. B. Wright and B. L. Miller. 

 Mr. A. Bibbins has also furnished numerous observations. 



