102 THE GEOLOGY OE PRIXCE GEORGE S COUXTY 



This is one of the longest and best kno\\Ti localities for fossils in the 

 Eocene of the Atlantic slope. The following section is exposed : 



Section east of bridge at Upper Marlboro, Md. 

 Naxjemoy: Feet. 



Glauconitic clay 22 



Pink clay, without glauconitic or fossils 22 



Aquia (Paspotansa substage) : 



Coarse glauconitic sand 32 



Shell marl M^ith Gibbula glandula, Fissuridea viarlboroensis. 

 ' Lucina aquiana, Diplodonta marlboroensis. Venericardia 

 planicosta var. regia, Pteria limula, Cucullaea gigantea, 

 Leda parilis, Nucula ovula 2 



Indurated ledge with Turritella mortoni. T. humerosa, 

 Mesalia obruta, Cahjptraphorus jacksoni, Panopea elon- 

 gata, Meretrix ovata var. pyga, Dosiniopsis lenticularis, 

 Venericardia planicosta var. regia, Crassatellites alaefor- 

 mis. Astarte marylandica. Glycymeris idonens, Cucullaea 

 gigantea, Leda parilis, Nucula ovula 5 



Glauconitic sand (known as Bryozoan sand) full of fine 

 fragments of shells accompanied by Bryozoa, echinoid 

 spines, and Foraminifera; and with Ostrea compressiros- 

 tra, Gryphaeostrea vomer, and Platidia marylandica .5 



Paleontologic Character. — A great many fossils are to he seen in 

 the outcrops of the Aquia along the Patuxent River and in the valley 

 of Piscataway Creek. An idea of the variety of fossils that occur in 

 these localities may be gained by consulting the section above. The 

 fossils of this formation have been described and illustrated in the 

 report on the Eocene issued by the Maryland Geological Survey. 



Strike, Dip, and Thickness. — The Aquia formation is about 100 

 feet thick in this county and gradually thickens toward the east, 

 beneath the later formations. It has a northeast-southwest strike and 

 dips to the southeast at the rate of about l^y^ feet to the mile. 



Stratigrapliic Relations. — The Aquia formation overlies the Mon- 

 mouth unconformably and is overlain conformably by the ISTanjemoy 

 formation. Where the ISTanjemoy has been removed by erosion it is 

 covered by Miocene, Lafayette, or Pleistocene beds. 



Subdivisions.- — The Aquia formation has been subdivided into two 

 members or substages known as Piscataway and Paspotansa, which 

 are distinguished from each other by their contained fossils. 



