SECTIONS IX POTOMAC RIVER VALLEY. 93 



the Potomac River the Aqiiia appears above tide from beneath the Nanjemoy 

 deposits about 4 miles below the mouth of Potomac Creek. The line of 

 contact can be followed to the west to the top of the divides between the 

 Potomac and Rappahannock rivers a short distance to the east of the R. F. 

 and P. R. R. The Aquia formation is also excellently exposed in numerous 

 places along nearly all the minor streams to the east of the railroad in Staf- 

 ford County and in many places along the lower courses of the leading 

 streams in northeastern Spottsylvania, northwestern Caroline, and western 

 King George counties. Along the James River the Aquia formation appears 

 in Richmond along Shockoe Creek beneath the clay and diatomaceous earth 

 deposits of the Calvert formation, and is similarly exposed in the valleys of 

 Gillis and Almond creeks. Probably the Eocene deposits exposed along 

 the ]S[ottoway River in Sussex County also belong to the Aquia formation. 



DETAILED SECTIONS. 



SECTIONS IN POTOMAC RIVER VALLEY. 



The Aquia formation is best exposed in the valley of the Potomac River 

 and its tributaries. Exposures can be traced from the high lands bordering 

 the District of Columbia southeastward until the formation reaches tide 

 along the Maryland bank of the Potomac River in Charles County and on 

 Aquia Creek in Stafford County, Virginia. Several sections from the 

 Maryland bank of the Potomac are given in order to show the relations and 

 detailed stratigraphy of the formation. 



I. Section at Glymont, north of ivharf and ravine. 



Feet 

 Pleistocene Gravel and loam 20 



Eocene. Aquia Piscatawaj' Light green glauconitic sand, underlain by 



argillaceous sand, with few fossils (Zone 



4) 10 



Indurated greensand (Zone 3) 1 



Greenish marl with numerous fossils includ- 

 ing Oslrea conipressirostra, Crassotellites 

 (daefonnis, Tnrritclla mortoni, Dosiiiiupsis- 

 lenficularis, Meretrix ovata var. pyga, etc. 



(Zone 2) 21 



Argillaceous glauconitic sand for the most 

 ))art without fossils, but containing inde- 

 terminate plant remains and molliisean 

 casts at the base (Zone 1 ) 8 



Lower Cretaceous. Patapsco Variegated clays of the Potomac group 20 



Total 80 



