SECTIONS IN THE KAPPAHAXNOCK RIVER VALLEY. 143 



thickness. The sand contains a great quantity of black grains, principally 

 magnetite. About one-quarter mile farther north near the mill dam the 

 St. Mary's outcrops beneath an ironstone about 1 foot in thickness, forming 

 the base of the Pleistocene, which in this region is 68 feet thick. The Mio- 

 cene consists of fine buff sand containing many mica flakes. 



On the north side of the dam at Chinn's Mill on Lancaster Creek, 8I/2 

 miles north of Litwalton sandy drab clay belonging to the St. Mary's for- 

 mation is exposed. 



Section exposed on south side of the mill pond at Union Mills, one 



mile north of Downings and two miles south of Farnhams. 



Feet 

 Pleistocene or Recent Brown sandy loam 



Miocene. St. Clary's Sliell Itecl consisting principally of Melina 



maxillata with some specimens of Gly- 

 cymeris 8-13 in. 



Brown sand 14-16 in. 



Shell bed principally composed of Melina 

 maxillata, some specimens of Pecten 

 and Discinisca 15 in. 



Sand filled with upright worm tubes .... 8 in. 



Shell bed composed of innumerable small 

 Pelcypods, in matrix of sand .... about 3 



Total 131/3 



SECTIONS EXPOSED IN RAPPAHANNOCK RIVER VALLEY. 



The St. Mary's formation outcrops in many places along the lower 

 •course of the Eappahannock Eiver and admirably reveals the lithologic 

 characteristics of the formation. Fossiliferous beds are numerous and have 

 yielded a great variety of species. 



I. Section riglit hank of Rappahannock River, one-quarter of a mile below 



Jones Point. 



Feet 

 Pleistocene Red gravelly sand with iron crust at base.. 10 



Miocene. St. Mary's Red and yellow sand grading down into 



greenish-gray sand 24 



Red and yellow sand slightly indurated in 

 places 5 



Yellow and greenish-gray loose sand 17 



Drab clay thinly interlaminated with sand 

 layers 25 



Greenish-gray fossiliferous sand 8 



Total 89 



