MARYLAND GEOLOGICAL SDKVET 123 



adjoining the Potomac and Patuxent rivers, where flowing wells can 

 be secured at moderate expense. Also in those localities the water in 

 the shallow wells is sometimes brackish and at times become stagnant 

 and unfit for drinking purposes. Few flowing wells are known within 

 the county with siifficient artesian pressure to force the water more 

 than a few feet above tide. The well at Chaptico, which rises 32 feet 

 above tide, is exceptional. The water obtained in the artesian wells 

 usually contains some mineral matter in solution but not sufBcient to 

 interfere with its use for most piirposes. When the wells are protected 

 from surface contamination, the artesian water is the most healthful 

 water obtainable in the county. 



There seems to be three distinct water horizons that furnish the supply 

 for artesian wells thus far sunk. One of these occurs in the deposits of 

 the Aquia formation, one of the members of the Eocene, which probably 

 underlies the entire county but nowhere appears at the surface in this 

 region. To the northwest of St. Mary's County, in Charles County, it 

 rises to the surface and outcrops along many of the streams. The other 

 horizons occur in the Miocene strata, one near the base of the Calvert 

 formation and the other probably in the Choptank formation. 



The Eocene Jiorizon. — Tliis horizon supplies several artesian wells 

 along the Potomac Eiver in the western part of the county. A well at 

 Chaptico from which the water flows to a height of 22 feet above tide 

 penetrates this horizon at a depth of 291 feet. Another well, 275 

 feet deep, 2 miles west of Maddox, obtains its water from the Eocene, 

 perhaps from strata somewhat higher than the water-bearing beds in 

 the Chaptico well. Other wells supplied with water from the Eocene 

 horizon include several wells at Oakley about 305 feet in depth, and 

 one at Bushwood 287 feet deep. This horizon undoubtedly extends to 

 the eastward, but since east of Oakley artesian water is obtainable from 

 Miocene strata at shallower deptlis borings have not been extended to the 

 Eocene horizon. 



The Miocene horizons. — The principal water-bearing horizon for the 

 greater part of the county lies near the base of the Calvert formation. 

 Many wells have been sunk to this horizon and a good supply of water 



