SHALLOW WELLS.-Shallow wells in Anne Arundel County include not only those wells drawing from Pleistocene deposits but also many wells which have penetrated some older formation close to or even forming the surface. In the southern portion of the county where the surficial deposits cover the most of the region the wells range from 15 to 35 feet in depth, reaching a somewhat irony water at the base of the Pleistocene gravels. This water of course being strictly dependent upon the downward percolation of rainfall in the immediate vicinity may show some effects of dry spells, but extended droughts are very rare. In the northern and western portion of the county the wells must be sunk somewhat deeper, and since most of these wells report appreciable heads they will be discussed along with the artesian wells. One well at Earleigh Heights 40 feet deep has a hard water from the Magothy which stands 5 feet in the well. PRINCE GEORGE'S COUNTY Prince George's County lies almost wholly within the Coastal Plain province, the underlying crystalline rocks, which represent the seaward extension of the Piedmont Plateau, rise from the mantle of Coastal Plain deposits in limited areas in the extreme northwestern part of the county near the Montgomery County and District of Columbia line. The elevations range from the level of tide in the estuaries to over 400 feet near the northwestern boundary of the county southwest of Laurel. From the fall line, which is close to the line of the Baltimore and Ohio Railroad, the stream divides slope gently to the southeast at an average elevation of about 140 feet. This originally gently sloping country of unconsolidated sands and loams has been deeply dissected by the streams tributary to the Potomac and Patuxent rivers and is now much broken by a complex network of hills and valleys. There are a few exposures of the crystalline rocks of the Piedmont in the deeper valleys along the northern border of the county. These are dipping steeply to the southeast, and throughout the balance of the county are deeply buried by the unconsolidated sediments of the Coastal Plain. The latter outcrop at the surface in bands crossing the county from northeast to southwest, each formation disappearing by passing under the next youngest one toward the southeast. The Lower Cretaceous gravels, sands, and clays constituting the Patuxent, Arundel, and Patapsco formations, outcrop in the northwestern portion of the county. The Upper Cretaceous, made up of sands, clays, greensands, and shell marls, and comprising the Raritan, Magothy, Matawan, and Monmouth formations, outcrops from the valley of the Patuxent River between Governor Bridge and Hicks Mill to the Potomac at Fort Washington. The Aquia and Nanjemoy formations of the Eocene comprise more or less glauconitic clays and shell marls and outcrop in a broad belt 10 miles. or more in width extending from the mouth of the Magothy River to the Western Branch of the Patuxent River. The sands, clays, diatomaceous earth, and marls of the Calvert and Choptank formations of the Miocene occupy a wide area southeast of the Eocene. They are largely buried, however, by a thin layer of terrace deposits belonging to younger formations, and exposures are generally limited to stream valleys. The Plio cene (?) is represented by the gravels, loams, and sands of the Brandywine terrace which forms the surface cover over the stream divides, especially in the southern portion of the county. The three Pleistocene terraces, Sunderland, Wicomico, and Talbot, form mantles of loam, sand, and clay, becoming lower in elevation and less dissected by erosion as they become younger the oldest and highest plain, known as the Sunderland, being much dissected and forming the surface of the secondary stream divides below the Brandywine surface. Its elevation ranges from 200 feet in the northern and central portions of the county to 180 feet in the southern portion. The next younger or Wicomico, which lies at elevations. of from 90 to 100 feet, is found in all the stream valleys and is especially well developed in the Potomac Basin. The youngest or Talbot terrace forms a but slightly broken plain lying below 45 feet in elevation. It is found in all the stream valleys and is especially well developed in the valleys of the Anacostia and Patuxent rivers. SURFACE WATERS Situated between the Patuxent and Potomac, both tidal rivers, the county is drained by small tributaries of these two streams. With the exception of the power developed in the Patuxent at Laurel there is no water power of any considerable value in the county, although small powers on tributary streams are utilized at several localities for grist mills. With the exception of Takoma Park in the District of Columbia, which utilizes the waters of Sligo Creek for the municipal water supply, the surface waters are not used for domestic purposes nor is such use to be recommended in areas as thickly settled as Prince George's County. UNDERGROUND WATERS Artesian supplies have been obtained in Prince George's County only from strata of Cretaceous age, and all of the wells except those at one locality, Upper Marlboro, where the Magothy vein is in use, draw from beds of the Lower Cretaceous. Of the other water horizons, the MatawanMonmouth, which in Calvert and St. Mary's counties assumes great impor tance, probably does not exist as a water-bearing bed, since these formations outcrop in continuous beds in only the lower part of Prince George's County and cannot be expected to furnish water except possibly at the southeastern tip around Trueman Point and Chalk Point. Here these lie at a depth of about 85 feet below sea level, and flows may be secured if the well mouth is located within 10 feet of tide. The Eocene horizons which also supply the water in some wells in the neighboring counties have not, so far as known, been tapped by any artesian well in Prince George's County, although they may be expected to yield flows in the valley of the Patuxent from depths ranging from about 100 feet below tide at Nottingham to around 130 feet below tide at Trueman Point. Like the Calvert the Eocene water will not flow at altitudes greater than 10 or possibly a maximum of 15 feet. The sandy strata of the Magothy formation are water bearing over wide areas. In Prince George's County the Magothy supplies the water for the wells at Upper Marlboro and the vicinity, but although it extends under the southeastern portion of the county at depths ranging to 400 feet below tide, it has not been further exploited. At Upper Marlboro and Marlboro there are six wells with depths around 220 feet. These wells have a small flow at an altitude of about 30 feet. The following section taken from Darton shows a greater thickness of Eocene than would be expected, but it is possible that the lower part of the "greensand" should be referred to the Monmouth. 1 White water-bearing sand, lignite and silicified coarse sand......215-222 The water from the Magothy has been stated by the authors of the Patuxent folio, and repeated by Miller, to be characteristically irony or 1 Darton, N. H. U. S. Geological Survey, Bull. 138, p. 134. 2 U. S. Geological Survey, Patuxent folio, p. 12. 3 Miller, B. L. Maryland Geological Survey, Prince George's County. |