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COUNTIES OF SOUTHERN MARYLAND

ANNE ARUNDEL COUNTY

Anne Arundel County lies wholly within the Coastal Plain province. The crystalline rocks which underlie the whole county and emerge beneath the sediments of the Coastal Plain to form the Piedmont Plateau country lying to the northwest, are exposed in the extreme western part of the county in the valley bottoms of the Big and Little Patuxent rivers.

The surface is rolling and much broken, particularly in the southern half of the county where the higher interstream divides are much dissected. Also along the boundary between Anne Arundel and Howard County some of the hills reach elevations of nearly 300 feet. The surficial deposits which constitute the plains of the Eastern Shore counties have been largely eroded in Anne Arundel County, where they are represented by remnants except the lowest or Talbot plain which is well developed on the necks of the northern part of the county. Broad tidal estuaries reach from the Patapsco and Chesapeake nearly half-way across the county.

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Nearly all the formations of the Coastal Plain are represented by outcrops in Anne Arundel County. They reach the surface in bands extending across the county from northeast to southwest and dip beneath the surface toward the southeast. The majority are unconsolidated sands and clays. The oldest of these, the Patuxent, Arundel, and Patapsco formations, form the surface in that part of the county lying northwest

of a line drawn from Hawkins Point to Patuxent Station on the Philadelphia, Baltimore and Washington Railroad. The more porous beds of these formations become important water horizons throughout most of the area of the county. The several formations of the Upper Cretaceous, which are exposed immediately southeast of the belt where the Lower Cretaceous lies at the surface, are thinner than the latter and of variable but in general sandy composition. Water is found in all of them, but especially in the older or Raritan and Magothy formations. Both the Aquia and Nanjemoy formations of the Eocene are represented at the surface. The former occupies considerable areas southeast of a line drawn from Gibson Island to Priest Bridge on the Patuxent River, and is an important horizon for underground water in the southeastern part of the county. The overlying Nanjemoy formation is exposed in only a limited area in the southern part of the county and is unimportant in this region as a source of underground water, although it becomes an important water horizon farther south in Calvert County. It must be repeatedly emphasized that an important water zone in the upper part of the Aquia formation has long gone by the name of the Nanjemoy water horizon, and this somewhat confusing usage is continued in the present report rather than cause greater confusion by the changing of the name, since the reader is more interested in the actual water zones than in the terminology of the water beds.

The Calvert formation of the Miocene is widely distributed in the southeastern part of the county, but is an unimportant water zone in this region. It becomes of great importance in Southern Maryland and on the Eastern Shore south of Kent County.

The surficial terrace formations of Pliocene (?) and Pleistocene age are all represented in Anne Arundel County, but are much dissected by erosion and are unimportant except as sources of small springs and shallow dug wells. They usually carry water at their base which can be obtained. at shallow depths, but is subject of fluctuations in amount and is readily contaminated by surface seepage, so that in a region as thickly settled as parts of Anne Arundel County these shallow waters can only be utilized with the greatest caution.

SURFACE WATERS

The principal streams of the county are tidal estuaries reaching back from the Patapsco River and the Bay. There is little swamp land, and these rivers are most important as sites for summer homes and avenues of communication between the truck farms of the county and the Baltimore market. As sources of water power or public or private supplies they are not utilizable since the larger estuaries are brackish and even the small streams have a low gradient, small supply, and are almost invariably subject to contamination. The Patuxent, which forms the southwestern boundary of the county, furnishes some water power at Laurel in the adjoining county of Prince George's, but it is of no importance as a source of water supply or power in this county since it is lined by swamps and full of organic matter. It only becomes navigable just before leaving the county.

UNDERGROUND WATERS
Artesian Waters

Because of the relief, and absence over wide areas of sands and gravels of Pleistocene age, the inhabitants of the greater portion of the county are forced to extend their wells down to some porous bed, usually the nearest to the surface at that point. Most of these shallow artesian wells draw a water that differs very slightly from the surface waters of the Pleistocene.

The Miocene deposits outcrop only in the southern portion of the county and do not, as far as available records show, yield any water. The base of the Calvert is exposed along the bay shore at the southern end of the county, preventing the storage of rainfall. Across the Calvert County line at Chesapeake Beach many wells have a flow of Calvert water from 85 feet.

Numerous wells in the lower part of the county draw water from beds of Eocene age, the majority of them tapping the horizon called Nanjemoy, which, as is explained earlier, is not stratigraphically Nanjemoy but Aquia. However, because of the presence of another, the basal Aquia water level, this upper horizon will continue to be called Nanjemoy in accordance

with the water-supply literature which in the past has rather accurately drawn its depth but has misinterpreted its position in the column. Little more closely approached the correlation here given when he states that "the water-bearing horizon seems to be about midway in the Aquia." Experience with the other counties puts it higher than this, about 75 to 90 feet above the base. This upper horizon is the level which furnishes the flowing wells in the low district east of Sudley, which range in depth from 90 to 160 feet. These wells flow a few gallons a minute at altitudes less than 12 feet above sea level. The water is hard and carries appreciably large amounts of iron.

An analysis of the water from a well at Galloway 72 feet deep, owned by William Smith, is given below:

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This horizon will not be of importance west of Sudley (where it might be expected about 100 feet below tide) since the head will be very low, although three wells at Tracy's Landing 135 and 140 feet deep have reached the Nanjemoy water, and with an elevation of 25 feet at the mouth of the well have small flows. There seems to be some slight variation in the depth to this water, due probably to the clays which may be locally developed. However, the deviation from normal is not very great.

Below the Nanjemoy level is the stream at the base of the Aquia which has been tapped by several wells in the county. One at Fairhaven 270 feet deep is thought to draw from this horizon, although definite information regarding the length of the casing could not be obtained. Several wells.

'Little, H. P. Md. Geol. Survey, Report on Anne Arundel County, p. 132, 1917.

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