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Richmond

National Battlefield Park

Virginia

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park geology subheading
battle reinactment at Richmond Battlefield
Ricmond National Battlefield Park, Virginia

All of the park units lie within the Atlantic Coastal Plain Physiographic Province, immediately east of the transition zone (the Fall Line) between the Piedmont and Atlantic Coastal Plain Physiographic provinces. The Fall Line, which separates the two physiographic provinces, trends roughly north to south in this area. The Atlantic Coastal Plain Physiographic Province (hereinafter referred to as the Coastal Plain) comprises approximately 10,000 mi2 in Virginia.

The Coastal Plain consists of Cretaceous- through Quaternary-age sediments that thicken eastward; at the Fall Line, the sediments are very thin, whereas at the Atlantic Ocean coastline, the sediments are over 5,000 feet thick (Meng and Harsh 1988). In general, Coastal Plain sediments consist of unconsolidated interbedded gravels, sands, silts, and clays (Meng and Harsh 1988).

The geology of the Richmond and Seven Pines 1:24,000-scale topographic quadrangles has been mapped by Daniels and Onuschak (1974), providing detailed mapping for the Beaver Dam Creek, Chickahominy Bluff, Cold Harbor, and Gaines' Mill units. Additional details on the geology of the Cold Harbor unit can be found in Inners et al. (1995). Detailed geologic mapping (at a scale of 1:24,000) does not exist for the Drewry's Bluff, Dutch Gap, or Roxbury topographic quadrangles, which encompass the Drewry's Bluff, Fort Harrison, and Malvern Hill/Glendale units, however some details on the geology of the Drewry's Bluff and Fort Harrison units can be found in Inners et al. (1995). Less detailed geologic mapping for the Drewry's Bluff, Fort Harrison, and Malvern Hill/Glendale units exists at a scale of 1:250,000 (Mixon et al. 1989).

The Beaver Dam Creek unit is predominantly underlain by recent alluvium of Beaver Dam Creek (Daniels and Onuschak 1974). The majority of this alluvium consists of organic and poorly sorted deposits ranging from clay to gravel (Daniels and Onuschak 1974). Older (Tertiary) clayey silt deposits are exposed along the eastern and western boundaries of the unit (Daniels and Onuschak 1974). Mixon et al. (1989) mapped this area as the Late Tertiary Chesapeake Group.

Three geologic units are exposed in the Chickahominy Bluff park unit. The highest elevations are underlain by undivided Late Tertiary - Early Quaternary upland sand and gravel deposits (Daniels and Onuschak 1974). The bluff is cut into underlying clayey silt deposits, also of Late Tertiary - Early Quaternary age, and the bottomlands are underlain by more recent alluvial deposits of the Chickahominy River (Daniels and Onuschak 1974). Mixon et al. (1989) mapped the clayey silt deposits as the Late Tertiary Chesapeake Group.

The Cold Harbor and Gaines' Mill units are situated on a dissected upland plain that consists of early Pliocene-age interbedded gravelly sand, sandy gravel, and fine-tocoarse- grained sand (Inners et al. 1995). Daniels and Onuschak (1974) describe these surficial sediments as fluvial clays, clayey silts, sands, and gravels. Marine-deposited clayey silts, partly fossiliferous, with firm, well-sorted basal sand underlie the surficial sediments at both sites. Mixon et al. (1989) mapped these surficial sediments as the Late Tertiary Chesapeake Group. At both sites, the creek bottomlands consist of recent alluvium, which comprises organic and poorly sorted fluvial deposits that range in size from clay to gravel (Daniels and Onuschak 1974).

The Cretaceous-age Potomac Formation and minor amounts of the Quaternary-age Charles City Formation (Mixon et al. 1989) underlie the Drewry's Bluff unit. The Potomac Formation is characterized by quartzofeldspathic fine to coarse sand, interbedded with massive sandy clay and silt (Mixon et al. 1989). The Potomac Formation forms the steep bluff at this park unit (Inners et al. 1995). The Charles City Formation consists of a discontinuous, thin cap of sand, silt, and clay (Mixon et al. 1989).

The Fort Harrison unit is underlain by the Quaternary-age Windsor Formation and the Tertiary age Bacon's Castle Formation (Mixon et al. 1989). The Windsor Formation consists of sand, gravel, silt, and clay (Mixon et al. 1989) with some glauconite (Inners et al. 1995). The Bacon's Castle Formation is subdivided and mapped as two units. The unit underlying the Fort Harrison unit is characterized by thick-bedded gravel, grading upward into sand and sandy and clayey silt (Mixon et al. 1989).

The Bacon's Castle Formation, as described above for the Fort Harrison unit underlies the higher elevations of the Malvern Hill and Glendale units. The Chesapeake Group is exposed on the steep slopes on the west side of the battlefield and on the slopes on the east side of the battlefield along Western Run (Mixon et al. 1989). The extreme western edge of the battlefield unit is underlain by the middle Pleistocene-age Chuckatuck Formation, a geologic unit containing sand, silt, and clay, with minor amounts of peat (Mixon et al. 1989).

Hydrogeology

The regional hydrogeology of the Coastal Plain Physiographic Province is controlled by the configuration of the Coastal Plain sediments, i.e., the sediments are interbedded in a more or less regular sequence of layers of high permeability alternating with layers of low permeability. The layers of high permeability, which are generally composed of sand and sandy sediments, transmit ground water readily and are known as aquifers. An aquifer is defined as a water-bearing geologic unit. The layers of low permeability, which are generally composed of clay and clayey sediments, do not transmit ground water readily and are called confining units, or aquitards. Aquifers that are located beneath or between aquitards are termed confined aquifers.

The surficial aquifer is composed of permeable geologic materials and extends downward from elevations at or near land surface to the top of the uppermost aquitard, or to bedrock along the western edge of the Coastal Plain. Because there is no upper confining unit, it is called an unconfined aquifer. This shallow ground water in the surficial aquifer supplies most of the water by seeps and springs to small streams and many wetlands. The top of the saturated zone, called the water table, is free to rise in response to recharge (i.e. precipitation) and fall in response to discharge (i.e. from drawdown induced by pumping from wells completed in the surficial aquifer, or by supplying water to streams). Pumping from wells completed in confined aquifers affects water levels in those aquifers to a greater extent than the affect on water levels in the surficial aquifer by pumping in wells completed there. In this report, water in a confined aquifer is referred to as deep ground water, and water in the surficial aquifer is referred to as shallow ground water. A generalized hydrogeologic section and direction of ground-water flow in the Coastal Plain Physiographic Province of Virginia (McFarland 1997) is shown in Figure 10.

The Beaver Dam Creek unit is underlain by bedrock at an estimated depth of 200 to 250 feet below sea level (Meng and Harsh 1988). The unconsolidated Potomac Formation sediments above the bedrock form a probable unconfined aquifer, though some confined or semi-confined zones within the Potomac Formation sediments may exist at depth. Depth to ground water is consistently shallow, as this area serves as a ground-water discharge zone.

The Chickahominy Bluff unit is underlain by bedrock at a depth probably in the range of 100 to 200 feet below sea level (Meng and Harsh 1988). The unconsolidated Potomac Formation sediments above the bedrock form a probable unconfined aquifer. Ground water likely flows north and east towards the Chickahominy River. Depth to ground water is variable, on the basis of the variable topography.

On the basis of data in Meng and Harsh (1988), the sequence of aquifers and confining units underlying the Cold Harbor and Gaines' Mill units, with approximate depths below land surface, are as follows: from land surface to 210 feet, surficial (unconfined) aquifer; 210 to 230 feet, Middle Potomac confining unit; 230 to 320 feet, Middle Potomac aquifer; 320 to 350 feet, Lower Potomac confining unit; 350 to 650 feet, Lower Potomac aquifer; and at 650 feet, basement rock.

The Drewry's Bluff unit is underlain by approximately 150 feet of unconsolidated sediment, which likely is an unconfined aquifer. In the higher elevations of the unit, from land surface, the first 10 feet consists of a shallow capping unit, probably Pleistocene-age sand and gravel (Inners et al. 1995). Underlying this capping unit is a thicker sequence of the Potomac Formation, which extends to the top of basement rock (Meng and Harsh 1988). Basement rock (probably the Petersburg Granite, Inners et al. 1995) is at a depth of approximately 55 feet below sea level (Meng and Harsh 1988). On the basis of the variable topography, depth to ground water at this site is highly variable. In general, the water table is deepest beneath the higher elevations along the river and shallower along the western edge of the unit and in the deep erosive cuts. Ground water movement is likely eastward towards the James River.

The Fort Harrison unit is underlain by basement rock at a depth of approximately 75 to 125 feet below mean sea level. The Lower Potomac Aquifer is partially present but probably does not attain its full thickness; it is unknown whether or not it is fully confined. The Lower Potomac confining unit may be partially present and is probably less than 20 feet thick (Meng and Harsh 1988). The Middle Potomac Aquifer is likely discontinuous and not of its full thickness; the altitude of the top of this aquifer is approximately 35 to 55 feet above mean sea level (Meng and Harsh 1988). The thickness of the Middle Potomac confining unit is approximately 20 feet (Meng and Harsh 1988). Sediments comprising the Aquia Aquifer, the Nanjemoy-Marlboro clay confining unit, the Calvert confining unit, and the Yorktown-Eastover Aquifer are likely present in the subsurface over portions of the unit, but if present below the local ground-water table, they may not occur in the distinct and orderly sequence in which they occur farther to the east. The condition of these formations, with respect to whether they occur as confined, semi-confined, or unconfined aquifers, is unknown. Two wells, however, are reportedly screened in the Yorktown-Eastover and the Aquia aquifers (White et al. 2001); see section on Ground-Water Resources of the Fort Harrison unit.

The Malvern Hill and Glendale units are underlain by basement rock at a depth of approximately 250 to 400 feet below mean sea level. The altitude of the top of the Lower Potomac Aquifer is approximately 200 to 300 feet below mean sea level (Meng and Harsh 1988). The thickness of both the Lower Potomac and the Middle Potomac confining units is approximately 15 to 20 feet (Meng and Harsh 1988). The altitude of the top of the Middle Potomac Aquifer is approximately 50 to 90 feet below mean sea level (Meng and Harsh 1988). The altitude of the top of the Aquia Aquifer, which may be confined, partially confined, or unconfined across the unit, is approximately 10 to 40 feet below mean sea level (Meng and Harsh 1988). The thickness of the Nanjemoy- Marlboro clay confining unit is approximately 20 feet (Meng and Harsh 1988). Sediments comprising the Chickahominy-Piney Point Aquifer, the Calvert confining unit, and the Yorktown-Eastover Aquifer may be present in the subsurface over portions of the unit, but if present below the local ground-water table, they may not occur in the distinct and orderly sequence in which they occur farther to the east. The condition of these formations, with respect to whether they occur as confined, semi-confined, or unconfined aquifers, is unknown.

Topography and Soils

Topography of the Coastal Plain Physiographic Province in general is characterized by large, relatively level terraces or plateaus. These upland areas are bounded by steep embankments that form the margins of waterways. Waterways are typically edged by swamps and other wetlands over much of their floodplains.

Topography in most of the park units is gently rolling and locally incised by streams; the exceptions are at Chickahominy Bluff and Drewry's Bluff, which have steep bluffs, and Malvern Hill, which has moderately steep slopes. Of the units addressed in this report, the minimum elevation is less than 10 feet (at the James River) in the Drewry's Bluff unit, and the maximum elevation is 185 feet in the Cold Harbor unit. The range in elevation for each unit shows that the Beaver Dam Creek unit has the flattest topography.

Hodges (1978) mapped soils in Chesterfield County. In general, soils in the Drewry's Bluff unit are on uplands and are of the Gritney-Atlee-Lenoir association, which is characterized as deep, well drained to somewhat poorly drained soils, having a clayey or loamy subsoil. Specific details on the soils underlying each unit are shown in Table 2.

Hodges et al. (1980) mapped soils in Hanover County. The soils underlying the Beaver Dam Creek, Cold Harbor, and Gaines' Mill units are classified as Coastal Plain soils, and include the Udults-Ochrepts-Suffolk association, the Ochrepts-Udults-Kempsville association, the Norfolk-Caroline-Dogue association, and the Norfolk-Orangeburg- Faceville association. These four soil associations are in general deep, moderately well to well drained and have a subsoil that is dominantly sandy, loamy, or clayey. These soils generally are found on uplands.

Clay (1975) mapped soils in Henrico County. The soils underlying the Chickahominy Bluff, Fort Harrison, Malvern Hill, and Glendale units are of the Kempsville-Atlee- Duplin association, the Ochrepts and Udults-Norfolk-Caroline association, or the Angie- Pamunkey-Lenoir association. These three soil associations are in general deep and well drained, some with gravel, some with a fragipan, and some poorly drained. These soils generally are found on uplands and stream terraces.

Source National Park Service, Water Resources Division

References

Inners, j., Inners, B., and Sayre, D. 1995 Militaery geology of the Richmond and Petersburg National Battlefield Parks, Virginia: Pennsylvania Geologic Survey Open File Report 95-08, Harrisburg, Pennsylvania, 75 p.

McFarland, E. 1997. Hydrogeologic framework, analysis of ground-water flow, and relations to regional flow in the fall zone near Richmond, Virginia. U.S. Geological Survey Water-Resources Report 97-4021, 56 p.

Meng, III, A. and Harsh, J. 1988. Hydrogeologic framework of the Virginia Coastal Plain: U.S. Geological Survey Professional Paper 1404-C, 82 p.

Mixon, R., Berquist, Jr., C., Newell, W., Johnson, G., Powars, D., Schindler, J., and Rader, E. 1989. Geologic map and generalized cross sections of the Coastal Plain and adjacent parts of the Piedmont, Virginia: U.S. Geological Survey Miscellaneous Investigations Series, Map I-2033, 2 maps, scale 1:250,000.

White, R., Powell, E., and Francisco, P. 2001. Water Resources Data Virginia , Water Year 2001, Volume 2. Ground-water level and ground-water quality records: USGS Water-Data Report VA-Q1-2, 319 p.



park maps subheading

The General park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

photo album subheading

A geology photo album for this park can be found here.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

books, videos, cds subheading

Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.



geologic research subheading

 

For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.



selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

Currently, we do not have a listing for any park-specific geology education programs or activities.

General information about the park's education and intrepretive programs is available on the park's education webpage.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/rich/index.cfm   I  Email: Webmaster
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