Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/229 

National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 
THIS PAGE:

Stone wall along the modern day location of the Sunken Road, one of the 

bloodiest sites during the Civil War. Of 

the 12,600 Federal soldiers killed, 

wounded, or missing during the Battle of

Fredericksburg, almost two-thirds fell in

front of the stone wall. 

ON THE COVER:

Cannons at Fairview, an important location during the Battle of Chancellorsville,

May 2-3 1863.

National Park Service photographs 

Courtesy Gregg Kneipp (Fredericksburg 

and Spotsylvania County Memorial Battlefields National Military Park)
Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park 

Geologic Resources Inventory Report 

Natural Resource Report NPS/NRPC/GRD/NRR—2010/229 

Geologic Resources Division 

Natural Resource Program Center 

P.O. Box 25287 

Denver, Colorado 80225 

August 2010 

U.S. Department of the Interior 

National Park Service 

Natural Resource Program Center 

Ft. Collins, Colorado
The National Park Service, Natural Resource Program Center publishes a range of reports that 

address natural resource topics of interest and applicability to a broad audience in the National 

Park Service and others in natural resource management, including scientists, conservation and 

environmental constituencies, and the public. 

The Natural Resource Report Series is used to disseminate high-priority, current natural 

resource management information with managerial application. The series targets a general, 

diverse audience, and may contain NPS policy considerations or address sensitive issues of 

management applicability. 

All manuscripts in the series receive the appropriate level of peer review to ensure that the 

information is scientifically credible, technically accurate, appropriately written for the 

intended audience, and designed and published in a professional manner. This report received 

informal peer review by subject-matter experts who were not directly involved in the 

collection, analysis, or reporting of the data. 

Views, statements, findings, conclusions, recommendations, and data in this report do not 

necessarily reflect views and policies of the National Park Service, U.S. Department of the 

Interior. Mention of trade names or commercial products does not constitute endorsement or 

recommendation for use by the U. S. Government. 

Printed copies of this report are produced in a limited quantity and they are only available as 

long as the supply lasts. This report is available from the Geologic Resources Inventory website 

(http://www.nature.nps.gov/geology/inventory/gre_publications.cfm) and the Natural 

Resource Publications Management website (http://www.nature.nps.gov/publications/

NRPM). 

Please cite this publication as: 

Thornberry-Ehrlich, T.. 2010. Fredericksburg and Spotsylvania County Battlefields Memorial 

National Military Park: geologic resources inventory report. Natural Resource Report NPS/

NRPC/GRD/NRR—2010/229. National Park Service, Fort Collins, Colorado. 

NPS 326/105337, August 2010 

ii NPS Geologic Resources Division 
FRSP Geologic Resources Inventory Report iii

Contents

List of Figures................................................................................................................ iv

Executive Summary ....................................................................................................... v

Acknowledgements and Credits.................................................................................. vi

Introduction ................................................................................................................... 1

Purpose of the Geologic Resources Inventory ...............................................................................................................1

History of Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park.....................................1

Geologic Setting ..........................................................................................................................................................1

Geologic Issues .............................................................................................................. 7

Introduction.................................................................................................................................................................7

Abandoned Mineral Lands ...........................................................................................................................................7

Channel Morphology ...................................................................................................................................................8

Siting of Future Facilities ..............................................................................................................................................8

Hydrogeology ..............................................................................................................................................................8

Slope Processes and Erosion.........................................................................................................................................9

Urban Encroachment ...................................................................................................................................................9

Surface Water and Sediment Loading.........................................................................................................................10

Connections between Geology and the Civil War History............................................................................................10

Potential Fossil Resources...........................................................................................................................................11

Geologic Features and Processes................................................................................ 15

Geology and History Connections...............................................................................................................................15

Mineral Resources......................................................................................................................................................15

Faults and Folds.........................................................................................................................................................16

Map Unit Properties .................................................................................................... 19

Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park Map Units..................................19

Geologic History .......................................................................................................... 29

Precambrian (prior to 542 million years ago)...............................................................................................................29

Paleozoic Era (542 to 251 million years ago)...............................................................................................................29

Mesozoic Era (251 to 65.5 million years ago)..............................................................................................................30

Cenozoic Era (the past 65.5 million years)...................................................................................................................31

Glossary........................................................................................................................ 37

Literature Cited............................................................................................................ 41

Additional References ................................................................................................. 43

Appendix A: Overview of Digital Geologic Data....................................................... 45

Appendix B: Scoping Meeting Participants................................................................ 47

Attachment: Geologic Resources Inventory Products CD
iv NPS Geologic Resources Division

List of Figures

Figure 1. Map of Fredericksburg and Spotsylvania County Memorial Battlefields National Military Park .............................3

Figure 2. Physiographic map of Virginia ...........................................................................................................................4

Figure 3. Geologic map of the Piedmont and Blue Ridge in central Virginia ......................................................................5

Figure 4. Union army pontoon bridges across the Rappahannock River...........................................................................11

Figure 5. Confederate earthworks along visitor trail at the Chancellorsville unit ..............................................................12

Figure 6. Terraces and River...........................................................................................................................................12

Figure 7. Urban development ........................................................................................................................................13

Figure 8. Battle Topography...........................................................................................................................................14

Figure 9. Map of the historic Fredericksburg landscape ..................................................................................................17

Figure 10. Map of gold mines and prospects in Virginia .................................................................................................18

Figure 11. Simplified map of geologic structures around Fredericksburg.........................................................................18

Figure 12. Geologic timescale ........................................................................................................................................32

Figure 13. Geologic timescale specific to Virginia ...........................................................................................................33

Figure 14 Geologic evolution of the Appalachian Mountains in the Fredericksburg area. ................................................34
FRSP Geologic Resources Inventory Report v

Executive Summary

This report accompanies the digital geologic map for Fredericksburg and Spotsylvania

County Battlefields Memorial National Military Park in Virginia, which the Geologic 

Resources Division produced in collaboration with its partners. It contains information 

relevant to resource management and scientific research. This document incorporates

preexisting geologic information and does not include new data or additional fieldwork.

The area surrounding Fredericksburg, Virginia, was the 

site of several major battles during the American Civil 

War, and is perhaps the most fought-for landscape in 

North America. The bloody fighting that took place here

in 1862 and 1863, resulted in 85,000 wounded and 15,000 

killed. Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park preserves 

the fading scars of battle, remnants of past land use, 

historic homesites of local families, and numerous 

monuments to the sacrifices made by Union and 

Confederate soldiers. 

Many geologic factors contributed to the landscape at 

Fredericksburg and its position as a strategic point

during the Civil War. The area’s geology is more than just 

a landscape of rocks and mineral resources: geologic 

features and processes affect topography, the location of 

streams and rivers, the formation of soils, wetlands, and 

bogs, the patterns of vegetation, and the animal life that 

thrives in the environment. In addition to cultural 

resources, the park protects thousands of acres of 

woodland and riparian habitat.

The city of Fredericksburg is located at the Fall Line—

the boundary between hard bedrock of the Piedmont 

physiographic province and the softer, sedimentary 

strata of the Atlantic Coastal Plain. The Fall Line

influenced the location of the town when it was founded. 

Below this line, the Rappahannock River is navigable. 

Above it, waterfalls and rapids create a barrier to oceangoing vessels.

Fredericksburg’s strategic military location between 

Washington, D.C., and Richmond, Virginia, focused 

Civil War activities here. Geologic features of the 

landscape were used to the Confederate army’s

advantage in the 1862 Battle of Fredericksburg. 

Furthermore, geologic resources contributed to the 

historic development of the area. Early mineral interest 

included mining for iron ore. Because smelting ore 

required a fuel source, the logging of local forests 

provided charcoal. Loss of trees resulted in the growth of 

heavy understory, which lent its name to the Battle of the

Wilderness. Prospects within the gold-pyrite belt are also 

present in this region. 

The following features, issues, and processes have a high 

level of geologic importance and management 

significance for the park:

• Disturbed Lands. There is a long history of mining in 

the park and surrounding area. Mineral resources 

include iron ore, gold, and sulfide minerals, as well as 

siltstone, gneiss, and basalt for crushed aggregate. 

Within park boundaries, abandoned mines, quarries, 

pits, and prospects create resource management issues. 

Acid mine drainage and heavy metal-laden sediments 

are issues for areas such as the brush covered pit on

the recently aquired land in the Chancellorsville unit. 

Hazards to visitor and animal safety associated with 

mine features is also a management concern. 

• Channel Morphology. The Rappahannock River has 

had a major influence on the landscape and history at 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park. Here, the river is 

narrow and swift, and is bordered by riparian zones, 

floodplains, and higher terraces. The meandering river 

channel changes the riverbank types and position. 

These changes threaten visitor safety, existing park 

facilities, and the historical context of the landscape. 

• Siting of Future Facilities. The historical features of the 

landscape are somewhat obscured at the park due to 

increased urban development, long-term agriculture, 

sedimentation, erosion, and vegetation. Park managers 

are discussing plans to restore battlefield-era

conditions and expand facilities at the park. Ground 

penetrating radar (GPR) surveys along the suspected 

site of the Sunken Road, and on the heights west of 

Fredericksburg, helped to identify the locations of 

several historic features of the battlefield. Many 

geologic factors such as shrink-and-swell clays, 

springs, slope stability, and flood potential provide 

challenges for the appropriate placement of 

infrastructure.

The glossary contains explanations of many technical 

terms used in this report, including terms used in the 

Map Unit Properties Table. A geologic time scale is 

presented as figure 12.
vi NPS Geologic Resources Division

Acknowledgements

The Geologic Resources Inventory (GRI) is one of 12 inventories funded by the National 

Park Service Inventory and Monitoring Program. The GRI is administered by the 

Geologic Resources Division of the Natural Resource Program Center.

The Geologic Resources Division relies heavily on 

partnerships with institutions such as the U.S. 

Geological Survey, Colorado State University, state 

geologic surveys, local museums, and universities in 

developing GRI products.

Special thanks to Gregg Kneipp (Fredericksburg and 

Spotsylvania County Memorial Battlefields National 

Military Park) for providing photos used in the report.

Credits

Author

Trista Thornberry-Ehrlich (NPS-Colorado State 

University)

Review

Mark Carter (U.S. Geological Survey)

Philip Reiker (NPS Geologic Resources Division)

Jason Kenworthy (NPS Geologic Resources Division)

Editing

Katie KellerLynn (NPS-Colorado State University)

Digital Geologic Data Production

Stephanie O’Meara (NPS-Colorado State University)

Ron Karpilo (NPS-Colorado State University)

Digital Geologic Data Overview Layout Design

Philip Reiker (NPS Geologic Resources Division)
FRSP Geologic Resources Inventory Report 1

Introduction

The following section briefly describes the National Park Service Geologic Resources 

Inventory and the regional geologic setting of Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park.

Purpose of the Geologic Resources Inventory

The Geologic Resources Inventory (GRI) is one of 12 

inventories funded by the National Park Service (NPS) 

Inventory and Monitoring Program. The GRI, 

administered by the Geologic Resources Division of the 

Natural Resource Program Center, is designed to 

provide and enhance baseline information available to 

park managers. The GRI team relies heavily on 

partnerships with institutions such as the U.S. Geological 

Survey, Colorado State University, state geologic surveys, 

local museums, and universities in developing GRI 

products.

The goals of the GRI are to increase understanding of the 

geologic processes at work in parks and to provide sound 

geologic information for use in park decision making. 

Sound park stewardship requires an understanding of 

the natural resources and their role in the ecosystem. 

Park ecosystems are fundamentally shaped by geology.

The compilation and use of natural resource information 

by park managers is called for in section 204 of the 

National Parks Omnibus Management Act of 1998 and in 

NPS-75, Natural Resources Inventory and Monitoring 

Guideline. 

To realize these goals, the GRI team is systematically 

conducting a scoping meeting for each of the 270 

identified natural area parks and providing a parkspecific digital geologic map and geologic report. These 

products support the stewardship of park resources and 

are designed for non-geoscientists. Scoping meetings 

bring together park staff and geologic experts to review 

available geologic maps and discuss specific geologic 

issues, features, and processes. 

The GRI mapping team converts the geologic maps 

identified for park use at the scoping meeting into digital 

geologic data in accordance with their Geographic 

Information Systems (GIS) Data Model. These digital 

data sets bring an interactive dimension to traditional 

paper maps. The digital data sets provide geologic data 

for use in park GIS and facilitate the incorporation of 

geologic considerations into a wide range of resource 

management applications. The newest maps contain 

interactive help files. This geologic report assists park 

managers in the use of the map and provides an overview 

of park geology and geologic resource management 

issues.

For additional information regarding the content of this 

report and current GRI contact information please refer 

to the Geologic Resources Inventory web site 

(http://www.nature.nps.gov/geology/inventory/).

History of Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park

Established on February 14, 1927, during Herbert 

Hoover’s administration, Fredericksburg and 

Spotsylvania County Battlefields Memorial National 

Military Park commemorates the sacrifices endured by 

Civil War soldiers during the fierce fighting that took 

place near the town of Fredericksburg, Virginia (fig. 1). 

Originally administered by the War Department, the 

National Park Service became its steward on August 10, 

1933. The park protects historic structures and Civil War 

battlefield sites, including Fredericksburg,

Chancellorsville, the Wilderness, and Spotsylvania Court 

House. These battles occurred on December 11–13, 

1862, April 27–May 6, 1863, May 5–6, 1864, and May 8–

21, 1864, respectively. Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park

covers 3,389 ha (8,374 ac). It is one of the largest military 

parks in the eastern United States. 

Geologic Setting

Fredericksburg’s strategic location between the Union 

capital of Washington, D.C., and the Confederate capital

of Richmond, Virginia, was the reason for intense 

fighting in the surrounding countryside. The area’s 

geography (affected by geology) influenced the battles 

that took place here. Three large regional rivers—the 

Rappahannock, the York, and the Rapidan—shaped the 

historical development of the Fredericksburg area and 

the course of military movements in the area before and 

during the battles. Safe river crossings and fords were 

vital to military success during the Civil War. Local 

streams such as Wilderness Run, Hazel Run, Ni River, 

Deep Run, Massaponax Creek, and other small-scale

waterways created important topographic and tactical 

targets. On the relatively gentle landscape in the area, 

troops on both sides of the conflict used even the 

smallest swell or depression to strategic advantage. 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park contains some of the 

most intriguing rocks of the Virginia Piedmont. The 

park’s acreage lies within the Piedmont Plateau and 

Atlantic Coastal Plain physiographic provinces. The 

following is a general description of several of the 

different physiographic provinces that span from the 

Atlantic Coastal Plain to the Appalachian Mountains

(fig. 2) and make up the region surrounding the park. 

This information is relevant to understanding the 

geologic history of the national military park.
2 NPS Geologic Resources Division

Atlantic Coastal Plain Province 

The Atlantic Coastal Plain physiographic province 

encompasses low, primarily flat terrain with elevations 

ranging from sea level to about 100 m (300 ft) in northern 

Virginia. The physiographic province extends from New 

York to Florida and stretches from the Fall Line east to 

the Chesapeake Bay and Atlantic Ocean. The province 

then continues as submerged Continental Shelf for 

another 120 km (75 mi) to the east. Over the past 100 

million years, sediments eroding from the Appalachian 

Highlands to the west intermittently spread across the 

province in a wedge-shaped sedimentary package more 

than 2,400 m (8,000 ft) thick at the Atlantic coast. 

Fluctuating sea levels and the erosive action of waves 

along the coastline reworked these deposits. Soils of the 

Coastal Plain province are commonly well-drained, 

sandy loams. Large streams and rivers in the Coastal 

Plain province—including the James, York, 

Rappahannock, and Potomac—continue to transport 

sediment eastward, extending the coastal plain. 

Piedmont Province

The “Fall Line” or “Fall Zone” marks a transitional zone 

where the softer, less consolidated sedimentary deposits

of the Atlantic Coastal Plain intersect the harder, more 

resilient metamorphic rock to the west. This intersection 

forms a zone of waterfalls and rapids along the major 

rivers and lower-order tributaries. The Rappahannock 

River crosses this line at the city of Fredericksburg,

creating a barrier to ocean vessel trade west of the city. 

Other examples of the Fall Line include the Potomac 

Gorge of the Chesapeake and Ohio Canal National 

Historical Park and at Great Falls Park just west of 

Washington, D.C. West of the Fall Line is the Piedmont 

physiographic province, which extends to the Blue Ridge

Mountains.

The eastward-sloping Piedmont Plateau was formed 

primarily through uplift and erosion, which produced a

landscape of gently rolling hills starting at 60 m (200 ft) 

above sea level. These hills become gradually steeper

towards the western edge of the province at 300 m

(1,000 ft) above sea level. The Piedmont Plateau is 

composed of folded and faulted igneous and 

metamorphic rocks, including schist, phyllite, slate, 

gneiss, and gabbro. Soils in the Piedmont Plateau are 

highly weathered and generally well drained.

A series of Triassic extensional basins occur within the 

Piedmont (fig. 3). During Mesozoic crustal extension

(pulling apart), normal faulting produced basins 

(graben), which filled with nearly horizontal layers of 

sediment. Examples include the Frederick basin in 

Maryland and the Culpeper basin of northern Virginia.

Culpeper Basin

The Culpeper basin is one of a series of basins that fringe 

the boundary between the Blue Ridge and Piedmont 

along the length of the Appalachian Mountains. The 

basin formed as an intermontane basin during Mesozoic 

crustal extension. It trends northeast-southwest and is 

about 120 km (75 mi) long and 30 km (20 mi) wide. The 

rocks in the basin are mostly flat-lying sedimentary 

sandstone, siltstone, and shale, with some igneous 

diabase and basalt. Manassas National Battlefield Park 

contains rocks from the Culpeper basin.

The eastern boundary of the Culpeper basin is generally 

a depositional contact between Mesozoic sedimentary 

rocks and older igneous and metamorphic rocks of the 

Piedmont. A topographic change—from the rolling hills 

of the Piedmont to the relatively flat topography in the 

valley of the basin—marks the boundary. The western 

boundary of the basin is a system of faults collectively

known as the Bull Run fault. West of the Culpeper basin 

is the Blue Ridge physiographic province.
FRSP Geologic Resources Inventory Report 3

Figure 1. Map of Fredericksburg and Spotsylvania County Memorial Battlefields National Military Park. National Park Service map.
4 NPS Geologic Resources Division

Figure 2. Physiographic map of Virginia. The figure shows the location of Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park relative to the physiographic provinces of Virginia. The green dot on the figure represents the location of Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park. 

Graphic modified from Bailey (1999) by Trista L. Thornberry-Ehrlich (Colorado State University).
FRSP Geologic Resources Inventory Report 5

Figure 3. Geologic map of the Piedmont and Blue Ridge in central Virginia. Heavy dashed line indicates state boundaries. The green dot 

on the figure represents the location of Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park. Graphic 

modified from Bailey (1999) by Trista L. Thornberry-Ehrlich (Colorado State University).

FRSP Geologic Resources Inventory Report 7

Geologic Issues

The Geologic Resources Division held a Geologic Resources Inventory scoping session for

Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park

on April 13, 2005, to discuss geologic resources, address the status of geologic mapping, 

and assess resource management issues and needs. This section synthesizes the scoping 

results, in particular those issues that may require attention from resource managers. 

Contact the Geologic Resources Division for technical assistance.

Introduction

Issues in this section are identified in relative order of 

resource management significance with the most critical 

listed first. Topics of general geologic interest and 

scientific research potential are presented towards the 

end of this section. Contact the NPS Geologic Resources 

Division for technical assistance.

Abandoned Mineral Lands

The history of mineral extraction from the rocks 

underlying Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park extends 

back to the 1600s. Small-scale abandoned mines, 

quarries, pits, and prospects dot the landscape within 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park. This includes many

pits and abandoned quarries that surround Catherine 

Furnace in the Chancellorsville unit. Iron ore was the

first mineral commodity to be mined and processed in 

this area. Mining for iron started here around the 

Revolutionary War and resumed during the Civil War to 

provide munitions for the Confederate army (GRI 

scoping notes 2005). 

While most of the abandoned mines in this area were 

probably iron ore mines, other mineral resources in the 

park area have fueled mining interest. For example, the

Virginia gold-pyrite belt (described in the “Geologic 

Features and Processes” section) transects the park. 

Some small-scale mine features within the park boundary 

are probably gold or sulfide mineral prospects. 

Other quarries in the region yield siltstone, sand and 

gravel (Rappahannock and Rapidan river deposits), 

granitic gneiss (quarry near Spotsylvania Court House in 

the Po River Metamorphic Suite), and basalt (quarry near 

Haymarket). These quarries provide crushed aggregate 

used in highway and building construction, roofing, 

erosion control, local landscaping, and leach fields 

(Culpeper Stone Company 1987).

There are more than 20 mineral extraction sites located

within the park boundaries, many more than 6.1 m-

(20 ft-) wide. A brush-covered pit on recently acquired 

land at the Chancellorsville unit is leaching arsenic into 

the groundwater and surface water.

According to the NPS Abandoned Mine Land (AML) 

inventory, the park contains two mine sites and three

hazardous mine openings. The Virginia Department of 

Mines, Minerals, and Energy (VDMME) maintained an 

inventory of mine features, as well as descriptions of the 

different mineral resources in the area.

Mine-related features pose several concerns for resource 

management at Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park. Visitor 

safety is a constant concern wherever open pits and loose 

tailings are associated with a mine feature. The potential 

for mine collapse of underground shafts within the 

park’s boundaries is unknown. Most mine features that 

are accessible to the public have been blocked or filled, 

but for those that have not, retaining access for animals 

that inhabit the mines (e.g., bats), while addressing public 

safety, is a concern. Acid mine drainage, associated with 

the exposure of mine tailings to weathering, causes 

increased acidity in the pH of surface water and 

groundwater. Heavy metals leached from the rocks by 

acid drainage may precipitate in local soils, floodplain 

deposits, and alluvium.

Resource Management Suggestions for Abandoned Mineral

Lands

• Continue to update the inventory of all mine-related 

features at Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park.

• Determine extent and nature of acid mine drainage 

from mine tailings and waste piles within the park. 

• Determine use of mine features during the Civil War 

battles for protection or strategic advantage.

• Perform a slope stability survey, focusing on mine

tailings within public zones. Where necessary, use 

slope stabilization techniques to ensure visitor safety.

• Prepare an interpretive program on historical 

prospecting, exploration, and extraction of mineral

resources from Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park.
8 NPS Geologic Resources Division

Channel Morphology

The Rappahannock River is a major landscapecontrolling feature at Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park. 

Riparian zones, floodplains, and higher terraces, as well 

as small-scale tributaries, border the river. The bends of 

the river and local streams are constantly changing as 

part of a natural, meandering river system. Outer bends 

continue to erode as sediments are deposited on the 

inside bend. Changes in riverbank type and position

(often changed due to bank failure and channel erosion)

are resource management concerns at the park. These 

changes threaten existing park facilities and the historical 

context of the landscape. 

The river is cutting into slopes near park headquarters. If 

the river undercuts this section of riverbank, a sudden 

collapse into the river could pose a threat to visitor safety 

and park infrastructure. 

The river also played a vital role in the battles fought in 

this area. North of the Chatham Park headquarters, 

Union forces crossed the Rappahannock River on 

pontoon bridges (fig. 4). They were subjected to intense 

gunfire by Confederate sharpshooters while crossing.

Erosion and seasonal flooding of the Rappahannock

River threatens this historically relevant area along the 

eastern shore of the river.

Many open fields existed during the time of the battles 

fought at Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park. Forests 

cover most of these areas now. In order to better 

interpret the cultural landscape and restore battlefield 

conditions, park managers are considering plans to clear 

these areas. However, soil erosion and subsequent 

sedimentation into nearby streams could result, 

degrading the river’s water quality. The NPS Water 

Resources Division and Geologic Resources Division 

could provide technical assistance for addressing this 

concern.

Resource Management Suggestions for Channel Morphology

• Monitor fluvial changes using aerial photographs. 

Historic photographs may be useful in tracing the 

evolution of the channel and watershed since the Civil 

War.

• Research bank-stabilization methods for sections of 

the river that threaten historic features or encroach on 

potential pollution sources such as mine tailings.

• Relate channel dynamics to land-use evolution 

including agriculture, logging, and urban development.

• Consult Lord et al. (2009) for stream system

monitoring techniques.

Siting of Future Facilities

Development, sedimentation, vegetation, and various

land-use practices since the Civil War have obscured

many historical features of the landscape. Park managers 

are discussing plans for restoring battlefield conditions 

and expanding facilities at the park (including the visitor 

center—possibly extending it underground beneath the 

existing parking lot). In 2003, ground penetrating radar 

(GPR) surveys along the suspected site of the Sunken 

Road (Telegraph Road) on the heights of Willis Hill 

(Marye’s Heights) helped identify the locations of several 

historic features of the battlefield, including the sunken 

road, stone walls, trenches, farm building foundations, 

and artillery positions (Frangos and Geier 2003). 

In addition to the potential for “obscured” cultural 

features, many geologic factors also affect park decision

making regarding siting future facilities. The potential for 

regular flooding and slope failure are factors in selecting 

appropriate sites for facilities. Additionally, the presence 

of shrink-and-swell clays could undermine the longevity

of any structure, road, or trail.

Understanding the nature of the substrate, locations of 

springs, and the hydrogeologic system would help avoid 

problems that could arise between groundwater flow and 

the siting of wastewater facilities.

Resource Management Suggestions for Siting of Future 

Facilities

• Consult local geologic experts when planning future 

facilities at the park.

• Perform GPR surveys to identify cultural and geologic 

features that may interfere with or influence the siting 

of future facilities and battlefield restoration (Frangos 

and Geier 2003).

• Locate areas of swelling clay, springs, groundwater 

flow, high slope, and unstable substrate to avoid for 

future facilities. 

• Incorporate slope, geologic, vegetation, and 

hydrologic data into a GIS to compare with battle-era 

photographs to determine the best approach to 

restoration. Consult 2009 NPS vegetation map for 

additional data (http://biology.usgs.gov/npsveg/

frsp/index.html).

Hydrogeology

Hydrogeology is the multidisciplinary study of the 

interaction between groundwater and subsurface

geologic features such as structures, permeability, 

porosity, degree of fracturing, and rock composition. 

Visitor and park use, as well as surrounding development 

and agriculture, are increasing the levels of pollutants in 

both surface water and groundwater at the park.

Nutrients from urban and agricultural waste are 

threatening the water quality of the region. Knowledge 

of the hydrogeologic system is critical to understanding 

the impacts of human-induced contaminants on the 

ecosystem and predicting ecosystem response.

Because municipal water and wells are the primary 

drinking water supplies for all the park units, an

understanding of how the water table changes over time

is significant for resource management and public safety. 

There are several wells throughout the park area that 

could be used for monitoring groundwater levels and 

quality. Monitoring groundwater flow via tracer studies 
FRSP Geologic Resources Inventory Report 9

in these wells would elucidate how quickly and in what 

direction water is moving through the system. 

Another aspect of hydrogeology is wetlands. The 

National Park Service manages wetlands in compliance 

with mandates and requirements of Executive Order 

11990 (Protection of Wetlands), the Clean Water Act, the 

Rivers and Harbors Appropriation Act of 1899, and the 

procedures described in Director’s Order 77-1 (Wetland 

Protection) (National Park Service 2006). There are 

several seasonal wetlands within the park boundary. 

Some are adjacent to visitor trails and subject to 

degradation. Beaver activity likely formed a few of the 

larger wetland areas. Because wetlands are general 

indicators of overall ecosystem health, identifying, 

researching, and periodically monitoring wetlands in the 

park is a practical solution to assessing the system’s 

condition.

Resource Management Suggestions for Hydrogeology

• Inventory, describe, and map any existing springs in 

the park.

• Contact the NPS Water Resources Division for 

additional information.

Slope Processes and Erosion

A major goal of park managers at Fredericksburg and 

Spotsylvania County Battlefields Memorial National 

Military Park is to present the historical context of the 

area, stemming from the pre-Revolutionary period 

through the Civil War. This process includes preserving 

and restoring earthworks, foundations, landscapes 

(fields, roads, and fences), and historic structures. 

Maintaining this historic context often means resisting 

natural geologic processes, which presents several 

management challenges.

Geologic slope processes such as landsliding, slumping, 

and slope creep can change the landscape at the park. 

Chemical weathering breaks down rock units causing 

instability in the rocks. Swelling soils, a product of the 

weathering of bedrock, occur throughout the park area. 

These soils contain clays that swell when saturated and 

shrink when dry. In extreme cases, this process can 

destroy roads, trails, visitor facilities, and building 

foundations.

Runoff erodes sediments from exposed soils and rock 

units (especially unvegetated and disturbed spots) and 

carries these sediments down to streams. Earthworks at 

the park are small, ranging in height from 1.0 to 1.5 m (3

to 5 ft) (fig. 5). These 140-year-old features are under 

constant threat of erosion. Geologic processes may also 

degrade bridge foundations, erode stream banks, and fill

in low-lying areas such as battle-era trenches, railroad 

cuts, and gullies, distorting the historical context of the 

landscape.

Some slope failure is occurring in the westernmost park 

units. However, maximum relief for Fredericksburg and 

Spotsylvania County Battlefields Memorial National 

Military Park is only 91 m (300 ft). These gentle slopes 

seldom experience catastrophic failure. However, the 

Rappahannock River and many lower-order tributaries

are undercutting riverbanks, posing potential hazards. 

Awareness of these processes is important for park 

decision making regarding the future locations of park 

facilities, restoration and preservation efforts, and visitor 

safety.

Resource Management Suggestions for Slope Processes and 

Erosion

• Monitor areas of higher slope for continuous slope 

creep.

• Map locations of swelling clays. Focus on areas with 

exposures of the Calvert Formation (Coastal Plain), 

Triassic units in the Culpeper basin, as well as 

amphibolites and other rock types in the Piedmont 

province.

• Identify areas prone to slope failure during intense 

storm events. Characteristics of such areas include 

undercut slopes, high clay content, high slopes, 

heterogeneous rock layers in close proximity, highly 

fractured units, and unvegetated slopes.

• Attempt to remediate slope processes that are 

threatening historic features on the landscape at 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park.

• Where appropriate, investigate restoration of 

earthworks damaged or obscured by extensive 

erosion.

• Wieczorek and Snyder (2009) suggest techniques for 

monitoring slope processes.

Urban Encroachment

Humans began settling the Fredericksburg and

Spotsylvania area in the late 1600s to early 1700s. Their 

farming and homestead activities altered the natural 

landscape. Impacts from their activities persist today at 

the national military park. Minor irrigation features, 

removal of soil and rocks to create stone fences and 

rock-free pastures for livestock grazing, extensive 

logging operations, and other homestead features are 

scattered throughout the landscape.

Rapid population growth and development are affecting 

the area surrounding Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park. As 

of 1995, office and commercial development has 

increased by more than 500% since the early 1970s and 

population increased by more than 50% along the 

Route-3 corridor through Fredericksburg. The area’s 

urban population continues to grow; the Wilderness 

Battlefield is on the National Trust for Historic 

Preservation and the Civil War Preservation Trust 

included on their 2010 list of the “most endangered 

historic places” as the pending construction (currently 

under litigation) of a Wal-Mart threatens part of the 

battlefield. Development results in the creation of 

surfaces such as parking lots, roads, and large buildings

that are impervious to rainwater infiltration, increasing

flood hazards (McConnell and Ulrich 1995). Flash 

flooding associated with seasonal tropical storms and 
10 NPS Geologic Resources Division

hurricanes has the potential to significantly alter the 

landscape (GRI scoping notes 2005). 

As development continues, conservation of any existing 

forest-meadow community types surrounding parklands

becomes a critical resource management concern (fig. 7). 

Understanding the nature of the geology beneath the 

biotic communities and their interrelationships becomes 

an integral part of their management. Park management 

of the landscape for historic preservation purposes 

complements the preservation of these forested areas.

Resource Management Suggestions for Urban Encroachment

• Using the geologic map, surficial maps, topographic 

maps, and hydrogeologic models, cooperate with local 

developers to minimize potential for geologic hazards, 

encroachment of contaminants, and invasive species

near park areas. 

Surface Water and Sediment Loading

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park protects reaches of the 

Rappahannock River and other local streams. As such, 

the quality of the surface water at the park is very 

important to surrounding communities as well as park 

resources and visitors. However, surrounding 

development affects water quality and the hydrogeologic 

system. 

Flooding and channel erosion are naturally occurring 

along most of the streams and rivers within the park. 

However, flooding and erosion exacerbated by 

development can threaten riparian zones and wetlands,

as well as visitor facilities, cultural features, and park 

infrastructure. Compaction due to increased visitor use, 

as well as impervious surfaces, is increasing seasonal 

runoff as sheet flow. Engineering solutions such as 

culverts and bridges can help mitigate runoff. However, 

facilities maintenance and expansion has not kept pace 

with regional development, and runoff often overwhelms 

outdated structures.

Soils along rivers and in wetlands are important for 

filtering excess nutrients and contaminants such as 

phosphates from the surface and near-surface water 

flow. Deeper soils (more than 50 cm [20 in]) have the 

highest capacity to remove phosphate from near surface 

and groundwater (Axt and Walbridge 1999). Knowledge 

of these types of relationships helps predict ecosystem 

response to anthropogenic environmental inputs, and is, 

therefore, important to resource management at the 

park. 

Alterations to vegetation along steep, exposed slopes 

lead to changes in the hydrologic regime in the park. For 

example, clearing of trees and their stabilizing roots for 

historical restoration can lead to increased erosion,

gullying, and sediment loads in nearby streams, and 

could potentially contribute to slumps, slope creep, and 

landslides. Earthworks, hiking trails, and other high-use, 

sparsely vegetated areas are also at risk of intense erosion 

and sediment loading.

Resource Management Suggestions for Surface Water and 

Sediment Loading

• Quantitatively determine the contaminant-filtering 

and adsorption capacity of the soil/substrate at the 

park based on spatial relationships between 

soil/substrate type, composition, and depth by using 

GIS layers of geology, hydrogeology, biology, and soils 

in concert with monitoring cores and wells.

• Map park administrative roads and target streams and 

areas of erosion for remediation.

• Research planting new vegetation along vulnerable 

reaches of park streams to prevent excess erosion and 

sediment loading.

Connections between Geology and the Civil War History

Because geology forms the basis of the ecosystem and 

landscape, geologic features and processes are directly 

responsible for the unique history at Fredericksburg and 

Spotsylvania County Battlefields Memorial National 

Military Park. In many military operations, familiarity 

with terrain is an advantage, and the proper utilization of

the natural features of the area such as valleys, river 

crossings, gaps, ravines, cuts, hills, and ridges may decide 

the outcome of a conflict. For example, at the Battle of 

Fredericksburg in 1862, the Confederates used the 

floodplains, river terraces (figs. 6, 8), and north-south 

trending ridges around the Rappahannock River to their 

advantage, stalling Union advance on the Confederate 

capital of Richmond for several years.

The underlying geology defines the rolling hills and 

gentle topography at Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park. 

Along the southeastern side of the Rappahannock River 

valley at the foot of the bluffs sits the sunken road (fig. 8, 

inside cover). During the battle in 1862, Confederate 

forces positioned heavy artillery above the road along 

Marye’s Heights and Willis Hill. This elevated position, 

proved insurmountable for Union General Burnside’s 

forces, and the Union attacks were repeatedly repulsed 

(Sherwood and Flora 2002). According to the park web 

site, of the 12,600 Federal soldiers killed, wounded, or 

missing, in the Battle of Fredericksburg, almost twothirds fell in front of the stone wall along the sunken 

road In addition to influencing battles, the landscape and 

topography affected the transport of troops and supplies 

during the Civil War.

Resource Management Suggestions for Connections between 

Geology and the Civil War History

• Create a general interest map with simple explanatory 

text on the geologic influences of battles for visitors to 

the park units.
FRSP Geologic Resources Inventory Report 11

Potential Fossil Resources

Fossils have not been formally documented from within 

the park; however, there is potential for future discovery 

(Kenworthy et al. 2006). While igneous and metamorphic 

rocks of the Piedmont rarely preserve fossils, rocks 

associated with the Coastal Plain province are more 

likely to preserve fossils. Regionally, all of the Cretaceous 

and Tertiary units mapped within the park contain 

fossilized plant debris, mollusks, marine vertebrate 

bones, and many other paleontological resources

elsewhere. Investigation of exposures in the park may 

yield paleontological resources. Fossils would be an 

important resource at the park as they contribute

stratigraphic information to the geologic history of the 

area. Fossils can also be targets of vandalism and theft.

Fossil resources require science-based resource 

management as directed by the 2009 Paleontological 

Resources Preservation Act (Public Law 111-11). The 

National Park Service is currently developing regulations 

associated with the Act (J. Brunner, Geologic Resources 

Division, personal communication, May 2010). Santucci 

et al. (2009) suggest strategies for monitoring in situ 

paleontological resources.

Resource Management Suggestions for Potential Fossil 

Resources

• Perform a field-based inventory to assess and 

document fossils within park boundaries, possibly 

collecting and preparing samples for a park collection.

Park managers may want to consider long-term 

monitoring of any significant localities.

• Create an interpretive exhibit highlighting the geologic 

story behind any paleontological resources at 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park.

Figure 4. Union army pontoon bridges across the Rappahannock River. The photograph shows the pontoon bridges just below Stafford 

Heights looking east from the north end of Fredericksburg. Note the lack of trees. Photograph by Timothy O’Sullivan (date unknown). 

Courtesy of the National Archives Still Photo Unit, College Park, Maryland.
12 NPS Geologic Resources Division

Figure 5. Confederate earthworks along visitor trail at the Chancellorsville unit. Signs discourage visitors from walking on the historic 

features; however, erosion is still beveling the historic battlefield. Photograph by Trista L. Thornberry-Ehrlich (Colorado State University).

Figure 6. Terraces and River. View from Chatham towards Fredericksburg over the Rappahannock River. The Rappahanock and terrace

topography associated with it were important influences in the outcome of the battles fought here during the Civil War. National Park 

Service photograph courtesy of Gregg Kneipp (Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park). 
FRSP Geologic Resources Inventory Report 13

Figure 7. Urban development encroaching on the Fredericksburg Battlefield of Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park (yellow outline). Aerial imagery compiled by Jason Kenworthy (NPS Geologic Resources Division) from 

ESRI ArcImage Service, USA Prime Imagery. Width of image is approximately 8 km (5 mi).
14 NPS Geologic Resources Division

Figure 8. Battle Topography. Modern day aerial view of Marye’s Heights, illustrating Union and Confederate positions during the Battle 

of Fredericksburg, December 13, 1862. The battle took place in a natural amphitheater, completely exposing advancing Federal troops to 

Confederate artillery fire from atop Marye’s Heights. After crossing the plains, Union troops confronted fortified Confederate infantry 

at the Stone Wall above the Sunken Road, resulting in extremely high Union casualties. National Park Service photograph modified by 

Philip Reiker (NPS Geologic Resources Division).
FRSP Geologic Resources Inventory Report 15

Geologic Features and Processes

This section describes the most prominent and distinctive geologic features and processes 

in Fredericksburg and Spotsylvania County Battlefields Memorial National Military 

Park.

Geology and History Connections

The geologic resources of the Fredericksburg and

Spotsylvania area have provided benefits for people for 

centuries. The town of Fredericksburg is situated along 

the Fall Line, which blocks boat transport upriver,

making this an important port area for the western 

reaches of the Virginia. Above the Fall Line, the river is 

narrow, with rocky rapids. Below the Fall Line, the river 

is tidal, and broadens downstream to more than 800 m 

(2,600 ft) wide at Port Royal (Ehlen and Abrahart 2002).

In addition to the regional transportation routes and

river crossings, effective military leaders needed to 

understand the nuances of the landscape. 

Fredericksburg’s strategic location between the 

Confederate capital of Richmond, Virginia, and the 

Union capital of Washington, D.C., made it an important 

area during the Civil War. At the time, the ranges and 

reliabilities of weapons and ammunition, the absence of 

adequate maps, supplies, and intelligence, as well as the 

poor physical conditions of the soldiers often made 

knowledge of the landscape decisive in major battles. 

Advantages such as line-of-sight, knowledge of state-ofthe-ground, and the location and effectiveness of 

obstacles affected military decisions and the outcome of 

the battles (Ehlen and Abrahart 2002).

In 1862, during the battle of Fredericksburg, Confederate 

forces held off many Union advances on the town of 

Fredericksburg, postponing the eventual capture of 

Richmond for almost three years. Though outnumbered 

and undersupplied, the Confederates were able to make 

strategic use of the local topographic landforms. Their 

knowledge of the area’s terrain, including high-level 

terraces(figs. 6, 9) along the Rappahannock River and 

gentle slopes below parallel north-south ridges, gave 

them a strong advantage (Ehlen and Abrahart 2002; 

Ehlen 2004). 

The Confederates set up defensive positions on the 

western north-south trending ridge at Marye’s Heights, 

Willis Hill, Telegraph Hill, and Prospect Hill. East of the 

Rappahannock River is Stafford Heights, where Union 

forces installed heavy artillery (figs. 8, 9). The river flows 

between two topographic highs (fig. 4)—Marye’s Heights

to the west, and Stafford Heights to the east. The two 

ridges form an amphitheatre, sloping down to the banks 

of the river.

Stafford Heights is composed of river terrace material

(see Map Unit Properties Table). Cretaceous and 

Tertiary sands and gravels underlie Marye’s Heights and 

the other hills along the western ridge (Ehlen 2004). 

Piedmont rocks underlie higher ridges to the west. 

East of the Fall Line, the Rappahannock and other local 

rivers incised through the softer, unconsolidated to 

loosely consolidated deposits of the Atlantic Coastal 

Plain. This created narrow stream valleys with steep 

slopes floored by wetlands such as Massaponax Creek. 

Ehlen and Abrahart (2002) detailed the course of the 

battle over these subtle topographic differences in the 

Fredericksburg landscape; readers are encouraged to use 

this resource for interpretation. 

Tactical advantages were also derived from 

anthropogenic obstacles, including major roads, stone 

walls, fences, buildings, agricultural ditches and 

irrigation canals, a railroad embankment (Richmond, 

Fredericksburg & Potomac Railroad), and the streets of 

Fredericksburg (Ehlen and Abrahart 2002). The famous 

stone wall along Sunken Road (Telegraph Road) (See 

inside cover photo). It is composed primarily of coarse 

sandstone known as the Aquia Freestone, derived from 

the Potomac Formation, as well as some igneous and 

metamorphic rocks. The sandstone contains quartz 

grains in a finer grained, feldspar-rich matrix. Mined 

from local quarries, gouges and grooves on these rocks 

are evidence of mechanical quarrying (Flora and 

Sherwood 2001).

Mineral Resources

Smelting operations started in the area, including the 

Catherine Furnace, because of the nearby iron ore 

deposits. Smelting of iron ore requires lime (obtained 

from oyster shells). Smelting also requires vast amounts 

of fuel for heat, traditionally produced from burning coal 

or charcoal. Before the Civil War, smelting operators 

cleared the entire Wilderness unit of the park of heavy 

timber, which allowed a thick understory to thrive in the 

clear-cut areas. This understory lent its name to the 

Battle of the Wilderness and forced fighting between 

Union and Confederate troops into the close quarters of 

bushy woods. Later, smelting operations were 

resurrected to supply Confederate forces with arms, 

including Catherine Furnace that had been shut down in 

the 1840s (GRI, scoping notes 2005; Rokus 2009).

Massive sulfide deposits (more than 13.5 million tons) 

occur in a volcanic-plutonic metamorphic belt (known as 

the Virginia gold-pyrite belt) (fig 10) that extends 175 km 

(110 mi) in the central Virginia Piedmont. The deposits 

occur in two parallel lenses that strike N40E and dip 

southeast at angles ranging from 60° to 70° (Seal et al.

2002). Minerals include pyrite (iron sulfide; FeS2), 

sphalerite (zinc sulfide; ZnS), galena (lead sulfide; PbS), 

chalcopyrite (copper-iron sulfide; CuFeS2), and 

pyrrhotite (iron sulfide; Fe1-xS) with some zinc (Zn) and 

lead (Pb) minerals in smaller deposits (Pavlides et al.
16 NPS Geologic Resources Division

1982; Seal et al. 2002). These minerals are likely 

associated with submarine volcanic exhalation, much 

like the white and black smokers (submarine vents) that 

occur along active plate boundaries such as the Atlantic 

mid-ocean ridge. The host rocks are predominantly lowpotassium granitoid rocks of the Piedmont.

The Virginia Lead and Zinc Company opened the 

Valzinco mine in 1914. However, exploration in the 

1940s discovered profitable sulfide-gold deposits in the 

area. This mine, as well as the Valzinco Halladay (or 

Holloday) and the Mitchell mine are all located within 

the Virginia gold-pyrite belt. There are also numerous 

other gold mines throughout Spotsylvania County that

include features such as pits, shafts, and covered dumps 

and tailings. Acid mine drainage and remobilization of 

heavy elements from dumps and tailings affects the entire 

watershed downstream from these mines (Seal et al.

2002)

Diamonds occur in Spotsylvania County. Local mines,

including the Vaucluse and Whitehall mines, hold 

potential for diamond exploration in this area. These 

diamonds are likely associated with scattered kimberlite 

dikes emplaced during regional extension in the Jurassic 

Period (Sweet 1996). The diamonds could also be from 

previously unrecognized and unmapped Eocene volcanic

rocks. These rocks would look very similar to the older 

Mesozoic volcanics and might go unnoticed without age

dating (M. Carter, U.S. Geological Survey, written 

communication, 2010).

Faults and Folds

Underlying geologic structures such as faults and folds 

within the Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park area have 

had a pronounced influence on landform development. 

They reflect the tectonic forces that crumpled, fractured,

or sheared deep underlying rocks as the Appalachian 

Mountains were forming (see “Geologic History”). The 

Rappahannock anticlinorium (a large-scale anticline, or 

convex upward fold, onto which smaller folds are 

superimposed) dominates the structural grain in the 

region surrounding the Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park. 

The anticlinorium extends from the Stafford, Virginia,

area southwards beyond the James River (fig. 11). The 

anticlinorium roughly trends and plunges to the 

northeast. The eastern portions of the anticlinorium are 

composed of island-arc deposits and some felsic plutons. 

Associated with the western side of the anticlinorium is

the parallel trending Quantico synclinorium. (Pavlides et 

al. 1982). The Spotsylvania thrust fault bounds the 

feature on the east, and the Long Branch fault bounds 

the feature on the west. Northwest of Fredericksburg, 

the right-lateral (strike-slip) Accokeek fault truncates the 

northern nose of the anticlinorium. Structures along the 

limbs of the anticlinorium suggest multiple phases of 

folding and at least two metamorphic events. (Onasch

1986; Mixon et al. 2000).

Several large, parallel, low- to high-angle thrust faults 

trend northeast-southwest through the region and dip to 

the southeast. From east to west, these are the 

Spotsylvania, Long Branch, Chopawamsic, and Lake of 

the Woods thrust faults. East of the Lake of the Woods 

thrust fault lies the Mountain Run fault zone, a 1.6-km-

(1-mi-) wide sheared zone (Mixon et al. 2000). These 

thrust faults moved large masses of Piedmont rocks and 

associated plutons atop younger rocks to the west. At the 

surface, most of these faults are not well exposed. The 

Spotsylvania thrust fault, referred to as the Central 

Piedmont/Spotsylvania high-strain zone, locally 

separates schist and gneiss from island-arc rocks of the 

eastern limb of the Rappahannock anticlinorium. It 

separates the Goochland and Chopawamsic terranes 

(Spears et al. 2004; Bailey et al. 2004). It may be the 

northern extension of the Lakeside fault zone in the 

central Virginia Piedmont and the Hyco shear zone, 

which is traceable for over 500 km (300 mi) in the 

southern Appalachians (Francis et al. 2001; Spears et al.

2004). Closer to the park are several high-angle reverse 

faults, including the Dumfries, Hazel Run, Brooke, and 

Fall Hill faults. These are part of the Stafford fault system 

within the inner Coastal Plain of Virginia. The Stafford 

fault system extends along the Fall Line 68 km (42 mi) 

from Spotsylvania northeastward to southern Fairfax 

County. These features are en echelon, or step-like in 

map pattern, and trend to the northeast. Vertical 

displacement along these features is minor, only 10–60 m 

(33–197 ft), but this amount of offset significantly affects

the thickness and distribution of Coastal Plain sediments 

(Mixon et al. 2000). Sediments present on the western, 

upthrown blocks are thinner than their counterparts on 

the eastern, downthrown blocks across these high-angle 

reverse faults. 
FRSP Geologic Resources Inventory Report 17

Figure 9. Map of the historic Fredericksburg landscape. The figure illustrates locations of military installments, topographic highs, river 

terraces, and floodplains relative to the river and the town of Fredericksburg during the 1862 Battle of Fredericksburg. Graphic adapted 

from Ehlen (2004) by Trista L. Thornberry-Ehrlich (Colorado State University).
18 NPS Geologic Resources Division

Figure 10. Map of gold mines and prospects in Virginia. The gold pyrite belt is also illustrated in purple. Fredericksburg is identified as a 

gold star. Graphic adapted by Philip Reiker (NPS Geologic Resources Division) from Sweet (2007).

Figure 11. Simplified map of geologic structures around Fredericksburg. Note the complexity of the structures at the nose of the 

anticlinorium, just west of Fredericksburg. The location of the Rappahannock anticlinorium axis and the Fall Line between the Piedmont 

and Atlantic Coastal Plain are estimates. Green outline shows the boundary of Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park. Graphic by Trista L. Thornberry-Ehrlich (Colorado State University), based on information from figure 1 

of Mixon et al. (2000).
FRSP Geologic Resources Inventory Report 19

Map Unit Properties

This section identifies characteristics of map units that appear on the Geologic Resources 

Inventory digital geologic map of Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park. The accompanying table is highly generalized and 

for background purposes only. Ground-disturbing activities should not be permitted or 

denied on the basis of information in this table.

Geologic maps facilitate an understanding of Earth, its 

processes, and the geologic history responsible for its 

formation. Hence, the geologic map for Fredericksburg 

and Spotsylvania County Battlefields Memorial National 

Military Park provided information for the Geologic 

Issues, Geologic Features and Processes, and Geologic 

History sections of this report. Geologic maps are twodimensional representations of complex threedimensional relationships; their color coding illustrates 

the distribution of rocks and unconsolidated deposits. 

Bold lines that cross or separate the color patterns mark 

structures such as faults and folds. Point symbols 

indicate features such as dipping strata, sample localities, 

mines, wells, and cave openings. 

Incorporation of geologic data into a Geographic 

Information System (GIS) increases the usefulness of 

geologic maps by revealing the spatial relationships 

among geologic features, other natural resources, and 

anthropogenic features. Geologic maps are indicators of 

water resources because they show which rock units are 

potential aquifers and are useful for finding seeps and 

springs. Geologic maps are not soil maps, and do not 

show soil types, but they do show parent material—a key 

factor in soil formation. Furthermore, resource managers 

have used geologic maps to make connections between 

geology and biology; for instance, geologic maps have 

served as tools for locating sensitive, threatened, and 

endangered plant species, which may prefer a particular 

rock unit. 

Although geologic maps do not show where earthquakes 

will occur, the presence of a fault indicates past 

movement and possible future seismic activity. Similarly, 

map units show areas that have been susceptible to 

hazards such as landslides, rockfalls, and volcanic 

eruptions. Geologic maps do not show archaeological or 

cultural resources, but past peoples may have inhabited 

or been influenced by depicted geomorphic features. For 

example, alluvial terraces may have been preferred use 

areas and formerly inhabited alcoves may occur at the 

contact between two rock units.

The geologic units listed in the following table 

correspond to the accompanying digital geologic data. 

Map units are listed in the table from youngest to oldest. 

Please refer to the geologic timescale (fig. 12) for the age 

associated with each time period. The table highlights 

characteristics of map units such as: susceptibility to 

erosion and hazards; the occurrence of paleontological 

resources (fossils), cultural resources, mineral resources, 

and caves or karst; and suitability as habitat or for 

recreational use. Some information on the table is 

conjectural and meant to serve as suggestions for further 

investigation.

The GRI digital geologic maps reproduce essential 

elements of the source maps including the unit 

descriptions, legend, map notes, graphics, and report. 

The following reference is the source for the GRI digital 

geologic data for Fredericksburg and Spotsylvania 

County Battlefields Memorial National Military Park: 

Mixon, R. B., L. Pavlides, D. S. Powars, A. J. Froelich, R. 

E. Weems, J. S. Schindler, W. L. Newell, L. E. Edwards 

and L. W. Ward. 2000. Geologic map of the 

Fredericksburg 30' × 60' quadrangle, Virginia and 

Maryland (scale 1:100,000). Miscellaneous 

Investigations Series I-2607. U.S. Geological Survey, 

Reston, Virginia, USA. 

The GRI team implements a geology-GIS data model 

that standardizes map deliverables. This data model 

dictates GIS data structure including data layer 

architecture, feature attribution, and data relationships 

within ESRI ArcGIS software, and increases the overall 

utility of the data. GRI digital geologic map products 

include data in ESRI personal geodatabase, shapefile, 

and coverage GIS formats, layer files with feature 

symbology, Federal Geographic Data Committee 

(FGDC)-compliant metadata, a Windows help file that 

contains all of the ancillary map information and 

graphics, and an ESRI ArcMap map document file that 

easily displays the map.

GRI digital geologic data are included on the attached 

CD and are available through the NPS Data Store at 

http://science.nature.nps.gov/nrdata/ (accessed June 2, 

2010).

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park Map Units

The map for Fredericksburg and Spotsylvania County 

Battlefields Memorial National Military Park by Mixon 

et al. (2000) covers parts of three physiographic 

provinces and one geologic basin: the Atlantic Coastal 

Plain, Piedmont, and Blue Ridge provinces, and the 

Culpeper basin. The oldest rocks in the area are altered 

greenstones (basalts) of the Catoctin Formation, and the 

metasiltstones and schists of the Charlottesville 

Formation of the Lynchburg Group. These units are 

Proterozoic in age and are located west of the park area 
20 NPS Geologic Resources Division

on the map. Granitic gneiss and diorite gneiss of the 

Potomac Creek pluton are Late Proterozoic to Early 

Paleozoic in age. Of similar age is the Po River 

Metamorphic Suite; it contains biotite and gneisses and 

schists, as well as amphibolite. This is a prominent unit in 

the southeastern park area. Within the Po River 

Metamorphic Suite are lenticular granitoid layers that 

may be the metamorphosed remnants of earlier intrusive 

plutons.

Latest Proterozoic to earliest Cambrian rocks include 

amphibolites, serpentinites, talcs, and other ultramafic 

rocks. These rocks occur as small xenoliths within 

Cambrian to Ordovician units, which dominate the 

bedrock underlying the park. 

Cambrian units include metagabbros, amphibolitebiotite gneisses of the Ta River Metamorphic Suite, 

altered tonalites and granites, and metavolcanic and 

metasedimentary rocks of the Chopawamsic Formation. 

The Chopawamsic contains lenses and tongues of 

feldspathic schist, phyllites, meta-arenites, amphibolite 

greenstones, and gneisses.

Spanning the Cambrian to Ordovician is the 

plagiogranite of the Richland Run pluton, in the 

northeast corner of the park area, as well as the highly 

variable mélange zones of the Mine-Run Complex. 

These zones include metasedimentary and metavolcanic 

blocks in a phyllitic to schistose matrix. Ordovician 

metasedimentary rocks, and phyllite and staurolite 

schists of the Quantico Formation, contain 

discontinuous lenses of quartzite in the eastern portions 

of the park. 

The Fall Line between the easternmost Piedmont and the 

western Atlantic Coastal Plain crosses the Rappahannock 

River at Fredericksburg. The rock units to the east of this 

line include the Lower Cretaceous Potomac Formation, 

which erosion has exposed along many of the rivers and 

streams in the area. This formation is composed of 

sandstone, silty channel-bar deposits, and lignitic sandy 

silt and clay layers. Atop the Potomac Formation is the 

upper Paleocene Aquia Formation, consisting of 

glauconitic sands, silts, clays, and containing some scant 

fossil layers. Deposits of Eocene Nanjemoy Formation 

overlie the Aquia Formation. These are glauconitic 

sands, clays, and silts. Miocene sands and gravels overlie 

the Aquia and Nanjemoy formations in the park area. 

Younger deposits include the Miocene Calvert 

Formation and the Pliocene Yorktown Formation. The 

Calvert Formation consists of silty sand and clay. The 

Yorktown Formation contains quartz and feldspar sands,

mixed with lesser clays and silts. The upper Pliocene 

Bacons Castle Formation includes gravelly sand and 

sandy-silty-clayey upper layers. Sediments of the Bacons 

Castle Formation crop out in high-level terrace areas. 

Younger deposits within the park include various 

Quaternary units. Fine to coarse sand, gravel, silt, and 

clay of the Windsor Formation is of upper Pliocene to 

lower Pleistocene age. The gravelly Charles City 

Formation, sands and silts of the Chuckatuck Formation, 

as well as coarse sands, gravels, pebbles and occasional 

boulders of the Shirley Formation are of middle 

Pleistocene age. The upper Pleistocene Tabb Formation 

contains sands, gravels, silts, and clays and underlies low 

terraces in the area. 

The youngest deposits at Fredericksburg and 

Spotsylvania County Battlefields Memorial National 

Military Park include thick alluvial floodplain deposits of 

sand, gravel, silt and clays; marsh and swamp deposits 

along the rivers; and artificial fill from construction of 

roads, dams, bridges, landfills, and highways. 
FRSP Geologic Resources Inventory Report 21

Map Unit Properties Table: Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park

Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

QUATERNARY - RECENT

Artificial fill

(af)

Mostly sand and gravel materials of varying 

thickness. Local to construction areas such as 

highways, bridges, roads, dams, and other 

facilities.

Low

Material is used in 

development 

projects

Prone to rockfall, 

slumps, slides, and 

other mass 

wasting if 

positioned on 

steep slopes, or 

undercut by 

additional 

construction or 

natural erosion 

Same as source 

material

May be useful 

to land-use 

evolution 

studies

Same as source 

material

Habitat for 

opportunistic 

plants and 

animals, 

including 

invasive plants 

along roadways

Used at 

recreation areas 

and along 

roadways

Eventual use for 

land-use evolution 

studies

QUATERNARY - HOLOCENE

Sand

(Qs) 

Swamp deposits 

(Qsw)

Qs—pale gray to light yellowish gray, fine to 

coarse grained, poorly to well sorted sand, 2–8 m 

(7–26 ft) thick. Present as low natural levees along 

the primary channel of the tidal Rappahannock 

River. Some beaches, sand bars, spits, and deltas 

developed along tributaries. 

Qsw—mud, muddy sand, muck, and organic 

material; brownish gray to grayish black color,

depending on the amount of decaying material; 

less than 3 m (10 ft) thick. Typically overlies 

alluvium.

Very low to 

low

Unsuitable for most 

development due to 

presence of marshy 

wetlands and 

saturated, 

unconsolidated 

sediments

Prone to erosion 

and flooding None documented

May contain 

historic 

artifacts and 

battleground 

relics

Heavy minerals, peat, 

and sand

Modern 

riparian habitat 

with wetland 

species.

Modern shell 

fragments and 

mollusk valves 

locally present.

Leaf, stem 

material, tree 

trunks, and 

pollen.

Unsuitable for 

most trails and 

other 

recreation due 

to water 

saturation and 

proximity to 

delicate 

wetland areas

Natural levees.

Riparian zone 

along 

Rappahannock 

River is vital 

natural buffer.

HOLOCENE -

PLEISTOCENE

Alluvium

(Qal)

Fine to coarse gravelly sand, sandy gravel, silt, 

and clay; mostly medium gray and yellowish gray;

grains of vein quartz, quartzite, and other 

metamorphic rocks; maximum thickness 15 m (49 

ft). Present as channel, point-bar, terrace, and 

floodplain deposits; grades into colluvium along 

steep slopes 

Low

Unsuitable for most 

development due to 

presence of 

saturated, 

unconsolidated 

sediments in 

floodplain areas

Prone to mass 

wasting. Flood 

hazard associated 

with this unit.

None documented

May contain 

historic 

artifacts and 

battleground 

relics

Metamorphic and 

other heavy minerals, 

clay, silt, gravel, sand, 

and quartzite pebbles

Riverine and 

floodplain 

habitats, 

modern/recent 

plant debris

Suitable for 

some stream 

edge recreation 

if not regularly 

flooded

Records

Pleistocene to 

Holocene 

transition along 

valley walls

PLEISTOCENE

Tabb Formation, 

undivided

(Qtu) 

Alluvial terrace 

deposits, undivided 

(Qatu) 

Shirley Formation, 

unit 1

(Qsh) 

Chuckatuck 

Formation

(Qc) 

Charles City 

Formation

(Qcc)

Qtu—sand, gravel, silt, and clay, underlying low 

terraces along the area’s larger rivers

Qatu—fine- to coarse-grained gravelly sand, 

sandy gravel, silt and clay lenses in surficial 

deposits along rivers and tributaries

Qsh—coarse sand, interbedded with pebbly and 

bouldery layers, with some light to medium 

grayish yellow silty fine sand and pinkish sandy 

silt; 10–20 m (33–66 ft) thick

Qc—cross-bedded gravelly sand, sandy silt, and 

light to medium yellowish gray clay; 5–15 m (16–

49 ft) thick. Sediments often weather reddish 

brown. Present in surficial deposits of mid-level 

estuarine terraces. 

Qcc—fining upward sequences of basal coarse 

gravelly sand to moderately sorted medium to 

fine sand, silt, and clay; oxidizes to a brownish 

color; maximum thickness 18 m (59 ft). Present 

along high-level terraces.

Low to 

moderately 

low for 

gravel-rich 

layers

Suitable for most 

development unless 

highly permeable 

and porous. Avoid 

steep margins of 

terraces, which may 

be undercut by 

rivers.

Prone to mass 

wasting, especially 

where steep 

slopes near 

waterways are 

present. Slumping 

of large blocks is 

possible.

Coral (Astrangia), 

peat, organic matter, 

pollen, and trace 

fossils (i.e., 

invertebrate burrows)

Cap rock 

(high ground 

in the area). 

Strategic 

points during 

battles.

Heavy minerals, 

gravel, boulders, 

sand, silt, and clay.

Borrow pits along 

Rappahannock River.

High-level 

terraces may 

provide habitat

for burrowing 

animals.

Suitable for 

most recreation 

unless undercut 

or near a cliff 

face or steep 

slope

Correlative 

throughout the 

region. Qsh

contains dateable 

U-Th coral 

(184±20 ka).

PLEISTOCENE 

AND (OR) 

PLIOCENE

Terrace deposits 

(QTt)

Well-bedded, gently sloping deposits of gravel, 

sand, silt, and clay along large rivers; <1 to 3 m 

(3.3 to 10 ft) thick and 60 m (197 ft) wide. Present 

above modern floodplain.

Low

Avoid for most 

development due to 

location along rivers 

and steep valley 

slopes

Prone to sliding 

especially if water 

saturated along 

valley slopes

None documented None 

documented

Greenstone, vein 

quartz, quartzite, 

phyllite, hornfels, and 

diabase cobbles, 

heavy minerals, 

gravel, pebbles, sand, 

silt, and clay

Habitat along 

major rivers

Good for most 

recreation 

unless undercut 

or water 

saturated

Records river 

migration along 

major waterways 

during sea-level 

highstands
Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

FRSP Geologic Resources Inventory Report 22

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

PLEISTOCENE AND 

PLIOCENE 

Colluvium

(QTc) 

Windsor Formation 

(QTw) 

Windsor Formation 

and (or) Moorings 

Unit of Oaks and 

Coch (1973) (QTmw)

QTc—gravel, sand, and silt, interbedded in 

lenticular deposits on slopes; clasts are typically 

subangular and occur in a yellowish-orange to 

greenish-gray silty sand and clayey silt matrix; up 

to 6 m (20 ft) thick

QTw—fine to coarse sand, gravel, silt, and clay in 

yellowish brown to reddish colored matrix; up to 

12 m (39 ft) thick in upper Rappahannock area.

Present on terraces.

QTmw—sand and gravel on high-level terraces

Low to 

moderately 

low for 

gravel- and 

clast-rich 

layers

Heterogeneous 

nature of unit may 

prove unstable on 

slopes and when 

undercut or water 

saturated.

Prone to mass 

wasting (e.g., 

rockfall)

Pleistocene-Pliocene 

estuarine floral and 

faunal remains

Chert within 

units may 

have been 

used for early 

tool material

Greenstone, 

quartzite, vein quartz, 

schist, chert and 

phyllite clasts, and 

amygdaloidal basalt, 

diabase, and gneiss 

cobbles, heavy 

minerals, sand, silt.

High-level 

terraces may 

provide habitat

for burrowing 

animals.

Good for most 

recreation 

unless undercut 

or water 

saturated

Records migration 

of Mattaponi River. 

QTw is correlative 

throughout the 

region.

TERTIARY - PLIOCENE

Moorings Unit of 

Oaks and Coch 

(1973)

(Tm)

Bacons Castle 

Formation

(Tb)

Sand and gravel 

(Tps)

Yorktown Formation

(Ty)

Tm—white, light gray, and grayish yellow 

quartzose sand and sandy gravel, with clasts of 

well-rounded pebbles, cobbles, and boulders; 3 to 

9 m (10 to 30 ft) thick. Occurs as surficial deposits 

in high-level terraces along the Rappahannock 

River.

Tb—yellowish orange in outcrop; fining upward 

sequence composed of two primary sediment 

types: the lower 3 to 6 m (10 to 20 ft) contains 

medium to coarse gravelly sand and sandy gravel, 

poorly sorted, with thick cross-beds; upper beds 

contain gray to pink, poorly sorted, sandy and 

clayey silt and silt clay, interbedded with fine 

sand, sandy silt, and clay; as much as 18 m (59 ft) 

thick.

Tps—yellowish to brownish gravelly sand, sandy 

gravel, and fine to coarse grained sand; some clay 

and silt lenses occur in trough cross-bedded 

layers; up to 18 m (59 ft) thick. Caps drainage 

divides.

Ty—yellowish to orangish gray, fine to coarse 

grained, poorly to well-sorted quartz and feldspar 

sands and gravels in planar and cross-bedded, 

thin to thick beds; some clay and silt occurs as 

matrix material; 3 m (10 ft) to as much as 25 m (82 

ft) thick with several fining upward sequences

Low to 

moderately 

low for 

coarser 

grained beds

High permeability of 

units may prove 

unsuitable for wastetreatment facility 

development.

Heterogeneity of 

layers may render 

them unstable along 

slopes, especially if 

undercut.

Prone to rockfalls 

from high-level 

terraces along the 

Rappahannock

River. Mass 

movements are 

likely for units 

when water 

saturated.

Trace fossils

(Ophiomorpha nodosa)

Chert within 

units may 

have been 

used for early 

tool material.

Iron-oxide 

cements may 

have been 

mined in 

colonial 

period as 

“bog iron.” 

Chert, weathered 

basalt, metamorphic 

rock pebbles, 

ilmenite, and 

magnetite grains, 

heavy minerals, 

gravel, sand, silt, clay, 

pebbles, and cobbles

High-level 

terraces may 

provide habitat

for burrowing 

animals. 

Present as cliffs 

along 

waterways. 

Good for most 

recreation 

unless undercut 

or water 

saturated

Overlapping 

terraces record 

migration of several 

rivers channels. 

Record Pliocene 

depositional 

environments that 

are correlative 

throughout the 

region.

TERITARY - MIOCENE

Sand and gravel 

(Tms)

Calvert Formation, 

undivided

(Tc)

Tms—yellowish orange and brown, fine to coarse 

gravelly sand, sandy gravel, silt, and kaolinitic clay 

in beds as much as 10 m (33 ft)thick. Occurs on 

higher topography throughout the region 

Tc—mostly fine to very fine quartzose sand with 

some silt and clay layers; thickly bedded, with 

mappable sand-silt-clay sequences; appears light 

gray to white, pinkish gray and pale yellowish 

orange in outcrop. Members of this unit include

(from bottom to top): Fairhaven (Tcf), Plum 

Point Marl (Tcp), and Calvert Beach (Tcc).

Moderately 

low

Suitable for most 

development. Avoid 

pebbly layers for 

waste-treatment 

facilities. Avoid 

expandable clay-rich 

layers for road and 

trail development. 

Avoid Tc during 

construction; it is 

rich in disseminated 

pyrite and other 

iron-sulfide 

minerals, and 

quickly produce acid 

drainage when 

exposed.

Massive bedding 

may be prone to 

large block slides 

when unit is 

undercut along 

rivers and gullies.

Diatoms (including 

Rhaphoneis 

diamantella), fish 

teeth, scales, shell 

fragments, lignitized 

wood, marine 

vertebrate bones, 

silicoflagellates, and 

dinocysts

Kaolinite may 

have been 

used for 

painting and 

dyes.

Kaolinite, quartzite,

and crystalline etched 

pebbles, heavy 

minerals, gravel, 

sand, kaolinitic clay 

(diatomaceous and 

expandable), pebbles

(including 

phosphate), and 

cobbles 

Support ridgetop forestsGood for most 

recreation 

Record Miocene 

marine 

depositional 

environments 
Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

FRSP Geologic Resources Inventory Report 23

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

TERTIARY - EOCENE

Nanjemoy 

Formation, 

undivided

(Tn)

Yellowish brown (weathered) to dark olive gray, 

greenish gray, and olive black glauconitic quartz 

sand; also fine to coarse, clayey and silty, 

micaceous and shelly interbeds of silty and sandy 

clay; lowermost beds are the highly glauconitic 

Potapaco Member (Tnp); upper Woodstock 

Member (Tnw) beds are more micaceous; up to 

64 m (210 ft) thick

Low

Generally suitable 

for most forms of 

development, but 

locally rich in 

disseminated pyrite 

and other ironsulfide minerals, 

which quickly 

produces acid 

drainage when 

exposed during 

construction. Ironrich nature of 

sediment generally 

produces poor 

groundwater quality.

Glauconitecemented sand 

may slide off 

slopes in large 

blocks or sheets, 

especially if water 

saturated

Trace fossils 

(bioturbation), shell 

fragments, and 

mollusks including 

Venericardia 

poapacoensis, 

Venericardia ascia, 

Macrocallista 

sumimpressa, Corbula 

aldrichi, Lucina 

dartoni, Lunatia sp., 

and Cadulus sp.

Iron sulfide 

concretions 

may have 

provided fire 

making 

materials.

Iron sulfide nodules, 

sand, gravel, silt, clay, 

and glauconite

None 

documented

Suitable for 

most forms of 

recreation 

Records Eocene 

marine 

depositional 

environments

TERTIARY - PALEOCENE

Aquia Formation 

(Ta)

Nearly massive glauconitic quartz sand; thickly 

bedded, fine to medium sands are interlayered 

with some clay and silt rich beds, as well as lenses 

of sandy and shelly limestone; up to 35 m (115 ft) 

thick. Fresh surfaces are dark olive gray and 

greenish black, whereas weathered exposures are 

yellowish gray to orange. 

Low

Supports an 

important 

freshwater aquifer.

Suitable for most 

development unless 

highly permeable 

layers are present, or 

significant 

heterogeneity exists 

locally, which may 

cause unit to be 

unstable.

Glauconitecemented sand 

may slide off 

slopes in large 

blocks or sheets, 

especially if water 

saturated or 

undercut along a 

poorly 

consolidated 

shelly layer.

Mollusks (Cucullaea 

gigantea, Ostrea 

alepidota, Crassatellites

sp., and Dosiniopsis

sp), ophiomorphatype burrows, 

gastropod (Turitella 

mortoni), bivalves 

(Ostrea sinuosa, 

Crassatellites 

alaeformis, and

Cucullaea sp.), 

foraminifera, 

dinocysts, 

nannofossils, and 

pollen

Stone wall 

along Sunken 

Road

Sand, glauconite, silt, 

and clay

Poor 

cementation 

may provide 

burrowing 

habitat.

Suitable for 

most forms of 

recreation 

Records marine to 

terrestrial 

depositional 

environment 

during the 

TertiaryQuaternary 

transition 

(Thanetian age)

CRETACEOUS

Potomac Formation 

(Kp)

Composed of three main sediment types: (1) fine 

to coarse feldspathic quartz sand and sandstone,

thickly bedded, with some trough cross-beds, in a 

poorly sorted clay-silt matrix; conglomerate beds 

present locally; (2) greenish gray to reddish 

brown silt and sandy clay, clayey silt, and clayey 

fine sand; some illite and smectite clay-silt plugs 

are present locally; (3) dark yellowish brown to 

olive gray lignitic sandy silt, clay, and silty fine 

sand and sandstone. Thickness <1 m (3.3 ft) to 

the west, to more than 500 m (1,640 ft) in the 

subsurface in the eastern part of the region. 

Low to 

moderately 

low for 

conglomerate 

layers

Supports an 

important 

freshwater aquifer in 

sandy layers.

Generally suitable 

for most 

development, but

variations in 

bedding, sediment, 

and degree of 

cementation may 

render unit unstable 

on slopes.

Susceptible to 

slumps and slides.

Clay-rich, massive 

bedded layers may 

spall in large 

blocks when unit 

is exposed on 

slopes.

Plant stems; silicified 

coniferous tree trunks;

leaf and stem 

impressions of ferns,

cycads, and other 

gymnosperms; pollen. 

Barremian?, Aptian, 

and Albian pollen and 

leaves 

May preserve 

ancient 

campsites 

and relics

Vein quartz, 

quartzite, illite, 

smectite clays, sand,

gravel, metamorphic 

rock cobbles and

pebbles, silt, boulders 

(some >1 m [3.3 ft] in 

diameter)

Supports 

eastern 

hardwood 

forests 

throughout 

region

Suitable for 

most forms of 

recreation 

unless present 

in bluffs along 

major 

waterways

Very widespread 

unit. Records 

Cretaceous 

environment along 

the Atlantic coast.

JURASSIC

Diabase and diabase 

dikes

(Jd)

Diabase, lowtitanium (Jdql)

Diabase, hightitanium (Jdqh)

Diabase, late-stage 

granophyric 

differentiates (Jdqhg)

Crystalline, fine- to medium-grained, dark gray to 

black diabase rocks; textures are generally 

intergranular to ophitic; primary minerals include 

bytownite-augite feldspar, minor biotite, with 

rare fayalitic olivine. Occur as narrow dikes with 

chilled aphanitic margins.

Jdql and Jdqh—light to dark gray, crystalline to 

porphyritic diabase

Jdqhg—sodic plagioclase, K-feldspar, quartz, and 

other minerals in small diabase pods 

High

Suitable for most 

development unless 

highly fractured or 

weathered (friable). 

Require blasting for 

excavation.

Rockfall potential 

if exposed on 

slope

None None 

documented

Sodium plagioclase, 

potassium feldspar, 

quartz, hornblende, 

biotite, pyroxene, 

calcic plagioclase, 

gabbro, granophyre, 

syenite, aplite, and 

olivine. Crystalline 

rocks may provide 

building material and 

crushed fill material 

for construction

May support 

localized plant 

species 

Suitable for 

most recreation 

unless exposed 

on a slope

Represents Jurassic 

volcanic activity 

accompanying 

Mesozoic 

extension

throughout the 

region. 

Radiometric age 

dates.
Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

FRSP Geologic Resources Inventory Report 24

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

TRIASSIC 

Mountain Run 

Member of the 

Tibbstown 

Formation (TRtmr) 

Balls Bluff Siltstone, 

lacustrine member 

(TRbl)

Balls Bluff Siltstone, 

fluvial member 

(TRbf)

Manassas Sandstone, 

upper unnamed 

member (TRmu)

Manassas Sandstone, 

Rapidan Member 

(TRmr)

Hornfels, 

metagraywacke and 

metaconglomerate 

(TRtm)

TRtmr—conglomerate containing pebble- to 

boulder-sized greenstones, interbedded with 

pebbly sandstone and upward-fining sequences; 

as much as 640 m (2,100 ft) thick. Lower portions 

contain metavolcanic rocks in a red to pale green 

clayey sandstone and siltstone matrix.

TRbl and TRmu—siltstone, mudstone, and shale, 

interbedded as fining-upward sequences. Color 

varies from reddish brown to dark gray to black 

and light purple. Mudstone is massive to 

laminated. TRbl is more than 1,000 m (3,280 ft) 

thick. TRfl is 100 to 200 m (328 to 656 ft) thick. 

Trmr—greenish gray to reddish arenitic 

sandstone, pebbly sandstone, siltstone, and minor 

shale, in fining-upward sequences. Lower beds 

consist of conglomerates containing rounded 

boulders, cobbles, and pebbles of metabasalt and 

other Piedmont rocks. 

TRtm—dark gray to bluish mauve, fine to coarse 

grained metasedimentary rocks present as 

contact aureoles around Jurassic diabase 

intrusions. Hornfels contains cordierite, epidote, 

and chlorite in a cooling-outward assemblage. 

Aureole is 60 to 120 m (197 to 393 ft) thick.

Moderate to 

moderately 

high for 

metamorphic 

rocks

Suitable for most 

development unless 

highly 

heterogeneous layers 

are present, or beds 

are heavily fractured. 

Avoid areas with 

high friability (due to 

weathering of 

carbonate cements). 

Swelling clays are 

locally abundant.

Large boulders 

and cobbles in 

TRtmr are 

susceptible to 

rockfall and mass 

wasting when 

exposed on slopes 

and undercut by 

local rivers. Clayand shale-rich 

layers are 

susceptible to 

slumping and 

sliding, especially 

when water 

saturated.

Triassic 

palynomorphs; TRbl

contains 

sporomorphs, root 

tubes, dinosaur and 

reptile trackways, 

stromatolitic 

limestone, shelly 

fossils, and paleosols.

Nodules of 

sulfides may 

have 

provided 

useful 

materials.

Greenstone pebbles, 

vein quartz clasts, 

caliche (carbonate 

nodules), chlorite, 

epidote, fragments of 

quartzite, metaarkose, marble, and 

phyllitic schist. 

Hornfels (cordierite, 

chlorite, and 

epidote). Sulfides 

(iron, copper, zinc, 

and lead). Hard rock 

for building 

materials. Attractive 

red stones for 

crushed aggregate 

and dimension stone.

Support 

eastern 

hardwood 

forests

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Type sections of 

the Mountain Run 

Member of the 

Tibbstown 

Formation and the 

Rapidan Member 

of the Manassas 

Formation.

Manassas 

Sandstone records 

fluvial environment 

following 

Alleghanian 

Orogeny.

CARBONIFEROUS

Falmouth Intrusive 

Suite (PMfi)

Masses of fine-grained monzogranite and 

pegmatitic (coarse-grained) granite, fine-grained 

granodiorite, and tonalite locally

High

Suitable for most 

development unless 

highly weathered or 

fractured

Susceptible to 

rockfall if exposed 

on slope

None

Large crystals 

may have 

provided 

trade 

material.

Tonalite and coarsely 

crystalline pegmatite. 

Attractive building 

stone material

None 

documented

May be friable, 

and unsuitable 

for climbing. 

Also may prove 

to be an 

unstable base 

for trails and 

other visitor 

facilities if 

highly 

weathered.

Dateable material

SILURIAN

Falls Run Granite (Sf)

Pale pink to nearly white hornblende and biotite 

granite gneiss. Composition ranges from 

monzogranite to granite and is strongly foliated.

High

Suitable for most 

development unless 

highly weathered or 

fractured. Avoid 

areas of intense 

preferential 

compositional 

weathering (along 

foliation). 

Susceptible to 

rockfall if exposed 

on slope

None None 

documented

Hornblende and

plagioclase. 

Attractive building 

stone material

None 

documented

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Dateable material. 

Records 

deformation and 

metamorphic 

conditions.

ORDOVICIAN

Quantico Formation 

(Oq)

Quantico Formation, 

quartzite (Oqq)

Metasedimentary 

rocks, undivided 

(Ou)

Metamonzogranite of 

Goldvein pluton (Og)

Phyllite (Op)

Phyllite with 

mylonitic rock 

(Opm)

Oq—dark gray phyllite and fine- to mediumgrained staurolite schist and biotite-muscovite 

schist. Some calc-silicate interbeds and quartzite 

lenses present locally. 

Ou—green silty phyllite and gray to white 

metasiltstone and fine-grained quartzite, finegrained mica schist, green slate and phyllite with 

scant quartzite and metagraywacke layers. 

Og—coarse- to medium-grained, mesocratic, 

foliated metamonzogranite. Green phyllites (Op)

may be highly sheared locally to mylonitic 

textures (Opm).

Moderate for 

highly 

deformed 

layers, high 

for 

undeformed

units

Heterogeneity of 

units may render 

them unstable locally 

for foundation, road, 

and facilities 

development.

Susceptible to 

spalling, rockfall, 

and other forms 

of mass wasting if 

undercut on 

slopes

None

Mineral 

inclusions

may have 

provided 

trade material

Staurolite, garnets, 

kyanite, quartzite 

lenses, and altered 

pink and green 

feldspar grains. 

Attractive building 

stone material (e.g., 

slate and granite)

Support large 

tracts of 

eastern 

hardwood 

forests

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Accreted terranes 

within the 

Piedmont province
Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

FRSP Geologic Resources Inventory Report 25

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

ORDOVICIAN AND (OR) CAMBRIAN

True Blue Formation 

(Oct)

True Blue Formation, 

Everona Limestone 

Member (OCte)

Mine-Run Complex, 

Melange Zone IV 

(OCmIV)

Mine-Run Complex, 

Melange Zone IV, 

metasedimentary 

(OCmIVq)

Mine-Run Complex, 

Melange Zone IV, 

metavolcanics 

(OCmIVv)

Mine-Run Complex, 

Melange Zone III 

(OCmIII)

Mine-Run Complex, 

Melange Zone II 

(OCmII)

Mine-Run Complex, 

Melange Zone I 

(OCmI)

Lunga Reservoir 

Formation (OCl)

Trondhjemite of the 

Horsepen Run 

pluton (OCtj)

Plagiogranite of the 

Richland Run pluton 

(OCpg)

Oct—calcareous and noncalcareous slate, 

siltstone, and some argillite; contains bodies of 

OCte as blue gray, fine-grained, metalimestone, 

which is about 160 m (525 ft) thick. 

OCm—contains four (I–IV) thrust slices of blockin-phyllite mélange. Rocks are gray to green. 

Zones are commonly phyllite, metasandstone and 

metasiltstone with some metavolcanic and 

phyllitic lenticular bodies. Zone III contains 

Proterozoic amphibolite, ultramafic rocks, biotite 

gneiss, granite gneiss, serpentinite, and foliated 

talc. Zones I and II contain Cambrian, felsic and 

mafic metavolcanic blocks. Mylonites are present 

locally. 

OCl—mélange consisting of nonstratified 

graywacke, surrounding blocks of greenstone and 

metamafic rocks. 

OCtj—granular, fine-grained, granophyric rock 

with intergrown albite and quartz. 

OCpg—plagiogranites and tonalites, present as 

metaintrusives, with intense deformation ranging 

from brittle cataclasis to ductile mylonitization.

Moderate for 

sedimentary 

and deformed 

rocks, high 

for crystalline 

intrusions

Suitable for most 

development unless 

calcareous layers are 

weathered, or the 

mylonites and 

cataclasites are 

highly deformed. 

Mafic rocks weather 

to clayey soils with 

high shrink-swell 

potential.

Contain large 

blocks separated 

by deformed 

zones of rock, 

which are 

susceptible to 

spalling and 

rockfall hazards 

on slopes. 

Carbonate 

minerals may 

weather 

preferentially, 

increasing the 

likelihood of 

failure and mass 

wasting. Clay 

(weathered rocks) 

layers may fail 

when water 

saturated. 

Some marine fossil 

remnants possible in 

sedimentary units

Chert and 

ironstone 

may have 

provided 

material for 

tools.

Chert, ironstone, 

phyllite, mylonite, 

euhedral magnetite, 

talc, serpentinite, 

blue green 

amphibole, and 

garnets. Limestone, 

slate, chips and 

pebbles of gneiss and 

schist, and quartz 

boulders

Widespread 

and support 

many habitats

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Accreted, exotic 

terranes

CAMBRIAN

Chopawamsic 

Formation (Cc)

Ta River 

Metamorphic Suite 

(Ct)

Metasedimentary 

rocks, undivided 

(Cm)

Cc—lenses and tongues of metavolcanic and 

metasedimentary rocks including silicic, 

intermediate, and mafic varieties, with some 

breccia and tuff layers present locally. 

Metasedimentary rock types include schist, metaarenite, and some gneiss. 

Ct—primarily dark gray to black, foliated 

amphibolitic gneisses. Some biotite rich areas 

present locally. 

Cm—mixture of tan, gray and light brown pebbly 

feldspathic quartzite, layered with purplish 

metasiltstone and phyllite. Quartzite is fine to 

coarse grained, with few preserved cross-beds, 

and deformed by slaty cleavage. 

Moderate to 

high 

depending on 

degree of 

deformation

Foliation and 

variability of rock 

types may render the 

units unstable for 

heavy development. 

Mafic rocks weather 

to clayey soils with 

high shrink-swell 

potential.

Slaty cleavage and 

deformation 

between large 

blocks may cause 

them to be 

susceptible mass 

wasting on slopes,

especially if 

undercut by 

erosion of 

weathered 

underlying units.

May contain traces of 

early life. Some 

metamorphosed 

burrows possible.

Caps ridges

Keratophyres, albitic

plagioclase, prismatic 

amphibole, 

greenstones, 

pyroxene, biotite, 

pyrite, sphalerite, and 

chalcopyrite. Lead 

and zinc ores, gold, 

and massive sulfide 

deposits mined near 

Mineral, Virginia.

Widespread 

and support 

many kinds of 

habitat

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Accreted, exotic 

terranes
Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

FRSP Geologic Resources Inventory Report 26

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

CAMBRIAN (?) 

Amphibole 

metagabbro

(Cg)

Felsic metavolcanic 

rocks (Cvf)

Mafic metavolcanic 

rocks (Cvm)

Altered tonalite and 

granodiorite 

granitoid blocks 

(Ctg)

Cg—massive, coarse to medium grained, and 

melanocratic. Some coarse-grained amphibole 

and epidote are abundant locally. 

Cvf—rare olistoliths 

Cvm—similar to Cc (described above)

Ctg—igneous intrusions of intermediate 

compositions (tonalites and granodiorites). 

Feldpsar minerals are preferentially weathered in 

these blocks.

High unless 

weathered, 

then 

moderate

Suitable for most 

development unless 

local blocks or 

plagioclase 

groundmass are 

altered and 

weathered,

rendering the unit 

friable. Mafic rocks 

weather to clayey 

soils with high 

shrink-swell 

potential.

Susceptible to 

spalling, rockfall, 

and other forms 

of mass wasting 

hazards

None None 

documented

Olistoliths, coarse 

grained amphibole, 

epidote, and quartz

None 

documented

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Oceanic crust and 

volcanic-arc 

material, as part of 

accreted terranes 

CAMBRIAN AND (OR) PROTEROZOIC

Blastomylonitic 

tonalite and 

granodiorite gneiss 

(CZg)

Amphibolitic 

xenoliths (CZa)

Ultramafic rocks 

(CZu)

Serpentinite (Czs)

Massive as well as 

foliated talc (CZt)

Biotite gneiss

(CZbg)

Serpentinite and talc 

(CZst)

Amphibolite and 

serpentinite (CZas)

Amphibolite and talc 

(CZat)

Serpentinite and 

mafic rock (CZsm)

Rock types include altered basalts, greenstones 

(serpentinite), and talc-rich layers. CZa contains 

muscovite-biotite granites. Present in pods and 

lenses locally throughout the western portions of 

the park area.

Moderate to 

high for 

crystalline 

blocks

Highly 

heterogeneous and 

typically heavily 

weathered, 

rendering units

rather weak for 

heavy development. 

Mafic rocks weather 

to clayey soils with 

high shrink-swell 

potential.

Unstable on 

slopes. Prone to 

mass wasting.

Records PrecambrianCambrian transitionNone 

documented

Talc, serpentinite, 

amphibole, 

plagioclase, quartz, 

epidote, chlorite, and 

xenoliths

Support 

species that 

prefer high 

iron, 

magnesium, 

and calcium

soils

Friable and

weathered (i.e., 

an unstable 

base for trails 

and other 

visitor facilities)

Accreted, exotic 

terranes

CAMBRIAN OR PROTEROZOIC

Holly Corner Gneiss 

(CZh)

Garrisonville Mafic 

Complex

(CZgn)

CZh—foliated hornblende and biotite rich gneiss, 

dark gray to black, fine to medium grained 

CZgn—fine to coarse grained, massive to foliated 

amphibolite and hornblendite. Some 

metapyroxenite, metawebsterite, and metanorite 

are present locally. Talc-amphibole schist is 

present near boundaries. 

High to 

moderately 

low for talcrich units

Not suitable for 

development. 

Typically weather to 

very clay-rich soils 

with very high 

shrink-swell 

potential. Avoid 

areas of intense 

preferential 

compositional 

weathering (along 

foliation).

May be 

susceptible to 

rockfall if exposed 

on slope. Talc and 

weathered areas 

may increase 

likelihood of 

sliding.

Records PrecambrianCambrian transition

Mineral 

inclusions

may have 

provided 

early trade 

material.

Andesine, quartz, 

epidote, diopside, 

amphibole, talc, and 

enstatite. Talc. 

Landscaping 

material. Attractive 

building stone.

None 

documented

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Accreted, exotic 

terranes
Gray-shaded rows indicate map units in the accompanying GIS data but not mapped within the park.

FRSP Geologic Resources Inventory Report 27

Age Map Unit 

(Symbol) Features and Description Erosion Resistance

Suitability for 

Infrastructure Hazards Paleontological Resources

Cultural 

Resources Mineral Resources Habitat Recreation Geologic Significance

PALEOZOIC AND (OR) PROTEROZOIC

Po River 

Metamorphic Suite, 

biotite gneiss and 

schist

(PZZp)

Po River 

Metamorphic Suite, 

quartzofeldspathic 

gneiss (PZZpm)

Po River 

Metamorphic Suite, 

amphibolite and 

amphibole gneiss 

(PZZpa)

Po River 

Metamorphic Suite, 

magnetite-bearing 

biotite gneiss 

(PZZpmb)

PZZp—primarily biotite gneiss and schist. Gneiss 

is dark-colored, layered and foliated, with 

micaceous materials concentrated in the dark 

layers, and quartz and feldspar concentrated in 

the lighter layers. Feldspar augens and 

hornblende gneiss present locally. Garnetiferous 

two-mica schist occurs locally. Many pegmatoids 

occur in tabular bodies forming concordant, silllike layers that range from less than 2.5 cm (1 in) 

to as much as 7.6 m (25 ft) thick. 

PZZpm—fine- to coarse-grained, strongly 

foliated, garnet-muscovite quartzofeldspathic 

gneiss 

PZZpa—fine- to coarse-grained, weakly to 

strongly foliated, irregularly layered amphibolite 

and amphibole gneiss 

PZZmb—quartz-rich, magnetite-bearing biotite 

gneiss

High to 

moderate 

where 

deformed

Avoid highly 

schistose layers as 

well as areas of 

intense preferential 

compositional 

weathering (along 

foliation). Mafic 

rocks weather to 

clayey soils with high 

shrink-swell 

potential.

Lenses of resistant 

rocks in schistose 

layers susceptible 

to block and 

rockfall

None None 

documented

Garnets, muscovite, 

amphiboles, 

magnetite, and 

feldspar augens. 

Landscaping 

material. Attractive 

building stone.

Garnets for abrasives.

May weather 

into soils that 

attract species 

preferring high 

sodium, 

calcium, and 

aluminum soils

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Po River accreted 

terrane

PALEOZOIC OR PROTEROZOIC

Diorite gneiss of the 

Potomac Creek 

pluton (PZZd)

Granite gneiss 

(PZZpg)

PZZd—gray quartz-plagioclase-biotite-rich 

diorite gneiss, with strong foliations and 

lineations; fine to medium grained and contains 

numerous cross-cutting dikes. 

PZZpg—fine- to medium-grained granite gneiss,

ranging in composition to tonalite. Numerous 

biotite gneiss, biotite schist, and amphibolite 

layers exist within this tabular to lenticular 

shaped unit. 

High

Highly 

heterogeneous and 

interlayered with 

younger units. 

Strong foliation 

creates zones of 

preferential jointing, 

which should be 

avoided for heavy 

development. May 

require blasting to 

excavate. Mafic 

rocks weather to 

clayey soils with high 

shrink-swell 

potential.

Lenses of resistant 

rocks in schistose 

layers may be 

susceptible to 

block and 

rockfall.

None None 

documented

Epidote, garnet, and 

muscovite. 

Landscaping 

material. Attractive 

building stone.

Garnet for abrasives.

Present near 

Fall Line; may 

correlate with 

specific species

Suitable for 

most forms of 

recreation, 

unless rocks are 

friable and 

weathered (i.e.,

an unstable 

base for trails 

and other 

visitor facilities)

Part of accreted 

terrane on the 

eastern edge of the 

Piedmont. Record 

later accretions 

onto the North 

American 

continent.

PROTEROZOIC

Catoctin Formation 

(Zc)

Charlottesville 

Formation of the 

Lynchburg Group 

(Zch)

Zc—dark green metabasalt, ranging in texture 

from aphanitic to medium-grained and massive. 

Local interbeds of phyllite and quartzite are 

present, with concordant slaty cleavage. 

Zch—primarily of miceaceous metasiltstone and 

massive quartz-muscovite-sericite schist with thin 

quartzite and brown meta-arkose interbeds;

typically very weathered, producing a light 

brownish gray sandy clay soil. 

Moderately 

high to 

moderate 

where unit is 

highly 

weathered

Avoid for most 

heavy development. 

Zc (metabasalts)

typically weather to a 

clay-rich soil with 

moderately high 

shrink-swell 

potential.

Susceptible to 

failure if exposed 

on slope or 

undercut . 

Rockfall hazard.

None

Greenstone 

may have 

been valued 

as trade 

material.

Quartz, muscovite, 

sericite, greenstone, 

chlorite, and epidote. 

Clay. Quartzite may 

provide flagstone 

material.

Support 

species that 

prefer high 

iron, 

magnesium, 

and calcium 

soils

Friable and

weathered (i.e., 

an unstable 

base for trails 

and other 

visitor facilities)

Zc represents

portions of ancient 

flood basalts that 

are correlative over 

a wide area. Rocks 

predate Paleozoic 

orogenic events 

and thus contain 

record of 

deformation 

throughout the 

Paleozoic orogenic 

cycle. 

FRSP Geologic Resources Inventory Report 29

Geologic History

This section describes the rocks and unconsolidated deposits that appear on the digital 

geologic map of Fredericksburg and Spotsylvania County Battlefields Memorial 

National Military Park, the environment in which those units were deposited, and the 

timing of geologic events that created the present landscape

Precambrian (prior to 542 million years ago)

The geologic history recorded in the Appalachian 

Mountains begins in the Mesoproterozoic Era (figs. 12, 

13, and 14A). The igneous rocks from this era crystallized 

over a period of 100 million years, and are more than a 

billion years old, making them among the oldest known 

rocks known from this region. They form a basement 

upon which all other rocks of the Appalachians were 

deposited (Southworth et al. 2001). At this time, the 

Grenville Orogeny (mountain-building event) was 

changing the landscape, raising and concentrating the 

continental crust of North America and Africa. 

Plutonism, volcanism, sedimentation, and deformation

that resulted from the orogeny are manifest in the 

metamorphic gneisses and granite-like rocks in the core 

of the present-day Blue Ridge Mountains west of 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park (Harris et al. 1997). 

The Neoproterozoic Era (fig. 14B), roughly 700 million 

years ago, is marked by extensional tectonism in this 

region, as the existing mass of continental crust broke 

apart and a sea basin formed, eventually becoming the 

Iapetus Ocean. This basin was a catchment for many of 

the sediments that now underlie the Blue Ridge

Mountains and Piedmont Plateau. In this continental 

rifting environment, flood basalts extruded onto the 

surface through cracks in the granitic gneisses of the Blue 

Ridge core, and other igneous rocks such as diabase and 

rhyolite crystallized within the North-American crust

(Southworth et al. 2001). The Catoctin Formation—

located in the western edges of the map for 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park—preserves the altered 

remains of the early flood basalts (Mixon et al. 2000). 

Paleozoic Era (542 to 251 million years ago)

During the Cambrian, deposition of significant deposits 

of sand, silt, and mud in nearshore, deltaic, barrier-island 

and tidal-flat areas was associated with the shallow 

marine setting along the eastern continental margin

(fig. 14C) (Schwab 1970; Kauffman and Frey 1979; 

Simpson 1991). As the Iapetus Ocean continued to 

expand, mid-ocean rift volcanism mixed basaltic lavas 

with marine sediments. Eventually, a grand carbonate 

platform, similar to present day Bahamas, developed in 

this region. This platform existed as an eastwardthickening wedge that persisted through the Cambrian 

and Ordovician periods (545–480 million years ago)

(fig. 14D). Meanwhile, episodes of mountain building 

and continental collision during the Paleozoic

contributed the heat and pressure needed to deform and 

metamorphose the entire package of intrusive rocks, 

basalts, and sediments into schists, gneisses, marbles, 

slates, and migmatites (Southworth et al. 2001). Many of 

these rocks occur in the Fredericksburg area.

By Early Ordovician time, orogenic activity along the 

eastern margin of the North American continent had 

begun again, this time involving the closing and eventual 

destruction of the Iapetus Ocean through subduction of 

oceanic crust. The process created volcanic arcs (like the 

Aleutian Islands in Alaska today) and uplifted the eastern 

margin of the North American continental crust

(fig. 14E) (Means 1995). The Taconic Orogeny

(approximately 440 to 420 million years ago in the central 

Appalachians) involved volcanic arc–continental margin

convergence. During convergence in the Iapetus Ocean 

basin, tectonic forces thrust oceanic crust, marine

sediments, and a volcanic arc onto the eastern edge of 

the North American continent. This mountain-building

episode caused initial metamorphism of the Catoctin 

Formation into metabasalts and metarhyolites, and 

sedimentary rocks of the ocean basin into quartzites and 

phyllites.

In response to the overriding plate thrusting westward 

onto the continental margin of North America, the crust 

bowed downwards, creating a deep basin that filled with 

mud and sand eroded from the highlands to the east 

(Harris et al. 1997). Present-day West Virginia was the 

center of the “Appalachian Basin” (fig. 14F). Sediments—

which eventually turned into sandstones, shales, 

siltstones, quartzites, and limestones—were deposited 

continuously in this shallow marine basin for about 200 

million years during the Ordovician to Permian periods.

During the Upper Ordovician, more oceanic sediments 

of the Iapetus Ocean were thrust westward onto other 

deepwater sediments of the western Piedmont along the 

Pleasant Grove fault. These rocks, now metamorphosed, 

currently underlie the Valley and Ridge province located 

west of the Blue Ridge (Fisher 1976).

The Acadian Orogeny (approximately 360 million years 

ago) continued the mountain building and regional 

metamorphism as the African Plate converged with the 

North American Plate, thrusting ocean sediments and 

volcanic rocks westward (Harris et al. 1997). 

Metamorphosed sedimentary rocks of the Piedmont 

record the transition from passive margin 

(“nonorogenic”) sedimentation to extensive, 

“synorogenic” sedimentation during Ordovician time 

(Fisher 1976). In the Fredericksburg area, these 

metasedimentary rocks include schists, metagraywackes, 
30 NPS Geologic Resources Division

phyllonites, mélanges, and metasiltstones. Oceanic crust 

caught up in these orogenic events now exists on the 

Piedmont Plateau as peridotites, metagabbros, 

serpentinites, and pyroxenites, along with other 

metamorphic and igneous rocks (Drake et al. 1994; 

Mixon et al. 2000).

The Iapetus Ocean basin completely closed during the 

Late Paleozoic Alleghany Orogeny (325–265 million 

years ago) as the North American continent collided 

with the African continent, forming the supercontinent 

Pangaea. This event also formed the present-day 

Appalachian mountain belt and was the last major 

collisional orogenic event in the evolution of the 

Appalachian mountains (fig. 14G) (Means 1995). This

collision deformed rocks by folding and faulting,

producing large-scale Appalachian structures. Presentday representatives of these structures are the Sugarloaf 

Mountain anticlinorium and the Frederick Valley 

synclinorium in the western Piedmont, as well as the Blue 

Ridge–South Mountain anticlinorium and numerous 

folds and faults of the Valley and Ridge province 

(Southworth et al. 2001).

Regionally deformed and metamorphosed rocks in the 

Fredericksburg and Spotsylvania area, are composed of a 

number of terranes with different origins and geologic 

histories (Spears et al. 2004). For example, the 

Chopawamsic terrane (not the Chopawamsic 

Formation) is an Ordovician volcanic and plutonic,

island-arc complex containing sedimentary rocks. 

East of the Chopawamsic volcanic arc is another exotic 

terrane, the Goochland terrane. This body of rock is a 

Meso- to Neoproterozoic basement massif. It contains 

gneiss, amphibolite, granite, and anorthosite. The rocks 

in this terrane underwent multiple stages of deformation 

and granulite-facies (high-pressure and temperature) 

metamorphism. Separating these two terranes is a highly 

deformed band of rocks known as the Spotsylvania highstrain zone (Spears et al. 2004).

Tectonic forces during the Alleghany Orogeny folded 

and faulted the Chopawamsic, Goochland, and other 

terranes south of the Fredericksburg area, reactivating

pre-existing thrust faults as both strike-slip and thrust 

faults (Southworth et al. 2001). Rocks of the Shenandoah

Valley, Blue Ridge, and Piedmont provinces were 

transported as a massive block (Blue Ridge–Piedmont 

thrust sheet) westward onto younger rocks of the Valley 

and Ridge along the North Mountain fault. The amount 

of compression was extreme, shortening the landscape 

by 20% to 50%, or approximately 125–350 km (75–

125 mi) (Harris et al. 1997). The Alleghany-aged

Appalachian Mountains were analogous to the modern 

day Himalaya Range in Asia. Now, erosion has exposed 

the metamorphosed core of the mountain range.

Mesozoic Era (251 to 65.5 million years ago)

Following the Alleghany Orogeny, during the Upper

Triassic (228–200 million years ago), an episode of 

continental rifting began (fig. 14H). At this time, Pangaea 

broke into the continents that exist today. This episode 

of rifting initiated the formation of the present Atlantic 

Ocean producing many block-fault basins along the 

continental margin of North America and was 

accompanied by volcanism. (Harris et al. 1997; 

Southworth et al. 2001). These Mesozoic basins lie to the 

west and south of the park, including the Culpeper and 

Taylorsville basins (Mixon et al. 2000). Igneous rocks

such as diabase accompanied rifting and intruded the 

new strata as sub-horizontal sheets, or sills, and nearvertical dikes that extend beyond the basins into adjacent 

rocks. Collectively, these Mesozoic basins make up the

Newark Basin system. This system of rift basins extends 

along the length of the Appalachians in a nearly linear 

trend from Massachusetts to South Carolina.

In Triassic time, streams feeding large alluvial fans 

carried sediments and debris from the recently uplifted 

Blue Ridge and Piedmont provinces, depositing them 

into these fault-bounded basins. These shallow-water, 

lacustrine deposits eventually became shales and 

sandstones. The Manassas Sandstone and the Balls Bluff 

Siltstone (named for exposures within and near 

Manassas National Battlefield Park) are part of these 

Newark Basin sedimentary rocks in the Fredericksburg 

and Spotsylvania County Battlefields Memorial National 

Military Park area.

After emplacement of igneous rocks during the Jurassic

Period (200 million years ago), the region underwent a 

period of slow uplift and erosion. The uplift was in 

response to isostatic adjustments within the crust, which 

forced the continental crust upwards and exposed it to

further erosion (fig. 14I). The igneous rocks, being 

harder than the surrounding sedimentary rocks, were 

more resistant to erosion and now cap many of the 

higher ridges, hills, and slopes in the region. Rocks 

exposed at the surface today in the Piedmont must have 

been at least 20 km (12 mi) below the surface prior to 

regional uplift and erosion.

Throughout the Mesozoic Era, thick deposits of 

unconsolidated gravel, sand, and silt shed from eroding 

mountains became alluvial fans. These fans spread 

eastward from the mountain front and covered the

metamorphic and igneous rocks of the Piedmont, 

eventually forming the lowermost strata of the Atlantic 

Coastal Plain (Duffy and Whittecar 1991; Whittecar and 

Duffy 2000; Southworth et al. 2001). The Cretaceous 

Potomac Formation is an example of a widespread clastic 

wedge of sediment. 

Since the regional uplift of the Appalachian Mountains 

and the subsequent breakup of Pangaea, the North 

American plate has continued to drift toward the west,

concentrating tectonic activity on the western edge and 

creating an eastern passive margin. The isostatic uplift

that occurred after the Alleghany Orogeny continued

throughout the Cenozoic Era (Harris et al. 1997). This

uplift and adjustment may be responsible for occasional 

seismic events felt throughout the region. 
FRSP Geologic Resources Inventory Report 31

Cenozoic Era (the past 65.5 million years)

Weathering and erosion has also continued throughout 

the Cenozoic Era lowering the height of the mountains

to west, and depositing alluvial terraces along major

rivers (fig. 14J). The geomorphology of the Potomac, 

Rappahannock, and other large river valleys is the result 

of erosion and deposition from the mid-Cenozoic to the 

present (or at least the last 5 million years). The 

distribution of floodplain alluvium and ancient fluvial 

terraces along the rivers and adjacent tributaries record 

the historical development of these drainage systems.

There is little evidence that the rivers migrated laterally 

across the broad, relatively flat regions of the Piedmont 

Plateau and upper Coastal Plain; these rivers may have 

simply cut downward through very old, resistant rocks, 

washing away their earlier courses as the landscape rose 

beneath them (Southworth et al. 2001).

Many terrace deposits occur in the Fredericksburg and 

Spotsylvania County Battlefields Memorial National 

Military Park, along the Rappahannock River. The 

position, distribution, thickness, and elevation of these 

terraces and their sediments vary by province, age, and 

rock type. The elevations of terraces along the rivers 

show that the slope values of the ancient and modern 

river valleys are similar, which suggests that the terraces 

formed as the result of either eustatic sea level drop or 

uplift (Zen 1997a,b).

Though glaciers of the Pleistocene ice ages never reached 

the central Virginia area (the southern terminus was in 

northeastern Pennsylvania), the intermittent colder 

climates played a role in the formation of the landscape 

at Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park. Freeze-and-thaw 

cycles at higher elevations led to increased erosion of 

large boulders and rocks by ice wedging. Sea level 

fluctuations throughout the Pleistocene caused the base

level of many of the area’s rivers to change. During 

regressions (sea level drops), the rivers eroded their 

channels, exposing the deformed bedrock of the 

Piedmont Plateau. During oceanic transgressions, the 

river basins flooded, which resulted in beach-sediment

deposition of younger Coastal Plain strata.
32 NPS Geologic Resources Division

Figure 12. Geologic timescale. Included are major life history and tectonic events occurring on the North American continent. Red lines 

indicate major unconformities between eras. Isotopic ages shown are in millions of years (Ma). Compass directions in parentheses indicate 

the regional location of individual geologic events. Adapted from the U.S. Geological Survey, http://pubs.usgs.gov/fs/2007/3015/ with 

additional information from the International Commission on Stratigraphy. http://www.stratigraphy.org/view.php?id=25.
FRSP Geologic Resources Inventory Report 33

Figure 13. Geologic timescale specific to Virginia. Dates are approximate and presented in thousands (ka) and millions of years (Ma) before 

present. Modified from Bailey (1997–2003) by Trista L. Thornberry-Ehrlich (Colorado State University).
34 NPS Geologic Resources Division

Figure 14 Geologic evolution of the Appalachian Mountains in the Fredericksburg area. Cross-sectional view is west to east. (A) Intrusions of 

granitic gneiss, metamorphism, and deformation related to the Grenville Orogeny lasted 60 million years, from 1.1 billion to 950 million years 

ago. These rocks occur in the Blue Ridge province. (B) Continental rifting and volcanic activity in the Grenville terrane (current Blue Ridge 

province) and deposition of turbidites in deepwater basin to the east (current Piedmont province) lasted about 200 million years, from about 

770 to 575 million years ago. (C) The margin of the continent became stable with quiet waters filling with carbonate sediments (rocks of the 

current Great Valley and Frederick Valley). Shelled organisms appeared about 545 million years ago. Deepwater sediments filled a basin east 

of the shelf margin for about 65 million years. 
FRSP Geologic Resources Inventory Report 35

Figure 14, continued. (D) Following deposition, the stable shelf foundered as the Taconic Orogeny (E) elevated the rocks to the east and 

provided a source for the clastic materials that make up the shale of the Martinsburg Formation. Plutonic rocks intruded the rocks in the 

Piedmont province. (F) A thick sequence of sediments began filling a deepening Appalachian basin over a span of 120 million years. Most of 

these rocks now occur in the Valley and Ridge province. About 370 million years ago, magma (igneous rock) intruded the rocks near Great 

Falls. 
36 NPS Geologic Resources Division

Figure 14, continued. (G) About 240 million years ago, the continental tectonic plates of North America and Africa collided, resulting in the 

Alleghany Orogeny. Many of the folds and faults in rocks west of the Piedmont province record this event. (H) About 20 million years later, 

continental rifting began and lasted for about 20 million years (220−200 million years ago). (I) Thick sequences of sediments filled faultbounded basins; volcanic activity (continental rifting) created the Atlantic Ocean. The Culpeper and Gettysburg basins in the western 

Piedmont are the result of this event. (J) For the last 200 million years, erosion has denuded the landscape and rivers have carried the 

sediment eastward to deposit the thick strata of the Atlantic Coastal Plain. The green star on the figure represents the location of 

Fredericksburg and Spotsylvania County Battlefields Memorial National Military Park. Diagrams are not to scale and are broadly 

representative of the tectonic settings. Adapted from Southworth et al. (2001) by Trista L. Thornberry-Ehrlich (Colorado State University).
FRSP Geologic Resources Inventory Report 37

Glossary

This glossary contains brief definitions of technical geologic terms used in this report. Not all 

geologic terms used are referenced. For more detailed definitions or to find terms not listed 

here please visit: http://geomaps.wr.usgs.gov/parks/misc/glossarya.html. Definitions are 

based on those in the American Geological Institute Glossary of Geology (fifth edition; 2005).

active margin. A tectonically active margin where 

lithospheric plates come together (convergent 

boundary), pull apart (divergent boundary) or slide 

past one another (transform boundary). Typically 

associated with earthquakes and, in the case of 

convergent and divergent boundaries, volcanism. 

Compare to “passive margin.”

alluvial fan. A fan-shaped deposit of sediment that 

accumulates where a hydraulically confined stream 

flows to a hydraulically unconfined area. Commonly 

out of a mountainous area into an area such as a valley 

or plain.

alluvium. Stream-deposited sediment.

amygdule. A gas cavity or vesicle in an igneous rock, 

which is filled with secondary minerals.

(“amygdaloidal” describes rocks with amygdules).

anticline. A convex-upward (“A” shaped) fold. Older 

rocks are found in the center.

anticlinorium. A large, regional feature with an overall 

shape of an anticline. Composed of many smaller 

folds.

aquifer. A rock or sedimentary unit that is sufficiently 

porous that it has a capacity to hold water, sufficiently 

permeable to allow water to move through it, and 

currently saturated to some level.

arenite. A general term for sedimentary rocks composed 

of sand-sized fragments with a pure or nearly pure 

chemical cement and little or no matrix material 

between the fragments.

augen. Describes large lenticular mineral grains or 

mineral aggregates that have the shape of an eye in 

cross-section. Found in metamorphic rocks such as 

schists and gneisses.

aureole. A zone surrounding an igneous intrusion in 

which the country rock shows the effects of contact 

metamorphism from the high temperature, molten 

material.

basement. The undifferentiated rocks, commonly 

igneous and metamorphic, that underlie rocks 

exposed at the surface.

basin (structural). A doubly plunging syncline in which 

rocks dip inward from all sides.

basin (sedimentary). Any depression, from continental to 

local scales, into which sediments are deposited.

bed. The smallest sedimentary strata unit, commonly 

ranging in thickness from one centimeter to a meter or 

two and distinguishable from beds above and below.

bedrock. A general term for the rock that underlies soil 

or other unconsolidated, surficial material.

bedding. Depositional layering or stratification of 

sediments.

block (fault). A crustal unit bounded by faults, either 

completely or in part.

bog iron ore. A general term for a soft, spongy, and 

porous deposit of impure hydrous iron oxides formed 

in bogs, marshes, swamps, peat mosses, and shallow 

lakes by precipitation from iron-bearing waters and by 

the oxidizing action of algae, iron bacteria, or the 

atmosphere.

calcareous. Describes rock or sediment that contains the 

mineral calcium carbonate (CaCO3).

cementation. Chemical precipitation of material into 

pores between grains that bind the grains into rock.

channel bar. An elongate deposit of sand and gravel 

located in the course of a stream. Common in braided 

streams.

chemical weathering. Chemical breakdown of minerals 

at Earth’s surface via reaction with water, air, or 

dissolved substances; commonly results in a change in 

chemical composition more stable in the current 

environment.

clastic. Describes rock or sediment made of fragments of 

pre-existing rocks (clasts).

clay. Can be used to refer to clay minerals or as a 

sedimentary fragment size classification (less than 

1/256 mm [0.00015 in]).

conglomerate. A coarse-grained, generally unsorted, 

sedimentary rock consisting of cemented, rounded 

clasts larger than 2 mm (0.08 in).

continental crust. Crustal rocks rich in silica and alumina 

that underlie the continents; ranging in thickness from 

35 km (22 mi) to 60 km (37 mi) under mountain ranges.

convergent boundary. A plate boundary where two 

tectonic plates are colliding.

craton. The relatively old and geologically stable interior 

of a continent.

cross-bedding. Uniform to highly varied sets of inclined 

sedimentary beds deposited by wind or water that 

indicate flow conditions such as water flow direction 

and depth.

cross section. A graphical interpretation of geology, 

structure, and/or stratigraphy in the third (vertical) 

dimension based on mapped and measured geological 

extents and attitudes depicted in a vertically oriented 

plane.

crust. Earth’s outermost compositional shell, 10 to 40 km 

(6 to 25 mi) thick, consisting predominantly of 

relatively low-density silicate minerals (also see 

“oceanic crust” and “continental crust”).

crystalline. Describes a regular, orderly, repeating 

geometric structural arrangement of atoms.
38 NPS Geologic Resources Division

debris flow. A moving mass of rock fragments, soil, and 

mud, in which more than half the particles of which 

are larger than sand size.

deformation. A general term for the processes of faulting, 

folding, and shearing of rocks as a result of various 

Earth forces such as compression (pushing together) 

and extension (pulling apart).

delta. A sediment wedge deposited where a stream flows 

into a lake or sea.

diabase. An intrusive igneous rock consisting primarily 

of the minerals labradorite and pyroxene.

dike. A narrow igneous intrusion that cuts across 

bedding planes or other geologic structures.

dip. The angle between a bed or other geologic surface 

and horizontal.

dip-slip fault. A fault with measurable offset where the 

relative movement is parallel to the dip of the fault.

discordant. Describes contacts between strata that cut 

across or are set at an angle to the orientation of 

adjacent rocks.

drainage basin. The total area from which a stream 

system receives or drains precipitation runoff.

eustatic. Relates to simultaneous worldwide rise or fall of 

sea level.

extrusive. Describes molten (igneous) material that has 

erupted onto Earth’s surface.

facies (metamorphic). The pressure and temperature 

conditions that result in a particular, distinctive suite 

of metamorphic minerals.

facies (sedimentary). The depositional or environmental 

conditions reflected in the sedimentary structures, 

textures, mineralogy, fossils, etc. of a sedimentary 

rock.

fault. A break in rock along which relative movement has 

occurred between the two sides.

felsic. Describes an igneous rock having abundant lightcolored minerals such as quartz, feldspars, or 

muscovite. Compare to “mafic.”

foliation. A preferred arrangement of crystal planes in 

minerals. In metamorphic rocks, the term commonly 

refers to a parallel orientation of planar minerals such 

as micas.

footwall. The mass of rock beneath a fault surface (also 

see “hanging wall”).

formation. Fundamental rock-stratigraphic unit that is 

mappable, lithologically distinct from adjoining strata, 

and has definable upper and lower contacts.

fracture. Irregular breakage of a mineral; also any break 

in a rock (e.g., crack, joint, fault)

frost wedging. The breakup of rock due to the 

expansion of water freezing in fractures.

gabbro. A group of dark-colored, intrusive igneous 

rocks. The intrusive equivalent of basalt.

geology. The study of Earth including its origin, history, 

physical processes, components, and morphology.

glauconite. A green mineral, closely related to the micas. 

It is an indicator of very slow sedimentation.

gneiss. A foliated rock formed by regional 

metamorphism with alternating bands of dark and 

light minerals.

hanging wall. The mass of rock above a fault surface 

(also see “footwall”).

igneous. Refers to a rock or mineral that originated from 

molten material; one of the three main classes of 

rocks—igneous, metamorphic, and sedimentary.

intrusion. A body of igneous rock that invades (pushes 

into) older rock. The invading rock may be a plastic 

solid or magma.

isostacy. The condition of equilibrium, comparable to 

floating, of the units of the lithosphere above the 

asthenosphere. Crustal loading (commonly by large ice 

sheets) leads to isostatic depression or downwarping; 

removal of the load leads to isostatic uplift or 

upwarping.

joint. A semi-planar break in rock without relative 

movement of rocks on either side of the fracture 

surface.

karst topography. Topography characterized by 

abundant sinkholes and caverns formed by the 

dissolution of calcareous rocks.

lacustrine. Pertaining to, produced by, or inhabiting a 

lake or lakes.

landslide. Any process or landform resulting from rapid, 

gravity-driven mass movement.

lava. Still-molten or solidified magma that has been 

extruded onto Earth’s surface though a volcano or 

fissure.

lens. A sedimentary deposit characterized by converging 

surfaces, thick in the middle and thinning out toward 

the edges, resembling a convex lens.

levee. Raised ridge lining the banks of a stream. May be 

natural or artificial.

lithosphere. The relatively rigid outmost shell of Earth’s 

structure, 50 to 100 km (31 to 62 miles) thick, that 

encompasses the crust and uppermost mantle.

mafic. Describes dark-colored rock, magma, or minerals 

rich in magnesium and iron. Compare to “felsic.”

magma. Molten rock beneath Earth’s surface capable of 

intrusion and extrusion.

mantle. T The zone of Earth’s interior between the crust 

and core.

massif. A massive topographic and structural feature, 

especially in an orogenic belt, commonly formed of 

rocks more rigid than those of its surroundings. These 

rocks may be protruding bodies of basement rocks, 

consolidated during earlier orogenies, or younger 

plutonic bodies.

matrix. The fine grained material between coarse (larger) 

grains in igneous rocks or poorly sorted clastic 

sediments or rocks. Also refers to rock or sediment in 

which a fossil is embedded.

mechanical weathering. The physical breakup of rocks 

without change in composition. Synonymous with 

“physical weathering.”

mélange. A mappable body of jumbled rock that includes 

fragments and blocks of all sizes, both formed in place 

and those formed elsewhere, embedded in a 

fragmented and generally sheared matrix.

member. A lithostratigraphic unit with definable contacts 

that subdivides a formation.

meta–. A prefix used with the name of a sedimentary or 

igneous rock, indicating that the rock has been 

metamorphosed.
FRSP Geologic Resources Inventory Report 39

metamorphic. Describes the process of metamorphism 

or its results. One of the three main classes of rocks—

igneous, metamorphic, and sedimentary.

metamorphism. Literally, a change in form.

Metamorphism occurs in rocks through mineral 

alteration, formation, and/or recrystallization from 

increased heat and/or pressure.

mid-ocean ridge. The continuous, generally submarine, 

seismic, median mountain range that marks the 

divergent tectonic margin(s) in the world’s oceans.

migmatite. Literally, “mixed rock” with both igneous 

and metamorphic characteristics due to partial melting 

during metamorphism.

mud cracks. Cracks formed in clay, silt, or mud by 

shrinkage during dehydration at Earth’s surface.

mylonite. A fine-grained, foliated rock typically found in 

localized zones of ductile deformation, often formed at 

great depths under high temperature and pressure.

normal fault. A dip-slip fault in which the hanging wall 

moves down relative to the footwall.

obduction. The process by which the crust is thickened 

by thrust faulting at a convergent margin.

oceanic crust. Earth’s crust formed at spreading ridges 

that underlies the ocean basins. Oceanic crust is 6 to 7 

km (3 to 4 miles) thick and generally of basaltic 

composition.

olistolith. A large block or other rock mass (usually

greater than 10 m or 33 ft) transported by submarine 

gravity sliding or slumping and included within a 

debris-flow deposit called an olistostrome.

orogeny. A mountain-building event.

outcrop. Any part of a rock mass or formation that is 

exposed or “crops out” at Earth’s surface.

overbank deposits. Alluvium deposited outside a stream 

channel during flooding.

Pangaea. A theoretical, single supercontinent that 

existed during the Permian and Triassic periods.

parent rock. Rock from which soil, sediments, or other 

rocks are derived.

passive margin. A margin where no plate-scale tectonism 

is taking place; plates are not converging, diverging, or 

sliding past one another. An example is the east coast 

of North America (compare to “active margin”).

pebble. Generally, small rounded rock particles from 4 to 

64 mm (0.16 to 2.52 in) in diameter.

permeability. A measure of the relative ease with which 

fluids move through the pore spaces of rocks or 

sediments.

phyllite. A metamorphosed rock, intermediate in grade 

between slate and mica schist, with minute crystals of 

graphite, sericite, or chlorite that impart a silky sheen 

to the surfaces (“schistosity”).

plateau. A broad, flat-topped topographic high 

(terrestrial or marine) of great extent and elevation 

above the surrounding plains, canyons, or valleys.

plate tectonics. The concept that the lithosphere is 

broken up into a series of rigid plates that move over 

Earth’s surface above a more fluid asthenosphere.

pluton (plutonic). A body of intrusive igneous rock that 

crystallized at some depth beneath Earth’s surface.

porosity. The proportion of void space (e.g., pores or 

voids) in a volume of rock or sediment deposit.

quartzite. Metamorphosed quartz sandstone.

recharge. Infiltration processes that replenish 

groundwater.

regression. A long-term seaward retreat of the shoreline 

or relative fall of sea level.

relative dating. Determining the chronological 

placement of rocks, events, or fossils with respect to 

the geologic time scale and without reference to their 

numerical age.

reverse fault. A contractional high-angle (greater than 

45°

) dip-slip fault in which the hanging wall moves up 

relative to the footwall (also see “thrust fault”).

rhyolite. A group of extrusive volcanic rocks, typically 

porphyritic and commonly exhibiting flow texture, 

with phenocrysts of quartz and alkali feldspar in a 

glassy to cryptocrystalline groundmass. The finegrained extrusive equivalent of granite.

rift valley. A depression formed by grabens along the 

crest of an oceanic spreading ridge or in a continental 

rift zone.

roundness. The relative amount of curvature of the 

“corners” of a sediment grain.

sand. A clastic particle smaller than a granule and larger 

than a silt grain, having a diameter in the range of 1/16 

mm (0.0025 in) to 2 mm (0.08 in).

sandstone. Clastic sedimentary rock of predominantly 

sand-sized grains.

scarp. A steep cliff or topographic step resulting from 

displacement on a fault, or by mass movement, or 

erosion. Also called an “escarpment.”

schist. A strongly foliated metamorphic rock that can be 

readily be split into thick flakes or slabs. Micas are 

arranged in parallel, imparting a distinctive sheen, or 

“schistosity” to the rock.

seafloor spreading. The process by which tectonic plates 

diverge and new lithosphere is created at oceanic 

ridges.

sediment. An eroded and deposited, unconsolidated 

accumulation of rock and mineral fragments.

sequence. A major informal rock-stratigraphic unit that 

is traceable over large areas and defined by a 

sediments associated with a major sea level 

transgression-regression.

shale. A clastic sedimentary rock made of clay-sized 

particles that exhibit parallel splitting properties.

sill. An igneous intrusion that is of the same orientation 

as the surrounding rock.

silt. Clastic sedimentary material intermediate in size 

between fine-grained sand and coarse clay (1/256 to 

1/16 mm [0.00015 to 0.002 in]).

siltstone. A variably lithified sedimentary rock composed 

of silt-sized grains.

slate. A compact, fine-grained metamorphic rock that 

can be split into slabs and thin plates. Most slate was 

formed from shale.

slope. The inclined surface of any geomorphic feature or 

measurement thereof. Synonymous with “gradient.”

slump. A generally large, coherent mass movement with a 

concave-up failure surface and subsequent backward 

rotation relative to the slope.

soil. Surface accumulation of weathered rock and 

organic matter capable of supporting plant growth and 
40 NPS Geologic Resources Division

often overlying the parent material from which it 

formed.

spring. A site where water issues from the surface due to 

the intersection of the water table with the ground 

surface.

strata. Tabular or sheet-like masses or distinct layers of 

rock.

stratigraphy. The geologic study of the origin,

occurrence, distribution, classification, correlation, 

and age of rock layers, especially sedimentary rocks.

strike. The compass direction of the line of intersection 

of an inclined surface with a horizontal plane.

strike-slip fault. A fault with measurable offset where the 

relative movement is parallel to the strike of the fault. 

Said to be “sinistral” (left-lateral) if relative motion of 

the block opposite the observer appears to be to the 

left. “Dextral” (right-lateral) describes relative motion 

to the right.

subduction zone. A convergent plate boundary where 

oceanic lithosphere descends beneath a continental or 

oceanic plate and is carried down into the mantle.

subsidence. The gradual sinking or depression of part of 

Earth’s surface.

syncline. A downward curving (concave-up) fold with 

layers that dip inward; the core of the syncline 

contains the stratigraphically-younger rocks.

synclinorium. A composite synclinal structure of regional 

extent composed of lesser folds.

synorogenic. Describes a geologic process or event 

occurring during a period of orogenic activity; also 

describes a rock or feature formed by those processes 

or event.

tectonic. Relating to large-scale movement and 

deformation of Earth’s crust.

terraces (stream). Step-like benches surrounding the 

present floodplain of a stream due to dissection of 

previous flood plain(s), stream bed(s), and/or valley 

floor(s).

terrane. A region or group of rocks with similar geology, 

age, or structural style.

terrestrial. Relating to land, Earth, or its inhabitants.

thrust fault. A contractional dip-slip fault with a 

shallowly dipping fault surface (less than 45°

) where 

the hanging wall moves up and over relative to the 

footwall.

tongue (stratigraphy). A member of a formation that 

extends and wedges out away from the main body of a 

formation.

topography. The general morphology of Earth’s surface 

including relief and location of natural and 

anthropogenic features.

trace (fault). The exposed intersection of a fault with 

Earth’s surface.

trace fossils. Tracks, trails, burrows, coprolites (dung), 

etc., that preserve evidence of organisms’ life activities, 

rather than the organisms themselves.

transgression. Landward migration of the sea due to a 

relative rise in sea level.

trend. The direction or azimuth of elongation of a linear 

geological feature.

ultramafic. Describes rock composed chiefly of mafic 

(dark-colored, iron and magnesium rich) minerals.

uplift. A structurally high area in the crust, produced by 

movement that raises the rocks.

volcanic. Describes anything related to volcanoes. Can 

refer to igneous rock crystallized at or near Earth’s 

surface (e.g., lava).

volcanic exhalation. An emission of gas or ash from a 

vent in a relatively short burst.

water table. The upper surface of the saturated zone; the 

zone of rock in an aquifer saturated with water.

weathering. The set of physical, chemical, and biological 

processes by which rock is broken down.

xenolith. A rock particle, formed elsewhere, entrained in 

magma as an inclusion.
FRSP Geologic Resources Inventory Report 41

Literature Cited

This section lists references cited in this report. A more complete geologic bibliography is 

available from the National Park Service Geologic Resources Division.

Anonymous. 1987. Culpeper Stone Company, Inc. 

Virginia Mineral Producers 1. Virginia Division of 

Mineral Resources, Charlottesville, Virginia, USA.

Axt, J. R., and M. R. Walbridge. 1999. Phosphate removal 

capacity of palustrine forested wetlands and adjacent 

uplands in Virginia. Soil Science Society of America 

Journal 63(4):1019–1031. 

Bailey, C. M. 1999. Generalized Geologic Terrane Map 

of the Virginia Piedmont and Blue Ridge. College of 

William and Mary. (http://www.wm.edu/geology/ 

virginia/terranes.html) Accessed 6 June 2005.

Bailey, C. M., B. E. Francis, and E. E. Fahrney. 2004. 

Strain and vorticity analysis of transpressional highstrain zones from the Virginia Piedmont, USA. Pages 

249–264 in G. I. Alsop, R. E. Holdsworth, K. J. W. 

McCaffrey, M. Hand, editors. Flow Processes in Faults 

and Shear Zones. Special Publications 224. Geological 

Society of America, Boulder, Colorado, USA.

Bailey, C. M. 1997–2003. Geologic Time Chart of 

Virginia. College of William and Mary, Williamsburg, 

Virginia. (http://web.wm.edu/geology/virginia/

provinces/geotime.html). Accessed 4 June 2010.

Cranford, S. L., A. R. Bobyarchick, L. Pavlides, and K.

Wier. 1982. Stream control by foliation, joints, and 

folds in the Rappahannock River drainage system near 

Fredericksburg, Virginia. Miscellaneous Investigations 

Series I-1285. U.S. Geological Survey, Reston, Virginia, 

USA.

Dodd, C. M., A. M. Tuomey, K. C. Ulrich, and R. L. 

McConnell. 1995. Development as a cause of flash 

flooding; the August 20, 1994 flood, Fredericksburg, 

Virginia. Geological Society of America Abstracts with 

Programs 27(2):49. 

Drake, A. A., Jr., A. J. Froelich, R. E. Weems, and K. Y. 

Lee. 1994. Geologic map of the Manassas Quadrangle, 

Fairfax and Prince William counties, Virginia (scale 

1:24,000). Geologic Quadrangle Map GQ-1732. U.S. 

Geological Survey, Reston, Virginia, USA.

Duffy, D. F., and G. R. Whittecar. 1991. Geomorphic 

development of segmented alluvial fans in the 

Shenandoah Valley, Stuarts Draft, Virginia. Geological 

Society of America Abstracts with Programs 23(1):24. 

Ehlen, J., and R. J. Abrahart. 2002. Effective use of terrain 

in the American Civil War; the battle of 

Fredericksburg, December 1862. Pages 63–97 in R. 

Doyle and M. R. Bennett, editors. Fields of Battle:

Terrain in Military History. Geojournal Library, 

Volume 64. Kluwer Academic Publishers [now 

Springer], New York, New York, USA.

Ehlen, J. 2004. Terrain and the Battle of Fredericksburg, 

December 13, 1862. Pages 247–261 in S. Southworth 

and W. Burton, editors. Geology of the National 

Capital Region; Field Trip Guidebook. Circular C1264. U.S. Geological Survey, Reston, Virginia, USA.

Fisher, G. W. 1976. The geologic evolution of the 

northeastern Piedmont of the Appalachians. 

Geological Society of America Abstracts with 

Programs 8(2):172–173.

Flora, S. P., and W. C. Sherwood. 2001. Study of the 

lithology and source of the stone wall along Sunken 

Road at Fredericksburg, Virginia. Virginia Journal of 

Science 52(2):110. 

Francis, B. E., D. B. Spears, and C. M. Bailey. 2001. A 

magnetic investigation of diabase dikes in the central 

Piedmont, Virginia. Geological Society of America 

Abstracts with Programs 33(2):22. 

Frangos, W., and C. R. Geier. 2003. Geophysical 

investigation in support of archeological studies at the 

Fredericksburg Civil War battleground. Pages 59–67 in

Symposium on the Application of Geophysics to 

Engineering and Environmental Problems (SAGEEP), 

Volume 16. Environmental and Engineering 

Geophysical Society (EEGS), Society of Exploration 

Geophysicists, Tulsa, Oklahoma, USA.

Harris, A. G., E. Tuttle, and S. D. Tuttle. 1997. Geology of 

national parks. Fifth edition. Kendall/Hunt Publishing 

Company, Dubuque, Iowa, USA.

Kauffman, M. E., and E. P. Frey. 1979. Antietam 

sandstone ridges; exhumed barrier islands or faultbounded blocks? Geological Society of America 

Abstracts with Programs 11(1):18.

Kenworthy, J. P., C. C. Visaggi, and V. L. Santucci. 2006. 

Paleontological Resource Inventory and Monitoring, 

Mid-Atlantic Network. TIC# D-800. National Park 

Service, Fort Collins, Colorado, USA.

Lord, M. L., D. Germanoski, and N. E. Allmendinger. 

2009. Fluvial geomorphology: Monitoring stream 

systems in response to a changing environment. Pages 

69–104 in Young, R. and L. Norby, editors. Geological 

Monitoring. Geological Society of America, Boulder, 

Colorado, USA.
42 NPS Geologic Resources Division

McConnell, R. L., and K. C. Ulrich. 1995. Development 

as a cause of flash flooding in northern Virginia; 

implications for the next hurricane. Geological Society 

of America Abstracts with Programs 27(6):143. 

Means, J. 1995. Maryland’s Catoctin Mountain parks; an 

interpretive guide to Catoctin Mountain Park and 

Cunningham Falls State Park. McDonald & 

Woodward Publishing Company, Blacksburg, Virginia, 

USA.

Mixon, R. B., L. Pavlides, D. S. Powars, A. J. Froelich, R. 

E. Weems, J. S. Schindler, W. L. Newell, L. E. Edwards 

and L. W. Ward. 2000. Geologic map of the 

Fredericksburg 30' × 60' quadrangle, Virginia and 

Maryland (scale 1:100,000). Miscellaneous 

Investigative Series I-2607. U.S. Geological Survey, 

Reston, Virginia, USA. 

National Park Service. 2006. Management policies 2006. 

U.S. Department of the Interior, National Park Service, 

Washington, D.C., USA.

(http://www.nps.gov/policy/MP2006.pdf). Accessed 

June 2010.

Oaks, R.Q., Jr. and N. K. Coch. 1973. Post-Miocene 

stratigraphy and morphology, southeastern Virginia. 

Bulletin 82. Virginia Division of Mineral Resources, 

Charlottesville, Virginia, USA.

Onasch, C. M. 1986. Structural and metamorphic 

evolution of a portion of the Blue Ridge in Maryland. 

Southeastern Geology 26(4):229–238.

Pavlides, L., J. E. Gair, and S. L. Cranford. 1982. Central 

Virginia volcanic-plutonic belt as a host for massive 

sulfide deposits. Economic Geology and the Bulletin of 

the Society of Economic Geologists 77(2):233–272. 

Rokus, J. W. 2009. Caught in the fury. Culpeper StarExponent. Published April 26, 2009. 

(http://www2.starexponent.com/cse/lifestyles/culpepe

r_news/article/caught_in_the_fury/34491/). Accessed 2 

June 2010.

Santucci, V. L., J. P. Kenworthy, and A. L. Mims. 2009. 

Monitoring in situ paleontological resources. Pages 

189–204 in Young, R. and L. Norby, editors. 

Geological Monitoring. Geological Society of America, 

Boulder, Colorado, USA.

Schwab, F. L. 1970. Origin of the Antietam Formation 

(late Precambrian?, lower Cambrian), central Virginia. 

Journal of Sedimentary Petrology 40(1):354−366.

Seal, R. R.II, A. N. Johnson, J. M. Hammarstrom, and A.

L. Meier. 2002. Geochemical characterization of 

drainage prior to reclamation at the abandoned 

Valzinco mine, Spotsylvania County, Virginia. OpenFile Report OF-02-0360. U.S. Geological Survey,

Reston, Virginia, USA.

Simpson, E. L. 1991. An exhumed Lower Cambrian tidalflat; the Antietam Formation, central Virginia, U.S.A. 

Pages 123−133 in D. G. Smith, B. A. Zaitlin, G. E. 

Reinson, and R. A. Rahmani, editors. Clastic tidal 

sedimentology. Canadian Society of Petroleum 

Geologists Memoir 16.

Sherwood, W. C., and S. Flora. 2002. The role of 

geomorphic features in the 1862 Civil War Battle of 

Fredericksburg. Geological Society of America 

Abstracts with Programs 34(2):105. 

Southworth, S., D. K. Brezinski, R. C. Orndorff, P. G. 

Chirico, K. M. Lagueux. 2001. Geology of the 

Chesapeake and Ohio Canal National Historical Park 

and Potomac River Corridor, District of Columbia, 

Maryland, West Virginia, and Virginia. (A) Geologic 

map and GIS files (disc 1); (B) Geologic report and 

figures (disc 2). Open-File Report OF 01-0188. U. S. 

Geological Survey, Reston, Virginia, USA.

Spears, D. B., B. E. Owens, C. M. Bailey. 2004. The 

Goochland-Chopawamsic terrane boundary, Central 

Virginia Piedmont. Pages 223–245 in S. Southworth

and W. Burton. Geology of the National Capital 

Region: Field Trip Guidebook. Circular C-1264. U.S. 

Geological Survey, Reston, Virginia, USA.

Sweet, P. C. 1996. Diamonds in Virginia. Virginia 

Minerals 42(4):33–40. 

Thomas, W. A., T. M. Chowns, D. L. Daniels, T. L. 

Neatherly, L. Glover, and R. J. Gleason. 1989. The 

subsurface Appalachians beneath the Atlantic and Gulf 

coastal plains. The Geology of North America, Volume 

F-2. Geological Society of America, Boulder, 

Colorado, USA.

Whittecar, G. R., and D.F. Duffy. 2000. Geomorphology 

and stratigraphy of late Cenozoic alluvial fans, Augusta 

County, Virginia, U.S.A. Pages 259–279 in G. M. Clark, 

H. H. Mills, and J. S. Kite, editors. Regolith in the 

Central and Southern Appalachians. Southeastern 

Geology, Volume 39, Number 3–4. Duke University, 

Durham, North Carolina, USA.

Wieczorek, G. F. and J. B. Snyder. 2009. Monitoring 

slope movements. Pages 242–272 in Young, R. and L. 

Norby, editors. Geological Monitoring. Geological 

Society of America, Boulder, Colorado, USA.

Zen, E. 1997a. The seven-storey river: Geomorphology 

of the Potomac River channel between Blockhouse 

Point, Maryland, and Georgetown, District of 

Columbia, with emphasis on The Gorge complex 

below Great Falls. Open-File Report OF 97-60. U.S. 

Geological Survey, Reston, Virginia, USA.

Zen, E. 1997b. Channel geometry and strath levels of the 

Potomac River between Great Falls, Maryland, and 

Hampshire, West Virginia. Open-File Report OF 97-

480. U.S. Geological Survey, Reston, Virginia, USA.
FRSP Geologic Resources Inventory Report 43

Additional References

This section lists additional references, resources, and web sites that may be of use to 

resource managers. Web addresses are current as of August 2010.

Geology of National Park Service Areas

National Park Service Geologic Resources Division 

(Lakewood, Colorado). http://nature.nps.gov/geology/

NPS Geologic Resources Inventory. 

http://www.nature.nps.gov/geology/inventory/gre_pu

blications.cfm

U.S. Geological Survey Geology of National Parks 

(includes 3D photographs). 

http://3dparks.wr.usgs.gov/

Harris, A. G., E. Tuttle, and S. D. Tuttle. 2003. Geology of 

National Parks. Sixth Edition. Kendall/Hunt 

Publishing Co., Dubuque, Iowa, USA.

Kiver, E. P. and D. V. Harris. 1999. Geology of U.S. 

parklands. John Wiley and Sons, Inc., New York, New 

York, USA.

Lillie, R. J. 2005. Parks and Plates: The geology of our 

national parks, monuments, and seashores. W.W. 

Norton and Co., New York, New York, USA.

NPS Geoscientist-in-the-parks (GIP) internship and 

guest scientist program. 

http://www.nature.nps.gov/geology/gip/index.cfm

Resource Management/Legislation Documents

NPS 2006 Management Policies (Chapter 4; Natural 

Resource Management): 

http://www.nps.gov/policy/mp/policies.html#_Toc157

232681

NPS-75: Natural Resource Inventory and Monitoring 

Guideline: 

http://www.nature.nps.gov/nps75/nps75.pdf.

NPS Natural Resource Management Reference Manual 

#77: http://www.nature.nps.gov/Rm77/

Geologic Monitoring Manual

R. Young and L. Norby, editors. Geological 

Monitoring. Geological Society of America, Boulder, 

Colorado. [Website under development]. Contact the 

Geologic Resources Division to obtain a copy.

NPS Technical Information Center (Denver, repository 

for technical (TIC) documents): http://etic.nps.gov/

Geological Survey Websites

U.S. Geological Survey: http://www.usgs.gov/

Geological Society of America: 

http://www.geosociety.org/

American Geological Institute: http://www.agiweb.org/

Association of American State Geologists: 

http://www.stategeologists.org/

Other Geology/Resource Management Tools

Bates, R. L. and J. A. Jackson, editors. American 

Geological Institute dictionary of geological terms (3rd 

Edition). Bantam Doubleday Dell Publishing Group, 

New York.

U.S. Geological Survey National Geologic Map Database 

(NGMDB): http://ngmdb.usgs.gov/

U.S. Geological Survey Geologic Names Lexicon 

(GEOLEX; geologic unit nomenclature and summary): 

http://ngmdb.usgs.gov/Geolex/geolex_home.html

U.S. Geological Survey Geographic Names Information 

System (GNIS; search for place names and geographic 

features, and plot them on topographic maps or aerial 

photos): http://gnis.usgs.gov/

U.S. Geological Survey GeoPDFs (download searchable 

PDFs of any topographic map in the United States): 

http://store.usgs.gov (click on “Map Locator”).

U.S. Geological Survey Publications Warehouse (many

USGS publications are available online): 

http://pubs.usgs.gov

U.S. Geological Survey, description of physiographic 

provinces: http://tapestry.usgs.gov/Default.html

Condie, K. C., and R.E. Sloan. 1998. Origin and evolution 

of the Earth: Principles of historical geology. PrenticeHall, Inc., Upper Saddle River, New Jersey, USA.

Other References regarding the Geologic Setting of 

Fredericksburg and Spotsylvania County Battlefields 

Memorial National Military Park

Bailey, C. M. 2004. Significant southwestward transport 

of the Goochland Terrane along the Spotsylvania highstrain zone, Virginia Piedmont. Geological Society of 

America Abstracts with Programs 36(2):106.

Bailey, C. M., C. E. Webber, B. E. Francis, and J. Felis. 

2003. Structural geometry and kinematics of the 

Spotsylvania Zone, central Virginia Piedmont. 

Geological Society of America Abstracts with Program 

35(1):7. 
44 NPS Geologic Resources Division

Crawford, Matthew M. 2001. Geologic mapping and

metamorphic petrology of part of the eastern 

Piedmont Goochland Terrane, Virginia; evidence for 

extending the Goochland granulite terrane. Geological 

Society of America Abstracts with Programs 33(2):70. 

Davis, A. M., C. S. Southworth, J. E. Reddy, and J. S.

Schindler. 2001. Geologic map database of the 

Washington D.C. area featuring data from three 30 ×

60 minute quadrangles; Frederick, Washington West, 

and Fredericksburg. Open-File Report OF 01-0227. U. 

S. Geological Survey, Reston, Virginia, USA.

Elder, J. H. 1985. Soil survey of Spotsylvania County, 

Virginia. 

Froelich, A. J., R. E. Weems, R. J. Litwin, and J. P. Smoot. 

2000. Triassic and Jurassic sedimentary and intrusive 

rocks of the Culpeper Basin. Pages 13–15 in R. B. 

Mixon, L. Pavlides, D. S. Powars, A. J. Froelich, R. E. 

Weems, J. S. Schindler, W. L. Newell, L. E. Edwards, 

and L. W. Ward. Geologic map of the Fredericksburg 

30' × 60' quadrangle, Virginia and Maryland. Geologic 

Investigations Series I-2607. U.S. Geological Survey, 

Reston, Virginia, USA.

Laczniak, R. J., and C. Zenone. 1985. Ground-water 

resources of the Culpeper Basin, Virginia and 

Maryland. Miscellaneous Investigations Series I-1313-

F. U.S. Geological Survey, Reston, Virginia, USA.

Mixon, R. B. 2000. Overview of the Fredericksburg 30' ×

60' quadrangle, Virginia and Maryland. Pages 1–2 in R. 

B. Mixon, L. Pavlides, D. S. Powars, A. J. Froelich, R. E. 

Weems, J. S. Schindler, W. L. Newell, L. E. Edwards, L.

W. Ward. Geologic map of the Fredericksburg 30' ×

60' quadrangle, Virginia and Maryland. Geologic 

Investigations Series I-2607, U.S. Geological Survey, 

Reston, Virginia, USA.

Mixon, Robert B., David S. Powars, Robert E. Weems, J. 

Stephen Schindler, Wayne L. Newell, Lucy E. 

Edwards, Lauck W. Ward. 2000. Pages 17–28 in R. B. 

Mixon, L. Pavlides, D. S. Powars, A. J. Froelich, R. E. 

Weems, J. S. Schindler, W. L. Newell, L. E. Edwards, L.

W. Ward. Geologic map of the Fredericksburg 30' ×

60' quadrangle, Virginia and Maryland. Geologic 

Investigations Series I-2607, U.S. Geological Survey, 

Reston, Virginia, USA.

Nickelsen, R. P. 1956. Geology of the Blue Ridge near 

Harpers Ferry, West Virginia. Geological Society of 

America Bulletin 67(3): 239–269.

Pavlides, L. 1990. Geology of part of the northern 

Virginia Piedmont. Open-File Report OF 90-0548. U.S. 

Geological Survey, Reston, Virginia, USA.

Pavlides, L. 1995. Piedmont geology of the Stafford, 

Storck, Salem Church, and Fredericksburg 

quadrangles, Stafford, Fauquier, and Spotsylvania 

counties, Virginia. Open-File Report OF 95-0577. U.S. 

Geological Survey, Reston, Virginia, USA.

Pavlides, L.. 2000. Geology of the Piedmont and Blue 

Ridge provinces. Pages 3–12 in R. B. Mixon, L.

Pavlides, D. S. Powars, A. J. Froelich, R. E. Weems, J. S.

Schindler, W. L. Newell, L. E. Edwards, L. W. Ward. 

Geologic map of the Fredericksburg 30' × 60' 

quadrangle, Virginia and Maryland. Geologic 

Investigations Series I-2607, U.S. Geological Survey, 

Reston, Virginia, USA.

Sweet, P. 2007. Gold in Virginia: Brochure (revised). 

Virginia Division of Mineral Resources. 

Charlottesville, Virginia, USA. 2p.

Weems, R. E., and J. M. Bachman. 2004. A dinosaurdominated ichnofauna from the Lower Cretaceous 

(Aptian) Patuxent Formation of Virginia. Geological 

Society of America Abstracts with Programs 36(2):116. 

Whisonant, R. C., S. A. Underwood, and J. D. Surber. 

2004. Geologic analysis of the Battle of 

Chancellorsville using GIS/remote sensing technology. 

Geological Society of America Abstracts with 

Programs 36(2):48. 

Wier, K., and L. Pavlides. 1985. Piedmont geology of the 

Spotsylvania quadrangle, Spotsylvania County, 

Virginia. Miscellaneous Investigations Series I-1568. 

U.S. Geological Survey, Reston, Virginia, USA.

Woodwell, G. R., and R. L. Crowder. 1988. Deformation 

mechanisms and paleostress levels recorded in 

crystalline thrust faulted rocks. Geological Society of 

America Abstracts with Programs 20(4):324. 
FRSP Geologic Resources Inventory Report 45

Appendix A: Overview of Digital Geologic Data

The following page is an overview of the digital geologic data for Acadia National Park.

For a poster-size PDF of this overview and complete digital data, please see the included 

CD or visit the Geologic Resources Inventory publications web site: 

http://www.nature.nps.gov/geology/inventory/gre_publications.cfm.



FRSP Geologic Resources Inventory Report 47

Appendix B: Scoping Meeting Participants

The following is a list of participants from the GRI scoping session for Fredericksburg and 

Spotsylvania County Battlefields Memorial National Military Park, held on April 13, 2005.

The contact information and e-mail addresses in this appendix may be outdated; please 

contact the Geologic Resources Division for current information. The scoping meeting 

summary was used as the foundation for this GRI report. The original scoping summary 

document is available on the GRI website at http://www.nature.nps.gov/geology/inventory/

gre_publications.cfm (accessed May 27, 2010).

NAME AFFILIATION PHONE E-MAIL

Kristen Allen Richmond National Battlefield 

Park 804-795-5019 kristen_allen@nps.gov

Rick Berquist Virginia Division of Mineral 

Resources 757-221-2448 rick.berquist@dmme.virginia.gov AND crberq@wm.edu

Tim Blumenshine Petersburg National Battlefield 804-732-0170 x303 tim_blumenschine@nps.gov

Mark Carter

American Association of State 

Geologists/Virginia Division of 

Mineral Resources

434-951-6357 mark.carter@dmme.virginia.gov

Jim Comiskey NPS Mid-Atlantic Network 540-654-5328 jim_comiskey@nps.gov

Tim Connors NPS Geologic Resources Division 303-969-2093 tim_connors@nps.gov

Nate Irwin Petersburg National Battlefield 804-862-3019 x301 nathaniel_irwin@nps.gov

Gregg Kneipp

Fredericksburg and Spotsylvania 

County Battlefields Memorial 

National Military Park

540-654-5331 gregg_kneipp@nps.gov

Stephanie O’Meara Colorado State University 970-225-3584 stephanie_o’meara@partner.nps.gov

Dave Shockley Petersburg National Battlefield 804-732-0171x305 dave_shockley@nps.gov

Trista Thornberry-Ehrlich Colorado State University 757-222-7639 tthorn@cnr.colostate.edu

The Department of the Interior protects and manages the nation’s natural resources and cultural heritage; provides scientific and other 

information about those resources; and honors its special responsibilities to American Indians, Alaska Natives, and affiliated Island 

Communities. 

NPS 326/105337, August 2010 
National Park Service 

U.S. Department of the Interior 

Natural Resource Program Center 

1201 Oakridge Drive, Suite 150 

Fort Collins, CO 80525 

www.nature.nps.gov 

EXPERIENCE YOUR AMERICATM