- City of Alexandria, Virginia
- Geologic Atlas of the City of Alexandria, Virginia and Vicinity – Plate 2E
- NW E
- E’ SE
GEOLOGIC CROSS SECTION
NORTHWEST
- FEET
- FEET
Claremont
FOUR MILE RUN
- 200
- 200
GT-112
191
Tcg
by Anthony H. Fleming, 2015
173
Kpl
Barcroft Park
Kpb
151
150 100
50
150 100
50
Kpcv
89
Kpcc
Kpcs
Lucky Run
Qc
BEVERLEY HILLS
Reservoir Woods
Charles
Qs
SHIRLEY HWY QUAKER LANE
Kpcg
Qaf
Barrett
MOUNT IDA
J-1
Qa
School
60
63
GT-42
55
GT-185
GT-85
Shirlington
GT-62
50
48
Qa
47
POTOMAC YARDS
Qto
Qcf
- GT-67
- GT-68
Arlandria
Qcf
- Qt
- Qt
- 44
- 45
Qcf
39
38
39
Rte 1
38
32
Four Mile Run Park
GT-4
Qa
Lynhaven
30
Hume Spring
31
Kpcc
30
30 Qt
s
28
25
GT-117
Qcf
GT-136
- OCi
- Qto
Kpcv
17
20
15
Kpcv Kpcc
F-3
16
11
Qa
af
- Qto
- Qto
- af
af
Kpcc
Qs
Kpcs
Kpch
Qt
3
Qe
0
- SL
- SL
-3
-7
Qto-c
Kpcc
org
-25
org
-38
Qto-c
Kpch?
- -50
- -50
Kpcc
Kpcc
-68
OCI
Kpcs
Ogu
-100 -150 -200 -250 -300
-100 -150 -200 -250 -300
Kpcv?
-120
Kpcc
-149
OCs
Kpcs?
-195
RCSZ
SEE PLATE 5 FOR EXPLANATION OF MAP UNITS
1000
VERTICAL EXAGGERATION 20X
- 0
- 1000
- 2000
- 3000
- 4000
- 5000
- 6000
- 7000
- 8000
- 9000
- 10000
FEET
EXPLANATION OF CROSS SECTION SYMBOLS:
WATER LEVELS REPORTED IN WELLS AND GEOTECHNICAL BORINGS
- WATER WELL
- GEOTECHNICAL BORING SITES
- OTHER SYMBOLS
WELL ID NUMBER AND SURFACE ELEVATION
J-60
GT-27
ID NUMBER AND HIGHEST
250
222
- (SOURCE: J-JOHNSTON; D-DARTON; F-FROELICH)
- SURFACE EXPOSURE. SOME EXCAVATIONS
COINCIDE WITH GEOTECHNICAL BORING SITES
SURFACE ELEVATION
47
WATER LEVEL MEASURED IN WELL OR CASED GEOTECHNICAL BORING COMPLETED IN THE CAMERON VALLEY SAND (LOWER
WELL CASING
119
GRAVELLY ZONES IN THE OLD TOWN TERRACE REPORTED IN GEOTECHNICAL BORINGS
AQUIFER OF THE POTOMAC FORMATION)
APPROXIMATE LATERAL AND
VERTICAL EXTENT OF SITE ALONG CROSS SECTION LINE
% SAND IN 100-FT INTERVAL REPORTED BY FROELICH (1985)
ORGANIC ZONES REPORTED IN GEOTECHNICAL BORINGS FROM THE POTOMAC FORMATION, QUATERNARY ALLUVIUM, AND OTHER SEDIMENTS. INCLUDES WOOD, PEAT, LIGNITE, LEAVES, DARK ORGANIC SILT, AND OTHER ORGANIC MATERIAL
WATER LEVEL MEASURED IN 1976 FROM WELL COMPLETED IN CAMERON VALLEY SAND (JOHNSTON AND LARSON, 1977)
ORG
WATER LEVEL
132
195
WELL SCREEN
WATER LEVEL
147
BEDROCK SURFACE
WATER LEVEL MEASURED IN WELL OR
GEOTECHNICAL BORING COMPLETED IN OTHER AQUIFERS. MAY REPRESENT A COMPOSITE OR AVERAGE WATER LEVEL AT GEOTECHNICAL SITES WITH MANY BORINGS
INTERSECTION WITH ANOTHER CROSS SECTION. CROSS SECTIONS ARE DISTINGUISHED BY NAME AND COLOR-CODED SECTION LINES AND TITLES
REPORTED BEDROCK LITHOLOGY BOREHOLE IN BEDROCK
MOUNT IDA
210
BOTTOM ELEVATION OF DEEPEST BORING
147
BOTTOM ELEVATION
127
cross section. The specific location of the cross section is indicated on Plate 1 by a blue section line. and organic horizons in the Old Town terrace that are present only in the subsurface and thus do not appear on Plate 5. impressive buried escarpment below Lynhaven (site GT-117), which appears to separate older and more deeply entrenched terrace sediments to the east from thinner and presumably younger terrace deposits to the west. The two prominent organic horizons reported in the borings at site GT-117 are suggestive of major periods of non deposition and weathering(?), accompanied by long-term growth of vegetation. The deep channel below this site may be the same as or connect with the deep channel seen much further to the south below Old Town, although a direct connection cannot be established from existing data. The substantial thickness of the Cameron Valley sand member (Kpcs - Kpcv) at the base of the Potomac Formation in this section is likely related to its location near the thalweg of the Four Mile Run bedrock valley (see Plate 3 and its expanded explanation).
GEOLOGIC CROSS SECTION 2E– FOUR MILE RUN
Cross section 2E follows Four Mile Run Valley downstream from Barcroft Park, in southern Arlington County, to the extreme northern end of Potomac Yards, near George Washington Memorial Parkway and the Potomac River. The section begins at the lowest bedrock outcrop on Four Mile Run, and traces the regular eastward slope of the bedrock surface and the corresponding thickening of the Potomac Formation and younger alluvial sediments. The view is northward along the section line, which locally bends to take in the locations of nearby geotechnical boring sites, historical water wells, and other places of interest (e.g., Reservoir Woods, Hume Spring). These features, and other sites of cultural, historical, and
The cross sections are intended to be used together with the geologic maps, particularly Plate 5, to illustrate the third dimension of the map units. Contacts between map units are approximately located and, in the Potomac Formation, are typically gradational or transitional. The abundance of control points (surface exposures, wells, geotechnical sites) along the cross section provides a general indication of the reliability of contact locations. Map units are depicted using the same colors, patterns, and labels as on Plate 5, and the explanation of map units on Plate 5 serves as the legend. The section also depicts some bedrock units and several gravelly zones
The dominant physiographic feature is the deeply entrenched valley of Four Mile Run, which is flanked by many large terraces. Some of these terraces are graded to the massive Old Town terrace, which occupies the eastern part of the section.
The Four Mile Run section depicts the array of terraces and other Quaternary deposits that flank Four Mile Run, as well as the sizable body of estuarine sediment at its mouth, most of which is now buried beneath artificial fill. The section also illustrates some of the internal architecture of the northern end of the Old Town terrace, including the environmental interest. are indicated by labels and symbols along the