DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY
PERIOD EPOCH
QUA TERNARY 1\ HOLOCENE PLEISTOCENE
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OLIGOCENE
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TRIASSIC, JURASSIC(?), PALEOZOIC AND
PRECAMBRIAN
STRATIGRAPHIC HYDROGEOLOGIC FORMATION UNITS
Undifferentiated
:'sacons Castl~ Formation !Oaks and Coch , 19731
Yorktown Formation
Eastover Formation
St. Marys Formation
Columbia aqu ifer
Yorktown-Eastover aquifer
St. Marys confining un it
GENERALIZEQ RESISTIVITY
AND LITHOLOGIC . COLUMN
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~--------------~--ss:t't .:-MM.a;;:ry;;;.;:.(c'hh;;o;;pt:ta;;n;;k~i. .. 5~.::~ i -. -:.: Choptank Format io n aqu_if er .. . . .
f---'------+-----'------l ,·: .. -:-o-.. ... .
Calvert Format ion
Nanjemoy Formation
Calv ert confining un it
Nanjemoy-Marlboro clay confining
unit
... .. r-----M_a_r_lb_o_ro __ c_la~y----1-------------------i·~:·.~-
B BB
A quia Formation
BriQhtseat Form atio n
Undifferentiated
Potomac Formation
Aquia aquifer
BGGB(3
1:' . Brightseat confining unit :¥:.
Brightseat aquifer
Upper Potomac confining unit
F -.-- ·
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Upper Potomac aqu ifer
Middle Potomac confining unit
M iddle Potomac aquif er
Lower Potomac confining unit
Lower _Potomac aquifer
Basement rock
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DOMINANT LITHOLOGIC CHARACTER AND REMARKS
Sand , fine to coa rse , and gravel , commonly c layey; interbedded with silts and clays; tan to rusty orange; generafly unconfined,
1\ confined locally
Clay , silty and shelly; locallY interbedded with fine sands; 1\ commonly lighf gray t o orange, or multicolored J
Sand, fine to coarse, commonly shelly; interbedded with si.lts , clays, shell beds, and gravels; shell beds locally indurated, whitish gray to yellow ; general ly confined ; unconfined updip ih outcrop area
Clay, silty and shelly ; interbedded with fine sands; light gray to blue
Sand , very fine to fine, si lty and shelly; interbedded with silty clays; white to light bluish gray; confined, restricted to nor.thea.stern area
Clay, silty, diatomaceous, sparse ly shelly and sandy ; co1tains basal phosphatic lag deposit ; greenish gray to dark green
Sand, fine to coarse , glauconitic; interbedded with shell beds, silts , and clays; shell beds comm only indurated ; speckled black , green , whit e, and gray; generally confined , unconfined where outcrops
in major stream valleys of west -central and northwestern areas
"clay, silty, shelly, glaucon itic, and sandy; interbedded with fine glauconitic sands; dark green to greenish gray in uppe· part
(Nanjemoy ), pink and gray in lower part_.( Marlboro clay)
Sand , fine to medium , glauconitic; interbedded w ith shell beds, sometimes indurated ; dark green; generaily confined , unconfined
-wtiere outcrops in nor thW estern area and major Stream valleys throughout western area
Clay, silty, sandy, micaceous, and lignitic; dark gray to black , top is oxidized orange -red
Sand , fine to medium, occasionally lignitic; interbedded with silty clay ; white; confined , restricted to north -central area
Clay, si lty, micaceous, chalky in eastern area; interbedded w ith fine sands
Sand , very fine to medium, micace·ous, lignitic, and clayey ; interbe~ded with silty clays; white to whitish gray; confined , restricted to central and eastern areas
Clay, silty; massive to laminated and carbonaceous; interbedded with scinds; variegated red, green, gray, orange, and purple
Sand , fine to mediumr' occasional gravels; interbedded with silty clays ; abrupt lateral and vertical litholog ic changes; gray; generally confined, unconfined where outcrops in northwestern area and m ajor stream valleys throughout western area
Clay, silty , sandy; massive: dark yellow, red! and brown
Sand, medium to coarse, and gravels, clayey; interbeCded with silty clays; abrupt lateral and vertical lithologic chang':!s ; gray ; generally confined, unconfined where outcrops in northwestei-n area
Sandstones, siltstones, and diabase sills
Sh ists, granites, gne isses, and gabbros
ORIGIN
Fluvial and marine
Shallow, open marine
Sh allow, open marine
Shallow, restricted marine
Shallow, open marine
Shallow, open marine
Quiet, restricted marine
Shallow, open marine , inner shelf basin
Shallow, open marine , inner to middle shelf basin
Shallow, open marine, innerSfffilf 5asin
Restr icted marine , inner to middle shelf basin
Restricted marine , near shore
Marine
Marginal marine
Continental and marginal marine, outer delta,
subaqueous
Continental, fluvial deltaic flood plains
Continental, fluvial deltaic, meandering streams and
flood plains, lower to middle Tlood pla in
Continental, fluvial deltaic, backswamp basins
Cont inental, fluvial deltaic,
MAJOR AREAS OF
AQUIFER USAGE
Throughout eastern area
Throughout central and eastern areas
Not used in Virginia
Throughout central and west-central areas
Throughout central and west -central areas north
of Norfolk arch
Throughout north-central area
Throughout central and southeastern areas
Throughout western and central areas
braide~ streams, subaerial, Throughout western area upper flood plain
Cont inental deposits and r\ volcanic intrusives
Metamorphic rocks
CORRELATION WITH ADJOINING RASA STUDIES
MARYLAND
Columbia aquifer
Upper Chesapeake confining unit
Upper Ch esa peake aquifer
St. Marys confining unit
Lower Chesapeake aquifer
Lower Chesapeake confining un it
Piney .Point -Nanjemoy aquifer
Nanjemoy-Marlboro confining unit
Aquia -Rancocas aquifer
Brightseat confining unit
Br ightseat aquifer
Patapsco confining unit
Patapsco aquifer
Potomac confining unit
PatuxenJ aquifer
Basement rock
NORTJ-:! CAROLINA
Surf icial aquifer
c_;:onfining unit ..
Yorktown aquifer
Confining unit
Pungo River aquifer
Con f in ing unit
Castle Hayne aquifer
Confining unit
Beaufort aqu ifer
Confining unit
Upper Cape Fear aquifer
Confining unit
Lower Cape .Fear aquifer
Confining unit
Lower Cretaceous aquifer
Basement rock
PROFESSIONAL PAPER 1404-C PLATE 1
EXPLANATION
D METAMORPHIC ROCKS
IE)~;! TRIASSIC ROCKS
t\':i •l GRAVEL AND SAND
~~,·; ·,:··:.i FINE, MEDIUM, OR COARSE SAND
§ CLAYEY SAND
§SANDY CLAY
~ CLAY
g2§ CHALKY CLAY
~COQUINA ~SHELLS GJ GLAUCONITE
0 DIATOMS
0MICA
0PHOSPHATE
GENERAL HYDROGEOLOGIC COLUMN AND CORRELATIONS FOR SEDIMENTS OF THE VIRGINIA COASTAL PLAIN
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