DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

PERIOD EPOCH

QUA TERNARY 1\ HOLOCENE PLEISTOCENE

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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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Calvert Format ion

Nanjemoy Formation

Calv ert confining un it

Nanjemoy-Marlboro clay confining

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A quia Formation

BriQhtseat Form atio n

Undifferentiated

Potomac Formation

Aquia aquifer

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Brightseat aquifer

Upper Potomac confining unit

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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