ZUSGS US. DEPARTMENT OF THE INTERIOR PREPARED IN COOPERATION WITH THE PROFESSIONAL PAPER 1622
cee foaceninawed U.S. GEOLOGICAL SURVEY HAMPTON ROADS PLANNING DISTRICT COMMISSION Stratigraphic columns of three key boreholes—PLATE 1

Powars, 0.S., 2000, The effects of the Chesapeake Bay impact crater on the geologic framework
and the correlation of hydrogeotogic units of southeastern Virginia, south of the James River

DISMAL SWAMP COREHOLE (2) FENTRESS COREHOLE (12) CHESAPEAKE NORTHWEST RIVER WTP BOREHOLE (3)
SPONTANEOUS: 2 3] 4 6 ‘SPONTANEOUS: " 2 3] 4 5
Soil FORMATIONOR | poreNTIAL AND [LITHOLOGY Mitiude. | GAMMA FFoRAM. POLLEN’) DATES | OSTRA SXSTEM FORMATION OR EQUIVALENT | POTENTIAL AND. LiTHoLoay'//Mtiude | GAMMA-RAY LOG FOBRMPOGEN Pic. /OSTRA. SYSTEM FORMATION OR SRONTANEOUS
AND SERIES EQUIVALENT | arsistivityLoGs in feet RAY LOG ZONE | ZONE pyySNPxre CODES ‘AND SERIES Aerio in feet ZONE | ZONE PYSTS/ CODES AGERE: Peale Sener Ne Limpowoay'4 Meat | GAMARAV LOG
(QUATERNARY Picts Joppa Shirley S Nao zl e = 40
Upper = Orion 4 z| 8 9 a Se [a ‘Sea
; = Nig— | vcughant 82] & 3 Preis id MPR
Pircene} ena Yorktown 5 N20° 7 é H Upper Tabb Nes? Ee pareiccon a eae oe
= i * Not sampled ‘SPR
MPR —_ [apne Chowan River (?) Nai xt geo
SP 16" 64" PX Formation ae 2
ae Eastover 2 | Upper wal & | Upper
Eastover ‘a Nie? (el 8 and Yorktown ck Nie— Oricbie vegans 8 and Yorktown 2
$ Bp rnaton = | tower N208 fa = | tower an
zl iz =. 2 [Reamer
=<} 8 R ‘Not sampled
E| & | Upper 3 s
ul = Zz
F = ‘
Barren of Pal 3 4
St. Marys i Nie PS diatoms mB
3 ae Eastover = cs Par! 7
aarp} ee sy EE S =
;__—Marlboro Clay | = P6a? egecceel =
Paleocene |_Upper Aquia® = PS [feoaean, > = 3 .
Tower;|—__ Brighiseat = Pic; kt g [= Ze 5 =
ee = zone V a & 3 = z
= m . 2 Ey
= | 5s “|i
Glauconitic sand unit “Se 2 2 Si me 8
7 aaa S = St. Marys
i ‘St. Marys = ni7® c . :
‘Upper Cenomanian beds zone IV = “
Upper 2
= ss Middle Calvert
> fotigocene| Lower Delmarva beds
= = ry ee
s Nariboro Clay
[Middle Calvert INTS-NI4| Paleocene! Upper Aquia 5
capooe [Lower Daimarva beds P20. + early Oligocene *
‘zone it? ee ey == Fe Soa Fore. it
vy. ~near Eocene Clayey silty quartz sand unit
leocene | Uy 7 PS oe U Cretac
[* a ae yl | pa \ a | andion | Organie-ieh clay unt
3 Sooo 2 paren} barren Paleocene (?)
foo y F
< zone V Glauconitic quartz sand unit «|
3 Red beds rijissusneen
- Red beds =
zg Glauconitic sand unit @
< Glauconitic sand unit =
< barren
7 ‘zone iy
ig
zone Il 7
Upper Cenomanian beds Upper Cenomanian beds :
x -<zone IV|
= Upper <
L-1,000 “S 3 Upgen as
Q = 5
3 a 3 |<zne mM)
fa] L 2
&
& /< barren|
L-1,100 = +0 b-.100
Lows | is i 8
er Potomac . 3 3
| -1,200 :
. co g a
& 5
& id
| &
zene
ree Se lt ee ee | As
L F4 ae =
u
Potomac
[--1,400 7 Potomac |
Lower
L-1,500
Lower
- i zone I? a
<a __—
= Leg
L -1,600
| 4,600 © a
L [ <a
A < barren)
3 "}-1,700
| 1.700 = = J< barren
= eo
cs < “
aa ‘Total depth = -1,769 feet
=
L ei
= L
76°30" 76°
Jurassic-Triassic (2) rift basin rocks r Se
Total depth = 4.827 feet L--1,900
Total depth = -2,005 feet
572)
EXPLANATION
LITHOLOGY
CLAY “$2 | PEBBLES SP SPONTANEOUS POTENTIAL LOG—Negative to the left, positive to the right Lithology shown is a generalized summary ® Cronin, T., USGS, written
== based on cored intervals. Dismal Swamp commun., 1995
tr77| PALEOSOLS SPR — SINGLE-POINT RESISTANCE LOG—Resistance increases to the right continuously cored down to -950 ft, and
CLAYEY SILT ms cored from -1,040 to -1,080 ft. Fentress 7 Potopaco Member
GA} SHELLS MPR MULTIPOINT RESISTIVITY LOG—16- and 64-inch multipoint resistivity log continuously cored down to -1,109 ft, and | ete e ime
SANDY SILTY CLAY TO zs TURRITELLA cored from -1,275 to -1,375 ft and from ® Paspotansa Member Se'S0'T SETS Tromonetens
SANDY CLAYEY SILT — N FORAMINIFERA NEOGENE ZONE -1,682 to -1,852 ft. EXPLANATION
~ 9 i
~< | UGNITIC MATERIAL P —_ FORAMINIFERA PALEOGENE ZONE Extrapolated from regional 3, a
CLAYEY SILTY SAND = 3 2 Gibson, T., formerly USGS, now with correlation including strontium Borenote snciinBer PCI Cotn tpt coleicts srt niente)
INDURATED LAYER (GENERALLY AZ ASSEMBLAGE ZONE ‘Smithsonian Institution, written isotape data. Location map of coreholes and borehole
VERY FINE CALCITE CEMENTED) x DIATOM SAMPLE commun., 1990
10) 4 i ” 7 .
FINE BURROWED CONTACT Lithology shown is a generalized summary based on a combination
MEDIUM + DINOCYST SAMPLE 3 Frederiksen, N., USGS, written of lithic and geophysical data from several boreholes at the Northwest
COARSE pak
NER eee = SHARK TOOTH POTIENEANIPLE commun., 1999 River Water Treatment Plant (WTP) site. Multipoint (16- and 64-inch)
GRANULES < and spontaneous potential (SP) logs come from borehole 3 (61A15).
—— 4 Andrews, G., USGS, written The gamma log comes from borehole 61A18. Cuttings descriptions
commun., 1989 from borehole 61A15 and 61A18 were used from the surface down to
- 990 ft. Core descriptions from borehole 61A16 were used from -990 to
5 Edwards, L., USGS, written -1,524 ft. Drillers logs from borehole 61A2 were also used, especially
commun., 1989 for the interpretation shown for the base of the Tertiary. The geophysical
logs guided a very generalized interpretation from -1,524 to -1,769 ft.

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STRATIGRAPHIC COLUMNS OF THREE KEY BOREHOLES

By
David S. Powars
2000