U.S. DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 1631
U.S. GEOLOGICAL SURVEY PLATE 1
42!

64°48" yore 12 13 46 ue 15 16 44/317 a a9 1.100000 FEET spieene 122 223 40" 125 126 ‘ar Ca
18°24" —- - z 18" 24

35"N
CORRELATION OF MAP UNITS
STRATIFIED ROCKS INTRUSIVE ROCKS
= } can
Red Hook
Tonalite Porphyry
> Tertiary
if
Tutu
Formation
i) | Upper
Obes ieee Cretaceous
Limestone
!
Loulsenho} {
Formation Hl
8 Lower
op Lameshur Volcanic-Intrusive Complex Cretaceous
: —— Water Island Formation ‘ Caren Hill Intrusive Suite
/
~~ a «| a |

=31

21'30" LIST OF MAP UNITS EXPLANATION OF MAP SYMBOLS
[Dikes 3 m or more in width are shown where space permits. Unit Te is not shown on [Where two or more symbols for planar or linear features are combined, their
geologic map; see “Map showing distribution and attitude of dikes on St. John" for intersection marks the point of observation. Where a single planar feature and a single
location, For complete Description of Map Units, see Appendix A, this report .] linear feature are combined, the center of the planar feature marks the point of
observation. For a linear symbol alone, the base of the arrow marks the point of
F observation.]
"30 Os Surficial deposits (Quaternary)

— Contact—Dashed where approximately located; dotted where concealed
Red Hook Tonalite Porphyry (new name) (Tertiary) Faults—Tick shows dip where known. Dashed where approximately

located; dotted where concealed

Explosion breccia (Tertiary?}—Shown only on inset map Diietile Skeid Ge ined alinnk eins:
Hsebbteeite taanieoptigne (Tein {= — Brittle fault—Sense of movement shown if known. Strike-slip motion

shown by arrows, or T (toward) and A (away) in cross section. For
dip-slip motion: U (up) and D (down)

Biotite-homblende tonalite (Tertiary, late Eocene)
= i —-~—4— ss High-angle reverse fault—Teeth on upper plate

Diabase, gabbro, and diorite (Tertiary) FOLDS
Py Tutu Formation (Upper Cretaceous; upper Turonian, upper Santonian, _— Anticline—Showing trace of axial surface
: or younger) 4 Synctine—Showing trace of axial surface
re Mandal Member (new name) MINOR FOLDS
a [May be combined with planar features}
i Congo Cay Limestone Lens +30 Bearing and plunge of fold axis

EY

~s*30__ Bearing and plunge of sinistral fold

Marble, cale-silicate and marble conglomerate
sa +20 Bearing and plunge of dextral fold

Te
PERE Pease Member (new name)
[xe] Marble conglomerate and calc-silicate-rich beds north of Maho Point PLANAR FEATURES ;
; Strike and dip of bedding—Ball indicates younging direction of beds
HEEB) Mecium-daricgray, porphuritc meta andesite south of Maho Point piinglr Ela mae ic rc
Eee Outer Brass Limestone (Upper Cretaceous; upper Turonian to 2, } Tae
upper Santonian) Inclined
+ Vertical
FBI tomo mn Ahn Tt Sani Ouran
@ Horizontal
Porphyritic, locally vesicular andesite lava
[tes ahs Generalized strike of vertical bedding
| Porphyritic, locally amygdaloidal basalt and pillow basalt Strike and dip of foliation
cu
2 Inclined
19f- ‘Lameshur Volcanic-Intrusive Complex (new name) (Lower Cretaceous;
Aptian to lowermost Albian)—Includes Careen Hill Intrusive Suite and + Vertical
Water Island Formation -«- Strike and dip of generalized foliation
Strike and dip of foliation parallel to bedding
[a] mma i eras
Careen Hill Intrusive Suite (new name) (Early Cretaceous) + — Coplanar, vertical
ye Coplanar, overturned
Cre] Trondiijernite 4 Parallel strike, different dip—Number closest to strike is dip value for
"25 Coarsely porphyritic keratophyre °
cs fee] =, Strike and dip of spaced cleavage
[Exe] Porphyritic keratophyre Strike and dip of joint set
2 Inclined
fe] Phenocryst-poor keratophyre — Vertical
Strike and dip of flow layering, layering of amygdules, or layering of
(Ege) Plagioclase-phyric keratophyre ah pillows—Ball indicates tops of pillow layering known from asymmetry
of pillows
"24 (iene Sertie mail ap of Ue 2 ot nate i ckneen— Son on ace
TITT/) Sheeted dike complex . Tpap where'ppace| penis other; soe mag showing dsbution
179.000 Water Island Formation (Lower Cretaceous) cae Enganed
FEET + Vertical
eee — er tn
[ee] Phanadiyeicr KaremapiR LINEAR FEATURES
[May be combined with planar features}
“2 [wt] Plagioclase-phytic keratophyre — > Bearing and plunge of axis of columnar joints
[wa] Basalt and t > Bearing and plunge of axes of boudinage
Pe =<
*F Fossil locality
[ieee] Radiolarian chert R Inactive quarry

a 1 Area of hydrothermal alteration
‘S| Pillow lava—Right-side up. Shown only on cross section BB’

* 16/30" Ss = : = 3 2 pasts =f Bu a 5 : = “ é as fits Sn 2 : < * Bod Seat : See i ry
10: 3P Seas! ag 1070000 FEET 212 BE} 46° 414 3 16 44" NF 18 19 29%E 42 2] 299 1119000 FEET 40° 226 8 2 64" son 1639
Base fram U.S. Geological Survey is SCALE 1:24 000 i % Geology mapped in 1985-1988 and 1995; assisted by M.L. Rankin
Western Si. John, 1958 Iphotorevised 1982) and Easten 1 % 0 1 MILE Be ; Se
St. John, 1958 (photorevised 1982) SSS SSS “tthe = a Manuseripcappravedt for patitca ony A5sthy26):1906
Polyconic projection, Puerto Rico Detum, 1940 adjustment 1 O58 9 1 KILOMETER ,
10,000-foot grids based on Puerto Rico coordinate system, te a a
Virgin Islands extension. 1000-meter Universal Transverse CONTOUR INTERVAL 40 FEET eo
Mercator grid , zone 20 APPROXIMATE MEAN DOTTED LINES REPRESENT 20-FOOT CONTOURS ‘VIRGIN ISLANDS
LTC a DATUM IS MEAN SEA LEVEL QUADRANGLE LOCATION
DEPTH CURVES AND SOUNDINGS IN FEET—DATUM IS MEAN LOW WATER
‘THE RELATIONSHIP BETWEEN THE TWO DATUMS IS VARIABLE
SHORELINE SHOWN REPRESENTS THE APPROXIMATE LINE OF MEAN HIGH WATER
THE MEAN RANGE OF TIDE IS APPROXIMATELY 0.8 FEET
Ss
reer A \ 23 Al reer
\ ae 5 33
3 ~ io) ee 2000
5 : Fs . é a 23
g 3 € é £ gos
2 a
wo = 8 E é 2 § | s000
8 3 é 4 } ATLANTIC OCEAN
SEA LEVEL —__ SEA LEVEL
+1000
+2000
3000
'
ret B WESTERN ST. JOHN QUADRANGLE EASTERN ST. JOHN QUADRANGLE 7 B' reer EXPLANATION
2000). g S_ 2000
e ze Minna Hil an Strike and dip of dikes—For some dikes, only strike is shown
i Zs 25 because dip cannot be measured. For unit name, see
wos & i i £5 +1000 classification of dikes
6 wa nd re
8 : 3 OF 3+ Strike and dip of inclined dike 3 m or more thick
SEA LEVEL —— SEA LEVEL Strike and dip of vertical dike 3 m or more thick
3 Strike and dip of inclined dike less than 3m thick
4000-4 Strike and dip of vertical dike less than 3 m thick
Classification of dikes
2000 4 L200 —G, Red Hook Tonalite Porphyry
Ve Explosion breccia
—{_, Hornblende lamprophyre
3000 3000 n
INTERISR-OEOLOGICAL SURVEY, RESTON WA-2002 co Tonalite

Tig, Diabase, gabbro, and dlorite—Mapped as Té on geologic map
Careen Hill Intrusive Suite (no sequence of intrusion implied)
Ther Fondhlemite
Fa (a Coarsely porphyritic keratophyre
“Tkep Se a: pry
Fy moa nhac erstontae

‘eeann 5

ie
—
(aL
eS,

ple

wana, tase
FA

Nisin
— ° - _ ~ 2 / | /
TM : MAP SHOWING DISTRIBUTION AND ATTITUDE OF DIKES ON ST. JOHN 7
GEOLOGIC MAP OF ST. JOHN, U.S. VIRGIN ISLANDS
By Ai ih adn hi, es coe iB a for oR
Douglas W. Rankin Fey See m,n Seven 2 U

ED Prac on wecycies pecer §=— gp anee for a changing world