Prepared by the
U.S. GEOLOGICAL SURVEY
under the auspices of the

DEPARTMENT OF THE INTERIOR
NATIONAL SCIENCE FOUNDATION

UNITED STATES GEOLOGICAL SURVEY

Area of +200 to +430 gammas magnetic.
intensity reported by Behrendt and
others (1973)

Area of +200 to +1100 gammas magnetic
intensity reported by Behrendt and
others (1973)

‘Area of 0 to +200 gammas magnetic
intensity reported by Behrendt
and others (1973)

me,
(DOh)

Alternate possible subice contact of Dufek
intrusion with sedimentary rocks,
according to geophysical interpretation
of Behrendt and others (1973).
Location highly uncertain

Area of +200 gammas magnetic \ A
intensity reported by Behendt \ Area of several tens of milligals positive \
and others (1973) gravity anomaly reported by Behrendt

and others (1973)

Alternate possible subice contact of Dufek ——~
intrusion with sedimentary rocks,
according to geophysical interpretation
of Behrendt and others (1973).
Location highly uncertain

9 48 oe
Base from U.S. Geological Survey, 1967 SCALE 1:250,000 Geology by A. B. Ford, W. W. Boyd, Jr.,
D. L. Schmidt, and W. H. Nelson, 1965-66;
z “ 3 Ge a Sy talte as Mount Lechner area by A. B. Ford, 1974
5 0 5 10 15. 20 25 30 Kilometers
a _ a LOCATION DIAGRAM
5 0 5 10 —_ 15 Nautical Miles can ete onp

C i - =
Polar Stereographic Projection—Standard Parallel 80°14’
CONTOUR INTERVAL 200 METERS—DATUM IS MEAN SEA LEVEL
Elevations and ice thickness in meters

Qe

Jfl

Sts

Jfss

U.S. ANTARCTIC RESEARCH PROGRAM
SARATOGA TABLE QUADRANGLE
ANTARCTIC GEOLOGIC MAP A-9

CORRELATION OF MAP UNITS
Units shown in parentheses where inferred to lie beneath ice

Sedimentary deposits

[% |

Forrestal Gabbro Group

ANGULAR UNCONFORMITY (Weddell orogeny)

PCE

z
eS DISCONFORMITY
3
5
ae
e DISCONFORMITY (?)
Fs
5 ee
2\fe

£8 DOel

2°

ANGULAR UNCONFORMIT 'Y (Ross and Beardmore? orogenies)
pep

su

DESCRIPTION OF MAP UNITS

GLACIAL AND TALUS DEPOSITS, UNDIVIDED (Quaternary) — Chiefly non-
weathered, nonsorted, unconsolidated talus and morainal materials of apparent
local derivation, in many places lying on ice. May locally include older deposits

FELSIC DIKE ROCK (Jurassic) — Felsite, aplite, pegmatite, alaskite, leucogabbro,
and granophyre of dikes apparently related to the Jurassic Dufek intrusion.
Locally zoned. Some may be coeval with Lexington Granophyre; others pos-
sibly coeval with local host cumulates. Except for a single occurrence on Grob
Ridge, all occur within boundaries of the Dufek intrusion

FORRESTAL GABBRO GROUP (Jurassic) — Includes, in descending order,
Lexington Granophyre, Saratoga Gabbro, Aughenbaugh Gabbro, and Walker
Anorthosite. Layered rocks of the Dufek intrusion; chiefly well-laminated mafic
cumulates of general gabbroic composition. Modal proportions of settled plagi-
oclase, two pyroxenes, and opaque oxides highly variable. Group includes pyrox-
ene cumulate, plagioclase cumulate, and magnetite cumulate in interlayers a few
millimeters to several meters thick, and a capping layer of granophyre. Pyroxenes
belong to two coexisting series, augite-ferroaugite and bronzite-inverted pigeonite.
The opaque oxides are chiefly composite grains of titaniferous magnetite and fer-
rian ilmenite. Stratigraphy and rock-stratigraphic nomenclature of group discussed
in Ford (1976). Jurassic age assignment based on K-Ar analyses that average
16843.4 m.y. (R. W. Kistler, unpub. data). Extent of group under cover of ice
inferred from geophysical data of Behrendt and others (1973). Group estimated
to be 8-9 km thick, of which about 1.8 km is exposed in Dufek Massif and 1.7 km
in the Forrestal Range. Lower units of group exposed to north in Davis Valley
quadrangle (Ford and others, 1978)

FORRESTAL GABBRO GROUP, UNDIVIDED — Undivided gabbroic and related rock
of the Dufek intrusion. Where shown under cover of ice, inferred from geophysical
surveys

LEXINGTON GRANOPHYRE ~ Cream to light-gray granophyre concordantly over-
lying layered mafic cumulates. Commonly microporphyritic, containing micro-
phenocrysts of zoned andesine and pale-green augite or ferroaugite in mesostasis
of alkali feldspar and quartz. A late-stage differentiate of the tholeiitic Dufek
magma. Composition approximates that of an iron-rich granodiorite. Sharp ba-
sal contact; top not exposed. At least 240 m thick, and probably about 300 m
thick

SARATOGA GABBRO — Generally well layered and laminated, medium- to dark-gray,
iron-rich gabbroic cumulates of upper part of the Dufek intrusion. Weathers dark
brownish gray. Includes numerous layers of leucocratic plagioclase-rich cumulate
(anorthosite and leucogabbro) and common thin dark-gray to black layers of mag-
netite-rich cumulate. Mineral-graded layering common. Mafic rock is chiefly two
pyroxene-plagioclase-magnetite cumulate. Scour channels (trough layering) ob-
served mainly in lowest member. Upper contact with granophyre sharp; base not
exposed. Exposed thickness about 1,400 m

Upper inclusion member — Medium- to dark-gray gabbroic cumulate containing
abundant small to large rounded and embayed inclusions of noncumulus anor-
thositic to leucogabbroic rock. Inclusions commonly 1-3 m across. Locally,
where inclusions are abundant, has appearance of a breccia-conglomerate. Con-
tacts of layer generally indistinct. Thickness ranges from about 64 m at Camp
Spur to 100-107 m at Sorna Bluff and Mount Lechner

Lower inclusion member — Lithology and contacts similar to those of upper inclu-
sion member. About 46 m thick at Mount Stephens

Stephens Anorthosite Member — A conspicuously layered sequence consisting of
four prominent light-colored mineral-graded layers, 7-15 m thick, of plagioclase
rich cumulate interlayered with medium- to dark-gray mafic cumulates. Scour
channels (trough-layered structure), filled with plagioclase cumulate, locally pres-
ent. Upper contact at top of highest leucocratic layer is gradational into over-
lying mafic cumulates; basal contact not exposed. Exposed thickness about 300 m

AUGHENBAUGH GABBRO — A generally well-layered sequence of mostly mafic
cumulates, at least 1,600 m thick, of the lower part of the Dufek intrusion. Differs
from Saratoga Gabbro chiefly by absence or, near top, by scarcity of cumulus iron
and titanium oxides, and by presence of pyroxene cumulate layers. Not exposed
but may occur at depth below the cumulate sequence of the Saratoga in the
Forrestal Range

Contact ~ Dotted where concealed; queried where highly uncertain
High-angle fault — U, upthrown side, D, downthrown side. Arrows indicate
relative horizontal movement. Dotted where concealed; queried where highly

uncertain

Anticline — Showing plunge. Dotted where concealed; queried where highly
uncertain

Syncline — Showning plunge. Dotted where concealed; queried where highly
uncertain

Strike and dip of beds in sedimentary rocks and of layers and lamination in
igneous cumulates

Inclined
Horizontal

Strike and dip of cleavage in sedimentary rocks and of microshear joints in igneous
rocks

Inclined

Vertical

2/8
2\2 -
i =|0 ole
3s ole 216 €
58 2/0 ale =
HS Par aa 2
A &3 alo 8 = i
METERS Lexington Table = METERS
2000 SUPPORT FORCE —— 2000
GLACIER
1000 — 7 1000
SEA LEVEL + }- SEA LEVEL
1000 + f- 1000
2000 + : }- 2000
x
z|2
$22 3 z
a=|o © So 5 &
Ce) e =2/6 °
7 ole 2 = 2/0 2
B $ € uly f Cc Median = gala 3 ,
8 Saratoga Table Snowfield 2 8
METERS {l 7 2 Jfsu- METERS. METERS bee [c} METERS
~ support FoRcE == eee Adf t 30
2000 — GLACIER 2000 2000 7 100
1000 FV 77; zy 1000 1000 1000
SEA LEVEL + = SEA LEVEL 4 SEA LEVEL
1000 + + 1000 1000 — 1000
2000 — f- 2000 2000 + 2000

Note: Folds in Patuxent Formation (p€p)
are diagrammatic

52°30"
133°00%

24" 00!
52°30)

45°00!
83°00}

scale 1:250,000.

84°00"

aso Antarctic:

Compiled from U.S.N.O.0. chart 1706S, 1965
ISOGONIC LINE DIAGRAM

Dufek intrusion:
Forrestal Range
section

Precambrian

PCg

DOel

su

ae

SELECTED REFERENCES

Behrendt, J.C., Rambo, W.L., Henderson, J.R., and Meister, Laurent, 1973,
Simple bouguer gravity and aeromagnetic maps of the Saratoga Table
quadrangle, Antarctica: U.S. Geol. Survey Geophys. Inv. Map GP-888,

Ford, A.B., 1976, Stratigraphy of the layered gabbroic Dufek intrusion,
Antarctica: U.S. Geol. Survey Bull. 1405-D, 36p.
Ford, A.B., Schmidt, D.L., and Boyd, W.W., Jr., 1978, Geologic map of the
Davis Valley quadrangle and part of the Cordiner Peaks quadrangle, Pensacola
Mountains, Antarctica: U.S. Geol, Survey Antarctic Geol.Map A-10, scale 1:250,000.
Himmelberg, G.R., and Ford, A.B., 1976, Pyroxenes of the Dufek intrusion,

Jour. Petrology.v. 17, pt, 2, p. 219-243.
Schmidt, D.L., and Ford, A.B., 1969, Geologic map, with accompanying text, of
the Pensacola and Thiel Mountains; sheet 5, Geologic maps of Antarctica:

New York, Am. Geog. Soc. scale 1:1,000,000.
Schmidt, D.L., Williams P.L., and Nelson, W.H., 1978, Geologic map of the
Schmidt Hills quadrangle and part of the Gambacorta Peak quadrangle, Pensacola

Igneous rocks

p QUATERNARY

ifs + JURASSIC

Jfss.

+ PERMIAN

PERMIAN(?) AND
CARBONIFEROUS(?)

+ DEVONIAN

| DEVONIAN() TO
ORDOVICIAN(?)

Upper | PRECAMBRIAN

PERMIAN(?) TO.
| PRECAMBRIAN(?)

WALKER ANORTHOSITE — The lowest known unit of the Dufek intrusion. Gen-
erally a poorly layered plagioclase cumulate, at least 230 m thick. Not exposed
but may occur at depth below the cumulate sequence of the Saratoga in the
Forrestal Range

BEACON(?) SUPERGROUP (Permian to Ordovician?) — Includes, in descending
order, Pecora Formation, Gale Mudstone, Dover Sandstone, and Neptune Group

PECORA FORMATION (Permian) — Gray tan-weathering thin-bedded fine-grained
quartz- and feldspar-bearing sandstone with many thin interbeds of carbonaceous
pyriti iitstone and shale. Sandstene commonly thinly crossbedded; forms ledges.
Two graphitic coaly beds, about 1 m thick, on Coal Rock contain plant debris
including a glossopterid flora of Permian age; nonfossiliferous rocks of Grob Ridge
may be younger. Rocks commonly altered to hornfels by the Dufek intrusion.
Base and top not exposed in Pensacola Mountains. Overlies Gale Mudstone with
apparent concordance. Maximum thickness of about 200 m exposed on Coal
Rock

GALE MUDSTONE (Permian? and Carboniferous?) ~ Massive dark-gray diamictite
(tillite) containing abundant dispersed pebbles, cobbles, and boulders of diverse
lithology generally similar to those in pre-Gale terrane of the Pensacola Mountains.
Coarse clasts mainly granite and gneiss and include schist, phyllite, quartzite, lime-
stone, and siltstone, Bedding generally indistinct to absent. Nonfossiliferous.
Strongly folded and locally well cleaved. Thermally indurated in contact aureole
of the Dufek intrusion. Base and top not exposed. Exposed mainly in Schmidt

Hills quadrangle where probably disconformable on Dover Sandstone above striated _
boulder pavements, and where thickness probably is several times a measured 315 m

DOVER SANDSTONE (Devonian) — White, tan-weathering, thick and evenly bedded,
well-sorted, medium- to coarse-grained quartz sandstone containing conspicuous,
widely scattered quartz pebbles. Coarsely crossbedded in places. Quartzite beds
common. Nonfossiliferous in the mapped area but elsewhere contains flora of
Middle Devonian age. Moderately to strongly recrystallized in thermal aureole
of Dufek intrusion. Base and top not exposed. Mainly exposed in Schmidt Hills
quadrangle where about 1,200 m thick

NEPTUNE GROUP (Devonian? to Ordovician?) — Includes, in descending order,
Heiser Sandstone, Elbow Formation, Elliott Sandstone, and Neith Conglomerate.

Poorly exposed sequence more than 1,500 m thick; well exposed to west in Schmidt

Hills quadrangle (Schmidt and others, 1978; Schmidt and Ford, 1969). Lower two
units not exposed. Fossils rare, nondiagnostic of age, and known only in the Heiser
Sandstone, which is believed to be correlative with a Devonian part of the Beacon
Supergroup elsewhere in Antarctica. Separated from Cambrian and older rocks by
angular unconformity

HEISER SANDSTONE — Well-bedded light-green brown-weathering quartz sandstone.
Slightly more silty than the Dover Sandstone. Characterized by abundant tubular
burrows 1 cm or less in diameter oriented normal to bedding. Base and top not
exposed. Thickness of about 320 m measured in Schmidt Hills quadrangle

ELBOW FORMATION — Light-gray argillaceous siltstone interbedded with light-gray
fine-grained quartz-rich sandstone, commonly in well-bedded cyclic pairs 0.3-2 m
thick. Well laminated and commonly crossbedded. Red coloration of this unit
in the adjacent Schmidt Hills quadrangle probably destroyed by thermal effects
from the Dufek intrusion. About 300 m thick to west in the Schmidt Hills quad-
rangle

ELLIOTT SANDSTONE — Quartz-rich, locally conglomeratic sandstone about 1,400 m

in maximum thickness in southern part of Schmidt Hills quadrangle. Not exposed
and possibly not present owing to northward thinning from type area

NEITH CONGLOMERATE — Shown only in cross sections. Exposed mainly in Schmidt

Hills quadrangle, where it is a poorly sorted, poorly bedded to massive, reddish-
brown conglomerate interlayered with moderately well bedded coarse sandstone.
Thickness not known but locally may be as much as 1,000 m

PATUXENT FORMATION (upper Precambrian) - Well-bedded, medium- to dark-
grayish- green, medium-grained argillaceous metasandstone (metasubgraywacke),
generally rhythmically interlaycred with dark-gray slate and minor amounts of grit-

stone. Locally conglomeratic. Poorly exposed. Mainly exposed in Schmidt Hills quad-
rangle, where felsic and mafic volcanic units also occur. Regionally metamorphosed

to greenschist facies. Intensely folded and generally well cleaved. Fossils rare and
nondiagnostic of age. Unconformably underlies Cambrian limestone in Schmidt
Hills quadrangle. Thickness estimated to exceed 10,000 m

SEDIMENTARY ROCKS, UNDIVIDED (Permian? to Precambrian?) — Sedimentary
rocks of unknown correlation that are inferred to lie beneath cover of ice

Strike and dip of joints
Inclined
Horizontal
Vertical
Dike — Showing dip
Inclined
Vertical
Trough-layered structure (scour channel) in cumulates, showing plunge
Area of geophysical anomaly

Bedrock outcrop

WEST OF GREENWICH
60°00" 52°30" 45° 37°30"
le2-00" = oo
CORDINER DAVIS ARGENTINA
PER VALLEY RANGE
mes | wars | sua wrL
83° aa 83°
scumiot | saratoga
HILLS Taale. | Su 21-25/15,
ea —__...
GAMBACORTA
PEAK sv 21-30/2
60°00" 52°30 37°30"

Sheet numbering system based on International

Map of the World

Mountains, Antarctica: U.S. Geol. Survey Antarctic Geol. Map A-8, 1:250,000.

GEOLOGIC MAP OF THE SARATOGA TABLE QUADRANGLE, PENSACOLA MOUNTAINS, ANTARCTICA

By

Arthur B. Ford, Dwight L. Schmidt, Walter W. Boyd, Jr., and Willis H. Nelson

1978

For sale by Branch of Distribution,

INDEX TO ADJOINING SHEETS

U.S. Geological Survey, 1200 South Eads Street,
Arlington, VA 22202 and Branch of Distribution,
U.S. Geological Survey, Box 25286, Federal Center,

Denver, CO 80225

Explanatory pamphlet accompanies map