DEPARTMENT OF THE INTERIOR
UNITED STATES GEOLOGICAL SURVEY

Base from U.S. Geological Survey
Davis Valley and Cordiner Peaks, 1968

METERS
2000

1000
SEA LEVEL
1000
2000

Prepared by the

U.S. GEOLOGICAL SURVEY
under the auspices of the

NATIONAL SCIENCE FOUNDATION

Area of +200 to +400 gammas ee /
intensity reported by Behrendt and /
others (1973) / /

/ Area of -200 to -400 gammas magneticn/
a intensity reported by Behrendt and
7 others (1973)

Area of +100 gammas magnetic
intensity reported by Behrendt

and others Cr ee

‘Area of +400 to +540 gammias magnetic
intensity reported by Behrendt and
others (1973)

\

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|
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| Area of +100 gammas
magnetic intensity

\ reported by Behrendt

\ and others (1973)

\

SALLE‘

SNOW

Areas of +200 to!

intensity reported:

others (197;

SCALE 1:250,000

5 ° 5 10 15 20 Statute Miles
5 ° 5 10 15 20 25 30 Kilometers
—=—— — -
5 ° - 5 10 15 Nautical Miles

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

‘Area of +200 to +540 gammas magnetic /
intensity reported by Behrendt and /
others (1973)

2°00"

/ Area of -200 to -515 gammas /
{Magnetic intensity reported by
// ~~ Bebrendt and others (1973) /

/ Mw i
_L areas of +600 gammas, ++
or greater magnetic | {
intensity reported by |
Behrendt and others
(1973)

S
&

ass

fo
T 6s Korman
<-Nunatak’

intensity reported by Behrendt and
others (1973)

Sy

is
a

83°00"
45°00
Geology by A.B. Ford, WW. Boyd, Jr., D.L. Schmidt,
and W.H. Nelson, 1965-66; Cordiner Peaks area by
A.B. Ford, 1974; western Dufek Massif area by
A.B. Ford, Christine Carlson, G.K. Czamanske,
W.H. Nelson, and C.J. Nutt, 1976

* al
3 rd
s a
E 2 = 2/2
A Jfay 2 2 i supporT FORCE A’ B UU ELT fells : Spanley Rocks :
Sfafy yf Forrestal Range : Elacien METERS METERS Z|9 Rosser Ridge METERS METERS a METERS
oF SALLEE  SNOWFIELD a Jil Tis 0 i: 2000 2000 ~ as 7 - 2000 2000, 7 il <DOn DOel 2000
a 1000 1000 + AT | 1000 1000 E = 1000
0h s =e \NEE sea Level 4 - SEA LEVEL SEA LEVEL
1000 1000 4 +1000 1000 1000
2000 2000 2000 2000 2000

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

LOCATION DIAGRAM
west O° East

60° 60°
90° 90°
120° 120°

Physiographic sketch of the western part of Dufek Massif, viewed south from Hannah Peak. WP, Walker Peak; Sketches by Tau Rho Alpha

NP, Neuburg Peak; AP, Aughenbaugh Peak. Horizontal distance seen is about 10 km.

Physiographic sketch of north face of Dufek Massif, viewed south from Cairn Ridge. WP, Walker Peak;
NP, Neuburg Peak; AP, Aughenbaugh Peak. Horizontal distance seen is about 18 km.

WEST 180° EAST

Interior — Geological Survey, Reston, Va.—1978—G76339 atl

Jdm

Sfl

Sfs

Sfa

Sfas

fw

U.S. ANTARCTIC RESEARCH PROGRAM

DAVIS VALLEY QUADRANGLE AND PART OF THE
CORDINER PEAKS QUADRANGLE

ANTARCTIC GEOLOGIC MAP A-10

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

Sedimentary deposits
an)

Qe | QUATERNARY
Igneous rocks
r = a 1
Forrestal :
Range
section
- -
Z Stas
Oo
Jd g
oe | Dufek
S | intrusi JURASSIC
a) omsen | Dufek a
e Massif +
5 section
4
Jew
ANGULAR UNCONFORMITY (Weddell orogeny) 7
PCe } PERMIAN(?) AND
Eee CARBONIFEROUS(?)
§ | _DISCONFORMITY
2 } DEVONIAN
a
&4 DISCO!
e| =
€|
=| 3
8| 6
3| 2 DEVONIAN(?) TO
a g ORDOVICIAN(?)
by
Z |
ANGULAR UNCONFORMITY (Ross and Beardmore? orogenies)
Upper
Ree ee } PRECAMBRIAN
Precambrian

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 some places lying on ice. May include deposits of older
moraines on Rosser Ridge, where boulders are slightly weathered and
are encrusted with salts (mainly gypsum) on undersides

FELSIC DIKE ROCK (Jurassic) ~ Aplite, pegmatite, and less common leucogabbro
and alaskite of dikes apparently related to the Dufek intrusion, From 1 cm to
several meters thick. Locally zoned

MAFIC DIKE ROCK (Jurassic) — Basalt and diabase of dikes a few centimeters to
several meters thick. Occur only on Rosser Ridge, where they cut rocks as young
as Gale Mudstone. Devitrified selvages common. Generally slightly altered.
Probably related to Dufek intrusion but may be of slightly different age

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 séttled plagio-
clase, 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. Pyrox-
enes belong to two coexisting series, augite-ferroaugite and bronzite-inverted
pigeonite. The opaque oxides are chiefly composite grains of titaniferous mag-

netite and ferrian ilmenite. Stratigraphy and rock-stratigraphic nomenclature

of group discussed in Ford (1976). Jurassic age assignment based on K-Ar anal-
yses that average 168+3.4 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. Upper units of group mainly exposed
to south in Saratoga Table 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 ~ Not exposed, but presence indicated in cross
section in ice-covered central highland of Forrestal Range. A late-stage dif-
ferentiate of the tholeiitic Dufek magma. Composition approximates that of
iron-rich granodiorite. 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 plagio-
clase-rich cumulate (anorthosite and leucogabbro) and common thin dark-gray
to black layers of magnetite-rich cumulate. Mineral-graded layering common.
Matic rock is chiefly two pyroxene-plagioclase-magnetite cumulate. Scour chan-
nels (trough layering) observed mainly in lower part. Contacts not exposed.
Thickness of about 1,400 m measured in Saratoga Table quadrangle

AUGHENBAUGH GABBRO ~ Chiefly light- to medium-gray medium-grained
mafic cumulate of general gabbroic composition. In places cavernously weathered.
Principally a two pyroxene-plagioclase cumulate, with minor cumulus magnetite
in upper 200 m. Scour channels (trough layering) locally present about 30 m
below Frost Pyroxenite Member. Generally well laminated and layered, but layer-
ing less conspicuous in interval between the two pyroxenite members. Basal con-
tact sharp; top not exposed. About 1,600 m thick

Spear Anorthosite Member — A sequence of three layers, 15-45 m thick, of cream
to light-gray plagioclase cumulate, locally with minor cumulus magnetite, and
interlayered medium- to dark-gray pyroxene-plagioclase cumulate. Plagioclase
cumulates characteristically spotted with coarse postcumulus pyroxene. Basal
contact sharp; top not exposed. At least 105 m thick

Frost Pyroxenite Member — A conspicuously layered sequence consisting of at
least six dark-brownish-gray to black mineral-graded layers of pyroxene-rich
cumulate, up to 4 m thick, interlayered with medium- to dark-gray pyroxene-
plagioclase cumulate. Darker layers typically poorly laminated plagioclase-bearing
two-pyroxene cumulate. Basal contact sharp; upper contact gradational. About
43 m thick

Neuburg Pyroxenite Member — A conspicuous single mineral-graded layer of dark-
brownish-gray plagioclase-bearing two-pyroxene cumulate. About 200 m above
base of Aughenbaugh Gabbro. Pyroxenes are augite and inverted pigeonite,
characteristically in unusually coarse clusters as much as 5-7 cm across. Basal
contact sharp; grades upward, with increasing amounts of cumulus plagioclase,
into overlying dark- to medium-gray two pyroxene-plagioclase cumulate. Thick-
ness of about 5 m nearly constant along entire 20-km extent of exposure

Lower anorthosite member — A locally conspicuous single isomodal layer of cream
to light-gray, mainly plagioclase cumulate. About 40 m above base of
Aughenbaugh Gabbro. Characteristically spotted with dark, coarsely poikilitic
postcumulus pyroxenes, Basal and top contacts sharp. About 12 m thick

WALKER ANORTHOSITE ~ White to light-gray, medium-grained, mainly plagio-
clase cumulate. Generally well laminated. Layering generally indistinct and
gradational but locally conspicuous where cumulus pyroxene present in thin
interlayers. Characteristically spotted with dark, coarsely poikilitic postcumulus
pyroxenes. Sharp top; base not exposed. At least 230 m thick

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

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 testane of the Pensacola Mountains.
Coarse clasts mainly granite and gneiss and include schist, phyllite, quartzite,
limestone, and siltstone. Bedding generally indistinct to absent. Nonfossiliferous.
Strongly folded and locally well cleaved. Top not exposed. Basal contact sharp,
probably a disconformity, where exposed on Rosser Ridge. Exposed mainly in
Schmidt Hills quadrangle where striated boulder pavements are present and where
thickness is probably several times a measured 315 m

} PERMIAN(?) TO
PRECAMBRIAN

DOVER SANDSTONE (Devonian) — White, thick and evenly bedded, well-sorted,
medium- to coarse-grained quartz sandstone containing conspicuous, widely
scattered quartz pebbles; weathers tan. Coarsely crossbedded in places. Quartzite
beds common. Nonfossiliferous here, but elsewhere contains flora of Devonian
age. Base not exposed. Upper contact probable disconformity. Exposed mainly in
Schmidt Hills quadrangle where thickness is about 1,200m

NEPTUNE GROUP (Devonian? to Ordovician?) ~ Includes, in descending order,
Heiser Sandstone, Elbow Formation, Elliott Sandstone, and Neith Conglomerate.
Sequence more than 1,500 m thick. Poorly exposed, but well exposed to south in
Schmidt Hills quadrangle (Schmidt and others, 1978; Schmidt and Ford, 1969)
Fossils rate, nondiagnostic of age, and known only in the Heiser Sandstone, which
is believed to be correlative with a Devonian part of the Beacon Supergroup else-
where in Antarctica. Separated from Cambrian and older rocks by angular un-
conformity

HEISER SANDSTONE ~- Well-bedded light-green quartz sandstone; weathers brown.
Slightly more silty than the Dover Sandstone. Characterized by abundant tubular
burrows 1 cm or less in diameter oriented normal to bedding. Silty sandstone and
quartzite beds, 1 m or less thick, commonly rhythmically interbedded. Base and
top not exposed. Thickness of about 320 m measured in Schmidt Hills quadrangle

ELBOW FORMATION ~ Red argillaceous siltstone interbedded with light-gray
fine-grained quartz-rich sandstone, commonly in well-bedded cyclic pairs 0.3-2 m
thick. Well laminated, commonly crossbedded, and locally ripple marked. Red
beds commonly mottled light gray. Base and top not exposed. Thickness of about
300 m measured in Schmidt Hills quadrangle

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 ~ Poorly bedded to massive, poorly sorted, coarse,
reddish-brown conglomerate interlayered with moderately well bedded coarse-
grained reddish-brown sandstone. Clasts derived chiefly from underlying sed-
imentary formations. Basal part dominantly conglomeratic, locally very thick;
upper part dominantly sandstone and possibly correlative with Elliott Sandstone.
Base and top not exposed. Thickness may be as much as 1,000 m in Schmidt Hills
quadrangle

PATUXENT FORMATION (Upper Precambrian)~ Well-bedded medium- to dark-
grayish-green medium-grained argillaceous metasandstone (metasubgraywacke)
generally rhythmically interlayered with dark-gray slate and minor gritstone.
Locally conglomeratic. Poorly exposed. Mainly exposed in Schmidt Hills
quadrangle 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

su SEDIMENTARY ROCKS, UNDIVIDED (Permian? to Precambrian?) — Sedimentary

rock of unknown correlation, mainly inferred beneath cover of ice

me

Contact — Dotted where concealed; queried where highly uncertain

High-angle fault — U, upthrown side; D, downthrown side
Dotted where concealed; queried where highly uncertain

—1—1— Trough-layered structure (scour channel) in cumulates
<1 antictine ~ showing plunge. Dotted where concealed; queried where highly uncertain
<{— synctine ~ Showing plunge. Dotted where concealed; queried where highly uncertain

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

ae Inclined
® Horizontal
Strike and dip of cleavage in sedimentary rocks and of microshear joints in igneous
rocks
a Inclined
+ Vertical
Strike and dip of joints
es Inclined
+ Horizontal
_ Vertical
jo Sttike and dip of dikes
as Inclined
+ Vertical
———— Area of geophysical anomaly

Bedrock outcrop

SELECTED REFERENCES

Behrendt, J. C., Rambo, W. L., Henderson, J. R., Wanous, R. E., and Meister,
Laurent, 1973, Simple bouguer gravity and aeromagnetic maps of the Davis
Valley quadrangle and part of the Cordiner Peaks quadrangle and vicinity,
Antarctica: U.S. Geol. Survey Geophys. Inv. Map GP-887, scale 1:250,000.

Ford, A.B., 1976, Stratigraphy of the layered gabbroic Dufek intrusion of
Antarctica: U.S. Geol. Survey Bull. 1405-D, p. D1-D36.

Ford, A. B., Schmidt, D. L., Boyd, W. W., Jr., and Nelson, W. H., 1978, Geologic map
of the Saratoga Table quadrangle, Pensacola Mountains, Antarctica: U.S. Geol.
Survey Antarctic Geol. Map A-9, scale 1:250,000.

Ford, A.B., Carlson, Christine, Czamanske, G.K., Nelson, W.H., and Nutt, C.J.,

1977, Geological Studies of the Dufek intrusion, Pensacola Mountains, 1976-
1977: Antarctic Jour. US., v. 12 ,p. 90-92.

Himmelberg, G. R., and Ford, A. B., 1976, Pyroxenes of the Dufek intrusion,
Antarctica: 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
Mountains, Antarctica: U.S. Geol. Survey Antarctic Geol. Map A-8, scale 1:250,000.

60°00
82°00" \

361————__]
3681

WEST OF GREENWICH
sa sora 1 aap
81700" Ss 81°00}
SU 21-25/5 27-25/7 |
ee - exe
CORDINERTM DAVIS. ARGENTINA
\, “Geans VALLEY RANGE
=e
scumor | saratoga |
| eee | eM leuerteere
84°00 — snag gg 88700

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

GEOLOGIC MAP OF THE DAVIS VALLEY QUADRANGLE AND PART OF THE CORDINER PEAKS QUADRANGLE, PENSACOLA MOUNTAINS, ANTARCTICA

By

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

1978

Sheet numbering system based on International
Map of the World
INDEX TO ADJOINING SHEETS

For sale by Branch of Distribution, 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