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Type Section of the 

Beacon Sandstone of 

Antarctica

GEOLOGICAL SURVEY PROFESSIONAL PAPER 456-A

Prepared on behalf of the 

National Science Foundation

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Type Section of the 

Beacon Sandstone of 

Antarctica

By WARREN HAMILTON and PHILIP T. HAYES

CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 456-A

Prepared on behalf of the 

National Science Foundation

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C., 20402
CONTENTS

Abstract_____-____________________________________

Introduction_______________ _ ______________________

Type section_______________________________________

Lower part-___________________________________

Middle part.___________________________________

Upper part---------------_____-----_-___-_-___-

Correlations between sections------_____-____-___-

Nomenclature._____________________________________

Past nomenclature._____________________________

Proposed nomenclature and stratigraphic summaryDiabase sheets. ____________________________________

Form________________________________________

Page

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1

4

4

6

7

9

12

12

Diabase sheets Continued Page

Petrology__-___________________________________ A12

Metamorphism of the Beacon Sandstone___________ 12

Age of diabase-__-__----------___-__--_-___---__ 12

Age of the Beacon Sandstone_____-_-----__-__-_______ 12

Fossils near type section_____-___________________ 12

Fossils from the Beacon Sandstone of other areas. __ 14

Age of rocks beneath the Beacon Sandstone ________ 14

Age of the Beacon Sandstane_-__--___--__-_______ 14

Conditions of deposition___----______________________ 16

Crossbedding_ __________________________________ 16

Paleoclimate_ __________________________________ 17

References cited_____-_--_._.-_-______.____________ 17

ILLUSTRATIONS

FIGURE 1. Index map of Antarctica_________________________

2. Index map of west coast of McMurdo Sound_________

3. Geologic map of Beacon Heights__________________

4. New Mountain from the north_____________________

5. Columnar sections of Beacon Sandstone _____________

6. West Beacon Heights from the northeast-___________

7. West wall of Beacon Dry Valley___-_-__________--__

8. West part of Finger Mountain from the north_______.

9. Pyramid Mountain from the northeast ______________

10. East end of Finger Mountain from the south_________

11. Molds of burrows.-_-___--____-____-___-_-_______-

12. Outcrop of upper part of sandstone of New Mountain13. Crossbedded strata----__-_____-------_____-__--_-

Page 

Al

2

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15

16

ni

CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

TYPE SECTION OF THE BEACON SANDSTONE OF ANTARCTICA

By WARREN HAMILTON and PHILIP T. HATES

ABSTRACT

The Beacon Sandstone of Carboniferous(?), Permian, and 

early Mesozoic(?) age is widely distributed in East Antarctica. 

The formation was named by Ferrar in 1907 for exposures 

in Beacon Heights, near Taylor Glacier west of McMurdo Sound, 

but no type section has previously been described. This paper 

presents a composite section in the type area, assembled from 

a published description of the basal strata by Zeller and others 

(1961), a previously unpublished description of the middle part 

by the present authors, and a published description of the 

upper part by McKelvey and Webb (1959).

The Beacon Sandstone in its type area consists largely of 

light-colored medium- to coarse-grained sandstone, much of it 

crossbedded. Beds of fine-grained sandstone and siltstone are 

subordinate. 1 Carbonaceous strata bearing constituents of the 

Glossopteris flora occur high in the formation. The middle 

part of the formation consists of cliff-forming sandstone, easily 

recognizable throughout the region, and is separated from the 

ledge-forming section beneath by a disconformity. Total thickness of the Beacon is about 4,000 feet. Intrusive into the 

Beacon are huge sills and inclined sheets of quartz diabase 

(the Ferrar Dolerites) of Mesozoic age, which have an aggregate thickness of about the same amount.

The three major units of the Beacon Sandstone in its type 

area are here referred to as the sandstone of New Mountain 

(the lower ledge-forming unit), the sandstone of Pyramid 

Mountain (the middle cliff-forming unit), and the sandstone 

of Finger Mountain (the upper ledge-forming fossiliferous unit). 

A thin sequence of diverse rocks, described by Zeller and others 

(1961), beneath the sandstone of New Mountain may not properly belong to the Beacon Sandstone.

Although several authors have proposed recently that the 

Beacon be elevated to group status, they have not established 

mappable formations within the Beacon; consequently, their 

proposals are premature. Because geologic fieldwork is' likely 

to be of reconnaissance character and in widely separated areas 

for some time to come, it seems preferable for the present to 

maintain formation status for the Beacon Sandstone and to 

subdivide it into local formal members only when the utility 

of these is demonstrated by detailed work.

INTRODUCTION

The Beacon Sandstone of Carboniferous(?), Permian, and early Mesozoic( ?) age forms a discontinuous 

cover upon much of East Antarctica, the large part of 

the continent lying mainly in east longitudes (fig. 1).

The sandstone carries a Glossopteris flora and shares 

many features with correlative rocks of the other

"Gondwana" landmasses of Australia, India, South 

Africa (Karroo System), and South America.

The Beacon Sandstone was named by Ferrar (1907) 

for exposures on West Beacon Heights on the south 

side of upper Taylor Glacier (figs. 2 and 3), South 

Victoria Land. He estimated that about 2,500 feet of 

sandstone are present there but did not describe a type 

section. McKelvey and Webb (1959) presented a detailed section of the upper part of the formation in the 

type area, and Zeller and others (1961) described the 

basal part. These partial sections are here tied to the 

section studied by us in the middle part of the formation on West Beacon Heights to give, for the first time, 

a reasonably accurate type section of the Beacon Sandstone.

The Ross Sea coast of East Antarctica is bounded by a 

range of high mountains, which forms a dam against the 

vast inland ice plateau. Valley outlet glaciers, one of

FIGURE 1. Index map of Antarctica. Asterisk indicates location of 

Beacon Sandstone type locality. Localities mentioned in text are 

Priestley Glacier, P; Mount Gran, M; Beardmore Glacier, B ; Mount 

Weaver, W; Horlick Mountains, H; and Amery locality, A.

Al
A2

160"

CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA 

161* 162" 163* 164° 165°

78°

10 MILES

20 KILOMETERS

FIGURE 2. Index map of mountains west of McMurdo Sound. Hatched line outlines area of geologic map (fig. 3).

which is Taylor Glacier, flow across these mountains 

from the plateau toward the sea through the major 

transverse valleys. Pre-Devonian granitic and metamorphic rocks form the coastal foothills and lower areas 

in the central part of the range. Above these basement 

rocks in the central part of the range, and forming 

nearly all the exposed rock of the western part of the 

range, is the almost undef ormed Beacon Sandstone and 

the diabase sheets intruded into it.

Our fieldwork on the type section was done during 

November 1958, from a camp on Taylor Glacier, to

which we were flown by a U.S. Navy ski-equipped airplane, as part of our study of the Taylor Glacier-Taylor 

Dry Valley region (Hamilton and Hayes, 1960).

We are much indebted to L. H. Daugherty, S. H. 

Mamay, J. J. Mulligan, and J. M. Schopf for permitting 

us to cite some of their unpublished data on the paleobotany of the Beacon Sandstone. To Schopf in particular must also go much of the credit for the discussion 

of paleobotany and age of the Beacon.

This work was carried out on behalf of the National 

Science Foundation.
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA

EXPLANATION

A3

Plutonic basement complex

Fault

Mountain peak

3 MILES

4 KILOMETERS

FIGCEE 3. Geologic map -of Beacon Heights and vicinity. Map prepared by photogrammetric methods from vertical aerial photographs, supplemented by field observations and by ground and oblique aerial photographs. Dashed contacts modified from McKelvey and Webb (1959). 

Arrows show direction of ice flow.
A4 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

TYPE SECTION

The Beacon Sandstone of the type area (fig. 3) is 

about 4,000 feet thick and dips 2°-4° westward. The 

few faults are short and of small displacement. Injected into the sandstone are huge sills and inclined sheets 

of quartz diabase with an aggregate thickness of about 

4,000 feet, so that the total thickness of sandstone and 

diabase is about 8,000 feet. The local relief is but 4,000 

feet, and it is necessary to define a composite type section 

from separate traverses.

The base of the Beacon Sandstone crops out at the 

southeast end of the mountain mass of the type area, 

and here Zeller and others (1961) described the lower 

part of the formation. We measured the middle part 

of the formation at West Beacon Heights, 7 miles to

the northwest. McKelvey and Webb (1959) described 

the upper part of the sandstone 3 miles farther west.

All but the basal strata of the Beacon are divisible 

into three easily recognized units in the type area and 

the surrounding region. The lower unit, here referred 

to as the sandstone of New Mountain, is ledge-forming 

sandstone. The middle unit, the sandstone of Pyramid 

Mountain, is thick bedded and cliff forming. The upper 

unit, the sandstone of Finger Mountain, is ledge forming 

and includes much siltstone and carbonaceous strata. 

These units are defined more fully on page 10.

LOWER PART

The base and lower part of the Beacon Sandstone 

were examined by Zeller and others (1961) on the

FIGURE 4. New Mountain, seen from the north, showing the lower part of the Beacon Sandstone. Pre-Devonian basement rocks crop out at 

base of bluffs by Windy Gully. A thick diabase sill lies near the base of the Beacon, and another is at the top of New Mountain. The 

cliff-forming sandstone of Pyramid Mountain, the middle part of the Beacon, is visible to the left of the upper sill. The summit of 

New Mountain (alt about 7,800 ft) is 4,000 ft above Taylor Glacier.
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA A5

lower northeast slope of New Mountain, a short distance 

northwest of Windy Gully (figs. 3 and 4), and in the 

Terra Cotta Hills on the southeast side of Windy Gully. 

The section they described is illustrated, diabase sills 

omitted, in figure 5.

The bedded rocks lie upon a surface with a local 

erosional relief of 100 feet cut into pre-Devonian plutonic rocks. A discontinuous basal conglomerate 0-5 

feet thick grades upward into sandstone 5-100 feet thick 

that contains thin cobble beds; this basal section was 

designated the "Windy Gully Member" by Zeller and

others (1961). Next above is the Terra Cotta Mountain 

Member of Zeller and others, which consists of 110 feet 

of interbedded green and purple shale and green, pink, 

white, and brown sandstone. This is succeeded, with 

what Zeller and others described only as a "decided 

break in sedimentation," by about 250 feet of white to 

buff sandstone, crossbedded in part, with pebbly beds. 

(At or near the top of this unit in this measured section 

is a diabase sill nearly a thousand feet thick). The next 

higher strata are 40 feet of thin-bedded buff and green 

sandstone, and above these is a thick sequence of beds

EXPLANATION

Sandstone, HBcrossbedded

Sandstone, not crossbedded

"".- -- ^ '-''. '-^ '

Sandstone, crossbedded in part

Sandstone, carbonaceous 

TERRA COTTA HILLS-NEW MOUNTAIN

l,350±feet o soft-weathering cliff-forming 800±feet ofsandstones sandstones =4.=. -» 

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Sandstone with conglomerate Granitic basement

 ' ^^-~

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Siltstone

=^

Shale

Shale, carbonaceous

FEET

-0

-100 

-200 

-300 

-400 

-500 

-600

 fli?°NFOR((/7v

 ^ L^i^^^-y PROBABLE MAJOR DISCONFORMirV

 ^z-^^ij=-=^rl Terra Cotta Mountain Member

;' TTT-.- ;-. :;.". ^ ot ieller and otners (]

 ^^"^T^fc, :'- - -S Windy Gully Member of 

_ ' ' 'T^ii^1 Zeller and others (1961)

961)

VEST BEACON HEIGHT 

SECTION

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BEACON DRY VALLEY 

SECTION2

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Estimated 400 feet of 

soft-weathering sand 

stone to base of exposure north ol 

Beacon Dry Valley 

sectionf

Member C of 

McKelvey and 

Webb (1959)

xMember B of 

McKelvey and 

Webb (1959)

Member A of 

McKelvey and 

Webb (1959)

1 Approximate 

11 base of cliff- 

| forming sand1 stone3

Modified from Zeller and others 

(1961) except as noted

Adapted from McKelvey and 

Vebb (1959) except as noted

Modifications or additions by 

Hamilton and Hayes

Pre-Devonian plutonic rocks 

if 7 MII F<; -*\* > MII re -.1

FIGURE 5. Columnar sections of Beacon Sandstone at and near West Beacon Heights.

type section.

6.78832 O 63 2

These three sections form a composite
A6 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

of alternately hard and soft thin-bedded to massive buff 

sandstone. Only the lower 350 feet of this upper part 

was measured. This upper unit was called "Member 

Al" by Zeller and others, who supposed it to correlate 

with the lower part of the section measured by McKelvey and Webb (1959). Because of the westerly regional 

dip, these rocks near Windy Gully actually lie far 

beneath the section studied by McKelvey and Webb.)

On vertical and oblique aerial photographs of New 

Mountain, alternate layers of hard and soft sandstone, 

weathering to form a rather smooth slope, can be seen 

to continue upward for a total thickness (including the 

350 ft. measured by Zeller and others) of about 1,700 

feet. The top of this slope-forming sandstone sequence 

is marked by an apparently disconformable contact

with cliff-forming thick-bedded sandstone, about 800 

feet thick% that continues to the base of the sill that caps 

New Mountain.

MIDDLE PART

The middle part of the type section of the Beacon 

Sandstone was studied by us on the lower north slope 

of West Beacon Heights (figs. 3, 5, and 6) above Taylor 

Glacier about 1% miles east of the mouth of Beacon 

Dry Valley. We measured the lower 1,200 feet of the 

section (fig. 3) and determined the character of higher 

strata by binocular inspection from the top of the 

measured section and by examination of talus fragments. Thicknesses of the measured section were determined by aneroid altimeter, supplemented by heightof-eye measurements for thin units; thicknesses of the

FIGURE 6. West Beacon Heights seen from the northeast, showing the middle part of the Beacon Sandstone cut by diabase dikes and sills. 

The cliff-forming sandstone unit (sandstone of Pyramid Mountain) extends upward from the level ofl the hanging valley on the left. Frost 

polygons mark the talus and sidehill moraine near Taylor Glacier at the base -of the mountain. The summit has an altitude of about 7,800 

ft and stands 4,000 ft above Taylor Glacier.
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA A7

overlying rocks, extending to the top of West Beacon 

Heights, were measured by rough triangulation from 

Taylor Glacier and confirmed photogrammetrically.

The. following is the description of the middle part 

of the type section of the Beacon Sandstone as exposed 

on the north slope of West Beacon Heights:

Top of section: base of diabase sill that caps West Beacon

Heights

Thickness

(feet)

10. Sandstone and quartzite, pale pink, buff, and white, 

medium- to coarse-grained; striped by irregular 

brown bands on weatherer outcrops; thick even 

beds form cliffs. (Diabase sill, 400 ft thick, injected into the middle of this unit is not included 

in the stratigraphic thickness) _ _ 1, 000±:

9. Sandstone, yellowish-gray, medium- to coarsegrained, quartzose, variably resistant; forms low 

ledges; some is evenly bedded, and some is in long 

sweeping crossbeds. Dark-brown concretions are 

abundant near top. Sparse thin intercalations of 

green sandstone and shale near base. Upper part 

of unit includes thick lenses of pink quartzite. 

Overlain by unit 10 with an apparently disconformable contact____________________ 1,250±

8. Sandstone, yellowish-gray, coarse-grained, slightly 

feldspathic, easily weathered; interbedded with 

platy beds of mottled light-olive-gray and greenish-yellow medium-grained micaceous sandstone, 

which constitutes about one-fourth of unit. 

Upper contact not exposed______________ 25

7. Sandstone, pinkish-gray, medium- to coarse-grained, 

feldspathic; bedded in long thin lenses, not crossbedded; interbedded with platy mottled lightolive-gray to greenish-yellow fine- to mediumgrained micaceous feldspathic sandstone. Both 

upper and lower contacts sharp and conformable ____________________________ 15

6. Sandstone, yellowish-gray, coarse-grained, slightly 

feldspathic, easily weathered; lenticular beds, 

discontinuously laminated, not crossbedded; a 

few beds of green argillite less than 2 in, thick_ 60

5. Sandstone, pinkish-gray, yellowish-gray, and white, 

medium- to very coarse grained, feldspathic; 

short lenticular beds, 2 in. to 1 ft thick, with 

steep internal crossbedding; interbedded with 

platy green micaceous sandstone and with several 

2-in.-thick seams of green argillite in top 15 ft_ 50

4. Sandstone, yellowish-gray, coarse-grained, feldspathic, easily weathered; thin beds in lower part 

but thick beds in upper, variably crossbedded; 

lenses of conglomerate common near base, contains pebbles of quartz, fewer of pegmatitic 

feldspar, fine-grained crystalline rocks to 1 in. 

in diameter, sparse cobbles of sandstone to 3 in. 

in diameter, and several thin beds, of platy green 

argillite. Basal contact of unit sharp and conformable ; upper contact not exposed_______ 170

3. Sandstone, yellowish-gray, thin-bedded; middle part 

medium grained and erossbedded in part; upper 

and lower parts fine grained and interbedded with 

numerous thin beds of pale-olive siltstone and 

micaceous sandstone_________________ 40

Top of section: base of diabase sill that caps West Beacon 

Heights Continued

Thickness

(feet) 

2. Sandstone, very-light- to yellowish-gray, medium- to

coarse-grained, very slightly feldspathic; in beds 

2-15 ft thick, internally marked by long gentle 

crossbeds; outcrop ledges locally pitted by numerous circular cavities. Base not exposed_____ 250 

1. Covered by talus and moraine; indications of pink 

and grayish-green siltstone and easily weathered 

sandstone in upper part _ ______ _ 200±

Base of section: bottom of hill, at edge of Taylor 

Glacier.

Approximate total thickness of sedimentary sequence _______________________ 3,000

UPPEK, PART

Most of the upper part of the Beacon Sandstone was 

measured by McKelvey and Webb (1959) on the west 

side of Beacon Dry Valley about 1 mile south of Pyramid Mountain (figs. 3, 5, and 7). They estimated the 

bottom of their measured section to be about 1,500 feet 

above the base of the formation. Their lowest unit, 

which they termed "member A," consists of more than 

1,400 feet of white, buff, and light-gray sandstone, 

mostly crossbedded. Above this is "member B," 60 

feet of red and green siltstone interbedded with white 

and green sandstone. Highest is their "member C," 565 

feet thick, which consists largely of sandstone, carbonaceous in part, in the lower 190 feet; next above 

within the "member" is 55 feet of interbedded finegrained sandstone and carbonaceous shale; next, 40 feet 

of massive sandstone containing thin beds of pebbles; 

then, 145 feet of interbedded sandstone and carbonaceous shale; and at the top 135 feet of crossbedded sandstone, carbonaceous in part. Still higher strata were 

not measured.

The carbonaceous strata of member C are displayed 

conspicuously on the north face of Finger Mountain 

(fig. 8).

McKelvey and Webb (1959) did not describe the outcrop characteristics of the rocks of their measured section nor did they indicate on any of their illustrations 

what members were pictured. The section measured by 

them presumably includes all the rocks illustrated in 

their figure 8. By comparing this figure with our own 

observations of that area from a distance and with 

our observations and photographs of Pyramid and 

Finger Mountains to the north of their measured section, 

we can supply this missing information with reasonable 

confidence and can correlate this section with the 

West Beacon Heights section.

Members B and C of McKelvey and Webb weather 

to long slopes formed of a series of ledges. The upper 

1,100 feet or so of their Member A crops out in formid-
A8 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

FIGURE 7. West wall of Beacon Dry Valley seen from the northeast. The sandstone of New Mountain underlies talus slopes; the sandstone of 

Pyramid Mountain forms the conspicuous light-colored cliffs ; and the sandstone of Finger Mountain forms highest slopes and capping 

ledges. Diabase sills form the thick dark layers. Pyramid Mountain is out of the picture to the right.

able cliffs, whereas the lower 300 feet that they measured 

of that member forms slopes composed of visible ledges 

or forms slopes that are in some places obscured by talus 

from the cliffs above. On the north face of Pyramid 

Mountain (fig. 9) and on the south face of Finger 

Mountain (fig. 10), about a thousand feet of this longer 

slope forming sandstone is exposed beneath the cliffforming rock.

CORRELATIONS BETWEEN SECTIONS

The Terra Cotta Hills-New Mountain section of 

Zeller and others (1961)., as extended upwards by us, is 

easily correlated with that of West Beacon Heights 

(fig. 5). In both sections, cliff-forming sandstone 

(our unit 10) is underlain by about 1,500 or 1,700 feet 

of ledge-making yellowish-gray standstone (our units 

4 through 9) ; this is underlain by 40 feet of yellow and 

green sandstone (unit 3); this by another 250 feet or so 

of yellowish-gray sandstone (unit 2); and this by varicolored siltstone and other fine-grained rocks (our unit 

1; Terra Cotta Mountain Member of Zeller and others).

The Beacon Dry Valley section of McKelvey and 

Webb (1959) is also easily correlated with the West

Beacon Heights section. The upper 1,100 feet or so of 

their member A corresponds to our unit 10 of cliffforming sandstone, whereas the basal part of their member A is the upper part of our unit 9. Their members 

B and C are stratigraphically above our West Beacon 

Heights section. McKelvey and Webb stated that still 

higher strata of the Beacon occur nearby but did not 

specify the character or location of these rocks. After 

studying the U.S. Navy vertical and oblique aerial 

photographs, we' conclude that such higher beds are 

unlikely to total more than a few hundred feet in 

thickness.

NOMENCLATURE 

PAST NOMENCLATURE

Ferrar (1907) applied the name Beacon Sandstone 

to the entire sedimentary sequence in the Taylor Glacier 

area and attempted no subdivision. The name Beacon 

Sandstone has been long and widely used throughout 

East Antarctica, and only recently have modifications, 

all of which appear improper, been proposed. Harrington (1958) suggested that the rocks should be called 

Beacon Sandstone Group, but as he proposed no formational subdivision his suggestion is premature. Me-
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA A9

Diabase

Sandstone of 

Finger Mountain

Sandstone of 

Pyramid MountainDiabase

Sandstone of ,. 

Pyramid Mountain "

FIGURE 8. West part of Finger Mountain. The sandstone and the thick lower sill of quartz diabase are cut obliquely by another sheet of 

diabase, which becomes a concordant sill at the top of the mountain. Dark bands in the sandstone of Finger Mountain are carbonaceous layers; this unit normally forms ledges and recessive outcrops. Altitude of the peak is about 7,100 ft, and the cliff is about 2,500 

ft high.

Kelvey and Webb in 1959 referred to the sedimentary 

rocks as the Beacon Formation, but in a later paper 

(McKelvey and Webb, 1961) they subdivided the 

sequence into five informal lithofacies and used the term 

"Beacon Group"; as they designated no formations, this 

elevation to group designation is also premature.

Zeller and others (1961) suggested that " * * * the 

Beacon sandstone and associated sills be raised to group 

status and that formational names be used to identify 

smaller * * * units within the group." Despite this 

suggestion, Zeller and others referred to the Beacon 

interchangeably as "Beacon sandstone," "Beacon sandstone formation," and "Beacon group." They proposed formal member (not formational) names for part 

of the section but left most of the section unnamed. 

Stratigraphic terminology so misused is only confusing. 

Furthermore, as the diabase sheets cut across all parts 

of the sandstone from the base to the top (see fig. 8, for 

example) and were thus obviously intruded after 

deposition was complete, they cannot be included 

properly as a part of the Beacon sequence as was done 

by Zeller and others (1961).

Long (1961b, p 127, 128) referred to the Beacon as 

the "Beacon series," subdivided informally into 

"Upper Beacon" and "Lower Beacon." This usage 

also is improper.

PROPOSED NOMENCLATURE AND STRATIGRAPHIC

SUMMARY

With the possible exception of basal strata in some 

parts of the region of the type section, the rocks named 

Beacon Sandstone by Ferrar (1907), and so called by 

many others since, comprise a remarkably homogeneous 

assemblage for which formational status seems more 

appropriate than group status at least until much more 

is known about the rocks. We recommend that the original name Beacon Sandstone be retained and that the 

type locality remain the vicinity of Beacon Heights as 

intended by Ferrar. We recommend further that the 

composite type section consist of the exposure of New 

Mountain, West Beacon Heights, and the west side of 

Beacon Dry Valley.

Three subdivisions of the Beacon Sandstone are 

widely recognizable in the region of the type locality. 

These units are indicated on some of the accompanying 

figures as the sandstone of New Mountain, sandstone of 

Pyramid Mountain, and sandstone of Finger Mountain 

in ascending order. The sandstone of Pyramid Mountain forms bold cliffs and the other two units generally 

form slopes of ledges. Beyond the vicinity of the 

type area of the formation (the area of fig. 3), we have 

observed these same three units along both sides of 

upper Ferrar Glacier, the Kukri Hills, and throughout
A10 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

the mountains between Taylor Glacier and Wright Dry 

 Valley from Solitary Dry Valley westward to the 

interior ice plateau (fig. 2).

These three distinctive units can be identified from a 

distance and are easily mappable and are thus particularly suitable for reconnaissance mapping such as is 

likely to predominate in this region for some time to 

come. (The "lithofacies" for which McKelvey and 

Webb (1961) suggested formational status are based on 

slight compositional distinctions largely independent 

of gross outcrop or bedding characteristics of the rocks 

and are probably not mappable under general Antarctic 

field conditions.) As the recent literature on the Beacon is overburdened with new and supposedly formal, 

but generally invalid, names for stratigraphic units, we 

are here using only informal designations for the units 

but recommend their elevation to formal member rank 

as soon as they prove useful to other geologists working in the region.

The middle unit provides the primary basis for subdivision of the Beacon into three major parts and is 

accordingly described first below.

The cliff-forming sandstone, about 1,100 feet thick 

in the type section (unit 10 of our Beacon Heights 

section, fig. 5, and the greater part of member A of 

the Beacon Dry Valley section of McKelvey and Webb,

1959), is an easily recognizable unit throughout the 

moutnain mass from Windy Gully to the interior ice 

plateau. It overlies a ledge-forming sandstone unit 

and underlies a ledge-forming unit composed of siltstone, sandstone, and carbonaceous shale; hence it is 

recognizable from a distance of many miles. We have 

observed the same unit to be widespread north of upper 

and lower Taylor Glacier and also in the western 

Wright Dry Valley region (fig. 2) (for example, see 

McKelvey and Webb, 1959, fig. 4), where it constitutes 

the upper part of the orthoquartzite lithofacies of McKelvey and Webb (1961). We will call this cliff-forming sandstone the sandstone of Pyramid Mountain, the 

name coming from a peak (fig. 9), in the type area, 

on whose cliffs it is well exposed. If additional fieldwork shows that this unit should be formally recognized, its type section might well be that of the west wall 

of Beacon Dry Valley (fig. 7), 2 miles south of the 

crest of Pyramid Mountain. The unit consists of about 

1,100 feet of buff, pink, and white cliff-forming mediumto coarse-grained sandstone and quartzite, in thick 

even beds, many of which are crossbedded. At Finger 

Mountain (fig. 10), this unit lies with obvious disconformity upon the rocks beneath.

That part of the Beacon above the sandstone of 

Pyramid Mountain is probably best designated as a

FIGURE 9. Pyramid Mountain seen from the northeast. The upper part of the mountain is formed of three thick diabase sills, the lower of 

which turns into the inclined sheet which forms the lower cliffs to the left. The sandstone of Pyramid Mountain jforms cliffs above the 

partly covered sandstone -of New Mountain at the base. The summit is about 7,000 ft. above sea level and about 3,000 ft. above Taylor' 

Glacier.
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA All

Diabase silff

FIGURE 10. East end of Finger Mountain showing south face. A westward-tapering wedge of sandstone, the basal part of the cliff-forming 

sandstone of Pyramid Mountain, lies disconformably upon the slope-forming sandstone of New Mountain. A thick sill of diabase at the 

left edge of the photograph becomes an inclined sheet dipping away from the observer in the rest of the picture. The pinnacle stands about 

1,800 ft. above Taylor Glacier.

single unit, which we will call the sandstone of Finger 

Mountain after the well-known landmark (figs. 8 and 

10) upon which it is well exposed. If this becomes a 

formally recognized unit as the result of additional 

work, its type section might be that west of Beacon 

Dry Valley 2% miles south of Pyramid Mountain (the 

lower part of this section is at the top of the right-hand 

mountain face of fig. 7) as measured by McKelvey and 

Webb (1959) and included in their members B and C. 

The sandstone of Finger Mountain, which lies conformably upon the sandstone of Pyramid Mountain, 

consists of sandstone, shale, and siltstone, weathering 

to slopes and ledges. Its known total thickness is 630 

feet in the study area, the top being absent. Carbonaceous shale and sandstone are conspicuously high in 

the known part of the unit (fig. 8), whereas the basal 

60 feet of the member at the type section consists of 

variegated siltstone. This basal siltstone is lacking at 

Finger Mountain (fig. 8) but is considered by McKelvey 

and Webb (1961) to be widespread in the region. They 

refer to a "red-green siltstone facies," 70-300 feet thick, 

in the same stratigraphic position in Wright and Victoria Dry Valleys (fig. 2). However, even if continuous, this siltstone is too thin for practical mapping in 

the Antarctic and furthermore cannot be distinguished 

at a distance from the thin-bedded rocks above.

Beneath the sandstone of Pyramid Mountain is a 

section composed largely of yellowish-gray crossbedded 

coarse-grained sandstone, which weathers to slopes and 

ledges and which we will call the sandstone of New 

Mountain. The name is derived from the peak west of 

Gully (fig, 4). If the results of further fieldwork show that this unit should be given formal status, 

its type section could be designated as the lower north 

slope of West Beacon Heights. The unit is about 1,850 

feet thick and comprises our units 2 through 9. Interbedded with the sandstone and most abundant in the 

lower part of the unit, are platy, micaceous finer grained 

sandstone, green argillite and sandstone, and pebble 

conglomerate. The sandstone is composed primarily 

of quartz, but some feldspar, mostly potassic, is present, 

especially in the lower part of the unit. The unit corresponds to the "arkose facies" and to the lower part of 

the "orthoquartzite facies" of McKelvey and Webb 

(1961); these "facies" are designated very arbitrarily 

within a gradational interbedded sequence and are 

not mappable units.

The stratigraphy of the basal part of the Beacon 

Sandstone is variable in the type area and classification must await more detailed knowledge of this part of 

the section. The 110-210 feet of variegated sandstone, siltstone, and shale that lie between the basement and the sandstone of New Mountain in the Beacon 

type area were subdivided by Zeller and others (1961) 

into two members, "Windy Gully" below, "Terra Cotta 

Mountain" above. North of Solitary Dry Valley (fig. 

2), we found the sandstone of New Mountain to lie 

directly upon the basement rocks, the variegated strata 

being absent. In Wright and Victoria Dry Valleys, 

McKelvey and Webb (1961) recognized a basal "subgraywacke facies" as thick as 300 feet lying upon the 

basement.

The apparently sporadic distribution of the basal 

sedimentary rocks, their general dissimilarity to rocks
A12 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

in most of the overlying Beacon, and the sharp and 

probably disconformable contact which separates 

these varied rocks from the sandstone of New Mountain, all suggest that they may not be properly assignable to the Beacon.

DIABASE SHEETS

FORM

Virtually coextensive with the Beacon Sandstone 

throughout East Antarctica are thick sheets of quartz 

diabase, for which Harrington (1958) proposed the 

name Ferrar Dolerites. The distribution and character of these sheets in the type area of the Beacon 

Sandstone are shown by some of the accompanying 

photographs and by figure 3.

The aggregate thickness of the sheets in the vicinity 

of Beacon Heights is on the order of 4,000 feet. Most 

of the individual sheets are thicker than 300 feet, and 

some are locally as thick as 1,500 feet. Although sills 

concordant to the bedding are most conspicuous, all the 

sills of the area of figure 3, except the one extending 

northwestward along Taylor Glacier from the junction 

of the Windy Gully glacier, branch, pinch out, or become markedly inclined to the bedding. The huge 

sheet capping Finger Mountain (fig. 8), for example, 

cuts obliquely upwards through 2,000 feet of sandstone 

and a concordant diabase sill, and, at the top of the 

mountain, itself becomes a concordant sill. The lower 

sill of Finger Mountain the sill cut by the sheet just 

noted is concordant with the Beacon for nearly 2 

miles along the mountain, but near the east end it abruptly becomes a crosscutting inclined sheet (fig. 10).

A thick sill lies near the contact between sedimentary 

rocks and the basement complex (fig. 4) not only in the 

map area but in a broad region to the east and north. 

This sheet is much more consistently concordant to 

bedding than are any of the higher sheets. Another 

thick widespread sill lies within the basement granitic 

rocks and follows exfoliation joints, related to the preBeacon erosion surface, 500-1,500 feet below the base of 

the Beacon.

PETROLOGY

The diabase sheets are highly silicic, their chilled 

margins and bulk compositions containing between 52 

and 56 percent SiO2 . The margins are texturally 

basalt which grades inward through diabase to gabbro, 

which forms the bulk of the sheets. Interstitial micropegmatite is present in the gabbro. Some of the sheets 

are markedly differentiated and contain layers of granophyre and gabbro-pegmatite near their upper surfaces; such a layer is shown by the light-colored streak 

one-sixth of the way down in the lower sill of figure 8. 

Augite is the dominant pyroxene; pigeonite, diallage,

and hypersthene are variably present. The plagioclase is chiefly labradorite. The rocks are conspicuously low in opaque constituents.

These rocks will be described in detail in another report.

METAMOBPHISM OF THE BEACON SANDSTONE

The entire Beacon Sandstone of the type section has 

been slightly metamorphosed thermally by the diabase. 

This metamorphism is apparent in the field only in the 

hornf elsed or metasomatized rocks within a few feet of 

the sheets, for the rest of the Beacon does not appear 

to the unaided eye to be altered; however, metamorphism is obvious in thin section. Argillaceous fractions 

are reconstituted to fine-grained mica throughout the 

section we studied, and most of the quartz has been 

recrystallized marginally to form mosaics and, locally, interlocking grains. Much feldspar has been reconstituted to fine-grained mica.

AGE OF DIABASE

The diabase sheets postdate the deposition of at least 

most of the Beacon for they intrude rocks very high in 

most sections of the sandstone yet seen in the Antarctic. 

The petrologic consistency of the diabase suggests that 

it may have been intruded within a rather short time 

period, possibly synchronous over all or most of the 

extent of the Beacon. A whole-rock potassium-argon 

age determination on a gabbro from lat 68°52' S., 

long, 154° 10' E., yielded a calculated age of 170 million years (Starik and others, 1959) probably Early 

Jurassic, possibly very late Triassic.

Eleven potassium-argon determinations made on 

separated minerals and chilled rock from a diabase sill 

in Tasmania, intrusive into sandstone similar to the 

Beacon, indicated a probable age of about 165 million 

years (McDougall, 1961). Similar diabase sheets in 

similar sandstone in South America, southern Africa, 

and southeastern mainland Australia are broadly dated 

geologically as of Triassic or Jurassic age.

AGE OF THE BEACON SANDSTONE

Nearly all fossils yet found in the Beacon Sandstone 

have been plants of the Glossopteris flora, similar to 

those of the Gondwana sequences of South America, 

southern Africa, India, and Australia. No animal remains save probable molds of burrows have been recognized.

FOSSILS NEAR TYPE SECTION

The only diagnostic fossils yet reported from the Beacon Sandstone near its type section were collected by 

Ferrar (1907) from carbonaceous strata high in the 

sandstone of Finger Mountain on the west side of Tabu-
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA A13

lar Mountain (fig. 2), about 9 miles southwest of West 

Beacon Heights. Although Arber (1907) and Seward 

(1914) found no recognizable fossils in this material, 

Edwards (1928) later broke up the material and discovered undoubted fronds of the large-leafed Glossopteris indica.

McKelvey and Webb (1959) noted unidentifiable 

plant remains from the same part of the section and 

"worm casts" from their member A. "Fucoids" were 

mentioned by Zeller and others (1961) as occurring low 

in the Beacon near Windy Gully but were not described. 

We noted small elliptical pellets, about 4 by 8 mm in 

size, which might have an organic origin but which are 

now only well-cemented packets of sandstone, high in

the sandstone of New Mountain at the north base of 

Pyramid Mountain. We submitted samples of siltstone from low in the sandstone of New Mountain for 

spore and pollen analysis, but nothing organic was found 

in them.

We found straight to slightly curved intersecting 

cyclindrical casts 70 feet above the base of the sandstone 

of New Mountain in the West Beacon Heights section 

(fig. 11). Prof. A. Seilacher (written communication, 

1959) of Frankfurt, an expert in such casts, could suggest only that they were burrows made by a shallowwater animal of unknown type, and that similar casts 

are known from rocks ranging in age from Cambrian at 

least to Jurassic.

$

FIGUEE 11. Casts of probable burrows of shallow-water animals In sandstone of New Mountain, West Beacon Heights.
A14 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

FOSSILS FROM THE BEACON SANDSTONE OF OTHER

AREAS

Constituents of the Glossopteris flora have been found 

in carbonaceous rocks high in the Beacon Sandstone in 

the trans-Antarctic Mountains at Priestley Glacier, 

Mount Gran, Beardmore Glacier, Mount Weaver, and 

the Horlick Mountains (fig. 1).

The Priestley Glacier material yielded only a gymnosperm branch for which Seward (1914) proposed a 

new genus and species, Antarcticoxylon priestleyi. 

Although Walton (1923, 1925, 1956) questionably 

designated this same branch as Rhexoxylon priestleyi 

and inferred for it a Triassic age, both Krausel (1956) 

and Archangelsky and Brett (1961) consider Walton's 

assignment to be erroneous. Archangelsky and Brett 

believe Antarcticoxylon to be a valid genus, unrelated 

to Rhexoxylon. Seward (1914) also recognized several 

microspores, possibly from a conifer of pine or fir type 

(Abietineae), for which he coined the name Pityosporites antarcticus. Seward regarded the material as 

probably indicating an early Mesozoic age.

The Mount Gran specimens were collected by J. J. 

Mulligan (written communication, 1960) of the U.S. 

Bureau of Mines and examined by S. H. Mamay and 

J. M. Schopf (written communications, 1960, 1961), 

who recognized Glossopteris indica and an unidentified 

species of Vertebraria.

The Beardmore Glacier material (Seward, 1914) 

contains fronds of Glossopteris indica, scale leaves probably also from Glossopteris, and stems of uncertain 

type referred to Vertebraria. The age suggested by 

Seward is only bracketed between late Carboniferous 

and Early Jurassic.

The Mount Weaver specimens contain poorly preserved leaf fragments that were assigned by Darrah 

(1936) to the gymnosperms Sagenopteris (seed-fern 

foliage), Taeniopteris (an artificial genus of cycadlike 

foliage) and Araucarites (cones probably referable to 

the Araucariaceae, a coniferous family with extant 

species in the southwestern Pacific region). Darrah 

suggested a Jurassic age for these specimens. L. H. 

Daugherty (written communication, 1961) examined 

a large number of other specimens from Mount Weaver 

and found no evidence of either Sagenopteris or Taeniopteris. He recognized instead leaves of Glossopteris, 

a stem (Vertebraria) , and a fruiting body probably also 

from Glossopteris. (The nomenclature of paleobotany 

is much complicated by the necessary independence 

of classification of different plant parts whose relation 

to each other is uncertain. Trunks, stems, foliage, fruiting bodies, and spores or pollen are commonly found 

separately, hence cannot be related to single plants, and 

are given unrelated taxonomic names until common

identity is established. In the present example, Vertebraria stems probably bore Glossopteris foliage.) 

Barghoorn (1961) and J. M. Schopf (written communication, 1961) also doubt the validity of Darrah's 

identifications.

In the Horlick Mountains, Long (1961b) collected 

plant remains that were identified by J. M. Schopf 

(written communications, 1960, 1961) as including 

Glossopteris indica, a small seed referable to Samwropsis, plant microfossils, and silicified wood with wide 

growth rings.

Sandstone probably correlative with the Beacon but 

named the Amery Formation by Crohn (1959) occurs 

near the outer coast of East Antarctica, at about lat 

70°30' S., long 68°15' E. (labeled Amery loc. fig. 1). 

Coal from this sandstone yielded pollen and microspores assigned to 14 different microfloral "sr^ies" 

(Crohn, 1959, p. 64). Although specific corrections 

between these "species" and macrofloral forms are not 

possible, gynnosperms are dominant and include 

gnetales (?), cycad, and pine types; ferns and allied 

plants are subordinate. Six probable "species" of the 

presumably gymnospermous pollen Lueckisporites 

were found, indicating a probable Late Permian age.

AGE OF ROCKS BENEATH THE BEACON SANDSTONE

In at least two places the Beacon Sandstone is underlain by little-deformed strata of Devonian age. Elsewhere the Beacon is underlain by crystalline rocks 

probably no younger than Ordovician.

In the central moraine of Mackay Glacier (fig. 2), 

Debenham (1921) found erratic boulders containing 

dermal plates and scales of fish. The boulders apparently had come from near the base of the sedimentary section that consists largely of the Beacon. Woodward (1921) considered these fossils to prove a Late 

Devonian age for the rocks containing them. No 

stratigraphic section has been published for this 

locality.

In the Horlick Mountains, Long (1961b) discovered 

a section about 1,300 feet thick conformably underlying 

rocks correlated with the Beacon. Near the base of 

this section he found abundant brachiopods that Boucot 

and Caster (1961) identified as belonging to a terebratuloid genus of Early Devonian age.

Elsewhere the Beacon rests upon plutonic rocks probably formed not later than Ordovician time (Hamilton, 

1963).

AGE OF THE BEACON SANDSTONE

The Beacon Sandstone lies above rocks as young as 

Devonian at least near the Mackay Glacier and in the 

Horlick Mountains and is intruded by diabase sheets 

for which meager data suggest an Early Jurassic or
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA A15

possibly Late Triassic age. All thick sections of the 

Beacon yet studied in the trans-Antarctic mountains, 

in which lies the type section, contain plant fossils near 

the top of the formation but have not yet yielded fossils 

in the rest of the formation. This consistency suggests 

that the carbonaceous upper part of the formation is 

broadly correlative throughout the mountains.

Only land plants have yet been found in the Beacon. 

These belong to the widespread Glossopteris flora of the 

Gondwana lands. The common Gondwana species 

Glossopteris indica has been identified from three localities high in the Beacon, including one near the type 

section. This species is abundant in the upper Carboniferous and Permian of Australia, India, southern 

Africa, and South America (Barbosa, 1958; David and 

Browne, 1950; Du Toit and Haughton, 1953; and 

Krishnan, 1956) and probably continues into the Triassic at least in India (Krishnan, 1956). The species 

is thus primarily a late Carboniferous and Permian 

form but may have survived locally into Triassic time.

Although Glossopteris indica is not by itself closely 

definitive of age, the lack of diagnostic Carboniferous 

or Triassic (for example, Thinnfeldia) elements is presumptive evidence that the plants are of Permian age. 

The Glossopteris-Vertebraria assemblage characterizes 

Permian strata of the other Gondwana regions. Although similar forms occur in those regions in Carboniferous and Triassic strata, they are there associated 

with more abundant plants definitive of Carboniferous 

or Mesozoic ages.

As previously stated, Walton (1923, 1925, 1956) and 

Darrah (1936) assigned some Antarctic specimens to 

Mesczoic genera, but their identifications have been discredited by other workers.

FIGURE 12. Outcrop of upper part of sandstone of New Mountain, at north base of Pyramid Mountain, showing diversely oriented crossbeds.
A16 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

The age of the bulk of the Beacon beneath the carbonaceous horizons cannot yet be denned more closely 

than Carboniferous or Permian, and whether or not 

strata above the fossiliferous section include rocks of 

Mesozoic age is unproved.

CONDITIONS OF DEPOSITION

The Beacon Sandstone in its type area consists of 

water-laid clastic sediments. The prevalent crossbedding and the lack of aquatic fossils suggest a general 

fluvial origin for most of the formation. The carbonaceous beds in the upper part of the formation probably 

were deposited in swamps or lagoons.

CBOSSBEDDING

Much of the medium- and coarse-grained sandstone 

of the Beacon is crossbedded, in beds 2-15 feet thick

(fig. 12). Foreset layers dip from 1° to 30° but most 

commonly are inclined between 5° and 20° from the 

major bedding planes (fig. 13); cross layers form long 

swooping curves rather than short steep ones. Crossbedded layers of the sandstone of New Mountain tend to 

be lenticular and discontinuous, in contrast to the more 

even bedding of the sandstone of Pyramid Mountain.

Observations on direction of crossbedding have not 

yet been reported in the literature, so only our own few 

data on the sandstone of New Mountain are available. 

In the West Beacon Heights section, crosslaminae most 

commonly dip westward in the lower 300 feet of the 

unit (fig. 13), dip in all directions without obvious 

preferential orientation where seen 300 to 500 feet above 

the base of the sandstone of New Mountain, and are 

mostly inclined eastward at the 1,000-foot level. At the 

base of the north face of Pyramid Mountain, perhaps

FIGURE 13. Crossbedded strata of lower part of sandstone of New Mountain, on the north slope of West Beacon Heights.

part of the section mostly dip westward (right).

Crossbeds in this
TYPE SECTION OF BEACON SANDSTONE OF ANTARCTICA A17

1,400 feet above the bottom of the same unit, crosslayers 

are oriented diversely (fig, 12), but eastward dips 

appear dominant. These few observations suggest 

dominantly westward-flowing streams during deposition of the lower part of the sandstone of New Mountain, streams flowing in variable directions during deposition of the middle part, and generally eastwardflowing ones as the upper part was laid down. If the 

changes in the crossbed directions with stratigraphic 

position are real and not the result of inadequate 

data the changes may indicate shifts in the location 

of the source area of the sediments from which the unit 

was formed. The relatively feldspathic and micaceous 

lower part of the sandstone of New Mountain may have 

come from a source to the east, whereas the quartz-rich 

upper part may have come largely from the west. It is 

of course possible that much of the crossbedding represents only local directions which bear little relation to 

the direction of the original source of the sediments.

PALEOCLIMATE

The Beacon, wherever it has been studied in Antarctica, consists almost exclusively of water-laid clastic 

sediments, the bulk of them probably deposited in shallow water. Quartz-rich sandstone dominates the formation, but feldspar, mica, and clay are locally important components. Glacial sediments, widespread 

in the lower part of correlative strata of southern 

South America, central and southern Africa, India, 

and Australia, apparently are not present in the Beacon 

of the type area but Long (1961a) and Grindley (1962) 

have found tillite beneath the Beacon farther south.

All known fossils are of terrestrial plants. Fossil 

wood in the Beacon has well-defined annual rings, 

showing that the climate was markedly seasonal. According to J. M. Schopf (U.S. Geol. Survey, 1961, p. 52) 

the annual rings of Glossopteris wood from the Horlick 

Mountains are so large as to indicate a climate at least 

as warm as temperate. There are nowhere any red 

beds to suggest a savannah or other tropical or subtropical climate, however, nor any evaporites or 

eolian deposits to indicate an arid one. Reasoning from 

the relation between morphology of living plants and 

climate, the large thick leaves of Glossopteris might be 

interpreted to indicate a nonfrigid climate, although 

there are no living1 analogues of the genus for direct 

comparison. The wide distribution of the Glossopteris flora throughout the Gondwana regions shows 

that, with or without postulating continental drift, the 

flora had a broad climatic tolerance.

These various criteria indicate that the upper part 

of the Beacon was deposited in a temperate climate but 

are not definitive enough to show whether the climate

was relatively cold or warm. A glacial climate prevailed shortly before the deposition of typical Beacon.

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A18 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

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US. GOVERNMENT PRINTING OFFICE: 1963 O 678832