Middle Paleozoic Sedimentary Phosphate 

in the Pensacola Mountains, Antarctica

GEOLOGICAL SURVEY PROFESSIONAL PAPER 45 6 E

Work done under the auspices of the

U.S. Antarctic Research Program and

financed by the U.S. National Science Foundation
Middle Paleozoic Sedimentary Phosphate 

in the Pensacola Mountains, Antarctica

By JAMES B. CATHCART and DWIGHT L. SCHMIDT 

CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 456-E

Work done under the auspices of the

U.S. Antarctic Research Program and

financed by the U.S. National Science Foundation

UNITED STATES G O V E RNMENT P RINTING OFFICE , WASHINGTON : 1977
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Cathcart, James Bachelder, 1917-

Middle Paleozoic sedimentary phosphate in the Pensacola Mountains, Antarctica

(Contributions to the geology of Antarctica)

Geological Survey Professional Paper 456-E

"Work done under the auspices of the U.S. Antarctic Research Program"

Bibliography : p. 17-18.

Supt. of Docs. No.: 119.16 :456-E

1. Geology, Stratigraphic-Paleozoic. 2. Sediments (Geology)-Antarctic regions-Pensacola Mountains. 3. Phosphates.

4. Sandstone. I. Schinidt, Dwight Lyman, 1926- joint author. II. Title. III. Series. IV. Series: United States

Geological Surevey Professional Paper 456-E.

QE654.C35 552'.5 77-608014

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

Washington, D.C. 20402

Stock Number 024-001-02965-1
CONTENTS

Page

Abstract .................................................................................................. El

Introduction .......................................................................................... 1

Acknowledgments ........................................................................ 3

General geologic setting .................................................................... 3

Stratigraphy and petrology .............................................................. 4

Elbow Formation ........................................................................ 5

Heiser Sandstone ........................................................................ 5

Dover Sandstone .......................................................................... 7

Phosphate occurrences ............................................................

Elbow Formation ..............................................................

Dover Sandstone ................................................................

Mineralogy ..................................................................................

Chemical analyses ....................................................................

Spectrographic analyses ..........................................................

Origin and depositional environments of sedimentary 

phosphate in Antarctica ......................................................

References cited ..........................................................................

Page

E8 

8 

8

10

11

13

15

17

ILLUSTRATIONS

FIGURE 1. Index map of Antarctica and the Pensacola Mountains ................................................................................................................

2. Composite stratigraphic column and diagram showing average modal composition of sandstones ....................................

3. Measured stratigraphic section of phosphate-bearing middle Paleozoic sandstones, Mount Feldkotter ............................

4. Photograph showing outcrop of lower part of Dover Sandstone........................................................................................................

5. Photograph showing outcrop of basal conglomerate of Dover Sandstone ....................................................................................

6. Photograph showing outcrop of basal conglomerate of Dover Sandstone ...............................................................................

7. Photomicrograph of silty phosphatic quartz sandstone, Elbow Formation..................................................................................

8. Photomicrograph of edge of silty phosphatic sandstone pebble and adjacent conglomeratic sandstone, Elbow 

Formation..................................................................................................................................................................................................

9. Photographof phosphate cobbles in the basal conglomerate, Dover Sandstone..... ................................ ..................................

10. Photomicrograph of edge of phosphate pebble and adjacent quartz sandstone ..........................................................................

11. Photomicrograph of edge of phosphate pebble, Dover Sandstone ....................................................................................................

12. Photograph of sample containing two generations of phosphate in basal conglomerate, Dover Sandstone ......................

13. Photomicrograph of phosphate-cemented sandstone, Dover Sandstone ......................................................................................

14. Plot of CO2 content and A 2 0 (O04)-(4io> showing relation of Antarctic phosphate rock to samples of the Phosphoria 

Formation from the Western United States and the Bone Valley Formation from Florida ..............................................

15. Reconstruction of Gondwanaland showing position of Pensacola Mountains relative to the polar-wandering curve 

for the Paleozoic of Gondwanaland ..................................................................................................................................................

Page

E2

4

9

10

10

11

11

12

12

17

TABLES

TABLE 1. Petrography of sandstone samples from across the phosphatic middle part of the Elbow Formation at Mount 

Feldkotter ........................................................................................................................................................................................................

2. Chemical analyses of phosphate samples from the Dover Sandstone............-......-.. .................................................. . ............

3. Semiquantitative six-step spectrographic analyses of samples of phosphate rockfrom Dover Sandstone ............................

4. Minor metal contents of phosphatic materials of this pa per ....................................................... ... ..........................................

Page

E7 

12

14

15

ill

CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE IN THE 

PENSACOLA MOUNTAINS, ANTARCTICA

By JAMES B. CATHCART and DWIGHT L. SCHMIDT

ABSTRACT

Primary sedimentary phosphorite was discovered in middle 

Paleozoic quartz sandstone about 600 km from the South Pole in 

the Neptune Range of the Pensacola Mountains, Antarctica. Both 

volume and grade of phosphate are low, and the possibility for any 

deposits of significant volume and grade is unfavorable.

Two principal types of carbonate fluorapatite are found: 

(1) primary sedimentary phosphorite and (2) secondary phosphate 

as cement. Both occur in the middle part of a 3,000-m section of 

quartz-rich sandstones that is equivalent to the widespread lower 

part of the Beacon Supergroup of the Transantarctic Mountains. 

The primary phosphorite is in several thin silty sandstone beds in 

the Elbow Formation which in most places consists of thin-bedded 

red siltstone interbedded alternately with thick-bedded quartzose 

sandstone. The age of the Elbow Formation is not younger than 

Early Devonian but may be as old as Ordovician. Black pebbles 

and cobbles of reworked phosphorite are found in a few places in 

sandstone beds directly overlying the primary phosphorite beds in 

the Elbow. Similar black pebbles and cobbles of phosphorite occur 

200 m above the Elbow Formation in the basal conglomerate of the 

Dover Sandstone. In addition, small areas of basal conglomerate 

of the Dover have been cemented by secondary phosphate. The 

Dover Sandstone is Middle Devonian age.

During the middle Paleozoic the Pensacola Mountains area 

was part of a large epicontinental sea in which the shallow-water 

accumulation of several thousand meters of quartz sandstones 

kept pace with slow basin subsidence. The Elbow Formation and 

its primary phosphorite were deposited in marine water that was 

restricted from open-ocean circulation. The basal conglomerate of 

the Dover was most likely a transgressive beach deposit where 

access to acid surface water may have resulted in the solution of 

some of the detrital phosphate. The P&s in solution precipitated 

as phosphate cement with a change in pH below the zone of 

aeration during early diagenesis.

Present-day offshore phosphorite occurs between lats 44° N. 

and 52° S., and ancient phosphorites probably were deposited 

between similar paleolatitudes. The primary phosphorite of the 

Elbow Formation is at present located atlat 84° S. Reconstruction 

of Gondwanaland and its paleopole positions for Ordovician(?) to 

Early Devonian time (the time within which the Elbow was 

deposited) suggests that the Elbow phosphorite may well have 

been deposited north of 40° S. paleolatitude in temperate marine 

waters.

INTRODUCTION

Sedimentary phosphate was first discovered in 

Antarctica in December 1963 during reconnaissance

geologic mapping of the Neptune Range, the middle 

range of the Pensacola Mountains (fig. 1). The 

phosphate at this Elliott Ridge locality consists 

mostly of sparse black pebbles in the basal conglomerate of the Middle Devonian Dover Sandstone. 

The conspicuous black phosphate pebbles make the 

light-colored quartz conglomerate an excellent marker horizon. Mapping during the 1963-64 (Schmidt, 

1964) and 1965-66 (Huffman and Schmidt, 1966) 

austral field seasons shows that the phosphatebearing basal conglomerate is exposed over an area 

of about 90 by 30 km (2,700 km2 ). A primary phosphate bed was discovered during the 1965-66 field 

season at the Mount Feldkotter locality (fig. 1). The 

bed is in the middle part of the Elbow Formation, 

about 200 m stratigraphically below the phosphatebearing conglomerate of the Dover Sandstone.

Phosphate has been reported from only one 

other area in Antarctica: in the Beardmore Glacier 

area of the central Transantarctic Mountains, where 

sparse phosphate pebbles are present in the Fremouw Formation of Triassic age (Barrett, 1969, p. 

54).

None of the known occurrences of phosphate in 

Antarctica are of economic significance, but the 

occurrence of sedimentary phosphate in Antarctica 

is, in itself, of special interest because known phosphate deposits characteristically form at low latitudes in temperate marine environments. The Neptune Range deposits, within 600 km of the South 

Pole, therefore, have important climatic implications that bear on the larger problem of movement of 

the Antarctic plate. The field study of the phosphate 

occurrences, because it was only one aspect of the 

work done in the Neptune Range, was necessarily 

limited in scope. Most of the data reported here were 

obtained from the phosphate-bearing sandstones at 

the Mount Feldkotter and Elliott Ridge localities (fig.

1).

El
E2 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

0"

500 1000 1500 KILOMETERS

Escarpment 

Hachures on downslope side

90°E

Base from uncontrolled planimetric map 

by U! S. Geological Survey, 1962

50 KILOMETERS

FIGURE 1. Index map of Antarctica and the Pensacola Mountains showing localities in the Neptune Range. Phosphate localities are

Elliott Ridge and Mount Feldkotter. Modified from Schmidt (1964).

The Neptune Range forms the central part of the 3,000-m-high interior Polar Plateau to the Weddell

Pensacola Mountains (fig. 1). It is separated from the Sea via the Filchner and Ronne Ice Shelves. SnowPatuxent Range to the south by the Academy Gla- fields and ice of local derivation separate the Nepcier, a major outlet glacier draining ice from the tune Range from the Dufek Massif and Forrestal
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E3

Range to the north. Mountain summits generally 

range in elevation from 1,000 to 2,000 m, and local 

relief ranges from about 200 to 1,400 m. Rock exposures are generally fresh owing to recent deglaciation and to frost riving. Climate is that of a cold 

desert: precipitation is slight, and summer temperatures range from about -18° to 4°C. Mean annual 

temperature, as determined from temperature at 

10-m borehole depth, is about -26°C (Boyd, in U.S. 

Geological Survey 1964, p. A121).

ACKNOWLEDGMENTS

Jerry D. Tucker, U.S. Geological Survey, Denver, 

Colo., prepared samples and ran the X-ray analyses. 

Paul L. Williams did the modal analyses. Williams, 

Willis H. Nelson, and John R. Ege shared with one 

author (D. L. S.) in the geologic mapping of the 

Neptune Range during the 1963-64 field season, and 

W. H. Nelson during the 1965-66 season. A. B. Ford 

and R. A. Gulbrandsen made helpful suggestions 

regarding presentation of the data. This study is part 

of a U.S. Geological Survey geologic study of the 

Pensacola Mountains under the auspices of the U.S. 

Antarctic Research Program and is financed by the 

National Science Foundation. Logistic support was 

given by the U.S. Navy Operation Deep Freeze and 

the U.S. Army Helicopter Detachment Antarctica.

GENERAL GEOLOGIC SETTING

The Neptune Range, along with the rest of the 

Pensacola Mountains, belongs physiographically 

and geologically to the province of the Transantarctic Mountains, a major mountain chain which 

marks the boundary between the Precambrian eraton of East Antarctica and the younger mobile 

region of West Antarctica (fig. 1). Lower(?) Precambrian crystalline rocks, although not exposed in 

the Pensacola Mountains and only sparsely exposed 

elsewhere in the Transantarctic Mountains, form a 

basement beneath strongly deformed geosynclinal 

rocks of late Precambrian to Cambrian age that, in 

turn, lie unconformably beneath little-deformed 

Paleozoic and younger platform deposits (Ford, 

1964).

In the Pensacola Mountains, the oldest rocks 

compose a thick sequence, the first sequence of figure 

2, of upper Precambrian eugeosynclinal graywacke 

and slate belonging to the Patuxent Formation that 

was strongly deformed and regionally metamorphosed prior to deposition of fossiliferous marine 

limestone (Nelson Limestone) during the Middle 

Cambrian (Palmer and Gatehouse, 1972). This limestone, along with overlying felsic volcanic and clastic rocks (Gambacorta and Wiens Formations),

forms the second sequence, which was folded and 

intruded by granitic plutons during early Paleozoic 

time.

The phosphate beds described in this report 

occur in the middle part of the third sequence in the 

Neptune Range. The third sequence correlates approximately with the Paleozoic part of the Beacon 

Supergroup (Harrington, 1965) that is widely distributed in the Transantarctic Mountains (Barrett, 

1970, p. 256) and regionally ranges in age from 

Ordovician(?) to Jurassic. The Beacon Supergroup is 

subdivided into a lower and an upper part in the 

Neptune Range. The lower Beacon consists largely 

of quartz-rich sandstones that contain sparse fish 

remains and plant fragments of Devonian age 

(Rigby and Schopf, 1969, p. 92). It was deposited in 

epicontinental basins. The base of the upper Beacon 

is marked by the upper Paleozoic (Permian) glacial 

deposits that are known throughout most of the 

Transantarctic Mountains (Barrett, 1970, p. 256). 

Carboniferous sedimentary rocks have not been 

reported, although the glacial rocks may in part be 

Carboniferous (Rigby and Schopf, 1969, p. 102). The 

upper Beacon consists of arkosic sandstones and 

siltstones and coal measures of dominantly continental origin, and it commonly contains abundant 

Permian and Triassic to Jurassic plant fossils; the 

Upper Permian coal measures are widespread 

(Rigby and Schopf, 1969). Only the Permian and 

older rocks of the Beacon are present in the report 

area.

Detrital phosphate pebbles are sparsely distributed in a quartzose part of the Triassic Fremouw 

Formation at three localities ranging over a distance 

of 125 km in the Beardmore Glacier area of the 

central Transantarctic Mountains (Barrett, 1969, p. 

54). The reported pebbles are dark gray, spheroidal 

1-4 cm in diameter, and consist of microcrystalline 

apatite, quartz, and sericite. The apatite mineral is a 

carbonate fluorapatite as determined by X-ray diffraction by J. B. Cathcart although it is reported 

simply as fluorapatite. The source of the phosphate 

pebbles is not known.

Phosphatic concretionary nodules and lenses 

occur at two different stratigraphic horizons in 

Gondwana rocks in South Africa. Although these 

horizons are widespread, neither has been successfully exploited (DuToit, 1954, p. 536). We do not know 

of any other phosphate occurrences in Gondwana 

sequences in Gondwanaland. On this hemispherical 

scale, the Beacon Supergroup of the Transantarctic 

Mountains has a gross lithology, lithologic succession, and paleobotany that is similar to that of 

middle Paleozoic to middle Mesozoic sedimentary
E4 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

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 Phosphate 

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Geologic unit

Pecora Formation 

Graywacke and siltstone with coal beds

Gale Mudstona 

Black pebbly mudstone

Dover Sandstone 

Tan quartzite

Helser Sandstone 

Quartz

Elbow Formation 

Red shale and siltstone and

Elliott Sandstone 

Calcarerous sandstone and 

conglomerate

Brown Ridge Conglomerate

Gambocorta Formation 

^Felsic flows and pyroclastic rocks 

Nelson Limestone

Patuxent Formation 

Green subgraywacke and 

slate with basalt flows 

and pillow lavas

Second ._.. 

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First sequence

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PALEOZOIC

UPPER PRECAMBRIAN

40

AVERAGE SANDSTONE MODE, IN PERCENT

100

FIGURE 2. Composite Btratigraphic column (modified from Schmidt and others, 1965) and average modal composition of sandstones 

in the Neptune Range. Average modes are shown only for formations that are dominantly sandstone, and only sandstone modes are 

used (data from Williams, 1969, p. 1458). For middle Paleozoic quartz sandstone formations that are of interest for phosphatic 

occurrences, the composition is shown by solid lines; for other formations it is shown by dashed lines. K, potash feldspar; 

P, plagioclase; R, detrital rock fragments. Where plagioclase is not shown, its mtodal composition is less than 0.5 percent.

rocks of Gondwanaland on the other southern hemisphere continents and India.

In the Pensacola Mountains the third sequence 

(fig. 2), equivalent to part of the Beacon Supergroup, 

consists of more than 4,000 m of clastic rocks, chiefly 

of Devonian and Permian age (Schmidt and others, 

1965; Schmidt and Ford, 1969). The predominantly 

quartzose sandstones, about 3,000 m thick, are equivalent to the lower Beacon strata and are subdivided 

into five formations, two of which, the Elbow Formation and the Dover Sandstone, contain phosphate 

(fig. 2). The Dover Sandstone in the Patuxent Range 

(fig. 1) contains several thin carbonaceous shaly-silt 

lenses with plant microfossils, apparently Middle 

Devonian in age (Schopf, 1968); associated plant 

megafossils of Haplostigma(?) and Cyclostima-type 

are also indicative of the Devonian (Rigby and 

Schopf, 1969, p. 92). The four formations below the 

Dover contain only trace fossils that are not identifiable and may be as old as Ordovician. Equivalents of 

the upper Beacon strata in the Pensacola Mountains

are the Gale Mudstone (Gondwanid tillite) and the 

overlying Pecora Formation. The Pecora is referable 

to the middle and late Permian as indicated by the 

presence of the characteristic GangamopterisGlossopteris flora and coalbeds. The Gale may be 

Early Permian (Rigby and Schopf, 1969, p. 103).

All Beacon-equivalent sedimentary rocks of the 

Pensacola Mountains were moderately deformed 

and folded during a regional orogeny, the Weddell 

Orogeny, in the early Mesozoic (Ford, 1972a; Ellsworth Orogeny of Craddock, 1972). Deformation was 

accompanied by a slight low-grade regional metamorphism during which argillaceous minerals in the 

matrix of the sedimentary rocks were recrystallized 

chiefly as sericite and chlorite (Beck and Schmidt, 

1971, p. C175).

STRATIGRAPHY AND PETROLOGY

The phosphate-bearing sandstones of the Neptune Range occur in a 3,000-m-thick succession of
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E5

sedimentary rocks consisting of the Neptune Group 

and Dover Sandstone (fig. 2). This succession of 

rocks represents a gradual change from a highenergy environment (locally derived coarse sediments of the Brown Ridge Conglomerate and Elliott 

Sandstone) to one of moderate energy (alternating 

fine sandstone and siltstone red beds of the Elbow 

Formation) and back to one of moderately high 

energy (quartz sandstone of the Heiser Sandstone 

and coarse well-sorted sparse quartz-pebble orthoquartzite of the Dover Sandstone) (Williams, 1969). 

The erogenic Brown Ridge Conglomerate consists 

largely of locally derived volcanic debris, whereas 

the Elliott Sandstone contains an average of only 8 

percent of such volcanic rock fragments; the Elbow 

and Heiser Formations have much less, and the 

Dover none (Williams, 1969). The total thickness of 

about 2,000 m of moderately well to well-sorted 

quartzose sandstones suggests that deposition was 

in relatively shallow water in a slowly subsiding 

basin of an epicontinental sea.

ELBOW FORMATION

The Elbow Formation (Schmidt and others, 

1965; Schmidt and Ford, 1969) gradationally overlies 

the Elliott Sandstone; the contact is placed below a 

conspicuous change to red clastic rocks. The formation is about 300 m thick at the type section at Elbow 

Peak (fig. 1) but thins to the east and south and is 

only about 140 m thick at Mount Feldkotter 65 km 

south-southeast (fig. 3).

The Elbow Formation throughout most of the 

Neptune Range consists of well-bedded red argillaceous siltstone and interbedded light-gray finegrained quartz-rich sandstone. Parts of the section 

consist of regularly alternating beds of sandstone 

and siltstone in pairs 0.3-2 m thick. Beds are commonly well laminated, and crossbedding and ripple 

marks are conspicuous. Irregular curved tubules, 0.5- 

2 cm in diameter, trend at a variable but commonly 

high angle to bedding and are mottled light gray in 

red siltstone beds; these are probably fossil burrows.

At Mount Feldkotter the Elbow Formation is 

thinner, slightly coarser grained, and more feldspathic than elsewhere in the Neptune Range, suggesting that this is a more shoreward facies. It is 

mostly nonred (fig. 3). The formation consists of 

thick crossbedded pale-greenish-buff quartz sandstone interbedded with thin medium-drab-green silty 

sandstone. In contrast to the red siltstone interbeds 

of the Elbow elsewhere, only the upper part of the 

silty sandstone beds is deep red brown. The basal 

part of many of the thick sandstone interbeds consists of gritstone or conglomeratic sandstone containing intraformational clasts of sandstone and 

siltstone. Sandstone and silty sandstone alternations are well developed. A middle 20- to 30-m-thick 

part of the Elbow section contains several thin silty 

phosphatic sandstone beds (fig. 3).

The average modal composition of eight samples 

of Elbow Formation from widely spaced localities 

within the Neptune Range is given in table 1 and is 

shown graphically in figure 2. Quartz sandstone 

from the Elbow Formation at Mount Feldkotter 

(samples a and d, table 1) contains more quartz and 

potash feldspar than the average mode, while the 

silty phosphatic sandstone (sample b, table 1) contains less quartz and more potash feldspar than the 

average. Whole-rock X-ray diffractometer patterns of 

two additional sandstone samples indicate compositions that are in close agreement with those counted 

microscopically. The X-ray patterns indicate about 

70 percent quartz (compared with the X-ray pattern 

of a quartz standard), 20 percent chlorite, and 10 

percent muscovite (based on relative peak heights), 

and a trace of pyrophyllite. The pyrophyllite was 

identified only by its major peak at about 3 nanometers, and the identification must be regarded as 

tentative. Apatite lines were not detected even 

though the samples are from the phosphate-bearing 

middle part of the Elbow Formation. Sericite, chlorite, and pyrophyllite, at least in part, are products of 

low-grade metamorphism.

HEISER SANDSTONE

The nonphosphatic Heiser Sandstone gradationally overlies the Elbow Formation; the contact is 

placed below the first trace-fossil bed which is 

located at approximately the top of the conspicuous 

red clastic rocks of the Elbow. The formation is about 

300 m thick throughout most of the Neptune Range 

(fig. 2), but it thins to 125 m at Mount Feldkotter. The 

stratigraphic section shown on figure 3, although 

thinner, is representative of the Heiser throughout 

the Neptune Range.

The Heiser Sandstone consists of thick-bedded 

(0.3-1 m) and crossbedded buff to medium-brown 

medium-grained quartz sandstone irregularly and 

cyclically interbedded with thin beds (0.03-0.6 m) 

of dark-drab-green to dark-brown silty sandstone. 

The Heiser is characterized by abundant narrow 

tubules, 2-5-mm diameter, in many of the thick 

sandstone beds; the tubules, probably fossil burrows, 

are perpendicular to bedding.

The average modal composition of five typical 

sandstones of the Heiser from well-distributed localities in the Neptune Range is shown graphically on 

figure 2. Two samples from the top of the section at
E6 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

DOVER SANDSTONE UNI 

Unit C Thick-bedded buff medium- to 

coarse-grained quartz sandstone and 

quartzite beds 2-3 m thick containing Q 

sparse round quartz pebbles

20 m thick 

UnitA-Well-bedded crossbedded

medium-red-brown quartz-pebble con- B - 

glomerate 3-4 m thick containing sparse 

black phosphatic pebbles and blocks A

HEISER SANDSTONE 

Cyclically interbedded thick-bedded 

crossbedded buff medium-grained 

quartz sandstone beds 0.3-1 m 

thick and thin dark-drab»green silty 

sandstone beds 0.03-0.6 m thick. 

Cycles of sandstone and silty sandstone average 1 m thick. Tubules (t) 

are characteristic of formation and are 

abundant and common in thick sandstone beds where they trend vertical 

to bedding; tubules are 2-5 mm in 

diameter 

Unit B Dark brown owing to interbedding 

of dark-red-brown sandstone with the

T

silty sandstone 

Unit A Light-tan faintly crossbedded f 

medium- to coarse-grained sandstone . j

I

ELBOW FORMATION 

Interbedded thick-bedded crossbedded 

buff medium-grained sandstone beds 

0.3-2 m thick and thin-bedded green 

and red-brown silty sandstone beds 

0.1-0.6 m thick. Bases of sandstone 

beds are commonly gritstone and 

conglomeratic. Alternations of sandstone and silty sandstone are common, 

especielly in upper half. Phosphatic 

silty sendstone occurs sparsely in a 10- 

to 20-m interval in middle part of 

formation. Total thickness of formation is 140 m

ELLIOTT SANDSTONE \ 

Thick-bedded crossbedded light-green V 

medium-grained sandstone and interbedded medium-green silty sandstone

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PHOSPHATE-BEARING BASAL 

CONGLOMERATE

Sandstone, thick-bedded, red-brown

Gritstone and sandstone, buff 

/Conglomerate, quartz-pebble, sandy, 

buff; rare black round phosphatic 

pebbles 

_ ndstone, crossbedded, buff

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buff; scattered round black phosphate 

p%bbles and cobbles and irregularly 

shaped lenses of phosphate-cemented 

_ sandstone

Sandstone, thick-bedded, yellow to 

medium-brown

PHOSPHATIC ZONE

Sandstone, buff

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 Gritstone, sandy, buff

(0

£ Sandstone, silty, dark-drab-green

'Sandstone; weathers pale red brown. 

Intraformational conglomeretic 

sandstone at base; scattered 

ct\ dark-gray phosphatic cobbles, 

°\_maximum 8-cm diameter

Sandstone, silty, 30-cm-thick. 

Upper two-thirds is dark-gray 

phosphatic sandstone that grades 

down to lower one-third, which is 

medium-gray silty sandstone

Sandstone, light-greenish-buff

FIGURE 3. Measured stratigraphic section of phosphate-bearing middle Paleozoic sandstones at Mount Feldkotter in the southernmost Neptune Range.

Elliott Ridge (fig. 1) give X-ray diffractometer pat- potash feldspar are also present. Mica recrystalterns indicating that quartz is the principal mineral lization in the matrix is suggestive of low-grade

phase (60-75 percent) and that chlorite, sericite, and metamorphism.
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E7

TABLE 1. Petrography of sandstone samples from across the phosphatic middle part of the Elbow Formation at Mount Feldkotter 

compared with average petrography of eight sandstone samples of the Elbow Formation from localities throughout the 

Neptune Range (Williams, 1969, p. 1458)

[ Modes by P. L. Williams; 500 points counted on thin sections, 

potash feldspar verified on stained rock slices]

Mode (percent)

No. Quartz Potash Plagioclase

feldspar

Matrix Rock size roundness 1

fragments (average)

Mount Feldkotter (phosphatic middle part of Elbow Formation)

a -

b _ .

c -----

d 

Quartz

sandstone.

Silty

phosphatic

sandstone.

Silty

sandstone.

Quartz

sandstone.

76

62

63

69

7.6

9.0

4.2

9.9

Trace

.4

Trace

.2

14

2 23

3 29

17

2.6

4.8

4.2

4.0

Medium 

--do 

 .do 

 doFair 

Good-

 do--

Fair 

SA

SA

SA

SR

Neptune Range (average of eight samples from Elbow Formation at widespread localities)

Sandstone- 71 2.8 0.5 21 4.5 Medium Good SR

1 SA, subangular; SR, subrounded.

2 Includes about 12 percent modal microcrystalline apatite. 

:1 Includes probably less than 1 percent apatite.

DOVER SANDSTONE

The Dover Sandstone overlies the Heiser Sandstone with apparent conformity (fig. 2), but a thin 

basal conglomerate may represent a considerable 

break in sedimentation. The formation is about 1,200 

m thick and is disconformably overlain by the Gale 

Mudstone. The lower 50 m of the Dover section at 

Mount Feldkotter is shown on figures 3 and 4. This 

section at Mount Feldkotter is representative of the 

lower Dover elsewhere in the Neptune Range.

The Dover Sandstone is a buff medium- to 

coarse-grained quartz sandstone and orthoquartzite, 

containing sparse round pebbles of quartz. The rock 

is thick bedded (beds 0.6-1 m thick) and is coarsely 

crossbedded in many places. The quartz grains are 

rounded and well sorted.

The base of the Dover is an irregularly bedded 

crossbedded buff to pale-red-brown conglomeratic 

sandstone, 3-7 m thick, that contains round quartz 

pebbles and a few round pebbles of black phosphate 

and black chert.

The average modal composition of seven samples of the Dover Sandstone (fig. 2) from welldistributed localities in the Neptune Range indicates 

a sandstone of high quartz content, about 80 percent. 

Two samples of quartz sandstone from the lower part 

of the Dover on Elliott Ridge give X-ray diffractometer patterns indicating major amounts of quartz

and minor amounts of muscovite (sericite) and potash feldspar; light-green shalelike pellets in the 

sandstone contain only quartz and muscovite (sericite). Minor pyrophyllite was tentatively identified 

by X-ray in another sandstone sample. In thin

FIGURE 4. Outcrop of lower part of Dover Sandstone overlying 

the Heiser Sandstone (H) at Mount Feldkotter. Above the 

contact is 3.3 m of basal conglomerate (A) that contains 

sparse phosphate. Units A, B, and C are shown on stratigraphic section (fig. 3).
E8 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

section, recrystallized sericite and pyrophyllite(?) in 

the matrix suggest low-grade metamorphism.

PHOSPHATE OCCURRENCES

Phosphatic beds are found in the middle part of 

the third sequence (fig. 2). Phosphate, as carbonate 

fluorapatite, has been found in the middle of the 

Elbow Formation only at Mount Feldkotter (figs. 5, 

6). No phosphate thus far discovered is economic.

ELBOW FORMATION

The phosphate in the Elbow Formation at 

Mount Feldkotter is a matrix mineral in a silty 

sandstone bed and also in silty sandstone pebbles 

and cobbles. The silty sandstone bed, about 30 cm 

thick (fig. 3), pinches down to a thin parting plane in 

a distance of 50 m along strike. The phosphate in the 

bed at the place of maximum thickness is confined to 

the upper 20 cm and is greatest in amount near the 

top of the bed. Other similar thin silty sandstone 

beds in the Elbow Formation possibly contain some 

phosphate but have not been studied. A sample (b, 

fig. 3; table 1) from the phosphate sandstone bed 

contains about 20 percent apatite, 60 percent quartz, 

and about equal amounts of muscovite (sericite), 

chlorite, and potash feldspar, as determined by X-ray 

diffraction. About 12 percent modal apatite was 

estimated in a thin section of the same sample (table

1).

In thin section, the silty phosphatic sandstone 

consists of medium-grained quartz and potash feldspar set in a matrix of brown microcrystalline 

apatite, quartz, sericite, and chlorite (fig. 7).

Most of the apatite appears to be primary. However, some apatite is recrystallized; patches of matrix 

containing abundant phosphate in places have clear 

or light-brown apatite centers (possibly the remnants of original apatite pellets) and thin rinds of 

apatite replacing quartz. The recrystallization is 

probably diagenic.

The thin basal conglomerate of the thick sandstone bed that overlies the silty phosphatic 

sandstone at Mount Feldkotter (fig. 3) contains 

locally derived intraformational pebbles, cobbles, 

and subangular blocks of dark-gray phosphatic 

sandstone (fig. 8) that are similar in composition to 

the underlying silty phosphatic sandstone. Other 

thick sandstone beds, which are located 2-30 m 

above the one described here, have conglomeratic 

parts that contain similar subangular black phosphatic sandstone clasts.

DOVER SANDSTONE

Two types of phosphate occur in the basal conglomerate of the Dover Sandstone, which is 3-7 m

FIGURE 5. Outcrop of basal conglomerate of the Dover Sandstone on Elliott Ridge showing typical occurrence of phosphate pebbles and cobbles (P) and phosphate-cemented conglomeratic sandstone (C) in well-crossbedded moderately 

channeled flat-lying quartz-pebble sandstone. Geologic hammer shows scale.

FIGURE 6. Outcrop of basal conglomerate of Dover Sandstone 

on Elliott Ridge showing phosphate cobbles and pebbles (P) in 

quartz-pebble sandstone that dips 50° to left. Ice axe shows 

scale.

thick throughout the Neptune Range (figs. 3, 4). In 

one type the phosphate consists of black phosphate 

pebbles and cobbles (fig. 6); in the other it is a black 

phosphate cement in quartz sandstone. The phos-
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E9

1 mm 1 mm

FIGURE 7. Photomicrograph of silty phosphatic quartz sandstone in middle part of Elbow Formation at Mount Feldkotter (sample b, fig. 3). Matrix (ps) is about half microcrystalline apatite and half microcrystalline quartz, sericite, 

and chlorite. Q, detrital quartz; kf, potash feldspar; R, argillaceous rock clast. Plane-polarized light.

phate-cemented sandstone occurs either as pods and 

lenses or as large blocklike clasts (fig. 5).

The phosphate pebbles and cobbles are subangular to rounded and as much as 15 cm across; 

most are only 1-2 cm in diameter. Many are flattened 

and oriented parallel to bedding (figs 5, 6, 9). Where 

abundant, the phosphate clasts are concentrated at 

the base of conglomeratic layers (fig. 9). The pebbles 

and cobbles are composed largely of microcrystalline 

apatite, but they also contain abundant silt-sized 

quartz and sericite. The sericite generally has a 

distinct preferred orientation that may have paralleled original bedding (fig. 10). The black phosphate 

pebbles and cobbles are transported clasts of unknown source. The only known phosphatic beds are 

those of the underlying Elbow Formation.

A few of the phosphate pebbles have a narrow 

rind of phosphate-cemented sandstone that is part of 

the sandstone enclosing the pebbles. This rind is 

about 3 mm thick on the pebble shown in figure 11.

FIGURE 8. Photomicrograph of edge of silty phosphatic sandstone pebble (left) and adjacent conglomeratic sandstone 

(right). Sample is from base of thick sandstone bed (a, fig. 3) 

and above the silty phosphatic sandstone bed (b, fig. 3) in 

middle part of Elbow Formation at Mount Feldkotter. Q, detrital quartz; S, sericitic matrix in conglomeratic sandstone; 

ps, microcrystalline apatite-sericite-chlorite matrix in pebble. 

Plane-polarized light.

The phosphate cement contains few fine-grained 

inclusions relative to the abundant argillaceous 

material in the phosphate pebbles. Most of the 

phosphate within the rind has extensively replaced 

coarse-grained quartz of the enclosing conglomeratic quartz sandstone.

Similar phosphate cement is locally much more 

extensive in the basal conglomerate. Elongate pods 

and lenses, as long as 60 cm and mostly concordant with bedding, consist of black phosphatecemented quartz gritstone and conglomeratic quartz 

sandstone (fig. 12). The phosphate has cemented 

pore space but more extensively has replaced quartz 

and argillaceous matrix (fig. 13).

Some large angular to subrounded blocks of 

black phosphate-cemented sandstone similar to the 

in situ pods and lenses have internal bedding that is 

discordant to the outcrop bedding. These blocks have 

been rotated and slightly transported penecontemp-
E10 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

FIGURE 9. Phosphate cobbles in sandy quartz-pebble conglomerate of the basal conglomerate of the Dover Sandstone on 

Elliott Ridge. View is perpendicular to bedding.

oraneously during deposition of the basal conglomerate. Some of the blocks are more than 15 by 30 cm in 

size and are elongate parallel to their internal bedding. The phosphate cement is relatively pure (fig. 

13) and free of the argillaceous inclusions that 

characterize the phosphate pebbles.

In summary, the two types of phosphate in the 

basal conglomerate of the Dover are readily distinguished at both outcrop scale and microscopic scale. 

Phosphate clasts less than pebble size are not found 

in the basal conglomerate. One possible explanation 

is that the smaller than pebble-size phosphate clasts 

were penecontemporaneously dissolved and were the 

source for the secondary phosphate that locally 

precipitated as cement in the in situ pods and lenses 

and as rinds on some phosphate pebbles. Clearly the 

secondary phosphate replacement and cementation 

followed deposition of the phosphate pebbles and the 

enclosing quartz sandstone. The evidence provided 

by the locally transported % blocks of phosphatecemented sandstone indicates that this secondary 

phosphate was precipitated between intervals of 

sedimentation of successive conglomeratic sandstone beds. Therefore, the secondary phosphate is 

early diagenic. Thin section study indicates that 

phosphate was not mobilized during the early Mesozoic metamorphism; at most, the phosphate was 

locally recrystallized along microscopic planes of 

strain (fig. 13).

1 mm

FIGURE 10. Photomicrograph of edge of phosphate pebble (left) 

and adjacent quartz sandstone (right). Pebble consists of 

microcrystalline apatite and abundant semioriented silt-sized 

sericite and quartz. Sample is from the basal conglomerate 

of the Dover Sandstone on Elliott Ridge. Q, detrital quartz; 

S, sericite and chloritic matrix. Crossed nicols.

MINERALOGY

The apatite mineral of marine phosphorites is a 

carbonate fluorapatite. Altschuler, Clarke, and 

Young (1958, p. 48) pointed out that carbonate 

fluorapatite "is generally characterized relative to 

fluorapatite by a deficit in P2O5 content of 3-6 

percent, an excess of F, OH (or both) of 0.5 to 1.0 

percent, and by the presence of 2-3 percent of carbonate."

Recent work by Lehr and his colleagues (Lehr 

and others, 1968; Smith and Lehr, 1966; McClellan 

and Lehr, 1969) established a relation between the 

carbonate substitution and the mineral's cell dimensions. Gulbrandsen (1970), using data from McClellan and Lehr (1969), showed that there is a direct 

correlation between the carbonate content and the acell dimension. Because the calculation of the a-cell
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA Ell

FIGURE 11. Photomicrograph of edge of phosphate pebble

with rind of phosphate-cemented sandstone (P2 ) that is part 

of the conglomeratic quartz sandstone enclosing the pebble. 

The phosphate cement (P2 ) contains few inclusions relative to 

the more abundant argillaceous material in the phosphate 

pebble (fig. 10). The phosphate within the rind has replaced 

quartz after the deposition of the pebble. Small quartz veinlets transect the rock. Sample is from the basal conglomerate 

of the Dover Sandstone on Elliott Ridge. Plane-polarized 

light.

dimension is time consuming, Gulbrandsen used a 

peak-pair method that requires only the measurement of the angular difference between two X-ray 

diffraction peaks to show the same correlation. 

Silverman, Fuyat, and Weiser (1952) also used a peakpair method to show the difference between the carbonate fluorapatite and other apatites. Gulbrandsen 

(1970, p. BIO) used the (410) and (004) peaks, which 

occur near 51.6° and 53.1° 26, and his data (shown on 

fig. 2 of his paper) are reproduced here on figure 14. 

Data from carbonate fluorapatite samples from the 

Pliocene Bone Valley Formation of Florida and data 

from samples from the phosphate of the Dover 

Sandstone from Elliott Ridge are also plotted on the 

diagram.

FIGURE 12. Sample containing two generations of phosphate in 

basal conglomerate of the Dover Sandstone on Elliott Ridge:

(1) detrital phosphate cobble 9 cm long (left of scale) and

(2) phosphate-cemented quartz-pebble sandstone (large dark 

zone, center of sample) containing partially replaced quartz 

grains and quartz pebbles floating in phosphate. This secondary phosphate tends to follow bedding but in places cuts 

irregularly across bedding.

The solid line on the diagram (fig. 14) is the leastsquares line calculated by Gulbrandsen using data 

from McClellan and Lehr. The plots of samples from 

the Permian Phosphoria Formation from Idaho and 

Wyoming fall on this line and indicate that the 

correlation is good. The plots of samples from the 

Bone Valley Formation of Florida do not plot on this 

line but seem to have a positive correlation. The 

samples from the Dover Sandstone fall on the line 

with the Phosphoria samples and, therefore, seem to 

be more closely allied with the samples from the 

Phosphoria Formation than they do with the samples from the Bone Valley Formation. The plots of 

the phosphate from the Dover Sandstone fall well 

within the area on the diagram that is characteristic 

of carbonate fluorapatite.

CHEMICAL ANALYSES

Chemical analyses (table 2) were made in the 

Denver laboratories of the U.S. Geological Survey 

under the direction of Claude Huffman, Jr. P2O5 

was determined volumetrically by G. D. Shipley. 

Acid insoluble and loss on ignition were determined 

gravimetrically by G. D. Shipley. A12O3 was determined, by Alizarin Red-S with cupferron separation, 

by H. H. Lipp. Total Fe, CaO, MgO, Na2O, K2O, Mn, 

Sr, and Zn were determined, by atomic absorption, 

by Johnnie Gardner. SiO2 was determined colorimetrically by H. H. Lipp. TiO2 was determined, by 

tiron spectrophotometric method, by Elsie Rowe. 

Fluorine (F) was determined volumetrically by Johnnie Gardner. Arsenic (As) was determined, by modi-
E12 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

6

1 mm

FIGURE 13. Photomicrograph of phosphate-cemented sandstone 

from the basal conglomerate of the Dover Sandstone on 

Elliott Ridge. Thin section is from phosphate-cemented zone 

of rock shown in figure 12. Light-brown microcrystalline 

apatite (P) cements quartz and potash feldspar chiefly 

through the replacement of preexisting sericitic matrix and 

fine-grained detrital clasts; in many places most clasts less 

than 0.5 mm across have been replaced. The phosphate is 

nearly free of argillaceous inclusions; black specks are iron 

oxide. Q, quartz clast; kf, potash feldspar; S, sericitic alteration product in feldspar. Recrystallized apatite fills white 

veinlets that parallel strain structures in quartz clasts 

both features are related to early Mesozoic orogeny. Planepolarized light.

fied Gutzeit method, by E. J. Fennelly. Total carbon 

was determined by induction furnace, mineral carbon was determined gasometrically, organic carbon 

was determined by difference, and total sulfur (S) 

was determined by induction furnace compared to 

Land Rock Phosphate Standard, all by I. C. Frost. 

eU was determined, by beta gamma sealer, by 

Johnnie Gardner.

The content of the major elements reflects the 

mineralogic composition of the analyzed samples; 

that is, major apatite, minor quartz and sericite, and 

a trace of potassium feldspar. The contents of P2O5 , 

CaO, and F and the ratios of CaO to P2O5 and F to

x

o

(

o 

o

\

I O \ 

0 0 \

o

\* 

, * 

EXPLANATION

Plot of sample from the 

Phosphoria Formation 

(from Gulbrandsen,1970)

0

Plot of sample from the 

Bone Valley Formation

D

Plot of sample from the 

Dover Sandstone

t 

Plots of A26 of samples 

not analyzed for CO2 

(Elbow Formation)

1 

nPebl: 

nC 

Pebble]

>le 

iment

rjCement

1.10 1.20 1.30

A20,

1.40 1.50 1.60 1.70

IN DEGREES

FIGURE 14. Plot of CO2 and A 2 6 (004)-(4iO) showing relation of 

samples of Antarctic phosphate rock to samples of the Phosphoria Formation from the Western United States and the 

Bone Valley Formation from Florida.

TABLE 2. Chemical analyses of phosphate samples from the 

Dover Sandstone, Elliott Ridge, Neptune Range

[Values are in percent except as notedl

Sample No ...............

Laboratory No .......

Sample type .............

P205 ..........................

CaO ............................

F.................................

SiO2 .............................

Acid insoluble ..... ..

A1 203 ........................

Fe203 3 .... ............. .....

MgO.............................

Na2O

K2O ............................

TiO2 ..........................

Mn ...............................

Sr ................................

Zn .................................

S ..................................

eU .................................

C(total) .......................

(organic) .................

C02< ...........................

Loss on ignition

........... A

........... D137451

... Apatite cement1

.......... 27.2

.......... 39.8

.......... 2.54

.......... 22.4

.......... 22.8

.......... 2.76

.......... 1.42

......... .14

.......... .05

......... 1.19

........ .3

.05

.......... .04

.003

.......... .30

.......... .037

......... .31

......... .15

.......... .2

.......... .55

125

1.3

B

D137452

Apatite cement1

26.1

38.2

2.46

18.8

20.3

4.68

2.06

.18

.04

1.66

.1

.17

.06

.005

.19

.020

.58

.03

.6

.11

35

2.1

C

D137453

Apatite pebble2

27.4

40.5

2.48

16.8

18.8

4.91

1.05

.22

.04

1.76

.3

.04

.04

.003

.08

.021

.34

.21

.1

.77

85

1.6

'Separated from matrix in bromoform (sp. gr. = 2.86). 

2Handpicked coarse black dense phosphate pebbles. 

3Total iron as Fe2O3- 

4CO2=mineraI carbon times 3.67.
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E13

P2O5 are within the range for the apatite mineral, 

and all these can be assigned to the apatite mineral. 

The CO2 content can be assigned to the apatite 

mineral because no other carbonate-bearing mineral 

has been detected in the samples.

The silica contents of the samples are high, 

reflecting the abundance of fine-grained quartz and 

silicate minerals, and the generally high content of 

A12O3 (considerably higher than phosphorite from 

the Bone Valley Formation or the Phosphoria Formation) reflects the high content of the aluminum 

silicate minerals sericite and feldspar.

The samples are low in Na2O content much 

lower than the Phosphoria Formation of the Western 

United States and Bone Valley Formation of 

Florida, both of which average about 0.6 percent 

Na2O but are high in K2 O content. Sodium is much 

higher than potassium in the Bone Valley phosphate, and the contents of these alkalies are about 

the same in the Phosphoria phosphates, in strong 

contrast to the Antarctic phosphates, where K2O is 

much more abundant than Na2O.

Sodium probably substitutes for calcium in the 

apatite mineral, whereas the potassium is present in 

one of the diluting minerals sericite or feldspar. 

The reason for the low sodium content is not known; 

all that can be said is that the Antarctic apatite 

samples are deficient in sodium, as compared with 

other apatite samples.

The content of TiO2 is low but is within the range 

shown by samples of marine apatites from the Bone 

Valley Formation and from the Phosphoria Formation. Titanium is probably present in one of the 

titanium-bearing minerals, but the mineral is in such 

small amounts that it cannot be detected by the Xray. The titanium may be present in the mineral 

leucoxene, tentatively identified from thin section 

study.

The amount of MgO in the samples of the Dover 

Sandstone is low and is at the lower end of the range 

of MgO content of samples of phosphate rock from 

the Phosphoria and Bone Valley Formations. The 

minor amounts of MgO in the samples from Antarctica may be in the mica chloritic or in the apatite 

minerals.

Sulfur, present in the Antarctic samples in 

minor amounts, probably is in the form of SO4 as a 

substitute for PO4 in the apatite mineral.

The content of organic matter in these samples 

generally is low, although the phosphate pebbles 

and cement are black in hand specimen. The content of organic carbon is less than 1 percent, much 

lower than that of the samples of the Phosphoria

Formation, and close to the content of the samples 

from the Bone Valley Formation.

The X-ray data (fig. 14) and the chemical analyses (table 2) clearly show that the apatite mineral is 

a carbonate fluorapatite. The apatite of the phosphate pebble contains more CO2 than does the 

phosphate cement. Mobilization of the phosphate 

and its precipitation as cement may have driven off a 

part of the CO2 . The cement is more similar to fluorapatite than is tlie phosphate pebble.

SPECTROGRAPHIC ANALYSES

Six-step semiquantitative spectrographic analyses were run on two samples of phosphate cement 

separated from the rest of the rock by bromoform, on 

one sample of phosphate pebble, and on one sample 

of phosphate cement handpicked under the microscope. The results (table 3) are to be identified with 

geometric brackets whose boundaries are 1.2, 0.83, 

0.56, 0.26, 0.18, 0.12, etc. but are reported arbitrarily 

as midpoints of these brackets, 1.0, 0.7, 0.5, 0.3, 0.2, 

0.15, 0.1, etc. The precision of a reported value is 

approximately plus or minus one bracket at 68- 

percent confidence or two brackets at 95-percent 

confidence. Elements looked for but not detected 

(those elements whose concentration is below the 

limit of detection), with their limits of detection 

shown in parentheses, include: As (200), Au (10), B 

(10), Bi (10), Cd (20), Pd (2), Pt (50), Sb (100), Te (2,000), 

U (500), W (50), Zn (200), Ge (10), Hf (100), In (10), Li 

(100), Re (50), Ta (200), Th (200), Tl (50), Eu (100), 

Tb (300), Er (50), Tm (20), Lu (30).

The minor element content (table 3) is about the 

same for the phosphate pebble (sample 3) and the 

phosphate cement (samples 1, 2, 4). The data do not 

preclude the possibility that the source of the phosphate cement may have been the phosphate pebbles. 

Evidence from thin section indicates the possibility 

that phosphate from the pebbles has been mobilized 

and moved outward from the pebble to cement the 

sandstone adjacent to the pebble (fig. 11).

The minor element content in the samples from 

the Dover Sandstone is compared with the content of 

trace elements in phosphorite from the Phosphoria 

Formation of the Western United States and from 

the Bone Valley Formation of Florida (table 4). In 

addition, the minor element content is compared 

with the crustal abundance of these elements relative to which an enrichment factor is recorded. The 

trace metals, Ag, Cr, Cu, Mo, Ni, V, Zn, and probably 

Co, are much more abundant in the Phosphoria 

Formation than in the samples of the Dover Sandstone but are present in samples of the Bone Valley
E14 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

TABLE 3. Semiquantitative six-step spectrographic analysis of 

sample of phosphate rock from Dover Sandstone, Elliott Ridge, 

Neptune Range

[Analysts: Samples 1, 2, 3, Harriet Neiman, U.S. Geological Survey, Denver; 

sample 4, W. R. Crandell, U.S. Geological Survey, Washington. G, greater than 10 

percent; N, not detected; L, detected, but below limit of determination]

Sample No .......

Lab. No .............

Fe .......... .. .........

Mg ........ ............

Ca .......................

Ti .....................

Si ....... ...............

Al .......................

Na .....................

K ........................

P .........................

Mn .......... .. .......

Ag.......................

Ba............ .........

Be.......................

Co......................

Cr .......................

Cu......... .............

La.................. ..

Mo .... ................

Nb .....................

Ni .......................

Pb .......................

Sc .......................

Sn .. ...................

Sr .......................

V.................... .

Y.........................

Zr .......................

Ce .......................

Ga.......................

Yb .......................

Nd .....................

Sm .....................

Gd......................

Dy.......................

Ho.......................

............. ..... 1

D137451

........... 1

........... .05

........... G

........... .2

........... 10

........... 2

........... .07

........... 1

........... 7

In

........... 500

........... N

........... 300

7

........... 5

........... 200

........... 10

........... 70

........... 7

........... L

100

........... 70

.......... 30

........... L

........... 700

........... 70

200

300

.......... 150

........... N

15

......... 100

........... N

N

N

......... N

2

D136452

In percent

1

.1

G

.05

10

2

.05

1.5

10

parts per million

1,500

N

500

10

5

150

15

150

7

N

50

100

15

10

700

15

200

100

500

5

15

200

100

50

50

L

3

D137453

0.7

.15

G

.1

5

2

.07

2

10

500

N

300

7

3

150

7

70

N

N

7

100

15

10

500

100

200

70

200

10

10

100

N

N

L

L

4

4128

0.7

.5

G

.015

5

2

.02

N

G

500

5

500

10

7

200

7

150

N

N

30

100

10

N

700

70

200

15

150

N

2

N

N

N

N

N

Sample:

1 and 2 Heavy mineral separate (bromoform sink) of phosphate cement.

3 Handpicked black pebble.

4 Handpicked black cementing material.

Formation in about the same amounts as in the 

Dover. In fact, these elements are enriched in the 

Phosphoria Formation and are, in general, depleted 

in the Dover and the Bone Valley. Krauskopf (1955) 

pointed out that Ag, As, Cr, Mo, Ni, V, and Zn 

probably are concentrated by organic matter associated with phosphates rather than by the phosphate 

mineral, and Gulbrandsen (1966) concluded that 

these elements plus Cd, Cu, Sb, and Se also are 

concentrated by organic material. These conclusions 

are supported by the data on phosphate rock from 

Antarctica, because those elements that are thought 

to be concentrated by organic material are in much 

lesser amounts in the relatively organic poor Florida 

and Antarctic phosphates than in the relatively 

organic rich Phosphoria Formation. Arsenic is a 

notable exception, being considerably enriched in

the Antarctic material, and it possibly is present in 

the apatite mineral. Young, Myers, Munson, and 

Conklin (1969) pointed out that arsenic is enriched in 

an igneous fluorapatite and that it probably replaces 

the phosphorus ion, and Krauskopf (1955) also noted 

that a part of the arsenic probably substituted for P 

in the apatite structure.

Lead, tin, and beryllium all seem to be present in 

the phosphate of Antarctica in larger amounts than 

in either the Bone Valley or Phosphoria phosphate. 

Krauskopf (1955) indicated that lead and beryllium 

may be concentrated by the apatite mineral, lead 

substituting for calcium, and that the mode of occurrence of beryllium is not known. The mode of 

occurrence of tin is not known, but probably it 

follows the other metals and is concentrated in the 

organic fraction.

Zirconium is present in larger amounts in the 

few samples of Antarctic phosphate rock than in 

either the Bone Valley or Phosphoria phosphate, but 

it is probably present in the mineral zircon.

Strontium, present in about the same amounts 

as in the other marine phosphate rocks, probably 

substitutes for calcium in the apatite mineral. Gallium, present in somewhat larger amounts in these 

rocks than in the phosphorites from the Bone Valley 

or the Phosphoria, probably is present as a substitute 

for aluminum in the aluminum-bearing minerals.

The presence of uranium in marine phosphorite 

is well known, and uranium substitutes for calcium 

in the apatite mineral (Altschuler and others, 1958). 

The uranium content of these rocks is somewhat 

larger than the average for the Bone Valley or the 

Phosphoria, but the uranium content of many individual samples from the Bone Valley Formation of 

Florida is as large as or larger than that of Antarctic 

samples. Manganese and barium are higher in these 

rocks than in the averages for the Phosphoria and 

Bone Valley, but the manganese contents are closer 

to those for Bone Valley than for the Phosphoria. 

Gulbrandsen (1966) pointed out that manganese is 

not likely to precipitate under the strongly reducing 

conditions typical of the Phosphoria environment, 

but according to Krauskopf (1957) manganese does 

precipitate in the sea under strongly oxidizing conditions. The manganese in these rocks is probably 

present as a manganese mineral, perhaps as a 

barium-manganese oxide such as psilomelane, but 

the mineral is present in amounts that are too small 

to be indicated by the X-ray.

The rare earth elements are concentrated in the 

apatite mineral. They are more abundant in the 

Western Interior phosphate than in either the Florida or the Antarctic material. It is thought that the 

rare earth elements substitute for calcium in the
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E15

TABLE 4. Minor metal contents of phosphatic materials of this paper compared with crustal flbundances of these metals and with

amounts in marine phosphorites

[Abundance values in parts per million. Numbers in parentheses after values for.elements are approximate enrichment factors for elements; numbers greater than 1.0 indicate 

enrichment, numbers less than 1.0 indicate depletion. N=not detected; P=present in some samples but not detected in most (element probably just below limit of detection)!

Marine phosphorite

Element

Ag.....................................

As.....................................

Ba .....................................

Be.....................................

Cr .....................................

Co.....................................

Cu.....................................

Ga.....................................

Mn ...................................

Mo ...................................

Ni .....................................

Pb .....................................

Sn .....................................

Sr .....................................

V........................................

U.......................................

Zr .....................................

Zn .....................................

Crustal 

abundance 

(Green. 1953)

................. 0.1

................. 5

................. 250

................. 2

................. 200

................. 23

................. 70

................. 15

................. 1,000

................. 1

................. 80

................. 16

................. 40

................. 450

................. 150

................. 2

................. 200

................. 130

This Phosphoria Formation of 

report 1 Western United States 

(Gulbrandsen, 1966)

N 

280 (16.0) 

300 (1.2) 

7 (3.5) 

150 (0.8) 

5 (0.2) 

10 (0.1) 

5 (0.3) 

500 (0.5) 

5 (5.0) 

50 (0.6) 

100 (6.3) 

10 (0.3) 

700 (1.6) 

70 (0.5) 

2260(130.0) 

100 (0.5) 

30 (0.2)

3(30.0) 

240 (8.0) 

100 (0.4) 

N 

1,000 (5.0)

3N

100 (1.4) 

N 

30 (0.03) 

30(30.0) 

100 (1.3) 

N 

N 

1,000 (2.2) 

300 (2.0) 

290(45.0) 

30 (0.2) 

300 (2.3)

Bone Valley Formation of 

Florida (J. B. Cathcart, 

unpub. data)

0.5 (5.0) 

220 (4.0) 

70 (0.3) 

1 (0.5) 

100 (0.5) 

3 (0.1) 

10 (0.1) 

P (0.3?) 

200 (0.2) 

10 (10.0) 

15 (0.2) 

10 (0.6) 

N 

1,000 (2.2) 

150 (1.0) 

140 (70.0) 

50 (0.3) 

100 (0.8)

Rare earth elements:

La........................................

Ce ........................................

Nd ......................................

Sm ......................................

Gd.......................................

Dy........................................

Ho........................................

Yb ........................................

Y..........................................

Sc ........................................

.............. 20

.............. 40

.............. 20

.............. 5

.............. 5

.............. 5

.............. 1

.............. 3

.............. 40

.............. 5

100

200

100

P

P

P

P

15

200

15

(5.0)

(5.0)

(5.0)

(5.0)

(5.0)

(3.0)

300(15.0)

3N

300(15.0)

N

N

N

N

10 (3.3)

300 (7.5)

10 (2.0)

100

200

150

P

P

P

P

10

200

7

(5.0)

(5.0)

(7.5)

(3.3)

(5.0)

(1.5)

1 Modes (most frequent number reported) from all samples on table 3.

- Arithmetic average of chemical determinations.

J Limit of detection of Co was 10 ppm and of Ce 1,000 ppm when this group of analyses was made.

phosphate mineral, and the enrichment factors for 

all of the rare earth elements are about the same for 

each occurrence.

Scandium is put with the rare earth elements, 

but it is not clear whether scandium tends to follow 

the rare earths. In any case, its enrichment factor is 

less, and it is present in minor amounts.

In summary, the data on table 4 indicate clearly 

that the content of trace elements of the phosphate 

rock from Antarctica is much closer to the content of 

phosphate rock from the Bone Valley Formation 

of Florida than it is to phosphate rock from the 

Phosphoria Formation.

ORIGIN AND DEPOSITIONAL ENVIRONMENTS 

OF SEDIMENTARY PHOSPHATE IN ANTARCTICA

The largest and richest of the marine phosphorite deposits are formed in warm waters mostly

between the 40th parallels (Sheldon, 1964) in areas of 

upwelling (McKelvey, 1967) and where clastic sedimentation is at a minimum; that is, in a miogeosynclinal environment. Deposits are characterized by a 

suite of rocks that consists of black shale, phosphorite, dolomite, limestone, and chert. Phosphate 

deposits formed in the adjacent stable shelf are 

associated with chert, sandstone, and shale, which 

generally are light colored in contrast to the black of 

the geosynclinal rocks. Large phosphorite deposits 

had to be deposited in areas that were in contact with 

oceanic circulation so that phosphate was continuously replenished as it was precipitated. A summary 

of the origin of phosphate deposits and of economic 

deposits of the world is given by Cathcart and Gulbrandsen (1973).

Sediments deposited during the middle Paleozoic in what is now the Neptune Range consist of
E16 CONTRIBUTIONS TO THE GEOLOGY OF ANTARCTICA

several thousand meters of quartzose sandy material 

which is relatively uniform in composition and 

texture and which probably accumulated in shallow 

water in a slowly subsiding basin. The areal extent 

and uniformity indicate that deposition may have 

been in a large epicontinental sea with the craton to 

the east. The Elbow Formation is characterized by 

abundant animal burrows and, except at Mount 

Feldkotter, by red sedimentary rocks. The beds, 

initially green, were oxidized possibly by periodic 

exposure. These features indicate deposition in shallow water. A restricted marine environment is suggested by regional paleogeography and by C13 and 

O18 isotopic ratios made from carbonate cement 

(Schmidt and Friedman, 1974). Phosphate has not 

been found in the characteristic red facies but is 

confined to a nearshore non-red-bed facies of the 

Elbow Formation at Mount Feldkotter.

Phosphate in the Elbow Formation at Mount 

Feldkotter is the only primary sedimentary phosphorite exposed in the Neptune Range. The shallow 

water in which the sediments were deposited is 

thought to have been within the zone of photosynthesis, where phosphate goes into the organic 

cycle. The phosphate, therefore, probably precipitated below the sediment-water interface during a 

low-energy interval. The change to higher energy 

deposition for the overlying sandstone beds resulted 

in the erosion and mechanical reworking of part of 

the underlying phosphatic material and the incorporation of subangular phosphatic sandstone clasts 

into the base of the overlying sediment.

The shoreward facies of the Elbow Formation at 

Mount Feldkotter that contains the primary phosphorite probably extends more widely beneath the 

extensive ice and snow cover east and north of 

Mount Feldkotter. However, the paleogeography of 

the area and the physical character of the phosphorite make it unlikely that this is a large-tonnage 

phosphorite deposit.

The Reiser Sandstone was deposited in the same 

shallow-water environment as the Elbow but under 

conditions of slightly higher energy. The Heiser 

contains much less silt and shale than the Elbow. 

Abundant fossil burrows throughout the Heiser suggest shallow-water deposition. No red beds and no 

phosphorite beds are known in the Heiser.

The environment of deposition of the Dover 

Sandstone was a moderately high energy broad 

shallow-water epicontinental basin. Sparse landplant fossils as detrital grains in association with 

carbonaceous silt lenses, the lack of marine fossils, 

the extensive crossbedding, and the basal conglomerate indicate that most of the formation was deposited in a continental environment. The basal conglomerate most likely was deposited as a transgressive beach deposit.

The occurrence of 1,200 m of clean quartz sandstone above the basal conglomerate of the Dover 

indicates deposition in the broad shallow-water 

slowly subsiding epicontinental basin. The waters of 

the basin during Dover time may have been fresh, as 

indicated by solution and redeposition of phosphate 

in the basal conglomerate, by the sparse occurrence 

of fossil plant remains, and by the isotopic study of 

C13 and O18 in the rocks above the Dover. The thick 

overlying Gale Mudstone (Gonwanid tillite) is entirely freshwater (Schmidt and Friedman, 1974). The 

source of the phosphate pebbles in the basal conglomerate of the Dover probably was the Elbow 

Formation, inasmuch as primary phosphate is 

known only in this formation.

The apatite mineral in all the occurrences in the 

Neptune Range is a carbonate fluorapatite that 

contains only small amounts of CO2 substituting for 

PO4 . The phosphate in the Elbow Formation is 

thought to be primary deposited in a restricted 

marine environment. Mechanically rounded and 

transported pebbles in the Dover probably were 

derived from the Elbow as are the subangular clasts 

within the Elbow itself. The secondary phosphate 

cement in the Dover was derived from solution of the 

detrital phosphate clasts and reprecipitation of 

P2 O5 , probably in freshwater in a subaerial environment. The fact that the reprecipitated cement 

contains less CO2 than the original material may be 

due to a progressive loss of CO2 during the long 

history of erosion, reworking, solution, and reprecipitation.

Slight regional metamorphism (Beck and Schmidt, 1971) of the Paleozoic rocks in the Neptune 

Range during the early Mesozoic orogeny (Ford, 

1972a) caused the recrystallization of argillaceous 

material to sericite and chlorite and the slight alteration of the primary and secondary phosphate mineral through additional loss of CO 2 .

The primary phosphate of the Elbow Formation 

likely was deposited at a lower and warmer latitude 

than its present-day position at 84° S. Evidence from 

the extensive literature pertaining to plate tectonics 

and the existence of Gondwanaland precludes the 

possibility of expanding the southern warm climatic 

zone to lat 84° S. as proposed by Meyerhoff (1970, p. 

17, 25). Sheldon (1964) suggested that when ancient 

phosphorite deposits are relocated relative to their 

paleolatitudes as determined from paleomagnetic 

data, their deposition occurred between the 40th 

parallels, where most deposits of upper Tertiary and
MIDDLE PALEOZOIC SEDIMENTARY PHOSPHATE, ANTARCTICA E17

EXPLANATION 

Polar-wandering curve

cO

Paleopole cluster 

eRz, early Peleozoic 

eC, early Carboniferous

O 

Pensacola Mountains

Trans-Antarctice Mountains

FIGURE 15. Reconstruction of Gondwanaland (position random 

in figure) showing position of Pensacola Mountains relative 

to the polar-wandering curve for the Paleozoic of Gondwanaland. Clusters of paleopoles for early Paleozoic and Early 

Carboniferous time independently agree roughly with the 

central areas of the African glaciation of northern Africa 

and the early Gondwana glaciation of southern Africa. The 

Elbow Formation of the Pensaeola Mountains was deposited 

some time between Ordovician(?) and Early Devonian time 

when the paleopole lay between the early Paleozoic and Early 

Carboniferous positions. Phosphorite in the Elbow Formation 

would have been deposited, therefore, when the paleopole 

was at lat 50°-20° S. Africa and South America fit from 

Bullard, Everett, and Smith (1965); Antarctic fit from Ford 

(1972b, p. 116); early Paleozoic and Early Carboniferous 

paleopoles and polar-wandering curve from Creer (1970, p. 63).

Quaternary phosphorite are found. More precisely, 

present-day offshore phosphorite occurs between 

lats 44° N. and 52° S. (McKelvey and Wang, 1969, pi. 

4).

The polar wandering curve for Gondwanaland

for the Paleozoic extends southward along the prerift 

suture line of western Africa and eastern South 

America as determined by paleomagnetic data for 

Africa, South America, and Antarctica (Creer, 1970, 

p. 63). The polar wandering curve likely represents 

movement of the Gondwanaland rigid plate across a 

fixed rotational pole. The pole positions are approximately and independently substantiated by the 

estimated centers of continental glaciation for the 

African glaciation in North Africa during the late 

Ordovician (Fairbridge, 1969) and the Gondwana 

glaciation in southern Africa during the Early Carboniferous, and in Antarctica during Late Carboniferous and Early Permian (Crowell and Frakes, 

1970).

The time of deposition of the Elbow Formation is 

bracketed between Middle Cambrian (Palmer and 

Gatehouse, 1972) and Middle Devonian (Schopf, 

1968). During the Ordovician and Silurian the paleosouth pole can be reasonably considered to be between northern Africa and southern Africa. Most 

reconstructions of Gondwanaland (for various 

choices see Ford, 1972b, p. 118) place Antarctica 

against Africa and South America such that the 

Pensacola Mountains are 30-70 degrees of latitude 

from any reasonable pole position during the Ordovician and Silurian (fig. 15). Elbow phosphorite was 

deposited in temperate marine waters.

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