Late Quaternary ice-surface fluctuations of Hatherton Glacier, Transantarctic Mountains

QUATERNARY

RESEARCH

31, 229-254

Late Quaternary

(1989)

Ice-Surface Fluctuations of Hatherton Transantarctic Mountains

JAMES G.BOCKHEIM

Glacier,

AND SCOTT C. WILSON

Department of Soil Science, University of Wisconsin, Madison,

Wisconsin 53706

GEORGE H. DENTON Department of Geological Sciences and Institute for Quaternary Studies, University of Maine, Orono, Maine 04469

BJ~RN G. ANDERSEN Geologisk Institutt,

Universitet i Oslo, Oslo, Norway

AND MINZE STUIVER Quaternary Research Center, University of Washington, Seattle, Washington 98195 Former longitudinal profiles of Hatherton Glacier, an outlet through the Transantarctic Mountains, constrain nearby polar plateau elevations and ice-shelf grounding in the southwestern Ross Embayment. Four gravel drift sheets of late Quatemary age beside Hatherton Glacier are, from youngest to oldest, Hatherton, Britannia I, Britannia II, and Danum. The Hatherton drift limit is uniformly 20 to 70 m above the present ice surface. The Britannia II drift limit is within 100 m of the present surface of uppermost Hatherton Glacier but is 450 m above middle Hatherton Glacier. Extrapolation of this profde downglacier indicates a surface elevation 1100 m above the present Ross Ice Shelf. The Britannia I drift limit is parallel to, but 50-100 m below, Britannia II drift. The Danum drift limit is parallel to, but 50-100 m above, the Britannia II profde. From correlation with drifts near McMurdo Sound and from local 14C dates, we assign an early Holocene age to Hatherton drift, a late Wisconsin age to Britannia drifts, and an age of marine isotope Stage 6 to Danum drift. By our age model, the upper reaches of Hatherton Glacier (and presumably the adjacent polar plateau) have not exceeded their current elevations by more than NO-150 m during the last two complete global glacial-interglacial cycles, whereas the middle and lower reaches of Hatherton Glacier have thickened considerably during the last two global glaciations (late Wisconsin and marine isotope Stage 6). The effect of ice-shelf grounding probably was the major control of these changes of Hatherton Glacier. Holocene ice-surface lowering probably represents the last pulse of grounding-line recession in the southwestern Ross Embayment. 0 1989 University of Washington.

tains. Limited exposures of multiple drifts also occur in discontinuous ice-free areas beside Darwin Glacier in the Darwin Mountains and near Tentacle Ridge. Undifferentiated drift is widespread in the Brown Hills near the Ross Ice Shelf. Our prime objective was to employ this rare occurrence of southern Transantarctic outlet glaciers with preserved lateral drift sheets in understanding the dynamics of the huge Ross ice drainage system described by

INTRODUCTION Hatherton and Darwin Glaciers together drain East Antarctic polar plateau ice through the Transantarctic Mountains into the Ross Ice Shelf (Fig. 1). The major flowline along Darwin Glacier projects far inland to Dome Circe in central East Antarctica. Multiple drift sheets are widely exposed alongside Hatherton Glacier in both the Britannia Range and the Darwin Moun229

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8 1989 by the Universtty of Washington. of reproduction in any fom reserved.

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ANTARCTIC

GLACIER

Denton et al. (1989). Our strategy involved combined geological and soil studies to differentiate drift sheets deposited by Hatherton and Darwin Glaciers. This allowed construction of former longitudinal surface profiles of Hatherton Glacier. To make full use of these surface profiles, we interpret their configuration, determine their numerical ages where possible, and compare them on the basis of soils data with longitudinal profiles in the Taylor Valley/McMurdo Sound area farther north in the Transantarctic Mountains. The results show the relative behavior of the polar plateau ice surface and the Ross Ice Shelf during Stage 2 and 6 of the marine oxygen isotope record that is illustrated in Figure 14 of Denton et al. (1989).

FLUCTUATIONS

231

Hatherton Glacier flows from the East Antarctic Ice Sheet into lower Darwin Glacier, which discharges into the Ross Ice Shelf (Fig. 1). Ice-free cirques and valleys in the Britannia Range and Darwin Mountains beside Hatherton and middle Darwin Glaciers (Fig. 2) are largely cut into dolerite (Ferrar Supergroup) and sandstone (Beacon Supergroup). Ice-free areas alongside lower Darwin Glacier are characterized by granite and metamorphic rocks (Haskell et al., 1965). Extreme cold desert climate marks the Hatherton Glacier area. Unfortunately no long-term climatic data exist. On the polar plateau near the glacier head the mean annual temperature is approximately -35” to -40°C and the accumulation about 10-15 g

FIG. 2. Landsat 1 digitally enhanced image of the Hatherton Glacier area. Figure provided by 9. K Lucchitta.

232

BOCKHEIM

cmm2yr-‘, whereas on the Ross Ice Shelf seaward of the glacier mouth the respective values are approximately -30°C and 20 g cmm2 yr- ’ (Weyant, 1967; Giovinetto and Bull, 1987). Winds from the polar plateau, which carry considerable snow, influence Britannia more than Darwin ice-free areas. In the summer the Darwin Mountains receive relatively moist easterly air flow. Therefore, summer temperature are milder in the Darwin Mountains than in the Britannia Range. Mean monthly temperatures recorded at Darwin Camp (Fig. 1) during the 1978-1979 field season were - ll”, - 3.5”, and - 2.8”C for November, December, and January, respectively (U.S. Navy, unpublished weather data from Darwin Glacier Camp). In the Britannia Range, 55 km southeast of Darwin Camp, daytime high temperatures during November 13-21, 1978ranged between - 13” and - 28°C and averaged - 18°C which is about 7°C colder than at Darwin Camp during the same period. Wind velocities were not taken regularly at either locality; however, it was not unusual for strong katabatic winds (20-30 m/set- ‘) to be blowing in the Britannia Range during dead calms at Darwin Camp. METHODS

We mapped multiple drift sheets in icefree valleys marginal to Hatherton Glacier, defining their outer limits by abrupt changes in surface morphology, surface boulder weathering, and soil development (staining and cohesion depth, solum thickness, morphogenetic salt stage, and weathering stage) (Figs. 1, 3, and 4). Because they are widespread and distinctive in appearance, the younger drifts can be traced physically from valley to valley alongside Hatherton Glacier. The older drifts occur discontinuously and thus their map pattern is less well established. We then correlated

ET AL.

drifts beside Hatherton Glacier with those in discontinuous ice-free areas beside middle Darwin Glacier by position in drift sequence and soil development. The results allowed former longitudinal surface profiles of Hatherton Glacier to be reconstructed for each mapped drift sheet. For control of relative elevations for these profiles, we used a network of altimeter measurements. These measurements were keyed to current ice surfaces in each area, because the elevation of drift limits above current ice surfaces were key to our study. We estimate that these elevation differences are accurate to within ?2 m. Soil sampling localities are shown in Figures 1, 3, and 4. Most localities were on mapped drift sequences alongside Hatherton Glacier, although some sample localities were on drifts beside Darwin Glacier. At each locality, surface boulder weathering and soil development were examined on a moraine crest. On each moraine crest a minimum of 100 boulders greater than 30 cm in diameter (short dimension) was tallied along line transects according to rock type and surface boulder weathering characteristics (Bockheim, 1979). Weathering features recorded include desert varnish, cavernous weathering (taffoni), spalling, pitting, fracturing, and striations. The surface boulder frequency and the dolerite: sandstone ratio were also noted. At least one soil pit was excavated on each selected moraine crest to a depth of 1 m, unless ice-cemented permafrost prevented digging to this depth. Morphologic properties of the soils exposed in each pit were measured in the field. Samples of each horizon were sieved and returned to the laboratory where the following analyses were made on I:5 soil:water extracts: electrical conductivity (EC), pH, and watersoluble ions (Na+, Ca’+, MgZf , K+,

FIG. 3. Drift sheets and moraines in Britannia Range beside Hatherton Glacier. Map is based on vertical aerial photographs taken by U.S. Geological Survey. See Figure 1 for location.

234

BOCKHEIM

ET AL.

FIG. 4. Drift sheets and moraines in the Darwin Mountains beside Hatherton Glacier. Map is based on vertical aerial photographs taken by U.S. Geological Survey. See Figure 1 for location.

Cl-) (American Public SOd2-) N03-, Health Association et al., 1975). Sodium and K+ were detected by flame photometry, and Ca2+ and Mg2+ by atomic absorption spectroscopy. Sulfate was measured by the turbidimetric method (nephelometry) and Cl- by the potentiometric method on a chloridometer. Nitrate was analyzed on a Technicon autoanalyzer (Anonymous, 1977). Particle-size distribution was determined using a modified Buoyoucos hydrometer procedure (Day, 1965). Prior to particle-size analysis, excess salts were removed by three washings with distilled water. Minerals in the <2pm fraction were identified by X-ray diffraction analysis employ-

ing CuK radiation and Ni filter. Samples were saturated with a 0.5 M solution of magnesium chloride, smeared onto glass microscope slides, and irradiated at room temperature prior to and following exposure to ethylene glycol fumes. A second slide containing clay saturated with 1 M KC1 was irradiated after exposure to each of three temperatures: 20, 300, and 550°C. RESULTS Drift Sheets Figures 1, 3, and 4 show the following drift sheets, from youngest to oldest. with increasing distance from the present-day ice margins: Hatherton, Britannia I, Britan-

ANTARCTIC

GLACIER

nia II, Danum, and Isca. The map pattern shows that these drifts were deposited by the Hatherton and Darwin Glaciers. These drifts are lithologically uniform (dolerite and sandstone with a few granite and metamorphic clasts). They lack a waterlaid component and consist of a thin sheet of unconsolidated gravel with a sandy matrix. Striated surface clasts occur on Britannia drifts. Thin boulder belt moraines are common on drift surfaces. Drift boundaries are marked by ramps, moraines, or boulder lines. These thin gravel drift sheets commonly rest without disturbance on preexisting morphological features. Individual gravel drifts show increasingly poor morphological preservation with distance from the current glacier margin. Morphological change is particularly abrupt at the Britannia II/Danum and Danum/Isca boundaries. Hatherton, Britannia I, and Britannia II drifts all show well-preserved constructional morphology (ice-cored hummocky terrain, moraine ridges with openwork gravel, perched boulders, kettles with small lakes) with only relatively minor dif-

FLUCTUATIONS

235

ferences across drift boundaries. In contrast, Danum drift shows little constructional morphology, whereas Isca drift has very subdued surface morphology and moraine ridges. Soil development (discussed below) served as a powerful discriminator among the gravel drifts and, in particular, showed major differences between Britannia WDanum and Danum/Isca drifts, consistent with the major changes in surface drift morphology. Surface boulder weathering was a less powerful discriminator, although the abrupt change of dolerite:sandstone ratio across the Britannia IIiDanum boundary yields a distinct color difference between these drifts (Fig. 5). On the basis of available data, we infer that Britannia I and II drifts represent the same major glaciation, with Britanma I drift reflecting a late readvance superimposed on ice recession from the Britannia II drift limit. But there are differences in soil development on Britannia I and II drifts (discussed below). Therefore, we leave open the possibility that a new numerical dating technique may show that these drifts repre-

FIG. 5. Oblique aerial photograph of Britamia I and II drift sheets (liiht colored) in Dubris Valley, Britannia Range. Hatherton Glacier is in the background.

236

BOCKHEIM

sent separate glacial events. From its irregular outer limit, we think that Hatherton drift represents the last pulse of ice-surface lowering associated with general recession from Britannia drift limits. Britannia II is the most continuous drift sheet alongside Hatherton Glacier in both the Britannia Range and the Darwin Mountains (Figs. 3 and 4). Because they have nearly identical surface morphology, Britannia II and Britannia I drifts can be separated only where the Britannia I drift is bound by a sandstone-rich moraine or boulder line. This situation occurs consistently in the Britannia Range (Fig. 3), but only sporadically in the Darwin Mountains (Fig. 4). Therefore, in the Darwin Mountains we mapped Britannia drifts as Britannia II except where we could clearly separate a Britannia I component. Buried Soils

Several buried soils occur on Danum Platform and help to distinguish among drift sheets (Fig. 6). A buried soil is present 83 cm beneath Britannia I drift. Because the buried soil morphologically resembles Britannia II surface soil, with slightly less development, it may represent a buried Britannia II soil. Alternatively, the buried soil could be a truncated remnant of Danum or an older soil. In like manner, a Danum surface soil is underlain by a buried soil at a

ET AL.

depth of 25 cm, with the buried soil possibly being an Isca surface. Soil Morphology

Of the soil morphologic features measured, staining depth evidences the least variation within individual drifts and the least overlap among drifts. Mean depth of staining increases progressively for Hatherton, Britannia I, Britannia II, Danum, and Isca drifts (Table 1). Colors of surface horizons intensify with increasing drift age. The color development equivalent (CDE) was estimated by multiplying a coded numerical notation of hue in the Munsell color notation by the numerical notation of the chroma (Buntley and Westin, 1965). The CDE values range from an average of 4 for the Hatherton drift to an average of 15 for the Isca drift. These values follow the same trend as staining depth. The depth of ghosts or “pseudomorphs” is reflective of the relative physical weathering or comminution of clasts in the profile. Ghosts were not observed in either the Hatherton or the Britannia I drifts; however, the average depth of ghosts increases from Britannia II to Isca soils. Most of the ghosts identified in the Britannia and Danum soils are of more readily weathered sandstone; many of the ghosts observed in the Isca soils are of resistant dolerite. Matrix salts were not observed in Hath-

Profile

Hatherlon

q

Buried Unoxidized

ERannia

I

Briiannia

811 Buried Oxidized

numbers

II

Danum Ei

Surlace Unoxidized

lsca

ka I

Surlace Oxidized

FIG. 6. Oxidation depths of groundsoils and buried soils on Danum Platform in the Britannia Range.

ANTARCTIC TABLE

GLACIER

237

FLUCTUATIONS

1. MORPHOLOGY OF SOILS ON DRIFTS IN THE HATHERTON GLACIER AREA* Depth (cm)

Drift unit Hatherton Britannia I Britannia II Danum Isca

No. of profiles 3 10 11 11

22

Staining

Ghosts

Matrix salts

Ocd 2d Scd 1Obc 19a

Ocd od 7cd 13bc 32a

Obc oc oc 8b 14a

Ice cement

salt stage

16 19+ 16-k

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erton or Britannia soils. Salt flecks in the weathering stage 2 (slightly developed), and soil matrix range between 1 and 5 mm in soils on Isca drift to weathering stage 3 diameter and are common in Danum and (moderately developed) (Table 1). Isca soils. The average depth of these matrix salts is 8 and 14 cm in Danum and Isca Surface Boulder Weathering soils, respectively (Table 1). Weakly ceThe percentage of boulders varnished, mented salt pans occur in some Isca soils. fractured, pitted, and spalled increases proUgolini (1964) suggested that salts dissemigressively from Hatherton to Isca drift (Tanated in the matrix of cold desert soils in- ble 2). Striated surface clasts are present on crease their coherence. To test this hypothboth Britannia drifts but not on Danum or esis, we performed paired t tests on the EC Isca drifts. Although surface boulder frevalues of 15 soil:water extracts from the quencies are twice as great on Hatherton lowermost coherent layer with those from moraines as on Isca moraines, these differthe underlying loose layer for 27 profiles in ences are not significant at P s 0.05. Althe Hatherton Glacier region. Our findings though the dolerite:sandstone ratio is genindicate that for all of the soils, the coherent erally variable and shows no distinct trend layers had significantly (P c 0.05) higher with drift age, a difference in this ratio EC values, and thus more salt, than the causes a distinct color difference between noncoherent layer below. Depth of coherthe Britannia and the Danum drifts. Varence and total soluble salt content in the nish on boulders also increases with age soils increase with relative soil age. Hathand contributes to this color difference. erton drift shows no cohesion, contains Isca drift contains nearly twice as many very little soluble salt, and rests on clean boulders with cavernous weathering (tafice. Soils on Britannia I and II drifts are foni), spalling, pitting, and fracturing as Britannia drifts. coherent to depths of 5-6 cm, whereas those on Danum and Isca drifts are coherent to 26 and 47 cm, respectively. Depth to Chemistry of Soil-Water Extracts ice-cemented permafrost is variable. The pH value of extracts from the surThe soils were placed into weathering face mineral horizon generally ranges bestages based on degree of soil horizon de- tween 6.4 and 7.7 on Hatherton and Britanvelopment, nature of salts, and condition of nia drifts (Table 3). However, on Danum surface boulders (Campbell and Claridge, and Isca drifts, pH values as low as 5.1 are recorded. These low values are attributed 1975). Soils on Hatherton and Britannia drifts were assigned to weathering stage 1 to salts, which depress the H-ion activity of (weakly developed), soils on Danum drift to the extracts. The increase in pH with depth

238

BOCKHEIM

ET AL.

in individual soil profiles corresponds to a decrease in salt content. Calcium and SOq2- and N03- are the dominant cation and anions, respectively, in soil-water extracts for most of the soils from the Hatherton Glacier region (Table 3). However, in some soils at high elevations in the Britannia Range, Na+ and NO3 - are dominant. Ion concentration of water extracts, particularly in the zone of salt enrichment, generally increases with drift age (Table 3). Total water-soluble salts were calculated to a depth of 70 cm using the equation of Bockheim (1979). Total water-soluble salts to a depth of 70 cm in the profile increase from the Hatherton drift to the Isca drift (Table 3). Concentration of ions in the soilwater extracts decrease with depth below the zone of maximum salt enrichment except where buried soils are present. Ion concentrations of water extracts from the horizon of salt enrichment generally increase from the Hatherton sediments to soils on Isca drift. Total water-soluble salts to 70 cm follow the same pattern. The increase in total salts with depth is greater in the Britannia Range than in the Darwin Mountains (Table 3). Particle-Size

Distribution

Particle-size distribution was measured in a sequence of soils on the Danum Platform in the Britannia Range (Fig. 3). The soils contain from 50 to 90% coarse material (>2 mm). Sand (2.0-0.05 mm) comprises from 91 to 99% of the tine-earth fraction (Table 4). With two exceptions, silt (0.05 mm to <2 pm) content is 4% or less, and with one exception, clay (<2 pm) content is 5% or less. Quartz and mica are the dominant minerals in the clay fraction of soils in the Hatherton Glacier area, with chlorite, vermiculite, and interstratitied mica-vermiculite being present in lesser quantities (Table 5). The clay-size fraction of ground sandstone and dolerite contains quartz and mica with

ANTARCTIC

GLACIER

smaller amounts of chlorite (Bockheim, 1982). Therefore, the presence of these minerals in soils of the Hatherton Glacier area can be attributed to inheritance from parent material. The small amounts of vermiculite and interstratified micavermiculite may be products of chemical weathering of mica (Claridge, 1%5). The peak-height ratio of the 001 reflections of mica (10 A) to that of chlorite vermiculite (14 A) generally is wider for Mg-saturated clays from B2 horizons and buried B horizons than from Cn horizons (Table 5). Similarly, the 1OA:14A ratio widens from Hatherton to Danum drift. These trends may be due to an increase in claysize mica from physical weathering of siltand sand-sized mica, resulting in proportionally lesser amounts of vermiculite (Bockheim, 1982). The height:width ratio of the 10 A peak is less in the B2 horizon than in the Cn horizon of all soils. This is due to mica hydration (Claridge , 1965). Therefore, clay mineral weathering of soils in the Hatherton Glacier area is restricted to alteration of mica to vermiculite, hydration of mica, and physical comminution of silt- and sand-sized mica. DISCUSSION:

SOIL DEVELOPMENT

General Statement

Our measurements of soil morphologic characteristics showed consistency on the individual drift units mapped and traced physically alongside Hatherton Glacier (Table 1). Reconnaissance pits showed that soil morphology changed abruptly at drift boundaries mapped on geologic criteria. The greatest change occurred at major boundaries (Britannia II/Danum and Danum/Isca) that were also recognized by geologic criteria. The variability of morphologic characteristics on individual drift sheets is far less than the variability on drift sheets separated by these major boundaries. For these reasons, we conclude that geologic and soil morphologic characteristics, aided in local sequences by surface

239

FLUCTUATIONS

boulder-weathering measurements (Table 3), form a powerful basis for deciphering local drift sequences and for correlating drift sequences of similar parent lithology in the Transantarctic Mountains. Origin of Salts and Influence on Soil Development

of Climate

The distribution of salts in Antarctic soils is dependent on (i) composition of the parent material, (ii) precipitation source, and (iii) extent of leaching within the profile (Claridge and Campbell, 1977). The dominant cations in soils of the Hatherton Glacier region are Ca” and M$ + (Table 3). These cations likely originate from weathering of ferromagnesian minerals contained in dolerite parent material (LaPrade, 1971). Potassium may be derived from weathering of muscovite mica and orthoclase feldspars contained in sandstone parent material. Sodium may come from weathering of albite feldspars (LaPrade, 1971) and from marine aerosols (Claridge and Campbell, 1977). Sublimation of snow deposited on Antarctic landscapes leaves a residue of surface salts. Dryfall supplies additional salts. Soil temperatures rise above freezing to depths of 50 cm in coastal localities during the austral summer months, with northerly aspects providing the maximum solar radiation (Nichols and Ball, 1964; Weyant, 1966). This thawing may provide liquid soil water for the downward movement of free soil salts. Ugolini and Anderson (1973) showed that salts may also migrate in unfrozen, interfacial films on colloid surfaces in frozen ground. They recorded movement of Na+ (as 22NaC1)and Cl- (as Na36C1)on the order of 5 to 10 cm over a 2-yr period. Yaalon (1%5) reported that Cl- is more mobile than SOf - in hot desert soils of the Negev Desert. Sulfate and NO,- are the dominant anions in water extracts of soils in the Hatherton Glacier area (Table 3). Claridge and Campbell (1977) showed that atmospheric

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D B2 Cln C2n

D B2 Cln C2n

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D B21 B22 B31

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0.1 3.5 2.0 1.6

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6.5 7.2 7.3 7.0

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6.3 6.5 6.9 7.0

6.2 6.3 6.6 6.8

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7.1 12 12 2.9

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0.0 0.3 0.3 0.2

7.0 39 7.6 6.3

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1.4 13 5.8 5.4

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Britannia Range (78-26) 1.6 0.1 0.1 1.1 13 0.5 3.5 21 3.9 0.3 0.1 18 2.9 0.3 0.1 20

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1.9 29 32 19

3.8 14 6.3 1.8

0.1 25 16 10

1.7 25 41 9.7

7.0 29 15 17

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Horizon

Cln C2n

B2 Cln C2n C3n IIB2b

B2 Cln C2n IIB2b

D B2 Cln C2n IIB2b IIB3b

D B2 Cln C2n

Note. See Figure

Depth (cm)

3 for location

80 82 94 87

93 80 55 48 46 51

80 89 88 58

48 63 75 45

94 84

Coarse material (>2 mm)

TABLE

of soil profdes.

75 16 29 35

48 28 18 19 14 15

24 15 13 15

9 6.2 4.4 3.5 9

5.3 5.9

coarse sand (2-l mm)

Very

4. PARTICLE-SIZE

18 27 35 35

32 32 27 26 24 22

29 23 25 26

31 18 23 23 23

12 14

Coarse sand (l-O.5 mm)

DISTRIBUTION

21 30 30 28 7 17 24 18 29 28

Britannia 19 23 23 21 Danum 11 15 19 15 20 20 Isca (78-l 4.3 21 18 17

1)

(78-12)

II (78-13)

2.4 25 12 9.9

29 36 38 37 36

Britannia 22 26 24 26 19

I (78-14)

38 39

BRITANNIA

0.3 6 2.6 1.4

1 3.6 4.3 4.2 7.2 7.5

3.8 4.2 4.2 5.7

4.6 5.9 3.9 4.5 6.3

6.6 6.6

Very line sand (0.10-0.05 nun)

PLATFORM,

Fine sand (0.25-0.10 mm)

% by mass Hatherton (78-15) 21 23

Medium sand (0.5-0.25 mm)

OF SOILS ON THE DANUM

100 95 97 98

99 % 92 82 94 92

97 95 95 96

95 92 93 94 93

83 88

Total sand

RANGE

-

0 3 2 2

1 2 2.8 4 2.5 2.8

1.5 2.8 2.8 2.2

2 2.2 2.2 2.2 2.8

12 7

silt (50-2 pm)

-

0 2 1 0

0 2.5 5.5 13 4 4.5

1.2 2 2 2.5

3 5 5 4.2 4.2

5 5

Clay (<2 pm)

F

2

8 2

O-5

04

48-83 83-86

O-5

62-67 14-62

0.5-20 45-75 75-82

O-17 4&100

Cln

B2

C3n IIB2b

B2

C2n IIB2b

B2 C2n IIB2b

B2 C2n

4 3

3 4 3-4

4

4

4 3

4

3

Mica

1 2

1 2 1-2

2

1

2 1

l-2

2

Vermiculite

OF MINERALS

A

1

-

l

-I

--

-

-

Danum (78-12) 2 1 Isca (78-11) -

-

-

Britannia II (78-13)

1 1-2

1 1 1

-1

1

11

1

Britannia I (78-14) 2-3

1

Chlorite

4 4

4 4

4

4

44

4

4

Quartz

BRITANNIA

2.7 1.4

6.5 2.3 1.7

32.1

2.4

2.2 4.2

3.1

1.4

10 Al14 A

PLATFORM,

8 11

9.3 9.6 12

9.1 8.8

6.8

8.6 6

6.3

7.8

10 d; Height/width

RANGE“

1 = 1 to 17%; 1-2 = 18 to 22%; 2 = 23 to 37%;

wm) OF SOILS ON THE DANUM

Mica-vermiculite

(~2

Hatherton (78-15) -

B

FRACTION

Vermiculite

IN THE CLAY

NOW. See Figure 3 for locations of soil profiles. u Numbers refer to relative abundance based upon X-ray diffraction peak heights (001 reflections): 2-3 = 38 to 42%; 3 = 43 to 57%; 3-4 = 58 to 62%; 4 = 63 to 77%.

Depth (cm)

5. DISTRIBUTION

Horizon

TABLE

gVI

;? 2 z z

F

$ b

5 ii

2 2

244

BOCKHEIM

deposition is the major source of these anions, as well as Cl-. Whereas soils in coastal areas of Antarctica are enriched in Cl -, soils occurring further inland are commonly enriched in NO,- and SOd2- (Claridge and Campbell, 1977; Keys 1980). Soils along the polar plateau commonly contain a predominance of N03-. Snow originating from the polar plateau is enriched in NO,and SOd2- (Wilson and House, 1965a; Boutron et al., 1972; Delmas et al., 1982). The N03- has been attributed to auroral furation in the upper atmosphere (Wilson and House, 1965b) and to marine sources (Claridge and Campbell, 1968). The ratios of ions in Antarctic snow and ice change from the coast inland (Brocas and Delwiche, 1963). Keys (1980) reported that the ratios of N03- to Cl- and SOd2to Cl- in salt efflorescences increase with distance from the coast. Ratios of Cl- to N03- + SOd2- (mmole liter- ‘) in soils of the Darwin Mountains, which are influenced by marine air masses, generally are greater than 0.1, whereas in the Britannia Range, which receives snow-laden katabatic winds from the polar plateau, they are less than 0.1 regardless of relative soil age (Table 3). There appears to be a difference in the extent of salt movement in soils of the Darwin Mountains and the Britannia Range. Whereas the Cl- to NO,- + SOd2- ratio generally increases with depth in soils of the Darwin Mountains, possibly due to greater leaching of Cl-, these ratios changes little with depth in soils in the Britannia Range (Table 3). Although the total amount of salts in the upper 70 cm of the profiles in the Hatherton Glacier area is quite variable, there is a greater amount of salts in soils of the Britannia Range than in equivalent-aged soils of the Darwin Mountains. This may reflect warmer soil temperatures and more melting on soils in the north-facing Britannia Range versus the south-facing Darwin Mountains, and/or more total precipitation from blowing polar

ET AL.

snow in the Britannia Range than in the Darwin Mountains. In summary, climate affects the origin and distribution of salts in soils of the Hatherton Glacier area. Soils in the Darwin Mountains contain a greater proportion of Cl- and a lower proportion of N03- than soils in the Britannia Range, reflecting a greater marine influence and a lesser influence from the polar plateau. The total amount of salts in the profile is greater in the Britannia Range than in equivalent-aged soils in the Darwin Mountains because of greater total snowfall input, lesser leaching, and possibly warmer soil temperatures. Stratigraphic

Significance

of Buried Soils

Buried soils were observed throughout the Hatherton Glacier area, particularly on the Danum Platform in the Britannia Range (Figs. 4 and 6). Buried soils were recognized on the basis of an increase in hue, the occurrence of ghosts and buried ventifacts below the C horizon of the surface soil, and an increase in salts and coherence. The thickness of the buried B2 horizon increases slightly with increasing soil age. Similarly, the EC and total salts in the buried B horizon increase progressively with increasing relative soil age (Table 3). From a stratigraphic standpoint, the buried soils may demonstrate that at least four glacial advances have occurred on Danum Platform. The area1 extent of the buried soils can be traced to the surface of the next distal moraine in the sequence. The occurrence of buried soils with relatively undisturbed horizons complete with ventifacts preserved in place suggests that the soils have not been eroded despite having been overridden by an expanded Hatherton Glacier. In addition, the anion rates of the buried B horizons are similar to anion ratios of the surface B horizons for those soils on the Danum Platform. From this it could be inferred that there has not been significant leaching of anions, at least to a depth of 75 cm.

ANTARCTIC

DISCUSSION:

GLACIAL

GLACIER

HISTORY

Former Ice Surface Profiles Our geologic mapping and soil studies permit reconstruction of the former longitudinal ice surfaces of Hatherton and lower Darwin Glaciers. Because they connect the Ross Ice Shelf and the East Antarctic polar plateau, these profiles are important clues to Antarctic glacial history. The Britannia ice surfaces are based on projection of drift limit elevations from icefree areas onto the longitudinal profile of Figure 7, whose position is shown in Figure 1. The Britannia II drift limit is clearly preserved, and hence determines the longitudinal surface profile (Fig. 7), between Venta Platform and Bellum Valley in the Britannia Range (Fig. 3) and between Lakes Hendy and Wellman in the Darwin Mountains (Fig. 4). Bellum Valley itself is marked by striated bedrock and basal till, it lacks clear drift limits. The most likely explanation is that ice flowing over the threshold at the head of Bellum Valley was a tributary of Hatherton Glacier during Britannia II glaciation. Because of this situation, we projected relative elevations of drift limits from Smith Valley and Darwin nunatak (Fig. 1) onto the profile to control the inland segment of the Britannia II ice surface. The Britannia II ice-surface profile in Figure 7 had to be extrapolated downglacier from Lake Wellman because drifts alongside lower Darwin Glacier do not form sequences with sharp boundaries and hence cannot be employed for reconstructing indisputable former profiles. This extrapolation is a simple projection of the nearly continuous elevation control on the upper limit of Britannia II drift. The result is a nearly flat profile that rises above lower Hatherton and Darwin Glaciers. This flat profile is consistent with the fact that undifferentiated drift high in the Brown Hills and on Diamond Hill beside lower Darwin Glacier shows soil development compatible with that of Britannia II drift beside Hatherton

FLUCTUATIONS

245

Glacier, despite differences in parent materials. The Britannia I ice-surface profile in Figure 7 is based on well-preserved Britannia I drift limits between Venta Platform and Bellum Valley in the Britannia Range (Fig. 3) and near Lake Hendy in the Brown Hills (Fig. 4). The Britannia II ice surface shows thickening of 100 m at its inland extremity, 250 m near Bellum Valley, and 450 m in middle reaches of Hatherton Glacier (Fig. 7). Downglacier extrapolation of the Britannia II ice surface suggests thickening of 1100 m above the present Ross Ice Shelf surface. The Britannia I ice surface is parallel to, but 50-100 m below, the Britannia II profile along Hatherton Glacier. The Danum ice surface is parallel to, but 50-100 m above, the Britannia II profile along much of Hatherton Glacier. We could not reconstruct Isca ice profiles because appropriate drift limits are not widely preserved. The Britannia II ice surface affords a limit of 100 m on the rise of the adjacent East Antarctic polar plateau coincident with substantial thickening near the Ross Ice Shelf. Our leading explanation is that this behavior reflects the damming effect of thick blocking ice near the mouth of Darwin Glacier. Because they parallel the Britannia II ice surface, the Britannia I and Danum profiles likewise reflect thick blocking ice. The presence of such thick blocking ice implies repeated grounding of the Ross Ice Shelf near Darwin Glacier. We acknowledge that our data permit the alternative explanation that increased ice flow from the polar plateau caused thickening of Hatherton and Darwin Glaciers. A critical test would be whether the 100-m thickening recorded at the glacier heads dies out at the plateau edge or continues inland unabated. We lack the information from inland ice-free areas to perform this test. In order to select between these explanations, therefore, we must compare the Hatherton ice-surface profiles with similar profiles farther north in the Taylor Valley/

246

BOCKHEIM

lUJOU8ld

umuaa

ET AL.

ANTARCTIC

GLACIER

FLUCTUATIONS

247

McMurdo Sound area, where ice-sheet ice surface would have been about 170 m grounding is firmly documented. This com- higher than present for Hatherton Glacier parison is based on numerical and relative to have dammed the high lake dated at 8430 chronologies in both areas. + 140(QL-1406) to 9420 + 140yr B-P. (QL1407). Subsequent ice-surface decline Hatherton Area 14C Chronology would have allowed progressively lower Radiocarbon dates listed in Table 6 af- lakes at 7770 + 180 (QL-1413) and 4040 + ford age control on Britannia and Hather- 40 yr B.P. (QL-1410). Although such an inton drifts and hence on their ice-surface terpretation is plausible because of the conprofiles in Figure 7. The most important i4C sistent pattern of most of the dates plotted samples come from near Lake Wellman in Figure 4, the presence of a young algae (Fig. 4), but other ice-free areas beside sample dated to 5740 2 90 yr B.P. (QLHatherton and Darwin Glaciers also af- 1411) shows that the alternate interpretaforded pertinent samples (Figs. 1 and 3). tion of non-ice-dammed lakes is equally These samples consist of blue-green algae plausible. Therefore, the most conservative that grew in former lakes on Britannia and course is to interpret these 14Cdates simply Hatherton drifts. Such algae is now pre- as minimum values for ice recession from served among and beneath surface clasts on the sample sites. drift surfaces. A second sequence of 14Cdates of former How should 14Cdates of these algae sam- lakes on Britannia and Hatherton drifts ples be interpreted? Present-day lakes oc- comes from near Derrick Peak (Fig. 1). The cur in kettles and small depressions on Bri- results do not show a clear pattern of age tannia and Hatherton drifts or else are with elevation. Therefore, the 14Cages are dammed by Hatherton Glacier (Figs. 3 and taken simply as minimum values for ice re4). 14Cdates of algae from former lakes of cession from the sample sites. either type afford minimum ages for underOther 14C dates supplement the Lake lying drift. Algae from glacier-dammed Wellman and Derrick Peak chronologies lakes can also afford ages for former more- (Figs. 1 and 4). At Tentacle Ridge beside extensive ice margins. Darwin Glacier, algae from a former lake Figure 4 shows drift sheets and 14Csam- on Britannia drift yielded a 14C date of ple sites near Lake Wellman. The Britannia 10,250 + 60 yr B.P. (QL-1421). 14Cdates of and Hatherton drift surfaces on which the algae from former lakes indicate ice recessamples occur slope uniformly toward sion from Britannia drift near the present present-day Lake Wellman and Hatherton glacier margin by 5210 ? 40 yr B.P. (QLGlacier. Each 14Cdate is minimum for gla- 1424)in Bibra Valley (Fig. 3), 5670 + 120yr cier recession from the sample site. Hence, B.P. (QL-1415) near Derrick Peak, 6020 2 Britannia drift antedates 9420 + 140yr B.P. 50 yr B.P. (QL-1423) in Onnum Valley, and (QL-1407) near its outer limit and is older 5740 + 50 yr B.P. (QL-1418) in the Brown than 7770 + 180yr B.P. (QL-1413) and 7400 Hills (Fig. 1). Recession from Hatherton + 170yr B.P. (QL-1412) about halfway be- drift in Magnis Valley occurred prior to tween its outer limit and Lake Wellman. 5270 + 40 yr B.P. (QL-1422) (Fig. 1). Figure 7 shows all available 14C dates Near the present-day glacier, Hatherton drift antedates 4040 + 40 yr B.P. (QL- from the Hatherton Glacier area projected onto former longitudinal ice-surface pro1410). A second type of information emerges if the former lakes represented by files. Ice recession from the Britannia II the 14C samples were dammed by Hather- drift limit antedates 9420-10,250 yr B.P., ton Glacier, similar to present-day Lake and the ice surface was very close to its Wellman. In such a situation, the topo- present level by 5740-6020 yr B.P. The graphical profile in Figure 4 shows that the available 14Cdates are consistent with, but

248

BOCKHEIM TABLE6.

ET AL.

RADI~~ARBONDATESFROMTHEHATHERTONGLACIERAREA

Laboratory number

“C Date (yr B.P.)

QL-1404

9320 f 60

Near Lake Wellman, Darwin Mountains. See Figure 4.

Blue-green algae in place. Occurs beneath and among surface clasts on drift sheet distal to Britannia II drift boundary. Represents a former lake that covered sample site. Postdates deposition of drift.

QL-1405

8790 f 140

Do.

Blue-green algae in place. Occurs beneath and among surface clasts on Britanma drift sheet. Represents a former lake that covered sample site. Postdates deposition of Britannia drift at sample site.

QL-1406

8430 f 140

DO.

DO.

QL-1407

9420 f 140

DO.

DO.

QL-1413

7770 2 180

DO.

DO.

QL-1411

5740 f 90

DO.

DO.

QL-1412

7400 + 170

DO.

DO.

QL-1408

4010 + 50

Do.

DO.

QL-1409

1710 2 40

DO.

DO.

QL-1410

4040+40

DO.

Blue-green algae in place. Occurs beneath and among surface clasts on Hatherton drift sheet. Represents a former lake that covered sample site. Postdates deposition of Hatherton drift at sample site.

QL-1424

5210 + 40

Bibra Valley, Britannia Range. See Figure 3.

Blue-green algae in place. Occurs beneath and among surface clasts on Britarmia I drift sheet. Represents a former lake that covered the sample site. Postdates deposition of Britannia I drift at sample site.

QL-1423

6020 2 50

Onnum Valley, Britannia Range. See Figure 1.

Blue-green algae in place. Occurs beneath and among surface clasts on Brikumia drift. Represents a former lake that covered the sample site. Postdates deposition of Britamria drift at sample site.

QL-1421

10,250 + 60

In valley below Tentacle Ridge, north side of Darwin Glacier. See Figure 1.

DO.

Description

Location

QL-1401

4890250

Near Derrick Peak, Brikxmia Range. See Figure 1.

QL- 1402

496ok4.0

Do.

DO.

QL-1403

4700 2 loo

DO.

DO.

QL-1415

5670 + 120

DO.

DO.

QL-1416

4320 + 50

DO.

Do.

QL-1417

3660 2 90

DO.

DO.

ANTARCTIC

GLACIER TABLE

249

FLUCTUATIONS

Lontinued

Laboratory number

14C Date (yr B.P.)

QL-1414

2130 2 40

DO.

Blue-green algae in place. Occurs beneath and between surface clasts on Hatherton drift. Represents a former lake that covered sample site. Postdates deposition of Hatherton drift at sample site.

QL-1418

5740 2 50

Brown Hills beside Darwin Glacier. See Figure 1.

Blue-green algae in place. Occurs beneath surface clasts on Britannia drift sheet. Represents a former lake that covered sample site. Postdates deposition of Britannia drift at sample site.

QL-1419

4ooo~60

Do.

DO.

QL- 1420

4510 ” 60

DO.

DO.

QL-1422

5270 e 40

Magnis Valley, Britannia Range. See Figure 1.

Blue-green algae in place. Occurs beneath and among surface clasts on Hatherton drift sheet. Represents a former lake that covered sample site. Postdates deposition of Hatherton drift at sample site.

Location

do not prove, a late Wisconsin and Holocene age for Britannia and Hatherton drifts. Correlation

of Hatherton-McMurdo

Drifts

We now correlate late Quatemary drift sheets between the Hatherton Glacier and the Taylor Valleyh4cMurdo Sound areas. We start by comparing the relative age of drifts beside upper Hatherton and Taylor Glaciers. Soil development bears on this question if time is assumed to be the predominant soil-forming factor. The justification for this assumption is that both areas have similar xerous climate, elevation range, bedrock, drift morphology, and drift composition (dolerite and sandstone). The major weakness is that our sampling of soil development is on drift sheets that are unevenly spaced in time. The results show significantly different soil morphological properties among drifts beside Hatherton and upper Taylor Glaciers. In order of increasing soil development, the drift sheets are Britannia I, Britannia II, “Taylor II”/ Bonney, Danum, and “Taylor III” (Fig. 8

Description

and Table 7). We take these results to mean that the associated fluctuations of Hatherton and Taylor Glaciers were asynchronous. We next compare drifts beside Taylor Glacier with those near McMurdo Sound. Figure 9, the basis of our discussion, shows ice profiles derived from these drifts. Taylor Glacier today drains into Taylor Valley from a small peripheral dome of the East Antarctic Ice Sheet (see Fig. 8 in Denton et al., 1989). The “Taylor I” ice surface represents minor expansion. The “Taylor II”/ Bonney ice surface represents thickening of 100-300 m along most of the glacier length, except near the polar plateau where the ice level rose only a few tens of meters. The Taylor III ice surface can be shown only along portions of the glacier, because pertinent drift is fragmentary. The Ross Sea ice surface in Figure 9 reflects an extensive grounded ice sheet in McMurdo Sound (Denton et al., 1989). Although not surficially exposed in Taylor Valley, Marshall drift along the west coast of McMurdo Sound represents a grounding episode

250

BOCKHEIM TABLE7.

ET AL.

SUGGESTED CORRELATIONSOF Dmrr SHEETS INHATHERTONGLACIERAND MCMURDO SOUNDITAYLORVALLEY AREAS McMurdo

Hatherton Glacier Area (this paper)

McMurdo

Sound/Taylor Valley Area (Denton et al., 1989)

Sound

Taylor Glacier “Taylor I” drift

Hatherton drift Britannia I drift Britannia II driR

Ross Sea drift

Danum drift

Marshall drift

“Taylor II”/Bonney “Taylor III”

older than the Ross Sea episode (Dagel et al., 1989; Denton et al., 1989). Radiocarbon dates show that the outer portion of Ross Sea drift is late Wisconsin (Stage 2) in age and that “Taylor II”/Bonney drift antedates the late Wisconsin (Denton et al., 1989). U/Th dates place “Taylor II”/ Bonney drift in marine isotope Stage 5, and Marshall drift in Stage 6 (Denton et al., 1989; Dagel et al., 1989). The asynchronous

drift

drift

behavior of Taylor Glacier and grounded ice sheets in McMurdo Sound implied by numerical dates is supported by crosscutting drifts in middle Taylor Valley. Here Ross Sea drift overlaps and therefore is younger than “Taylor II”/Bonney drift (Denton et al., 1989). We conclude by outlining the most likely correlations of drifts beside Hatherton Glacier with those near McMurdo Sound. Soil

30

25

10

5

Britannia

I

Britannia

II

“Taylor

II*

DWIUIll

'Taylor III*

FIG. 8. Comparison of morphological properties of soils from drift sheets beside Hatherton Glacier and from drift sheets in Arena and Beacon Valleys beside upper Taylor Glacier described in Denton et al. (1989). “Taylor I,” “ Taylor II,” and “Taylor III” are temporary names for drift sheets alongside upper Taylor Glacier. Taylor II drift corresponds with Bonney drift in Taylor Valley.

.-5 H 2 w

1

---

Distance

from

Explorers

Cove

(km)

m

PreHnt

ice surtace

I” ice surtace

II” I Bonny

‘Taylor

Taylor -------------

,,,” ,oe *“llaC*

ice surface

ROSS %a ‘-Taylor

----------------ice sutlsce

FIG.

9. Present and former longitudinal ice surfaces of Taylor Glacier and in Taylor Dry Valley. Drift elevations are projected onto the profiles from adjacent ice-free areas. See Figure 12a of Denton er al. (1989) for position of T’-T”““.

0

500

1000

1500

2500

3000

3500

T”’

252

BOCKHEIM

development cannot be used for direct correlation because of differing lithologic composition of drifts in the two areas. We start by noting that “Taylor II”/Bonney drift is older than Britannia drifts near Hatherton Glacier (soil development) and older than Ross Sea drift near McMurdo Sound (crosscutting relationships and numerical dates). This suggeststhat one or both of the Britannia drifts corresponds with Ross Sea drift. In view of our previous discussion in which we argued that Britannia I and II drifts represent the same glaciation, we think that the Britannia II drift limit most likely corresponds with the Ross Sea drift limit. However, there are several alternative correlations, given the potential problems with using soil development to compare drift sequences. One is that the Britannia I drift limit corresponds with the Ross Sea drift limit and that the Britannia II limit is older (isotope Stage 4?). We think this alternative is not likely because it implies two grounding episodes in McMurdo Sound subsequent to the “Taylor II”/Bonney advance, a situation not shown in the geologic record. A second alternative is that the Britannia I drift limit is older than late Wisconsin. We also think this alternative to be unlikely, because it means that there would be no equivalent in the Hatherton Glacier area of the massive Ross Sea grounding event in McMurdo Sound. We finish by noting that Danum and Marshall drifts are both immediately older than “Taylor II”/Bonney drift by our relative and numerical chronologies. Therefore, the line of reasoning used previously suggests correlation of these drifts and assignment to isotope Stage 6. Summary

Table 7 shows our preferred correlation of Hatherton-McMurdo drifts. The results support our previous contention that the Britannia and Danum profiles represent a damming effect on the Hatherton and Darwin Glaciers of a grounded Ross Ice Shelf.

ET AL.

If this is correct, repeated grounding of ice sheets in the Ross Embayment near the Transantarctic Mountains dominated late Quatemary glacial history. The Hatherton and Darwin Glaciers, both East Antarctic outlets through the Transantarctic Mountains, fed these ice sheets. Through-flowing East Antarctica outlet glaciers were not present in the McMurdo Sound/‘I’aylor Glacier area. Consequently, grounded ice flowed into McMurdo Sound from the Ross Sea and sent westward-flowing ice lobes into Taylor Valley. The last grounding episode occurred during late Wisconsin time, as dated in Taylor Valley (Stuiver et al., 1981; Denton et al., 1989). Recession began in late Wisconsin and was completed in Holocene time (Stuiver et al., 1981; Denton et al., 1989) and the Hatherton Glacier had dropped from the Britannia drift limits to near its present configuration by 574&6020 yr B.P. and from the Hatherton drift limit by 5270 yr B.P. The penultimate grounding episode occurred during deep-sea isotope Stage 6. This chronology is consistent with sea-level control of grounded-ice events in the western Ross Embayment, for it closely fits the marine oxygen isotope record (which reflects sea level) through at least the past 200,000 yr (Denton et al., 1989, Fig. 14). Why would Hatherton and Taylor Glaciers have fluctuated asynchronously as suggested by geologic and soil data? The major difference is that Hatherton and the lower Darwin Glacier are through flowing into the Ross Ice Shelf, whereas Taylor Glacier terminates in an ice-free valley. Hence, the out-of-phase behavior most likely reflects repeated grounding of an ice sheet in McMurdo Sound and the southwestern Ross Embayment that dammed HathertonDarwin but not Taylor Glacier. We have already noted that Britannia ice surfaces are consistent with thick blocking ice near the Ross Ice Shelf. The effect of such blocking on the ice profile was greatest in middle and lower reaches and least in

ANTARCTIC

GLACIER

upper reaches of the glacier near the polar plateau. Because it drains high-elevation ice and terminates in Taylor Valley, Taylor Glacier, along with other alpine glaciers in the Dry Valleys, can fluctuate independently of the Ross Ice Shelf. Major sealevel changes induced by Northern Hemisphere ice sheets are the most probable cause of the ice-sheet grounding episodes in the Ross Sea (Hollin, 1962; Stuiver et al., 1981), although changes in subice shelf melting might also have been important. The most likely explanation for the outof-phase behavior of Taylor Glacier is varying precipitation during glacial/interglacial cycles. CONCLUSIONS (i) The Britannia I, Britannia II, and Danum drift limits produce former longitudinal profiles for Hatherton/lower Darwin Glaciers that are close to the current ice surface near the polar plateau but rise far above the present surface near the Ross Ice Shelf. The Hatherton drift limit produces a profile that is uniformly 20 to 70 m above the current ice surface. (ii) From a correlation exercise of drifts in the Hatherton Glacier and McMurdo Sound areas, we match Britannia II and outer Ross Sea drifts, as well as Danum and Marshall drifts. Britannia I drift represents a readvance superimposed on general recession from the Britannia II drift limit. This means that Britannia II drift is late Wisconsin (isotope Stage 2) and Danum drift equivalent to isotope Stage 6 in age. (iii) From their configuration and age, we conclude that the Britannia and Danum profiles represent thickening of Hatherton and Darwin Glaciers in response to Ross Ice Shelf grounding during the global glaciations of Stage 2 and Stage 6, respectively. Radiocarbon dates indicate that recession of Hatherton Glacier to near its present level occurred by 5740-6020 yr B.P. (iv) The Hatherton drift is older than 5270

2.53

FLUCTUATIONS

yr B.P. and probably represents recession of the grounding line to its current position. ACKNOWLEDGMENTS This research was funded by the Division of Polar Programs of the National Science Foundation. We appreciate the assistance of personnel at the Darwin Camp and the LC-130 and helicopter support of VXE6. J. F. Splettstoesser aided greatly in scheduling logistic support, R. Ackert, hi. Leinmiller, T. V. Lowell, and P. J. Wolcott assisted in the field work. Laboratory analyses were conducted by J. E. Leide and K. J. Zuelsdorff. T. J. Hughes, J. E. Leide, M. L. Prentice, J. F. Splettstoesser, and D. E. Sugden greatly improved early versions of the manuscript. R. Kelly drafted the maps and longitudinal sections. N. Kealiher processed the manuscript. B. K. Lucchitta provided Figure 2.

REFERENCES American Public Health Association, American Water Works Association, Water Pollution Control Federation. (1975). “Standard Methods for the Examination of Water and Wastewater,” 14th ed. Anonymous. (1977). “Nitrate and Nitrite in Water and Seawater.” Industrial Method No. 158-71 W/A. Technicon Industrial Systems, Tarrytown, NY. Bockheim, J. G. (1979). Relative age and origin of soils in eastern Wright Valley, Antarctica. Soil Science 128, 142-152.

Bockheim, J. G. (1982). Properties of a chronosequence of ultraxerous soils in the Trans-Antarctic Mountains. Geoderma 28, 239-255. Boutron, C., Echevin M., and Lorius, C. (1972). Chemistry of polar snows. Estimation of rates of deposition in Antarctica. Geochimica et Cosmochimica Acra 36, 1029-1041. Brocas, J., and Delwiche, R. (1963). Chloride, K, and Na concentrations in Antarctic snow and ice. Journal of Geophysical

Research

68, 39994OOQ.

Buntley, G. J., and Westin, F. C. (1%5). A comparative study of developmental color in a chestnutchemozem-brunizem soil climosequence. Soil Science Society

of America

Proceedings

29, 579-582.

Campbell, I. B., and Claridge, G. G. C. (1975). Morphology and age relationships of Antarctic soils. In “Quaternary Studies” (R. P. Suggate and M. M. Cresswell, Eds.). New Zealand Royal Society Builetin

13, 83-88.

Claridge, G. G. C. (1%5). The clay mineralogy and chemistry of some soils from the Ross Dependency, Antarctica. New Zealand Journal of Geology and Geophysics 8, 186220. Claridge, G. G. C., and Campbell, I. B. (1%8). Origin of nitrate deposits. Nature (London) 217, 428-430.

254

BOCKHEIM

ET AL.

Geophysics”(R. J. Adie, Ed.). Universitetforlaget, Claridge, G. G. C., and Campbell, I. B. (1977). The salts in Antarctic soils, their distribution and relaOslo. tionship to soil processes. Soil Science 123, 377Nichols,R. L., andBall, D. G. (1964).Soil tempera384. tures,Marble Point, McMurdo Sound,Antarctica. Journal of Glaciology 5, 357-359. Dagel, M. A., Hendy, C. H., Denton, G. H., and Stuiver, M. (1989).Stratigraphyandchronologyof Stuiver, M., Demon,G. H., Hughes,T. J., andFastook, J. L. (1981).History of the marineice sheetin Stage6 and2 glacialdeposits,MarshallValley, AntWestAntarcticaduringthe lastglaciation:A workarctica.Boreas,in press. ing hypothesis.In “The Last Great Ice Sheets” Day, P. R. (1%5).Particlefractionationandparticle(G H. DentonandT. J. Hughes,Eds.),pp. 31w36. sizeanalysis.In “Methodsof SoilAnalysis” (C. A. Wiley-Interscience,New York. Blacket al., Eds.),Part 1, pp. 545-566.Agron. No. Ugolini, F. C. (1964).Soil investigations in the lower 9, AmericanSocietyof Agronomy,Madison,WI. Wright Valley. In “PermafrostInt. Conf., ProceedDelmas,R., Briat, M., and LeGrand, M. (1982). ings,Natl. Acad. Sci., Nat. ResourceCoun.Publ., Chemistryof south polarsnow.Journal ofGeophys1287,61: ical Research 87,4314-4318. Ugolini,F. C., andAnderson,D. M. (1973).Ionic miDenton,G. H., Bockheim,J. G., Wilson,S. C., and grationand weatheringin frozen Antarctic soils. Stuiver, M. (1989).Late Wisconsinand early HoSoil Science 115, 461470. loceneglacialhistory,innerRossEmbayment,Ant- Weyant, W. S. (1%7). “The Antarctic Atmosphere: arctica.Quaternary Research, 31, 151-182. Climatologyof the SurfaceEnvironment.”AntarcGiovinetto, M., and Bull, C. (1987).Summaryand tic Map Folio Series.Folio 8. AmericanGeographanalysisof surfacemassbalancecompilations for ical Society,New York. Antarctica, 1960-1985. Byrd Polar Research Center Weyant, W. S. (1966).Antarctic climate.In “AntReport 1, l-90. arctic SoilsandSoil FormingProcesses”(J. C. F. Tedrow, Ed.), Antarctic ResearchSeries,Vol. 9, Haskell,T. R., Kennett, J. P., and Prebble,W. M. pp. 47-59.AmericanGeophysicalUnion,Washing(1965).Geology of the Brown Hills and Darwin ton, DC. Mountains, southernVictoria Land Antarctica. Wilson,A. T., and House,D. A. (1%5a).Chemical Transactions of the Royal Sociev of New Zealand composition of South Polarsnow.Journal of Geo2, 231-247. physical Research 70, 5515-5518. Hollin, J. T. (1%2).On the glacialhistory of AntarcWilson,A. T., andHouse,D. A. (l%Sb). Fixation of tica. Journal of Glaciology 4, 173-195. nitrogenby auroraandits contributionto the nitroKeys, J. R. (1980).“Saltsandtheir distributionin the genbalanceof theearth.Nature (London) 205,793McMurdo region,Antarctica.” Ph.D. dissertation, 194. Victoria University, Wellington. Yaalon,D. H. (1%5).DownwardmovementanddisLaPrade,K. E. (1971).Preliminaryreporton petrolotributionof anionsin soilprofdeswith limitedwetgy of the BeaconSupergroup,ShackletonGlacier ting. In “Experimental Pedology” (E. G. Hallsarea, QueenMaud Range,TransantarcticMounworthandD. V. Crawford,Eds.),pp. 157-164.Buttains, Antarctica, In “Antarctic Geology and terworth, London.