IMMEDIATE SCIENCE REPORT
K047: Climate and Landscape History from shallow Drilling in the Dry Valleys
Antarctica New Zealand 2002/03
1 Popular Summary of Scientific Work Achieved
A model to explain the occurrence of ground ice in glacial sediments and bedrock at high altitudes (>1000m) throughout the Dry Valleys where liquid water is rare was developed from work on Table Mtn. (Dickinson and Grapes 1997; Dickinson and Rosen 2003). The model is based on mineralogical, chemical and isotopic analyses of ground ice and frozen sediments that come from cores of Sirius Group sediments at Table Mtn. It indicates that the ground ice and diagenetic minerals accumulated over long periods of time from atmospheric water vapour and brine films formed on the surface of the ground. Although this model may apply at Table Mtn. for the very old glacial sediments of the Sirius Group, it has yet to be tested at other locations in the Dry Valleys.
Sugden et al. (1995) reported occurrence of massive ground ice believed to be at least 8 Ma old from Beacon Valley but this age was obtained by indirect dating of presumed in situ volcanic ash. Ice similar to that of the Beacon Valley was discovered in Pearse Valley during field season 2001/02. Pearse Valley ice originates from either the Taylor or local Schlatter glacier, but the main objective of this project is to establish whether it has the potential to yield palaeoclimatic data. In the 2002/03 season, massive ice was also found in Victoria Valley. Some of this ice was left behind by the retreat of the Lower Victoria glacier but other occurrences appear to have fed from the subsurface by ground water.
The field programme of the 2002/03 season aims to obtain representative cores and samples of this ice for isotopic dating and chemical analysis. Evaluation of analytical results may lead to deep core drilling of some of the sites to clarify further the glacial history of Pearse and Victoria Valleys
2 Proposed Programme
To investigate the nature and origin of massive ground ice and to establish whether it has the potential to yield palaeoclimatic data, a set of shallow ice cores and samples are needed for chemical analysis and cosmogenic isotope dating. The pits to be cored should represent the known distribution of the massive ground ice. In addition to the ice core pit soil profiles will be obtained by sampling the pit walls and the surface material on site to clarify any possible relationship of the ice and the overlying sediments. Evaluation of analytical results may lead to further shallow core drilling of certain sites in the future.
3 Scientific Endeavours and Achievements
Various people from the event spent 24 days in the field from 16 Nov to 9 Dec. Daniel Pringle (VUW) from K131 joined K047 at Table Mountain to reprogram the data loggers on two temperature probes for 2003. Samples and soil pits were dug as outlined in Table 1. Soil pits were generally dug either in the centers of polygons or between them, and in locations picked in relation to the previous pits containing massive ground ice. Polygon centres are thought to be the least active area and hence should contain the oldest most chemically developed soil.
The following method was used in digging most all of the soil pits: In the area to be excavated (1m × 1m × .5m), the surface material was scrapped off and placed on a 2m square polythene tarpaulin. The underlying soil was then dug out and placed on another 2m square polythene tarpaulin. Loose soil material was dug to a depth of one metre or the top of the ice-cemented soil which ever was the shallowest. After the final pit depth, soil profile and possible permafrost or massive ground ice were described and sampled, all material from the respective polythene tarpaulins was replaced. The ground surface was raked and swept to restore as much as possible of the original appearance. Analyses of the samples will include; OSL (Optically Stimulated Luminescence) of selected dune and pit soil samples, stable oxygen and hydrogen isotopes and 10Be dating for the ice core, and major cation and anion chemistry of soluble salts for the soil samples.
The term "ground ice" refers to all types of ice formed in freezing and frozen ground (Permafrost Subcommittee, 1988 p 46). Permafrost refers to the permanently frozen (<0° C) condition and includes both dry and wet (ice) materials. "Massive ground ice" in this report refers to clear ice with a variable content of sediment >10% of the ice by weight.. Subsurface conditions in the Dry Valleys are generally different from those in arctic and alpine environments in that there is usually 30 to 60 cm of dry frozen sediments above ice cemented sediments. However, because most workers think of permafrost as ice cemented, the term permafrost in this report will include only the ice cemented materials.
The Table Mountain camp site was chosen close to the temperature probes on a patch of snow at S77°57.631′ E161°57.324′, altitude 1850m. We experienced winds of up to 40 knots with the temperatures remaining relatively constant around –18 °C.
On the floor of Columnar Valley (adjacent to Table Mtn) polygons have a diameter of 4-10 m and <1 m height differential between trough and polygon centres. Polygons extend from the valley floor up the valley walls up to slopes dipping up to 25° right to the debris flow boundary. The distribution and appearance of the surface material of the polygons in Columnar Valley varies with some polygons having a "brick wall-like page 4 appearance with whilst others were covered by randomly distributed boulders and cobbles of varying sizes.
Six pits were dug in total and in all pits permafrost was encountered at depths between 7 and 16 cm. Three pits dug in the cracks between the polygons contained clear ice at depths between 14 and 23 cm. The permafrost boundary appears to follow the surface topography of the polygon.
In general, the activity of any single polygon or part of it may be reflected by the distribution of the material in the troughs. Parts of troughs are flat having been filled with sand while other parts are steep and rocky with angular cobbles and boulders. This angular material may be sorted or unsorted. On the active part of a polygon, clasts may roll off the steep sides and into the trough. Sorting of clasts in the trough may occur by what the center crack is able to accommodate. On the inactive part of a polygon, wind blown sand may accumulate in the trough. This observation suggests that polygon activity may be dynamic so parts of it are active while at the same time other parts are inactive.
A major problem apparent from the fieldwork is to understand what controls the age of the surface and the relationship to polygon development in Columnar Valley. Alternatively, it may be the ice content below the surface that controls polygon development. Soil development and age may be more of a function of the material, aspect and moisture regime, rather than the depositional age of the material in which the soil is forming.
Our camp in Pearse Valley was on an alluvial terrace located at the eastern edge of Lake House (325m; S77°42.101′ E161°26.924′) and was selected for its proximity to a source of water (Schlatter Glacier). Wind direction and strength seems highly variable throughout the valley and diurnal variations were common. During the field visit, winds did not exceed 20 knots and seemed strongest from 2 – 5 am. Pearse Valley contains mostly glacial deposits representing the retreat of the main Taylor Glacier and subsequent retreat of the lateral valley glaciers. Polygonal ground covers 40 – 50% of the valley floor and slopes at different altitudes.
About 10% of the valley floor is covered by sand from eolian deposition and this does not include numerous pockets of sand lodged in troughs of polygons and in other sheltered areas. Much of this sand is protected by a lag of 5 – 8 mm granules and therefore is not mobile under winds of about 50 knots. Much of the sand probably came from stream systems draining meltwater from the retreating glaciers. The main sand dune, climbing the northeast slope of the valley apparently has brine flowing on top of ice cemented sand which accumulates in salt pond (dry on the surface) at the base of the dunes.
Sixteen pits were dug out of which three were also cored and sampled for OSL and soil chemistry. Depth to ice cement and massive ground ice under moraines varied from 0.25 m to >1m and was encountered in 8 out of 16 pits. In the eastern part of the valley clear ice was found extruding from a slope side of what looked like a gelifluction lobe. It is not clear what factors control the depth to ice cement and the massive ground ice but aspect and moisture regime do not seem to have a direct relationship.page 5
In addition to the ice core and soil samples a comprehensive set of hand specimens and surface material was collected. These samples represent the petrologic modal distribution in the till within the valley and reflect the different source areas from which they were transported (ie. direction of glacial transport).
The massive ground ice possibly represents an ice cored moraine which may have derived from the Schlatter Glacier. The surface of this ice is smooth and undulating and it is not clear how the contact between it and loose sand above can be so sharp. Why there is not ice cemented sand above, suggests the clear ice is ablating under the sand. Although the clear ice seems to have a limited extent, it may have a greater extent if it lies below ice cemented soil in other parts of the valley. It is also possible that the ice is somehow related to development of patterned ground which in Pearse Valley is still of relatively limited extent. Initial visual analysis of the ice core at Scott Base confirms the appearance of remnant basal glacier ice. If the ice originates exclusively from ancient glaciers it should be geochemically distinguishable from modern glacier ice.
If the massive ground ice in Pearse Valley is remnant ancient glacier ice it is the oldest preserved ice on earth and has the potential to significantly expand the current palaeoclimatic record obtained from ice cores. Furthermore, preservation of ancient basal glacier ice underneath the valley floors would provide evidence for the stability of the climate in the area for extended periods of time despite of the Holocene climatic fluctuations.
A preliminary report on the massive ground ice descriptions and pit profiles from Pearse Valley will be published as an Antarctic Research Centre Report in June 2003. Results from the dune OSL sampling and profiling from Pearse and Victoria Valleys will be published as an Honours thesis during 2003. Copies of these will be sent to Antarctica NZ.
Further publications of the scientific results will be published in international peer-reviewed scientific journals. Copies of this work will also be sent, when available, to Antarctica NZ.page 6
|Name and Location of Pit/Drillhole/Sample||Type and approximate quantity of sample|
|TMCV-7 S77 58.071, E161 55.623||1 kg ice chunks|
|TMCV-1 S77 .58.217, E161 56.694||No samples collected|
|TMCV-2 S77 58.700, E161 58.137||No samples collected|
|TMCV-3 S77 59.135, E161 59.258||No samples collected|
|TMCV-4 S77 58.548, E161 56.096||No samples collected|
|TMCV-5 S77 58.411, E161 55.764||No samples collected|
|TMCV-6 S77 58.241, E161 55.762||No samples collected|
|PVP-1 S77 42.405′, E161 28.881′||800g soil sample|
|PVP-2 S77 42.168′, E161 30.340′||75 cm ice core, 7 soil samples totalling < 3kg, 500g surface gravel|
|PVP-6 S77 42.274′, E161 30.257′||75 cm ice core, 3 soil samples totalling < 1.5 kg; 500g surface gravel, 500g ice chips|
|PVP-16 S77 42.167′, E161 30.318′||78 cm ice core, 500g ice chips, 2 soil samples totalling < 1kg, 500g surface gravel|
|PVRG-1 S77 42.259′, E161 35.062′||1 kg ice chunks|
|PVRG-2 S77 42.211′, E161 35.242′||1 kg ice chunks|
|PV Schlatter Glacier||1 kg ice chunks|
|PV Taylor Glacier/Lake Joyce tongue,||2 kg ice chunks|
|Various locations in Pearse Valley||36 hand samples of surface lithology, totalling <10 kg|
|PVP-3 S77 42.479, E161 28.595||No samples collected|
|PVP-4 S77 42.515, E161 28.506||No samples collected|
|PVP-5 S77 42.516, E161 28.912||No samples collected|
|PVP-7 S77 42.383, E161 31.185||No samples collected|
|PVP-8 S77 42.358, E161 30.715||No samples collected|
|PVP-9 S77 42.356, E161 30.656||No samples collected|
|PVP-10 S77 42.280, E161 31.912||No samples collected|
|PVP-11 S77 42.590, E161 29.189||No samples collected|
|PVP-12 S77 42.553, E161 29.636||No samples collected|
|PVP-13 S77 42.347, E161 30.153||No samples collected|
|PVP-14 S77 42.307, E161 30.414||No samples collected|
|PVP-15 S77 42.293, E161 30.327||No samples collected|
|VV1-RB S 77 22.114′, E162 12.454′||500g soil sample|
|VV-C1 S 77 22.250′, E162 12.330′||500g soil sample|
|VV-C2 S 77 22.130′, E162 13.720′||500g soil sample|
|VV-C3 S 77 22.323′, E162 10.713′||500g soil sample|
|VV-C4 S 77 22.528′, E162 08.555′||500g soil sample|
|LB-1 S 77 22.533′, E161 54.803′||500g soil sample|
|LB-2 S 77 22.499′, E161 55.859′||500g soil sample|
|LVG-1 S 77 22.087′, E162 17.470′||500g soil sample|
|LVG-2 S 77 22.326′, E162 18.341′||500g soil sample|
|Various locations in Victoria Valley||40 hand samples of surface lithology, 20 kg|
Thanks to the following:
Prof Peter Barrett, (Director, Antarctic Research Centre, VUW)
Dean Peterson, Paul Woodgate and Jim Cowie, (Antarctica NZ)
All of the Scott Base personnel (Nov-Dec 2002)
Special thanks to Steve Brown at Scott Base for the ice core light table
Funding and Support Antarctica New Zealand, Strategic Development Fund, VUW Foundation of Research and Technology, NZ
Berg, T.E., and Black, R.F., 1966, Preliminary measurements of growth of non-sorted polygons, Victoria land, Antarctica, in Tedrow, J.C.F., ed., Antarctic Soils and Soil forming Processes: Antarctic Research Series:, American Geophysical Union, p. 61-108.
Bockheim, J.G., 1982, Properties of a chronosequence of ultraxerous soils in the Trans-Antarctic mountains: Geoderma, v. 28, p. 239-255.
Bockheim, J.G., and Ugolini, F.C., 1972, Chronosequences of soils in the Beacon Valley, Antarctica, in Adams, W.P., and Helleiner, F.M., eds., International Geography:, p. 301-303.
Dickinson, W.W., and Grapes, R.H., 1997, Authigenic chabazite and implications for weathering in Sirius Group diamictite, Table Mountain, Dry Valleys, Antarctica: Journal Sedimentary Research, v. 67, p. 815-820.
Dickinson, W.W., and Rosen, M.R., 2003, Antarctic ground ice and diagenetic minerals from atmospheric moisture and brine films: Geology (March 2003, in press).
Linkletter, G.O., Bockheim, J.G., and Ugolini, F.C., 1973, Soils and glacial deposits in the Beacon Valley, southern Victoria Land, Antarctica: New Zealand Journal of Geology and Geophysics, v. 16, p. 90-108.
Marchant, D.R., Denton, G.H., Swisher, C.C.I., and Potter, N.J., 1996, Late Cenozoic Antarctic paleoclimate reconstructed from volcanic ashes in the dry valleys region of southern Victoria Land: Geological Society of America Bulletin, v. 108, p. 181-194.
McKelvey, B.C., and Webb, P.N., 1959, Geological investigations in southern Victoria land, Antarctica. Part 2 - Geology of the upper Taylor Glacier region: New Zealand Journal of Geology and Geophysics, v. 2, p. 718-728.
Potter, N.J., and Wilson, S.C., 1983, Glacial geology and soils in Beacon Valley: Antarctic Journal of the US; 1983 Review, v. 18, p. 100-103.
Sugden, D.E., Marchant, D.R., N., P., Souchez, R.A., Denton, G.H., Swisher, C.C.I., and Tison, J.-L., 1995, Preservation of Miocene glacier ice in East Antarctica: Nature, v. 376, p. 412-414.
Ugolini, F.C., Bockheim, J.G., and Anderson, D.M., 1973, Soil development and patterned ground evolution in Beacon Valley, Antarctica: Permafrost: North American Contribution to the Second International Conference, p. 246-254.