Microclimate and weathering processes in the area of Darwin ...
relationship between the folds reported by Burgess (in press) and those described here cannot be determined from present evidence.
Findlay, R. H. 1978. Provisional report on the geology of the region between the Renegar and Blue Glaciers, Antarctica. New Zealand Antarctic Record, 1, 39-44.
Skinner (1964, 1965) named the rocks at Mt. Madison the Selborne Marble and distinguished them from the Shackleton Limestone due to their higher metamorphic grade. He suggested that they may be Precambrian in age, correlative with the Nimrod Group in the Miller Range (Grindley, McGregor, and Walcott 1964). If this is the case, deformation at Mt. Madison is probably not related to the Shackleton Limestone south of Byrd Glacier.
Grindley, G. W., McGregor, V. R., and Walcott, R. I. 1964. Outline of the geology of the Nimrod-Beardmore-Axel Heiberg Glaciers region, Ross dependency. In R. J. Adie (Ed.), Antarctic geology. Amsterdam: North-Holland Publishing.
To me, lithologies at Mt. Madison appear similar to those of the Shackleton Limestone and pelitic Dick Formation (Skinner 1965), and I would suggest that the Selborne Marble is a metamorphosed equivalent of those two formations. The metamorphic grade suggests an adjacent granitic pluton north of Mt. Madison removed and buried by Byrd Glacier. This work was supported by National Science Foundation grant DPP 76-82040. References Burgess, C.J. In press. Geology of the Shackleton Limestone (Cambrian) in the Byrd Glacier area. New Zealand Antarctic Record.
Microclimate and weathering processes in the area of Darwin Mountains and Bull Pass, Dry Valleys FRANTZ-DIETER MIOTKE
Geographisches Institut Universitat Hannover Hannover, West Germany
During December 1978 and January 19791 studied microclimate, weathering processes, and antarctic landforms in the area of Darwin Mountains (80°S) and Bull Pass, Dry Valleys (77°30'S). Antarctic rocks disintegrate by the combined action of several different processes. Joints existing due to endogenic activity (Gerber and Scheidegger 1969) open primarily because of temperature-caused tension, frost cracking, and salt fretting. Chemical weathering processes are limited to the short summer period when temperatures of rock surfaces can reach as high as 30°C and reflect daily temperature variations and moisture in rocks and soil. 14
Skinner, D. N. B. 1964, A summary of the geology of the region between Byrd and Starshot glaciers, south Victoria Land, In R. J. Adie (Ed.), Antarctic geology. Amsterdam: North-Holland Publishing. Skinner, D. N. B. 1965. Petrographic criteria of the rock units between the Byrd and Starshot Glaciers, south Victoria Land, Antarctica. New Zealand Journal of Geology and Geophysics, 8, 292-303. Skinner, D. N. B. In press. Stratigraphy and structure of lower grade metasediments of Skelton Group, McMurdo Sound—Does Teall Graywacke really exist? In C. Craddock (Ed.), Antarctic Geoscience. Madison: University of Wisconsin Press. Smithson, S. B., Fikkan, P. R., and Toogood, D. J . 1970. Early geologic events in the icefree valleys, Antarctica. Geological Society of America Bulletin, 81, 207-210. Stump, E., Sheridan, M. F., Borg, S. G., Lowry, P. H., and Colbert, P. V. 1980. Geological investigations in the Scott and Byrd Glacier areas. Antarctic Journal of the U.S., 14(5), 39-40.
Daily temperatures were recorded by thermistors installed: 1. Into dark dolorites, light sandstones, and granites having different albedos; 2. Into small rocks, large boulders, and bedrock; 3. Immediately below the rock surface, into the rock center, and under rocks; 4. Into rocks with different exposures to sun radiation; 5. Into soils down to 100 centimeters; 6. Into snow down to 70 centimeters; and 7. Along snow margins. Figure 1 illustrates the variations in temperature in rocks and soil in the Darwin Mountains. Microclimatic differences were of special interest and these proved to be considerable within very limited environments. Temperature variations within soils and rocks and their daily changes affect the existence of algae, lichens, and other microforms of life in Antarctica. Not too much is known so far about the microclimate of ice-free areas in Victoria Land. Moisture in soils is normally very low at the upper surface (to 5 centimeters deep), mostly below 0.1 percent, but it can be higher where meltwater infiltrates along the margin of snowfields. Soil moisture can be as high as 20 percent where locally existing ice (up to 20 centimeters deep, as in the Darwin Mountains) melts somewhat during summer. Due to differences in heat conductivity, daily heat flow into ANTARCTIC JOURNAL
Hellgraue Sandsteinplatte Dunkle Doloritplatte
22,23 nach Norden exponiert nach Norden exponiert 24.25
Darwin Mountains O('1
light grey sandsone plate dark dolorite plate exposed to north exposed to north
22 23 24
20
\I \','
12 18 0 6 12 18 06 .......................... 18 15.12.78 16.12.78 17.12.78 23..12 ...78
Darwin Mountains
Moränenschutt, Polygonmitte 37-44 moraine renter of nn1vunn
Figure 1. Temperature in Darwin Mountains (altitude 1,400 meters). Upper diagram:A dark dolorite plate and a light sandstone plate about 2 centimeters thick were put above sand. Both plates were oriented to the north so that sun radiation hit the rock surface vertically during noon. Into each plate was set a thermistor 4 millimeters below rock surface (25 in dolorite, 23 in sandstone). Thermistors were also placed directly behind the two plates into the sand (24 behind dolorite, 22 behind sandstone). Lower diagram: Thermistors were installed in various depths in the center of a polygon within moraine. Daily temperature variations reach only to about 25 centimeters of depth. Thermistors in 30 centimeters, 45 centimeters, 65 centimeters, and 95 centimeters deep (data not shown here) gave nearly constant temperatures between —8°C to - 10°C. Measurements were taken every 20 to 30 minutes from 14 to 17 December and again on 23 December 1978. In the afternoon of 16 December the sky became cloud covered and later a light snowfall occurred. December 23 was another clear day. 1980 REvIEw
15
rocks reaches deeper than into soils. Temperatures rise highest where rocks rest on fine-grained material (to a maximum of 30°C) (Miotke 1979b). Salt-enriched water in the soil is drawn to zones of maximum evaporation, where salt accumulation is especially favored. Salt crystallization within rocks causes salt fretting. I studied these processes with regard to tafoni forming at Bull Pass. X-ray analysis applied to salt samples from the Darwin Mountains mainly showed calcite, gypsum, thenardite, and mirabilite. Salt samples from Bull Pass showed halite, calcite, gypsum, and thenardite. Chemical analysis of salt compositions and thin-sections of salts in rock are in progress. Although running water on slopes is very rare and soils are dry, there seems to be a general movement indicated by a predominant downslope orientation of the long axle of debris (figure 2). The upper ends of large boulders sticking out of loose, fine-grained soils often are covered by slope debris; the lower ends in the shadow of restrictions, show a material deficit.
I- flttfll
Jc '
0
&
•••
axle
:
0 Slope 0
Figure 2. Slope creep at Bull Pass, Dry Valleys, Antarctica.
Wind activity also affects slope formation (Miotke 1979a). When fine grains are blown out, bigger rock particles start to slide, orienting their long axis downslope. Talus cones in the Darwin Mountains proved to be quite active. Their slopes are unstable; rocks start sliding and rolling when
Rubidium-strontium age determination of part of the basement complex of the Brown Hills, central Transantarctic Mountains ROBERT P. FELDER
and GUNTER FAURE
Institute of Polar Studies and Department of Geology and Mineralogy The Ohio State University Columbus, Ohio 43210 16
-
LI
p.
Figure 3. Bull Pass, Dry Valleys: The photograph illustrates the heating up of rocks by sun radiation.
walked on. Most of the slopes in the Darwin Mountains also show polygons The field party, working from 12 November 1978 to 14 January 1979, included Ran Gerson, of the University of Jerusalem Geographical Institute, and Bernd Janke of the University of Hannover Geographical Institute. This work was supported by National Science Foundation grant DPP 77-22182 and Deutsche Forschungsgemeinschaft. References Gerber, E. and Scheidegger, A. E. 1969. Stress-induced weathering of rock masses. Eclogae geologicae Helvetiae, 62(2), 401415. Miotke, F. -D. 1979. Formung und Formungsgeschwindigkeit von Windkantern in Victoria-Land, Antarktis. Polarforschung, 49(1), 30-43. (a) Miotke, F. -D. 1979. Zur physikalischen Verwitterung im Taylor Valley, Victoria-Land, Antarktis. Polarforschung, 49(2), 117-142. (b)
During the 1978-79 field season, we collected approximately 35 samples of the crystalline basement complex of the Brown Hills (158°33'E 79°46'S) to determine the age and cooling history of this portion of the Transantarctic Mountains. We did the field work between 5 November and 10 December 1978. Logistics included helicopter support from the Darwin Glacier camp and extended stays at various remote camps near the Darwin and Byrd Glaciers. The rocks in the study area have been described by Haskell, Kennett, and Prebble (1963, 1965) and by Grindley and Laird (1969), and have been subdivided on the basis of textural and structural criteria into the Carlyon Granodiorite, the Mt. Rich Granite, and the Hope Granite. Field observations indicate that the Carlyon grades into the Mt. Rich and that both are intruded by the Hope Granite. ANTARCTIC JOURNAL
Findlay, R. H. 1978. Provisional report on the geology of the region between the Renegar and Blue Glaciers, Antarctica. New Zealand Antarctic Record, 1, 39-44.
Skinner (1964, 1965) named the rocks at Mt. Madison the Selborne Marble and distinguished them from the Shackleton Limestone due to their higher metamorphic grade. He suggested that they may be Precambrian in age, correlative with the Nimrod Group in the Miller Range (Grindley, McGregor, and Walcott 1964). If this is the case, deformation at Mt. Madison is probably not related to the Shackleton Limestone south of Byrd Glacier.
Grindley, G. W., McGregor, V. R., and Walcott, R. I. 1964. Outline of the geology of the Nimrod-Beardmore-Axel Heiberg Glaciers region, Ross dependency. In R. J. Adie (Ed.), Antarctic geology. Amsterdam: North-Holland Publishing.
To me, lithologies at Mt. Madison appear similar to those of the Shackleton Limestone and pelitic Dick Formation (Skinner 1965), and I would suggest that the Selborne Marble is a metamorphosed equivalent of those two formations. The metamorphic grade suggests an adjacent granitic pluton north of Mt. Madison removed and buried by Byrd Glacier. This work was supported by National Science Foundation grant DPP 76-82040. References Burgess, C.J. In press. Geology of the Shackleton Limestone (Cambrian) in the Byrd Glacier area. New Zealand Antarctic Record.
Microclimate and weathering processes in the area of Darwin Mountains and Bull Pass, Dry Valleys FRANTZ-DIETER MIOTKE
Geographisches Institut Universitat Hannover Hannover, West Germany
During December 1978 and January 19791 studied microclimate, weathering processes, and antarctic landforms in the area of Darwin Mountains (80°S) and Bull Pass, Dry Valleys (77°30'S). Antarctic rocks disintegrate by the combined action of several different processes. Joints existing due to endogenic activity (Gerber and Scheidegger 1969) open primarily because of temperature-caused tension, frost cracking, and salt fretting. Chemical weathering processes are limited to the short summer period when temperatures of rock surfaces can reach as high as 30°C and reflect daily temperature variations and moisture in rocks and soil. 14
Skinner, D. N. B. 1964, A summary of the geology of the region between Byrd and Starshot glaciers, south Victoria Land, In R. J. Adie (Ed.), Antarctic geology. Amsterdam: North-Holland Publishing. Skinner, D. N. B. 1965. Petrographic criteria of the rock units between the Byrd and Starshot Glaciers, south Victoria Land, Antarctica. New Zealand Journal of Geology and Geophysics, 8, 292-303. Skinner, D. N. B. In press. Stratigraphy and structure of lower grade metasediments of Skelton Group, McMurdo Sound—Does Teall Graywacke really exist? In C. Craddock (Ed.), Antarctic Geoscience. Madison: University of Wisconsin Press. Smithson, S. B., Fikkan, P. R., and Toogood, D. J . 1970. Early geologic events in the icefree valleys, Antarctica. Geological Society of America Bulletin, 81, 207-210. Stump, E., Sheridan, M. F., Borg, S. G., Lowry, P. H., and Colbert, P. V. 1980. Geological investigations in the Scott and Byrd Glacier areas. Antarctic Journal of the U.S., 14(5), 39-40.
Daily temperatures were recorded by thermistors installed: 1. Into dark dolorites, light sandstones, and granites having different albedos; 2. Into small rocks, large boulders, and bedrock; 3. Immediately below the rock surface, into the rock center, and under rocks; 4. Into rocks with different exposures to sun radiation; 5. Into soils down to 100 centimeters; 6. Into snow down to 70 centimeters; and 7. Along snow margins. Figure 1 illustrates the variations in temperature in rocks and soil in the Darwin Mountains. Microclimatic differences were of special interest and these proved to be considerable within very limited environments. Temperature variations within soils and rocks and their daily changes affect the existence of algae, lichens, and other microforms of life in Antarctica. Not too much is known so far about the microclimate of ice-free areas in Victoria Land. Moisture in soils is normally very low at the upper surface (to 5 centimeters deep), mostly below 0.1 percent, but it can be higher where meltwater infiltrates along the margin of snowfields. Soil moisture can be as high as 20 percent where locally existing ice (up to 20 centimeters deep, as in the Darwin Mountains) melts somewhat during summer. Due to differences in heat conductivity, daily heat flow into ANTARCTIC JOURNAL
Hellgraue Sandsteinplatte Dunkle Doloritplatte
22,23 nach Norden exponiert nach Norden exponiert 24.25
Darwin Mountains O('1
light grey sandsone plate dark dolorite plate exposed to north exposed to north
22 23 24
20
\I \','
12 18 0 6 12 18 06 .......................... 18 15.12.78 16.12.78 17.12.78 23..12 ...78
Darwin Mountains
Moränenschutt, Polygonmitte 37-44 moraine renter of nn1vunn
Figure 1. Temperature in Darwin Mountains (altitude 1,400 meters). Upper diagram:A dark dolorite plate and a light sandstone plate about 2 centimeters thick were put above sand. Both plates were oriented to the north so that sun radiation hit the rock surface vertically during noon. Into each plate was set a thermistor 4 millimeters below rock surface (25 in dolorite, 23 in sandstone). Thermistors were also placed directly behind the two plates into the sand (24 behind dolorite, 22 behind sandstone). Lower diagram: Thermistors were installed in various depths in the center of a polygon within moraine. Daily temperature variations reach only to about 25 centimeters of depth. Thermistors in 30 centimeters, 45 centimeters, 65 centimeters, and 95 centimeters deep (data not shown here) gave nearly constant temperatures between —8°C to - 10°C. Measurements were taken every 20 to 30 minutes from 14 to 17 December and again on 23 December 1978. In the afternoon of 16 December the sky became cloud covered and later a light snowfall occurred. December 23 was another clear day. 1980 REvIEw
15
rocks reaches deeper than into soils. Temperatures rise highest where rocks rest on fine-grained material (to a maximum of 30°C) (Miotke 1979b). Salt-enriched water in the soil is drawn to zones of maximum evaporation, where salt accumulation is especially favored. Salt crystallization within rocks causes salt fretting. I studied these processes with regard to tafoni forming at Bull Pass. X-ray analysis applied to salt samples from the Darwin Mountains mainly showed calcite, gypsum, thenardite, and mirabilite. Salt samples from Bull Pass showed halite, calcite, gypsum, and thenardite. Chemical analysis of salt compositions and thin-sections of salts in rock are in progress. Although running water on slopes is very rare and soils are dry, there seems to be a general movement indicated by a predominant downslope orientation of the long axle of debris (figure 2). The upper ends of large boulders sticking out of loose, fine-grained soils often are covered by slope debris; the lower ends in the shadow of restrictions, show a material deficit.
I- flttfll
Jc '
0
&
•••
axle
:
0 Slope 0
Figure 2. Slope creep at Bull Pass, Dry Valleys, Antarctica.
Wind activity also affects slope formation (Miotke 1979a). When fine grains are blown out, bigger rock particles start to slide, orienting their long axis downslope. Talus cones in the Darwin Mountains proved to be quite active. Their slopes are unstable; rocks start sliding and rolling when
Rubidium-strontium age determination of part of the basement complex of the Brown Hills, central Transantarctic Mountains ROBERT P. FELDER
and GUNTER FAURE
Institute of Polar Studies and Department of Geology and Mineralogy The Ohio State University Columbus, Ohio 43210 16
-
LI
p.
Figure 3. Bull Pass, Dry Valleys: The photograph illustrates the heating up of rocks by sun radiation.
walked on. Most of the slopes in the Darwin Mountains also show polygons The field party, working from 12 November 1978 to 14 January 1979, included Ran Gerson, of the University of Jerusalem Geographical Institute, and Bernd Janke of the University of Hannover Geographical Institute. This work was supported by National Science Foundation grant DPP 77-22182 and Deutsche Forschungsgemeinschaft. References Gerber, E. and Scheidegger, A. E. 1969. Stress-induced weathering of rock masses. Eclogae geologicae Helvetiae, 62(2), 401415. Miotke, F. -D. 1979. Formung und Formungsgeschwindigkeit von Windkantern in Victoria-Land, Antarktis. Polarforschung, 49(1), 30-43. (a) Miotke, F. -D. 1979. Zur physikalischen Verwitterung im Taylor Valley, Victoria-Land, Antarktis. Polarforschung, 49(2), 117-142. (b)
During the 1978-79 field season, we collected approximately 35 samples of the crystalline basement complex of the Brown Hills (158°33'E 79°46'S) to determine the age and cooling history of this portion of the Transantarctic Mountains. We did the field work between 5 November and 10 December 1978. Logistics included helicopter support from the Darwin Glacier camp and extended stays at various remote camps near the Darwin and Byrd Glaciers. The rocks in the study area have been described by Haskell, Kennett, and Prebble (1963, 1965) and by Grindley and Laird (1969), and have been subdivided on the basis of textural and structural criteria into the Carlyon Granodiorite, the Mt. Rich Granite, and the Hope Granite. Field observations indicate that the Carlyon grades into the Mt. Rich and that both are intruded by the Hope Granite. ANTARCTIC JOURNAL
