relationship between the folds reported by Burgess (in Findlay, R. H. 1978. Provisional report on the geology of the region press) and those described here cannot be determined from between the Renegar and Blue Glaciers, Antarctica. New Zealand present evidence. Antarctic Record, 1, 39-44. Skinner (1964, 1965) named the rocks at Mt. Madison the Grindley, G. W., McGregor, V. R., and Walcott, R. I. 1964. Outline Selborne Marble and distinguished them from the Shack- of the geology of the Nimrod-Beardmore-Axel Heiberg Glaciers region, Ross dependency. In Adie (Ed.), leton Limestone due to their higher metamorphic grade. He R. J. Antarctic geology. Amsterdam: North-Holland Publishing. suggested that they may be Precambrian in age, correlative with the Nimrod Group in the Miller Range (Grindley, Skinner, D. N. B. 1964, A summary of the geology of the region McGregor, and Walcott 1964). If this is the case, deforma- between Byrd and Starshot glaciers, south Victoria Land, In Adie (Ed.), Antarctic geology. Amsterdam: North-Holland tion at Mt. Madison is probably not related to the Shackle- R. J. Publishing. ton Limestone south of Byrd Glacier. Skinner, D. N. B. 1965. Petrographic criteria of the rock units To me, lithologies at Mt. Madison appear similar to those between the Byrd and Starshot Glaciers, south Victoria Land, of the Shackleton Limestone and pelitic Dick Formation Antarctica. New Zealand Journal of Geology and Geophysics, 8, (Skinner 1965), and I would suggest that the Selborne Mar- 292-303. ble is a metamorphosed equivalent of those two formations. Skinner, D. N. B. In press. Stratigraphy and structure of lower The metamorphic grade suggests an adjacent granitic pluton grade metasediments of Skelton Group, McMurdo Sound—Does north of Mt. Madison removed and buried by Byrd Glacier. Teall Graywacke really exist? In C. Craddock (Ed.), Antarctic This work was supported by National Science Founda- Geoscience. Madison: University of Wisconsin Press. tion grant DPP 76-82040. Smithson, S. B., Fikkan, P. R., and Toogood, D. J. 1970. Early geo- logic events in the icefree valleys, Antarctica. Geological Society of America Bulletin, 81, 207-210. References Stump, E., Sheridan, M. F., Borg, S. G., Lowry, P. H., and Colbert, Burgess, C.J. In press. Geology of the Shackleton Limestone (Cam- P. V. 1980. Geological investigations in the Scott and Byrd Glacier brian) in the Byrd Glacier area. New Zealand Antarctic Record. areas. Antarctic Journal of the U.S., 14(5), 39-40.

Microclimate and weathering Daily temperatures were recorded by thermistors installed: processes in the area of Darwin 1. Into dark dolorites, light sandstones, and granites hav- Mountains and Bull Pass, ing different albedos; 2. Into small rocks, large boulders, and bedrock; Dry Valleys 3. Immediately below the rock surface, into the rock cen- ter, and under rocks; 4. Into rocks with different exposures to sun radiation; 5. Into soils down to 100 centimeters; FRANTZ-DIETER MIOTKE 6. Into snow down to 70 centimeters; and 7. Along snow margins. Geographisches Institut Figure 1 illustrates the variations in temperature in rocks Universitat Hannover Hannover, West Germany and soil in the Darwin Mountains. Microclimatic differences were of special interest and these proved to be considerable within very limited envi- During December 1978 and January 19791 studied micro- ronments. Temperature variations within soils and rocks climate, weathering processes, and antarctic landforms in and their daily changes affect the existence of algae, lichens, the area of Darwin Mountains (80°S) and Bull Pass, Dry and other microforms of life in Antarctica. Not too much is Valleys (77°30S). known so far about the microclimate of ice-free areas in Antarctic rocks disintegrate by the combined action of Victoria Land. several different processes. Joints existing due to endogenic Moisture in soils is normally very low at the upper sur- activity (Gerber and Scheidegger 1969) open primarily be- face (to 5 centimeters deep), mostly below 0.1 percent, but cause of temperature-caused tension, frost cracking, and it can be higher where meltwater infiltrates along the mar- salt fretting. Chemical weathering processes are limited to gin of snowfields. Soil moisture can be as high as 20 percent the short summer period when temperatures of rock sur- where locally existing ice (up to 20 centimeters deep, as in faces can reach as high as 30°C and reflect daily tempera- the Darwin Mountains) melts somewhat during summer. ture variations and moisture in rocks and soil. Due to differences in heat conductivity, daily heat flow into

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Hellgraue Sandsteinplatte Dunkle Doloritplatte 22,23 nach Norden exponiert nach Norden exponiert 24.25 Darwin Mountains light grey sandsone plate dark dolorite plate exposed to north exposed to north O(1 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 sand- stone). Lower diagram: Thermistors were installed in various depths in the center of a polygon within moraine. Daily tem- perature 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 max- imum of 30°C) (Miotke 1979b). p. Salt-enriched water in the soil is drawn to zones of maxi- mum evaporation, where salt accumulation is especially LI favored. Salt crystallization within rocks causes salt fret- ting. 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 Figure 3. Bull Pass, Dry Valleys: The photograph illustrates debris; the lower ends in the shadow of restrictions, show the heating up of rocks by sun radiation. a material deficit. 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. I- 0 This work was supported by National Science Founda- & tion grant DPP 77-22182 and Deutsche Forschungsgemein- flttfll Jc : schaft. ••• 0 Slope axle 0 References Figure 2. Slope creep at Bull Pass, Dry Valleys, Antarctica. 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 Wind activity also affects slope formation (Miotke 1979a). Windkantern in Victoria-Land, Antarktis. Polarforschung, 49(1), When fine grains are blown out, bigger rock particles start 30-43. (a) to slide, orienting their long axis downslope. Talus cones in Miotke, F. -D. 1979. Zur physikalischen Verwitterung im the Darwin Mountains proved to be quite active. Their Taylor Valley, Victoria-Land, Antarktis. Polarforschung, 49(2), slopes are unstable; rocks start sliding and rolling when 117-142. (b)

Rubidium-strontium age During the 1978-79 field season, we collected approxi- mately 35 samples of the crystalline basement complex of determination of part the Brown Hills (158°33E 79°46S) to determine the age and of the basement complex cooling history of this portion of the Transantarctic Moun- tains. We did the field work between 5 November and 10 of the Brown Hills, December 1978. Logistics included helicopter support from central Transantarctic Mountains 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 Has- kell, Kennett, and Prebble (1963, 1965) and by Grindley and ROBERT P. FELDER and GUNTER FAURE Laird (1969), and have been subdivided on the basis of textural and structural criteria into the Carlyon Granodi- Institute of Polar Studies and Department of Geology and Mineralogy orite, the Mt. Rich Granite, and the Hope Granite. Field The Ohio State University observations indicate that the Carlyon grades into the Mt. Columbus, Ohio 43210 Rich and that both are intruded by the Hope Granite.

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