ROBERT H. RUTFORD Department of Geology, University of Nebraska-Lincoln, Lincoln, Nebraska 68508 PARKER E. CALKIN Department of Geological Sciences, State University of New York at Buffalo, Buffalo, New York 14214

Reversing Barchan in Lower Victoria Valley, : Discussion

The paper by Lindsay (1973) describing the unique field in reversed (eastward) lee slope deposits or what McKee and Douglas lower Victoria Valley, Antarctica, presents some new and interest- (1971, p. D114) have called "counterdunes." However, because ing observations concerning this polar erg. We (Calkin and Rut- they form on the windward (eastward) slope, they must normally ford, 1974) have also studied the dune field, including field obser- be eroded away quickly; we did not observe their occurrence in vations during three summers since 1960. This dune area, first de- lower Victoria Valley. Such stepped slopes are apparently very scribed by Webb and McKelvey (1959) has since been discussed in common in the Kelso Dunes of the Mojave , , the literature by Cailleux (1962), Calkin (1963, 1964, 1971), where constantly reversing occur (Sharp, 1966). Nichols (1963, 1966), Calkin and Nichols (1972), Cameron Movement of the dunes of lower Victoria Valley has been moni- (1969), and Morris and others (1972a, 1972b), among others. tored by Calkin both in the field and on air photographs, and a There appears to be much agreement between Lindsay and our- mean westerly migration is clearly evident. Migration rates are er- selves, but some significant differences do exist on the interpreta- ratic over several seasons, and there is some evidence for actual re- tion of this area and we wish to make the following brief comments treat of dune fronts and necessarily eastward movement of on Lindsay's paper. over the dune field in winter (Calkin and Rutford, 1974). However, One of Lindsay's three main themes is th at the dunes are "revers- there appears to be little planimetric alteration of the barchan- ing." This theme, together with our assessment of his possible transverse form that cannot be related to easterly winds and no in- overemphasis of it, is what we wish to discuss herein. dication of coherent dune migration eastward. The reason seems to We assume from the term "reversing" that Lindsay means that be due to the fact that the dunes and surrounding sources of sand the dune form migrates in more than one direction or that it re- are much more stable in winter than in summer. verses direction. Lindsay (1973, p. 1799) cited meteorologic data We also wish to point out that all of the snow and interbedded from Vanda Station, which lies some 22 km to the southwest in the sand layers that we observed, including broad areas of eroded dune much lower lying Wright Valley. He failed to note the data pub- strata of windward and lee faces (Calkin and Rutford, 1974), could lished by Bull (1966) from lower Victoria Valley itself, which be ascribed to the normal dune-building easterly winds. The fact shows that the over the dunes is almost exclusively easterly that these beds are formed at all by easterly winds may not be throughout summer months and is apparently often more persis- grasped by the reader of Lindsay's (1973) paper. Thus, such state- tent and of higher velocity than his observations suggest. Further, ments as, "Consequently, a stratigraphy of interbedded snow and there is much geomorphic evidence for extremely strong westerly sand units develop on the eastern slopes of the dunes when winds winds, necessarily in winter, over the dunes (Calkin and Rutford, blow from the west" (Lindsay, 1973, p. 1804) may be misleading; 1974). Therefore, there is good reason to expect "reversing" such stratigraphy develops when wind blows from the east also — movement of the dunes in this area. However, surprisingly and perhaps even more frequently. contrary to normal expectations, reversed (eastward) migration of the dune form appears to be limited, a fact we believe Lindsay REFERENCES CITED (1973) did not emphasize enough. Bull, C. A., 1966, Climatological observations in ice-free areas of southern The crux of Lindsay's argument, that the dunes "reverse," ap- Victoria Land, Antarctica, in Rubin, M. J., ed., Studies in Antarctic pears to be based on the presence of east-dipping sequences of in- meteorology: Am. Geophys. Union, Antarctic Research Ser., v. 9, p. terlaminated sand and snow buried in the windward (easterly) 177-194. slopes of at least two dunes. His use of "windward" and "leeward" Cailleux, A., 1962, Études de geologie au Detroit de McMurdo (Antarcti- (without other directional terms) to describe the slopes of a dune que): Comité National Français pour les Reserches Antarctiques, (dunes?) that is purported to be changing directions because of a Paris, no. 1,41 p. change in wind direction, is a bit difficult to interpret. Figure 2 has Calkin, P. E., 1963, Geomorphology and glacial geology of the Victoria Valley system, southern Victoria Land, Antarctica [Ph.D. dissert.]: no compass orientation, so it is not obvious that the east = right, Columbus, Ohio State Univ., 292 p. west = left convention has been broken here. In at least some 1964, Geomorphology and glacial geology of the Victoria Valley sys- places, Lindsay (p. 1801) noted that dips of the upper (usually tem, southern Victoria Land, Antarctica: Ohio State Univ. Inst. Polar steeper) laminae of the snow-sand sequences reached a maximum Studies Rept. 10, 66 p. of 28° eastward. We agree that these observations provide good 1971, Glacial geology of the Victoria Valley system, southern Victoria evidence that there are superimposed on the main dune form some Land, Antarctica, in Crary, A. P., ed., Antarctic snow and ice studies

Geological Society of America Bulletin, v. 85, p. 1011-1012, June 1974

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II: Am. Geophys. Union, Antarctic Research Ser., v. 16, p. 363-411. dry valleys of south Victoria Land, Antarctica — Possible analogues of Calkin, P. E., and Nichols, R. L., 1972, Quaternary studies in Antarctica, in Martian surface features: U.S. Dept. Interior Interagency Rept., As- Adie, R. J., ed., Antarctic geology and geophysics: Oslo, Universitets- trogeology 52, Geol. Survey (prelim, rept.), 156 p. forlaget, p. 625-643. Nichols, R. L., 1963, Geologic features demonstrating aridity of McMurdo Calkin, P. E., and Rutford, R. H., 1974, Sand dunes of Victoria Valley, Sound area, Antarctica: Am. Jour. Sci., v. 261, p. 20—31. Antarctica: Geog. Rev. (in press). 1966, Geomorpholojjy of Antarctica, in Tedrow, J.C.F., ed., Antarctic Cameron, R. E., 1969, Cold cesert characteristics and problems relevant to soils and soil forming processes: Am. Geophys. Union, Antarctic Re- other arid lands, in McGinnies, W. G., and Goldman, B. J., eds., Aric. search Ser., v. 8, p. 1-46. lands in perspective: Washington, D.C., Am. Assoc. Adv. Sci., anc Sharp, R. P., 1966, Kelso Dunes, , California: Geol. Soc. Tucson, Univ. Press, p. 169-205. America Bull., v. 77, p. 1045-1074. Lindsay, J. F., 1973, Reversing barchan dunes in lower Victoria Valley. Webb, P. N., and McKelv;y, B. C., 1959, Geological investigations in south Antarctica: Geol. Soc. America Bull., v. 84, p. 1799-1806. Victoria Land, Antarctica. Pt. 1, Geology of Victoria Dry Valley: New McKee, E. D., and Douglas, J. R., 1971, Growth and movement of dunes al Zealand Jour. Geology and Geophysics, v. 2, p. 120—136. White National Monument, New Mexico: U.S. Geol. Surve) Prof. Paper 750-D, p. D_08-D114. Morris, E. C., Holt, H., Mutch, T., and Lindsay, J., 1972a, analog studies in Wright and Victoria Valleys, Antarctica: Antarctic Jour. U.S., v. 7, p. 113-114. Morris, E. T., Mutch, T., and Holt, H., 1972b, Atlas of geologic features in MANUSCRIPT RECEIVED BY THE SOCIETY SEPTEMBER 4,1973

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