This research was supported by National Science Foundation of Sessrumir Valley, western Asgard Range, Antarctica: Implications rant DPP 89-18942. Dick Kelly drafted the figure. for late Tertiary ice-sheet overriding. Antarctic Journal of the U.S., 25(5),53-55. Pi entice, M. L. 1982. Surficial geology and stratigraphy of central Wright Valley, Antarctica: Implications for Antarctic Tertiary glacial history. References Master of Science thesis, University of Maine, Orono, Maine. Prentice, M. L., C. H. Denton, L. H. Burckle, and D. A. Hodell. 1987. /ckert, R. P., Jr. 1990. Surficial geology and stratigraphy in Njord Valley, Evidence from Wright Valley for the response of the antarctic ice sheet western Asgard Range, Antarctica: Implications for late Tertiary to climate warming. Antarctic Journal of the U.S., 22:56-58. glacial history. Master of Science thesis, University of Maine, Orono, Shackleton, N. J. and J. P. Kennett. 1975. Paleotemperature history of the Maine. Cenozoic and the initiation of antarctic glaciation: Oxygen and carbon tenton, G. H., M. L. Prentice, D. E. Kellogg, and T. B. Kellogg. 1984. Late isotope analyses in DSDP sites 277,279, and 281. Initial Reports of the Tertiary history of the antarctic ice sheet: Evidence from the dry Deep Sea Drilling Project, 29:743-755. valleys. Geology, 12:263-7. Webb, P. -N., D. M. Harwood, B. C. McKelvey, J. H. Mercer, and L. D. all, B. L. 1992. Surficial geology and geomorphology of eastern Wright Scott. 1984. Cenozoic marine sedimentation and ice volume variation Valley, Antarctica: Implications for Plio-Pleistocene ice-sheet dynam- on the east antarctic craton. Geology, 12:287-291. ics. Master of Science thesis, University of Maine, Orono, Maine. Webb, P. -N. and D. M. Harwood. 1991. Late Cenozoic glacial history of archant, D. R. 1990. Surficial geology and stratigraphy in Arena Valley, the Ross Embayment, Antarctica. Quaternary Science Reviews, 10:215- Quartermain Mountains, Antarctica: Implications for late Tertiary 224. glacial history. Master of Science thesis, University of Maine, Orono, Wilch, T. I. 1991. Surficial geology and geochronology of middle Taylor Maine. Valley, Antarctica: Implications for Plio-Pleistocene glacial history. ¶archant. D. R., C. H. Denton, and D. E. Sugden. 1990. Surficial geology Master of Science thesis, University of Maine, Orono, Maine.

Taylor Dome ice-core study than the apparent seasonal cycles of about 20 centimeters in pit profiles. The strong winds may cause erosion, as evidenced by a board at iON that had been undercut by about 5 centimeters. Sastrugi were more pronounced than the previous year, espe- P. M. GR0OTES AND E. J. SmIG cially along the N line. Snow in pits along this line (50N, a repeat of a 1990-1991 snowpit, and 20N) showed rapid metamorphosis Quaternary Isotope Laboratory AK-60 with coarse depth hoar near the surface as in 1990-1991. Pits were also repeated at lOS in the high snow accumulation area, and at University of Washington 20C near the camp and the future drill site. Little direct snowfall was observed during either field season, yet significant drifts accumulated. This indicates that a signifi- From 30 November 1991 until 22 January 1992, two field cant fraction of accumulating snow consists of reworked snow, parties of four (Grootes, Steig, Merrand, and Tramoni, Quater- much of it probably transported from the interior of East Antarc- nary Isotope Laboratory; and Waddington, Morse, Balise, and tica. This snow may have an isotopic composition different from Paur, Geophysics Program, University of Washington) contin- that of local snow fall. To check this we sampled two snowpits, ued the 1990-1991 surface reconnaissance and drill site selection one on top of Mt. Feather, the other on Mt. Crean (figure 1). These (Grootes et al. 1991; Waddington et al. 1991) on Taylor Dome mountains rise several hundred meters above the surrounding (7740 S 158 E) and the upper Taylor Glacier (see also Waddington glaciers and Taylor Dome, and may be expected to collect pre- and Morse). dominantly local snow. Both sites however, exhibit features of A survey of boards and stakes placed the previous year strong firnification, having almost continuous depth hoar. Isoto- showed low, irregular accumulation across most of the area. (See pic enrichment by mass loss must thus be considered in their figure 1 for explanation of location names.) Nine of 18 boards interpretation. A significant change in the wind pattern from were still exposed at the surface, one was not found, and the 1990-1991 was the presence of a second preferred wind direction remaining were covered by snow ranging from 4 to 42 centime- from the southeast, from the Ross Ice Shelf, in addition to the ters. Excluding the Skelton Névé southwest of Taylor Dome katabatic winds from the southwest. The southeasterly winds proper, the average accumulation is 9.8±1.5 centimeters of snow. tended to be associated with clouds at about the 2,500-meter level Accumulation over the period from January to December 1991 and higher temperatures. was about half of that estimated from the 1990-1991 snowpit Two 4-inch cores, the first to 128 meters at 20C and the second studies (Grootes et al. 1991). Further observations are needed to to 100 meters at the entrance to Taylor Valley, were drilled by determine whether this period is representative for accumulation PICO. Drilling ended when the quality of the cores deteriorated in the Taylor Dome area. significantly. Observations during both field seasons of snow drifts and Stratigraphy, density, electrical conductivity measurement frequent wind-packed hard layers in pit profiles indicate that an (ECM), and isotope sampling of most of the 128 meter and the firn important part of the accumulation may occur as drifts, and thus part of the 100 meter core were done in the field using a snow is not uniform over the area. Annual layers may be missing at trench to keep the core below -15 C. Above this temperature a some locations and the mean annual accumulation will be less film of liquid water may develop on crystal surfaces and affect the

1992 REVIEW 57

0 composition of trapped air (CO2) The density-depth profile indi- cates the firn-ice transition is at about 76 meter (p-0.82) depth. The isotope-depth profiles of the 11 pits of 1990-1991 docu- ment important isotope differences across the Taylor Dome field area. Figure 2 shows the isotope-depth profiles of the pits along the S. C, and N line averaged per depth interval. Excluded from the average were the pits at lOS and iON, both of which are 50- located below Taylor Dome in the Portal and the entrance to Taylor Valley respectively, because they differed significantly from the others. The three lines display a clear change in average -. E isotope values, which get heavier from S (-42J%) through C U (-41.0%) to N (-39.2%), as well as poor preservation of the seasonal signal in the two N pits. The results of two chemistry and -c three microparticle profiles by P. Mayewski and E. Mosley- cl Thompson indicate about nine cycles per 2 meters like the oxy- cii gen isotopes. D The additional results obtained in the field this year and the laboratory results from last year support the choice of the 20C area as a prospective drill site. They also show interesting vari- 150 ability over the Taylor Dome area which, combined with the continuous automated weather stations results of Waddington N-- and Morse, may lead to new insights on the air-to-firn transfer function for isotopes and other ice-core parameters of interest.

References 200 I 1 I . I -45 -40 -35 Grootes, P. M., E. J Steig and C. Massey. 1991. "Taylor Ice-Dome ice" . 18 study: Reconnaissance 1990-1991. Antarctic Journal of the U.S., 26(5): S 0 (V-SM0) (%) 69-71. Waddington, E. D., D. Morse, M. J . Balise, and J. Firestone. 1991. Glacier Figure 2. Average 8180 profiles for snowpits along N, C, and S geophysical studies for an ice core site at "Taylor Dome." Antarctic transects (see figure 1) of the Taylor Dome. Journal of the U.S., 26(5):71-73.

158 00 E 159 E 160 00 £ 161 00 £ • 157 00 E 162 00 E ±J + 77 30 S + 77 309 + (y\o

•. ASGMRD RANGE z

lbep II fH/ 77 45 S + Ur Y^UKR%

Mt Crn \ 2550 J L M(I / tO km - 2200 H A

Mt Feather + + + 2985 + 78 00 S + 78 00 S +

Figure 1. Map of the Taylor Dome area. Snowpits were sampled at most Intersections of the survey grid, denoted by the lines marked N, C, and, S, and 10 through 80. Stars show locations of last years camp near 40 O and this years camp and future drill site at 20°C.

58 AN-r/acnc JouRNAL