Oxygen isotope studies at the South Pole
Oxygen isotope studies at the South Pole P. M. GR0OTES and M. STUIVER Quaternary Isotope Laboratory University of Washington Seattle, Washington 98195
Measurements of the deuterium and/or oxygen-18 content of long ice cores have provided valuable information on the climate of the past 100,000 years (Dansgaard et al. 1971; Johnsen et al. 1972; Lorius et al. 1979; Dansgaard et al. 1982). Yet data from additional cores are needed to make a better assessment of the contributions of local effects versus those of climate to the isotope record obtained. The South Pole is an attractive location for drilling, because there firnification and the relationship between the isotopic composition of the snow and seasonal temperature have been extensively studied (Epstein, Sharp and Cow 1965; Cow 1965; Picciotto, Deutsch, and Aldaz 1966; Aldaz and Deutsch 1967; Jouzel et al. 1983), and the presence of Amundsen-Scott South Pole Station provides good support. We here report recent isotopic oxygen (6180)* results obtained on South Pole samples in the Quaternary Isotope Laboratory. During November and December 1982 field parties from Ohio State University (osu), the University of Bern, Switzerland, and the University of Washington (uw) worked with personnel of the Polar Ice Coring Office (Pico) at the South Pole to obtain a core from 106- to 227-meter depth and to sample this core and the overlying 103-meter core, obtained from the same hole in 1980, for 8 11 0, microparticles, trapped gases and electrical conductivity (Kuivinen 1981, 1983; Mosley-Thompson and Thompson 1983; Stauffer and Schwander 1983). During this period, several snow pits were studied and sampled by the osu field party. Figure la shows the 180/depth profile from the Cwall of pit I located 4 kilometers from the station along 128° Eastern longitude (Mosley-Thompson, Kruss, and Bain 1983). Figures lb and ic are 8180 profiles from pits at a distance from the station of 1 kilometer along 110° and about 3 kilometers along 130° eastern longitude, that were sampled by osu field parties going to Dome C in November 1979 and coming from Dome C in late February 1979 respectively (Bolzan personal communication; Bolzan, Palais, and Whillans, 1979). Both the average 8180 of the different profiles (a. -51.23 parts per thousand; b. -52.66 parts per thousand; c. -51.07 parts per thousand) and the minimum and maximum values (a. -42.34/-55.84 parts per thousand; b. -44.58/-56.46 parts per thousand; c. -42.86/-55.65 parts per thousand) are similar to the values reported earlier by Epstein, Sharp, and Cow (1965), Picciotto, Deutsch, and Aldaz (1966), and Jouzel et al. (1983). A detailed comparison of the profiles a, b, and c and of these with the 6D profile of Jouzel et al. (1983) covering the same period shows significant differences. This is caused by the irregular snow deposition in which some area's may not accumulate any snow
* 180
is the relative deviation in oxygen-18 concentration of a sample from Vienna Standard Mean Ocean Water (v-sMow) expressed in parts per thousand- %).
62
during a particular year (Cow 1965). An estimated 1 out of every 10 years may be missing (J. R. Petit quoted in Mosley-Thompson and Thompson, 1982). It should be noted here that in the 180 profile an annual cycle may be lost, even though snow was accumulated during the year, when the distinctive, isotopically heavy summer accumulation is (partially) missing. Partial preservation of summer snow gives summer maxima more as humps than as distinctive peaks (Jouzel etal. 1983). The result is that isotope/depth profiles from the same general area can be visually quite different. Discrepancies between isotopic profiles are also evident in the five pits compared by Picciotto, Deutsch, and Aldaz (1966). For climate reconstruction or correlations on a yearly basis several isotope profiles have to be available that are independently dated using stratigraphic or other means. -42 -44 -46 -48 -50 -52 -54 -56 -58 -44 0 0 0
-46 -48
0
-50
>
-52
0
-54
e
0
-56 -58 -44 -48 -48 -50 -52 -54 -56 -58 Depth (m)
Figure 1. Oxygen isotopic composition (6180) [expressed as relative deviation from the international Atomic Energy Agency, Vienna Standard Mean Ocean Water (v-sMow), in parts per thousand—%4 of snow, as a function of depth in three snow pits near the South Pole. A. 4 kilometers (direction 128 0 E) from South Pole Station, November-December 1982. B. 1 kilometer (direction 110 0E) from South Pole Station, November 1979. C. about 3 kilometers (direction 1300 E) from South Pole Station, January 1979. (Profiles B and C were shifted to match the surface with its probable position in A. "m" denotes meter.) ANTARCTIC JOURNAL
Figure la shows four summer peaks with snow significantly heavier than the rest of the profile. The records of monthly average temperature at Amundsen-Scott South Pole Station show above average temperatures for December 1957 through February 1958, November 1966 through January 1967, November 1971 through February 1972, November 1976 through January 1977, and November 1980 through February 1981 (Amundsen-Scott South Pole Station climatological data summary). Counting from the December 1982 surface at the top correlates the isotopically heavy snow at 50- to 60-centimeter depth with the warm 1980-1981 summer, and makes it likely that the peaks at 150-centimeter and at 250-centimeter depth contain the 1976-1977 and 1971-1972 summer snow respectively. The uncertainty in ascribing the two peaks is caused by the 8 11 0 profile between 50- and 100-centimeter depth. The detailed microparticle and stratigraphic study of MosleyThompson at osu may confirm our conclusion. It is interesting to note here that years with above average summer temperatures at the South Pole are, with the exception of 1980-1981, associated with strong El Nino/Southern Oscillation events over the Pacific Ocean. This deserves further study. The 1982 profile contains 12 annual layers if we accept the correlation of the less negative isotope peaks with the warm summers. These annual layers give a snow accumulation of 23.8 ± 6.5 centimeters per year. The pit study of Jouzel et al. (1983) showed a density of 0.35 grams per cubic centimeter at the surface increasing to 0.41 grams per cubic centimeter at 3-meter depth. To estimate the accumulation in water equivalent we assume the same density profile for the 1982 snow pit and approximate the change in density with depth by a linear relation. This gives 8.9± 2.5 grams per square centimeter for the annual accumulation and an uncertainty of ± 0.7 grams per square centimeter for the average. This is in good agreement with the 8.74 grams per year of Mosley-Thompson and Thompson (1982) for the period 1974-1955 and with the 8.5 grams per year for the period 1978-1930 of Jouzel et al. (1983). Figure lb and ic do not show the above clear correlation with summer temperature. This may be due to the irregular deposition and partial preservation discussed above. The 8180 maxima and minima are less well defined due to the larger sample interval (4 centimeters compared with 2 centimeters in la). The 818 results from these three pits confirm the earlier work that the snow deposited at the South Pole shows a clear annual cycle in its oxygen isotopic composition that can be preserved during the initial stages of firnification. Yet the low average accumulation results occasionally in partially or completely missing years so the correlation between 18 0/depth profiles on an annual basis will be poor. The analysis of the two long South Pole cores [226.7 meters from 1980 and 1982, described above, and 202.4 meters from a nearby hole in 1981-1982 (Kuivinen et al. 1982)] that are currently being studied in our laboratory is therefore directed toward 8180 fluctuations on a time scale of decades or longer. Figure 2 shows results for the 226.7-meter core. Samples were cut as thin, 25-centimeter long strips parallel to the core axis. A three-point moving average is used to reduce the noise introduced by the large annual 11 0 cycle. A discussion of this profile and its correlation with the adjacent 1981-1982 core will be published elsewhere. This work was supported by the National Science Foundation grant DPP 80-19756. E. Mosley-Thompson and I.M. Whillans, Ohio State University, kindly supplied samples of their pit studies for oxygen isotope analysis. 8
1984 REVIEW
-47 -48 -49 -50 C/)
-51 0
a)
ca
-52
a)
-53 -54 L_LLLLL I 0 50 100 150 200 Depth (m)
Figure 2. Oxygen isotope composition (6180) [expressed as relative deviation from the International Atomic Energy Agency, Vienna Standard Mean Ocean Water (v-sMow), in parts per thousand -%0] as a function of depth in a 226.7-meter ice core from the South Pole (900 S). Samples cover 25-centimeter depth intervals. A three-point moving average is used to suppress noise caused by the annual cycle. ("m" denotes meter.)
References A!daz, L., and S. Deutsch. 1967. on a relationship between air temperature and oxygen isotope ratio of snow and firn in the South Pole region. Earth and Planetary Science Letters, 3, 267-274. Amundsen-Scott South Pole Station climatological data summary, obtained on station, December 1982. Boizan, J.F. 1979. Personal communication. Boizan, J.F., J.M. Palais, and I. Whilans. 1979. Glaciology of Dome C area. Antarctic Journal of the U.S., 14,(5)100-101. Dansgaard, W., S.J. Johnsen, H.B. Clausen, and C.C. Langway, Jr. 1971. Climatic record revealed by the Camp Century ice core. In K.K. Turekian (Ed.), The Late Cenozoic glacial ages. New Haven, Conn.: Yale University Press. Dansgaard, W., H.B. Clausen, N. Gundestrup, C.U. Hammer, S.F. Johnsen, P.M. Kristinsdottir, and N. Reeh. 1982. A new Greenland deep ice core. Science, 218, 1273-1277. Epstein, S., R.P. Sharp, and A.J. Gow. 1965. Six-year record of oxygen and hydrogen isotope variations in South Pole firn. Journal of Geophysical Research, 70, 1809-1814. Gow, A.J. 1965. On the accumulation and seasonal stratification of snow at the South Pole. Journal of Glaciology, 5, 467-477. Johnsen, S.J., W. Dansgaard, H.B. Clausen, and C.C. Langway, Jr. 1972. Oxygen isotope profiles through the Antarctic and Greenland ice sheets. Nature, 235, 429-434. Jouzel, J., L. Merlivat, J.R. Petit, and C. Lonus. 1983. Climatic information over the last century deduced from a detailed isotopic record in the South Pole snow. Journal of Geophysical Research, 88, 2693-2703. Kuivinen, K.C. 1981. Ice core drilling, 1980-1981. Antarctic Journal of the U. 5., 16(5), 78. Kuivinen, K.C. 1983. A 237-meter ice core from South Pole Station. Antarctic Journal of the U. S., 18(5), 113-114. Kuivinen, K.C., B.R. Koci, G.W. Holdsworth, and A.J. Gow. 1982. South Pole ice core drilling, 1981-1982. Antarctic Journal of the U. S., 17(5), 89-91. Lorius, C., L. Merlivat, J . Jouzel, and M. Pourchet. 1979. A 30,000-year isotope climatic record from Antarctic ice. Nature, 280, 644-648. Mosley-Thompson, E., and L.G. Thompson. 1982. Nine centuries of microparticle deposition at the South Pole. Quaternary Research 17, 1-13. 63
Mosley-Thompson, E., P.D. Kruss, and T. Bain. 1983. South Pole pit the South Pole. An example of an unusual meteorological event stratigraphic studies. Antarctic Journal of the U.S. 18(5), 116-118. recorded by the oxygen isotope ratios in the firn. Earth and Planetary Mosley-Thompson, E. and L.G. Thompson. 1983. South Pole ice core Science Letters, 1, 202-204. processing and microparticle analysis. Antarctic Journal of the U.S. Stauffer, B., and J. Schwander. 1983. Core processing and analyses of ice cores drilled at South Pole. Antarctic Journal of the U.S. 18(5), 18(5), 118-119. Picciotto, E., S. Deutsch, and L. Aldaz. 1966. The summer 1957-1958 at 114-116.
Vostok tephra-An important englacial stratigraphic marker? P. R. KYLE
Department of Geoscience New Mexico Institute of Mining and Technology Socorro, New Mexico 87801 J. PALAIS
Institute of Polar Studies Ohio State University Columbus, Ohio 43210
E. THOMAS Department of Geology Arizona State University Tempe, Arizona 85281
Tephra (volanic ash) layers, if they are widespread, have the potential to provide important stratigraphic markers in ice cores. If the source of the tephra can be identified and an age assigned to the eruption, then the tephra layer can also provide a valuable time plane (Kyle, Palais, and Delmas 1982). Hammer (1980) and Hammer, Clausen, and Dansgaard (1981) have demonstrated the value of tephra in ice cores from Greenland. Using surface conductivity measurements they located volcanicderived acid layers, which were in some cases correlated with known eruptions. Such work has not been conducted on antarctic ice cores and most tephra layers are located either by (1) visual inspection (Gow and Williamson 1971), (2) detailed chemical analyses of the ice (Delmas and Boutron 1980), or (3) continuous microparticle measurements (Mosley-Thompson 1980). We have been examining visible volcanic layers from several antarctic ice cores. The objectives being to determine the source of the eruptions, evaluate possible climatic impact of the eruptions and to establish the volcanic record for the Southern Hemisphere. A 0.05-meter thick tephra layer was discovered in the bottom of a 101-meter long ice core drilled at Vostok Station in December 1979 (Parker, Zeller, and Gow 1982). An age of 3,300 years was assigned to the tephra based on snow accumulation rates and the ice stratigraphy. The layer was informally called the Vostok tephra by Kyle et al. (1982). We have examined the Vostok tephra in more detail and have identified the source of the eruption. The ice associated with the tephra layer has concentrations of sulphate which exceed 550 milligrams per liter. This is an exceedingly high value and suggests the eruption 64
responsible for the tephra was large and had a significant aerosol (H 2 SO 4 ) component. The tephra is composed of glass shards and rounded cryptocrystalline lithic material. Petrographic and scanning electron microscope measurements show the grains to range up to about 40 micrometers in length. The mean grain size is between 15 and 30 micrometers. Semi-quantitative and quantitative analyses of the glass shards have been made using an energy-dispersive analyzer on a scanning electron microscope and by electron microprobe. Analyses are listed in the table. The Vostok tephra is andesitic and characterized by high iron concentrations. Enrichment of iron is a characteristic feature of tholeiitic suites. Taking the prevailing wind directions into account, three major sources for the Vostok tephra can be considered: the South Sandwich Islands, the South Shetland Islands, and the Southern Andes. Fortunately, the three provinces are easily distinguished, and we suggest the South Sandwich Islands is the source area. The Southern Andes volcanoes are calc-alkaline andesites and although only a few analyses are available they have lower iron contents than the Vostok tephra (Katsui 1982). The South Shetland Islands have a much higher total alkali content than the South Sandwich (Baker 1968; GonzalezFerran 1982). Based on the available analyses of the South SandAnalyses of the Vostok tephra Compound Electron microprobe Energy dispersive Wet chemical analysisa analysis' analysisc d Si02 60.56 (0 . 42)d 59.73 (1.79) 60.90 Ti02 0.74 (0.07) 0.90 (0.16) 0.95 Al203 14.92 (0.82) 14.84 (0.66) 14.80 FeOe 9.15 (0.57) 10.25 (1.23) 8.34 MnO 0.23 (0.04) 0.15 (0.12) 0.11 MgO 2.39 (0.34) 2.44 (0.48) 2.35 CaO 6.72 (0.26) 6.64 (0.76) 6.09 Na20 3.31 (0.38) 4.46 (0.57) 3.67 K20 0.44 (0.05) 0.63 (0.19) 0.39 -f - f Total 98.46 100.04 97.72 Number of 9 analyses
37
Los Alamos National Laboratory (Analyst: J. Palais). Using a scanning microscope, Arizona State University (Analyst: E. Thomas). Aphyric andesite, Cauldron Lake lava flow, northern Candelmas Island (Tomblin 1979). d One standard deviation. Total iron as ferrous oxide. Not analyzed. ANTARCTIC JOURNAL
Measurements of the deuterium and/or oxygen-18 content of long ice cores have provided valuable information on the climate of the past 100,000 years (Dansgaard et al. 1971; Johnsen et al. 1972; Lorius et al. 1979; Dansgaard et al. 1982). Yet data from additional cores are needed to make a better assessment of the contributions of local effects versus those of climate to the isotope record obtained. The South Pole is an attractive location for drilling, because there firnification and the relationship between the isotopic composition of the snow and seasonal temperature have been extensively studied (Epstein, Sharp and Cow 1965; Cow 1965; Picciotto, Deutsch, and Aldaz 1966; Aldaz and Deutsch 1967; Jouzel et al. 1983), and the presence of Amundsen-Scott South Pole Station provides good support. We here report recent isotopic oxygen (6180)* results obtained on South Pole samples in the Quaternary Isotope Laboratory. During November and December 1982 field parties from Ohio State University (osu), the University of Bern, Switzerland, and the University of Washington (uw) worked with personnel of the Polar Ice Coring Office (Pico) at the South Pole to obtain a core from 106- to 227-meter depth and to sample this core and the overlying 103-meter core, obtained from the same hole in 1980, for 8 11 0, microparticles, trapped gases and electrical conductivity (Kuivinen 1981, 1983; Mosley-Thompson and Thompson 1983; Stauffer and Schwander 1983). During this period, several snow pits were studied and sampled by the osu field party. Figure la shows the 180/depth profile from the Cwall of pit I located 4 kilometers from the station along 128° Eastern longitude (Mosley-Thompson, Kruss, and Bain 1983). Figures lb and ic are 8180 profiles from pits at a distance from the station of 1 kilometer along 110° and about 3 kilometers along 130° eastern longitude, that were sampled by osu field parties going to Dome C in November 1979 and coming from Dome C in late February 1979 respectively (Bolzan personal communication; Bolzan, Palais, and Whillans, 1979). Both the average 8180 of the different profiles (a. -51.23 parts per thousand; b. -52.66 parts per thousand; c. -51.07 parts per thousand) and the minimum and maximum values (a. -42.34/-55.84 parts per thousand; b. -44.58/-56.46 parts per thousand; c. -42.86/-55.65 parts per thousand) are similar to the values reported earlier by Epstein, Sharp, and Cow (1965), Picciotto, Deutsch, and Aldaz (1966), and Jouzel et al. (1983). A detailed comparison of the profiles a, b, and c and of these with the 6D profile of Jouzel et al. (1983) covering the same period shows significant differences. This is caused by the irregular snow deposition in which some area's may not accumulate any snow
* 180
is the relative deviation in oxygen-18 concentration of a sample from Vienna Standard Mean Ocean Water (v-sMow) expressed in parts per thousand- %).
62
during a particular year (Cow 1965). An estimated 1 out of every 10 years may be missing (J. R. Petit quoted in Mosley-Thompson and Thompson, 1982). It should be noted here that in the 180 profile an annual cycle may be lost, even though snow was accumulated during the year, when the distinctive, isotopically heavy summer accumulation is (partially) missing. Partial preservation of summer snow gives summer maxima more as humps than as distinctive peaks (Jouzel etal. 1983). The result is that isotope/depth profiles from the same general area can be visually quite different. Discrepancies between isotopic profiles are also evident in the five pits compared by Picciotto, Deutsch, and Aldaz (1966). For climate reconstruction or correlations on a yearly basis several isotope profiles have to be available that are independently dated using stratigraphic or other means. -42 -44 -46 -48 -50 -52 -54 -56 -58 -44 0 0 0
-46 -48
0
-50
>
-52
0
-54
e
0
-56 -58 -44 -48 -48 -50 -52 -54 -56 -58 Depth (m)
Figure 1. Oxygen isotopic composition (6180) [expressed as relative deviation from the international Atomic Energy Agency, Vienna Standard Mean Ocean Water (v-sMow), in parts per thousand—%4 of snow, as a function of depth in three snow pits near the South Pole. A. 4 kilometers (direction 128 0 E) from South Pole Station, November-December 1982. B. 1 kilometer (direction 110 0E) from South Pole Station, November 1979. C. about 3 kilometers (direction 1300 E) from South Pole Station, January 1979. (Profiles B and C were shifted to match the surface with its probable position in A. "m" denotes meter.) ANTARCTIC JOURNAL
Figure la shows four summer peaks with snow significantly heavier than the rest of the profile. The records of monthly average temperature at Amundsen-Scott South Pole Station show above average temperatures for December 1957 through February 1958, November 1966 through January 1967, November 1971 through February 1972, November 1976 through January 1977, and November 1980 through February 1981 (Amundsen-Scott South Pole Station climatological data summary). Counting from the December 1982 surface at the top correlates the isotopically heavy snow at 50- to 60-centimeter depth with the warm 1980-1981 summer, and makes it likely that the peaks at 150-centimeter and at 250-centimeter depth contain the 1976-1977 and 1971-1972 summer snow respectively. The uncertainty in ascribing the two peaks is caused by the 8 11 0 profile between 50- and 100-centimeter depth. The detailed microparticle and stratigraphic study of MosleyThompson at osu may confirm our conclusion. It is interesting to note here that years with above average summer temperatures at the South Pole are, with the exception of 1980-1981, associated with strong El Nino/Southern Oscillation events over the Pacific Ocean. This deserves further study. The 1982 profile contains 12 annual layers if we accept the correlation of the less negative isotope peaks with the warm summers. These annual layers give a snow accumulation of 23.8 ± 6.5 centimeters per year. The pit study of Jouzel et al. (1983) showed a density of 0.35 grams per cubic centimeter at the surface increasing to 0.41 grams per cubic centimeter at 3-meter depth. To estimate the accumulation in water equivalent we assume the same density profile for the 1982 snow pit and approximate the change in density with depth by a linear relation. This gives 8.9± 2.5 grams per square centimeter for the annual accumulation and an uncertainty of ± 0.7 grams per square centimeter for the average. This is in good agreement with the 8.74 grams per year of Mosley-Thompson and Thompson (1982) for the period 1974-1955 and with the 8.5 grams per year for the period 1978-1930 of Jouzel et al. (1983). Figure lb and ic do not show the above clear correlation with summer temperature. This may be due to the irregular deposition and partial preservation discussed above. The 8180 maxima and minima are less well defined due to the larger sample interval (4 centimeters compared with 2 centimeters in la). The 818 results from these three pits confirm the earlier work that the snow deposited at the South Pole shows a clear annual cycle in its oxygen isotopic composition that can be preserved during the initial stages of firnification. Yet the low average accumulation results occasionally in partially or completely missing years so the correlation between 18 0/depth profiles on an annual basis will be poor. The analysis of the two long South Pole cores [226.7 meters from 1980 and 1982, described above, and 202.4 meters from a nearby hole in 1981-1982 (Kuivinen et al. 1982)] that are currently being studied in our laboratory is therefore directed toward 8180 fluctuations on a time scale of decades or longer. Figure 2 shows results for the 226.7-meter core. Samples were cut as thin, 25-centimeter long strips parallel to the core axis. A three-point moving average is used to reduce the noise introduced by the large annual 11 0 cycle. A discussion of this profile and its correlation with the adjacent 1981-1982 core will be published elsewhere. This work was supported by the National Science Foundation grant DPP 80-19756. E. Mosley-Thompson and I.M. Whillans, Ohio State University, kindly supplied samples of their pit studies for oxygen isotope analysis. 8
1984 REVIEW
-47 -48 -49 -50 C/)
-51 0
a)
ca
-52
a)
-53 -54 L_LLLLL I 0 50 100 150 200 Depth (m)
Figure 2. Oxygen isotope composition (6180) [expressed as relative deviation from the International Atomic Energy Agency, Vienna Standard Mean Ocean Water (v-sMow), in parts per thousand -%0] as a function of depth in a 226.7-meter ice core from the South Pole (900 S). Samples cover 25-centimeter depth intervals. A three-point moving average is used to suppress noise caused by the annual cycle. ("m" denotes meter.)
References A!daz, L., and S. Deutsch. 1967. on a relationship between air temperature and oxygen isotope ratio of snow and firn in the South Pole region. Earth and Planetary Science Letters, 3, 267-274. Amundsen-Scott South Pole Station climatological data summary, obtained on station, December 1982. Boizan, J.F. 1979. Personal communication. Boizan, J.F., J.M. Palais, and I. Whilans. 1979. Glaciology of Dome C area. Antarctic Journal of the U.S., 14,(5)100-101. Dansgaard, W., S.J. Johnsen, H.B. Clausen, and C.C. Langway, Jr. 1971. Climatic record revealed by the Camp Century ice core. In K.K. Turekian (Ed.), The Late Cenozoic glacial ages. New Haven, Conn.: Yale University Press. Dansgaard, W., H.B. Clausen, N. Gundestrup, C.U. Hammer, S.F. Johnsen, P.M. Kristinsdottir, and N. Reeh. 1982. A new Greenland deep ice core. Science, 218, 1273-1277. Epstein, S., R.P. Sharp, and A.J. Gow. 1965. Six-year record of oxygen and hydrogen isotope variations in South Pole firn. Journal of Geophysical Research, 70, 1809-1814. Gow, A.J. 1965. On the accumulation and seasonal stratification of snow at the South Pole. Journal of Glaciology, 5, 467-477. Johnsen, S.J., W. Dansgaard, H.B. Clausen, and C.C. Langway, Jr. 1972. Oxygen isotope profiles through the Antarctic and Greenland ice sheets. Nature, 235, 429-434. Jouzel, J., L. Merlivat, J.R. Petit, and C. Lonus. 1983. Climatic information over the last century deduced from a detailed isotopic record in the South Pole snow. Journal of Geophysical Research, 88, 2693-2703. Kuivinen, K.C. 1981. Ice core drilling, 1980-1981. Antarctic Journal of the U. 5., 16(5), 78. Kuivinen, K.C. 1983. A 237-meter ice core from South Pole Station. Antarctic Journal of the U. S., 18(5), 113-114. Kuivinen, K.C., B.R. Koci, G.W. Holdsworth, and A.J. Gow. 1982. South Pole ice core drilling, 1981-1982. Antarctic Journal of the U. S., 17(5), 89-91. Lorius, C., L. Merlivat, J . Jouzel, and M. Pourchet. 1979. A 30,000-year isotope climatic record from Antarctic ice. Nature, 280, 644-648. Mosley-Thompson, E., and L.G. Thompson. 1982. Nine centuries of microparticle deposition at the South Pole. Quaternary Research 17, 1-13. 63
Mosley-Thompson, E., P.D. Kruss, and T. Bain. 1983. South Pole pit the South Pole. An example of an unusual meteorological event stratigraphic studies. Antarctic Journal of the U.S. 18(5), 116-118. recorded by the oxygen isotope ratios in the firn. Earth and Planetary Mosley-Thompson, E. and L.G. Thompson. 1983. South Pole ice core Science Letters, 1, 202-204. processing and microparticle analysis. Antarctic Journal of the U.S. Stauffer, B., and J. Schwander. 1983. Core processing and analyses of ice cores drilled at South Pole. Antarctic Journal of the U.S. 18(5), 18(5), 118-119. Picciotto, E., S. Deutsch, and L. Aldaz. 1966. The summer 1957-1958 at 114-116.
Vostok tephra-An important englacial stratigraphic marker? P. R. KYLE
Department of Geoscience New Mexico Institute of Mining and Technology Socorro, New Mexico 87801 J. PALAIS
Institute of Polar Studies Ohio State University Columbus, Ohio 43210
E. THOMAS Department of Geology Arizona State University Tempe, Arizona 85281
Tephra (volanic ash) layers, if they are widespread, have the potential to provide important stratigraphic markers in ice cores. If the source of the tephra can be identified and an age assigned to the eruption, then the tephra layer can also provide a valuable time plane (Kyle, Palais, and Delmas 1982). Hammer (1980) and Hammer, Clausen, and Dansgaard (1981) have demonstrated the value of tephra in ice cores from Greenland. Using surface conductivity measurements they located volcanicderived acid layers, which were in some cases correlated with known eruptions. Such work has not been conducted on antarctic ice cores and most tephra layers are located either by (1) visual inspection (Gow and Williamson 1971), (2) detailed chemical analyses of the ice (Delmas and Boutron 1980), or (3) continuous microparticle measurements (Mosley-Thompson 1980). We have been examining visible volcanic layers from several antarctic ice cores. The objectives being to determine the source of the eruptions, evaluate possible climatic impact of the eruptions and to establish the volcanic record for the Southern Hemisphere. A 0.05-meter thick tephra layer was discovered in the bottom of a 101-meter long ice core drilled at Vostok Station in December 1979 (Parker, Zeller, and Gow 1982). An age of 3,300 years was assigned to the tephra based on snow accumulation rates and the ice stratigraphy. The layer was informally called the Vostok tephra by Kyle et al. (1982). We have examined the Vostok tephra in more detail and have identified the source of the eruption. The ice associated with the tephra layer has concentrations of sulphate which exceed 550 milligrams per liter. This is an exceedingly high value and suggests the eruption 64
responsible for the tephra was large and had a significant aerosol (H 2 SO 4 ) component. The tephra is composed of glass shards and rounded cryptocrystalline lithic material. Petrographic and scanning electron microscope measurements show the grains to range up to about 40 micrometers in length. The mean grain size is between 15 and 30 micrometers. Semi-quantitative and quantitative analyses of the glass shards have been made using an energy-dispersive analyzer on a scanning electron microscope and by electron microprobe. Analyses are listed in the table. The Vostok tephra is andesitic and characterized by high iron concentrations. Enrichment of iron is a characteristic feature of tholeiitic suites. Taking the prevailing wind directions into account, three major sources for the Vostok tephra can be considered: the South Sandwich Islands, the South Shetland Islands, and the Southern Andes. Fortunately, the three provinces are easily distinguished, and we suggest the South Sandwich Islands is the source area. The Southern Andes volcanoes are calc-alkaline andesites and although only a few analyses are available they have lower iron contents than the Vostok tephra (Katsui 1982). The South Shetland Islands have a much higher total alkali content than the South Sandwich (Baker 1968; GonzalezFerran 1982). Based on the available analyses of the South SandAnalyses of the Vostok tephra Compound Electron microprobe Energy dispersive Wet chemical analysisa analysis' analysisc d Si02 60.56 (0 . 42)d 59.73 (1.79) 60.90 Ti02 0.74 (0.07) 0.90 (0.16) 0.95 Al203 14.92 (0.82) 14.84 (0.66) 14.80 FeOe 9.15 (0.57) 10.25 (1.23) 8.34 MnO 0.23 (0.04) 0.15 (0.12) 0.11 MgO 2.39 (0.34) 2.44 (0.48) 2.35 CaO 6.72 (0.26) 6.64 (0.76) 6.09 Na20 3.31 (0.38) 4.46 (0.57) 3.67 K20 0.44 (0.05) 0.63 (0.19) 0.39 -f - f Total 98.46 100.04 97.72 Number of 9 analyses
37
Los Alamos National Laboratory (Analyst: J. Palais). Using a scanning microscope, Arizona State University (Analyst: E. Thomas). Aphyric andesite, Cauldron Lake lava flow, northern Candelmas Island (Tomblin 1979). d One standard deviation. Total iron as ferrous oxide. Not analyzed. ANTARCTIC JOURNAL
