Structural laboratory studies were made of ice collected at the surface and from a shallow bore hole in the bare ice near the Allan Hills, Victoria Land, Antarctica. The results obtained were combined with glaciological survey data to describe the mechanism of accumulation of meteorites by ice flow in a marginal area of the East Antarctic ice sheet. The age of the bare ice, approximately 20 ka, was estimated by fabric characteristics and grain size of the ice. This conforms to the minimum value of the terrestrial age of the meteorites found in the same area. The several hundred meteorite finds concentrated in the bare-ice area can be explained by an expanded catchment area during a previous ice age, or by a correction factor for the estimate of the influx rate of meteorite fall, or more probably by a combination of both.
Preliminary results of the analyses on 700 m ice cores retrieved from Mizuho Station, Antarctica, in 1983 and 1984 are presented. The majority of the physical properties, density, grain-size and shape, and total gas content, were measured at the drilling site. Fabrics, microparticle concentration, electrical conductivity, and stable-isotope concentration 6 18 0 were measured in laboratories after the cores had been taken to Japan.In spite of inaccuracy in measuring both density and total gas content in the ice, due to interlocking cracks in cores, several attempts were made to correct the data. The coincidence between the incremental peaks in the depth profile of the microparticle concentration, as well as in the electrical conductivity and the warm trend indicated by the 6 18 0 profile is discussed. The shape of the 6 18 0 profile is characterized by two inflection points and is compared with results obtained from the Byrd Station, Dome C and Vostok cores. From this comparison, it is tentatively concluded that the bottom of the Mizuho core may be an age of the order of 10 ka B.P .
The Japanese Antarctic Research Expedition (JARE) has conducted glaciological studies on Mizuho Plateau since 1981. We have already reported that the ice sheet flowing from Mizuho Plateau into Shirase Glacier is thinning at a rate of about 70 cm/year and that the profile of the distribution of basal shear stress is similar to that of surging glaciers.A 5 year glaciological programme on Mizuho Plateau and in east Queen Maud Land is now being carried out and we have obtained the following new results:(1) The ice sheet in the down-stream region (where ice elevation is lower than about 2400 m) is thinning, based on measurements of horizontal and vertical flow velocity, strain-rate, the slope of the ice surface, the accumulation rate and densification of snow.(2) δ18O analysis of deep ice cores obtained at Mizuho Station (2240 m a.s.l.) and point G2 (1730 m a.s.l.) shows that δ18O increased about 200 years ago at Mizuho Station and about 400 years ago at point G2. If we can assume that the increase in δ18O is caused by the thinning of the ice sheet, then this result means that this thinning propagates to up-stream areas.(3) Radio-echo-sounding measurements on Mizuho Plateau show that the ice base in the down-stream region is wet. This supports the result described in (1), since the basal sliding due to a wet base causes ice-sheet thinning, as proposed in our previous studies.In summary, a possible explanation of ice-sheet variation on Mizuho Plateau is as follows: the thinning of the ice sheet, caused by the basal sliding due to basal ice melting, started at Shirase Glacier and has been propagating up-stream to reach its present position. A simple calculation, using flow velocities, shows that the thinning started at Shirase Glacier about 1500–2000 years ago.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.