Reckling Moraine and Allan Hills

The isotopic data summarized in Fig. 17.14 support the conclusion that the calcite in the Elephant Moraine was deposited from glacial meltwater at the base of the ice sheet, whereas the opaline silica precipitated from warm groundwater discharged by springs at the base of the ice sheet. These conclusions raise questions about the existence of liquid water at the base of the East Antarctic ice sheet and about the enrichment of glacial meltwater and groundwater in the ions that allowed calcite and opaline silica to precipitate. 

The moraine in Fig. 17.16 is about 6 km long and 1.5 km wide and has the shape of a horse shoe opening to the northeast. The interior of the moraine in Fig. 17.16 contains an irregularly-shaped clast-free area which resembles the Gingerbread Man of Mother Goose fame. The southern branch of the moraine contains numerous parallel bands of sediment-laden ice. Such bands are less abundant in the northern branch. 

Peak which is the only outcrop of bedrock in this belt of blue ice. dreds of meteorite specimens that are released by sublimation of 

The ice fields are generally located north of a complicated sys- the ice in which they were embedded (WhiUans and Cassidy, 

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The ablation rates of ice within the Reckling Moraine and on the adjacent ice fields were measured by means of 77 wooden dowel rods that were planted in December 1986, 63 of which were recovered in December of 1988. The results in Table 17.4 demonstrate that the average ablation rates of the ice fields adjacent to the Reckling Moraine and Allan Hills are 4.11 0.17 cm/year and 4.29 0.24 cm/year, respectively. These values are indistinguishable from the average ablation rate of the ice fields around the Elephant Moraine in Table 17.1 (i.e., 4.12 0.15 cm/ year). The ablation rate of ice within the Reckling Moraine (1.51 0.60 cm/year) is markedly lower than... 

The ablation rates of ice within the Reckling Moraine and in the surrounding ice fields were determined by Faure and Buchanan (1991). The results in Table 17.4 also include ablation rates of the main ice field adjacent to the Allan Hills where several hundred meteorite specimens have been recovered by personnel of Project ANSMET (Antarctic Search for Meteorites) (Score and Lindstrom 1990). 

The values of ice from the Allan Hills in Fig. 17.19c differ markedly from the values in the Reckling and Elephant moraines. Therefore, the ice exposed in the ice field adjacent to the Allan Hills originated from a different source area than the ice of the two moraines. This conclusion is consistent with the results of a triangulation survey of the Main Allan-Hills ice field in Fig. 17.20 by Annexstad and Nishio (1979) and Annexstad and Schultz (1982) who reported that the velocity of ice flowing east from the plateau into the... 

Main Allan-Hills ice field decreases from about 1 m per year to near zero close to the Allan Hills. Therefore, the ice west of the Allan Hills is stagnant and is not flowing in the direction of the Reckling Moraine. 

Fig. 17.22 The topography of the ice sheet adjacent to the Allan Hills is strongly affected by the bedrock at the base of the ice sheet. This profile of the ice sheet indicates that a bedrock ridge over which the ice if flowing forces basal ice to the surface which ablates to form a small supraglacial moraine on the surface of the ice. The Elephant and Reckling moraines probably form in the same way as a result of the interaction between the flow of the ice sheet and the mountainous topography of the subglacial bedrock (Adapted from Faure and Buchanan 1987)...

In addition, the values of snow that can be calculated from the 5D values measured by Lorius and Merlivat (1977) rise from -48%o to -20%o with increasing average annual temperature from -60°C near Dome C and -20°C at the Adelie Coast. The resulting graph in Fig. 17.27 includes the values of ice at the Elephant and Reckling moraines (E and R) and the Allan Hills (A). These empirical relationships relate the and 5D values of the ice to the climatic conditions at the time the snow was deposited. Although the climate history that is contained in the ice is destroyed by the deformation of the ice when it flows from its source to the area adjacent to the Transantarctic... 

Reckling (R) moraines and at the ice fields adjacent to the Allan Hills (A). These measurements are used here to estimate the average annual temperatures of the source regions of the ice. The data point labeled S is the measured value of snow deposited in the Reckling Moraine in December of 1986, which therefore indicates that the average annual temperature at the Reckling Moraine at the present time is -32.1°C (Based on data by Lorius and Merlivat 1977)... 

East Antarctic ice sheet located west of the Allan Hills in southern codes. The supraglacial Elephtuit and Reckling moraines were... 

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