Peleus Till

The Peleus till covers the floor of east-central Wright Valley up to an elevation of about 1,150 tn (Prentice 1982 Hall et al. 1993), but it does not form moraines or other kinds of glacial landforms. It consists of a pale yellow to yellowish brown diamicton with a silty or sandy matrix containing clasts of dolerite, granitoids, and metasedimentary rocks, as well as of orthoquartzite and porphyritic dike rocks, all of which occur within the Wright Valley. However, the Peleus till does not contain clasts of late Cenozoic basalt of the McMurdo Volcanic Group. Evidently the Peleus till was deposited before the start of volcanic eruptions in the area. 

The soil that has developed on the Peleus till is oxidized to a depth of about 30 cm and contains salt crystals and encrustations in the upper 20 cm (Bockheim 1978). The extent of weathering of the Peleus till generally corresponds to stage 4 of Campbell and Claridge (1987). Hall et al. (1993) concluded that  

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The most recent contributions to the history of glaciation of Wright Valley are by Prentice (1982), Prentice et al., 1987), and Hall et al. (1993) which led to a new synthesis by Denton et al. (1993). Hall et al. (1993) recognized three kinds of glacial deposits in Wright Valley Peleus till, Alpine moraines, and Ross Sea drift. The stratigraphy in Table 19.8 indicates that these deposits formed in a glaciated landscape which existed when the Peleus till was deposited at >3.8 Ma. 

Fig. 19.24 The Peleus till was deposited by a temperate wet-based glacier that flowed across the rocky threshold into the Wright Valley during the early Pliocene less than 4-5 miUion years ago. The thickening of the East Antarctic ice sheet was caused by an episode of climatic warming. The surface of the...

Fig. 19.26 Pecten shells of Chlamys tufiensis occur in a gravel bed that overhes the Peleus till at Prospect Mesa which is located at the mouth of BuU Pass in central Wright Valley (Photo by R.D. Turner reproduced with permission)...

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