Gravel lag

The region is substantially covered by regolith sediments, which conceal prospective bedrock sequences. The regolith sediments include windblown sand, alluvial gravels, and caliche horizons. Commonly, the vertical profile of the regolith sediments consists of surface lag or loosely windblown sand underlain by weakly cemented sands and dense caliche-cemented sediments with gypsum. 

The Elephant Moraine is composed primarily of rock clasts and large boulders. Fine grained sediment is preserved only in areas where it is protected by lag gravel. The clasts and residual fines occur in bands on the surface of bare (blue) ice. Snow and fim occur only locally depending on the time that has elapsed since the most recent snowstorm. 

Fig. 19.25 A well preserved layer of white tiir-fall volcanic ash occurs in the central Wright Valley between the Heut and Goodspeed alpine glaciers. The deposit was preserved in-situ and is covered by a thin layer of lag gravel which Heill et al. (1993) identified as Ross-Sea drift. The K-Ar date (3.9 0.3 Ma) of volcanic glass in the Hart Ash is tui important reference point in the glacial history of the Wright Valley (Reproduced by permission from Hg. 11 of Hall et al. 1993)...

---