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Immediate report of Victoria University of Wellington Antarctic Expedition 1988-89: VUWAE 33

Aeolian Features of Miers Valley

Aeolian Features of Miers Valley

An attempt is also being made to describe and explain the aeolian features found in the upper Miers Valley. A series of "megaripples" originate on the Miers-Adams delta at the western end of Lake Miers and appear in a series of swales delineated by lateral moraines paralleling the north side of the valley.

The "megaripples" or granule/pebble ripples (Sharp, 1963) are low amplitude ripples of relatively long wavelength, having a ripple index of about 20-23, and are asymmetrical in shape. They are chiefly composed of granule to pebble size material and are formed by the impact of saltating sand particles creating surface creep rather than direct movement by the wind (Sharp, 1963). Such ripples have been described before in the Antarctic Dry Valleys (Selby et al 1974; Smith, 1966) and in other parts of the world (Bagnold, 1941; Sharp, 1963; Weir, 1962).

These ripples were mapped and measurements taken of their size (windward and lee slope heights and angles) and extent. Their orientation and the general ground slope on which the features were located were also recorded. Profiles were surveyed across the area in which the features occurred to aid their description and to place them in topographic context.

Samples were taken of the source material; of the material forming the windward and lee slopes of the ripples; the material forming the "armouring" layer at various locations; and the subsurface material.

A number of "tails" formed in the lee of large rocks were also measured for height, slope, and length for study in relation to the size of the obstacle i.e., rock.

In addition, a number of simple aeolian sediment traps were set to sample the sediment being moved by the wind during our time in the valley. Ten traps were positioned about the upper Miers Valley in locations determined by potential sediment supply and wind direction.

The traps were also positioned at various heights above ground level to check for any vertical stratification in particle size and quantity within the air mass. These traps were moved on several occasions to provide as complete information as possible of the summer aeolian sediment transport pattern.