Late Pleistocene historical geomorphology of the Lake Pukaki area, New Zealand

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Abstract
A sequence of Pleistocene valley glaciers is discussed in terms of a new geomorphic mapping unit, analogous to the formation in stratigraphy. A landform association is defined as a subdivision of a landscape in which the landforms have such an ordered arrangement, consistency of slopes, uniformity of erosional development and degree of obliteration of detail as would indicate that they originated together as a land surface. Within a setting of tilted fault blocks and locally derived gravels, five such associations are defined, described (with stratigraphic sections where available), and interpreted. The Stevenson Association is a deformed alluvial plain of weathered gravels, which may have been proglaeial to an ice advance of the Waimaunga glaciation. The Irishman Association includes remnants of subdued glacier-margin landforms descending radially from high altitudes in the Tasman valley, probably a product of an early Otiran glacial advance. Massive, fresh, outer and inner loop of moraines about Lake Pukaki, with kame terraces, kames, eskers, washboard moraines, ice-contact river channels and terraces, and fluted surfaces, together with outwash channels and plains covering much of the floor of the Mackenzie Basin comprise the Pukaki and Maryburn As:mciations, which provide evidence on the shape and behaviour of successive late Otiran glaciers. Moraines of the Birch Hill Association define a glacier terminus intermediate in position between that of the Pukaki Association and those of glaciers now active. The Birch Hill Association, which is extensively represented by glacial troughs and cirques, is thought to be of Late Glacial age. If the Maryburn Association is correlated with deposits radiocarbon-dated at 22,300 years B.P., proportional uplift of surfaces on a fault at the Irishman Creek gorge indicates ages of 51,000 years and 105,000 years for the Irishman and Stevenson Associations respectively.