Loess Deposits of the South Island, New Zealand, and Soils Formed on them

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Abstract
Loess deposits from 1 to more than 25 ft thick are widely distributed over the eastern and southern downlands, hills, and older plains of the South Island from Marlborough to Southland. They are wind-borne deposits derived from (1) greywackes of the Southern Alps in Marlborough, Canterbury, and north-east Otago, (2) metamorphic schists elsewhere in Otago, and (3) tuffaceous greywackes, basic igneous rocks, and schists in Southland. The loess deposits are in most places compact, of low permeability, and, with minor exceptions, contain no free lime. At least six layers of loess can be distinguished, three being assigned to the Last Glaciation and three to the Penultimate. Periods of loess deposition correspond with glacial stadia, and periods when little or no loess fell with interglacial and interstadial periods. Slight to moderate weathering took place during interstadial periods and more advanced weathering during the last interglacial period. Present and fossil yellow-grey earths formed on the South Island loess have a subsoil pan that is considered to express compaction that took place mainly during the period of loess accumulation. Increased biological activity and more active soil formation during the warmer and wetter interstadial and interglacial periods caused fragmentation of the pan to a greater or less extent. The pan is thought therefore to be a feature inherited from the period of loess deposition and not a product of the current pedological environment.

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