Dune sands with four different stages of soil development cover 330 square miles in the coastal Manawatu district. The oldest-the Koputaroa Phase-is restricted to small ar'eas at the north and south; the other three phases-the Foxton, Motuiti, and Waitarere----form belts parallel to the coast, the oldest belt being the furthest inland. The Koputaroa Phase is considered to be Late Pleistocene or early Holocene and 20,000 to 10,000 years old. The Foxton Phase is older than the eruption of the Taupo Shower and about 4,000 to 2,000 years old. Sands of the Motuiti Phase overlie traces of Maori occupation and a stump that is about 750 years old, and are about 1,000 to 500 years old. The Waitarere Phase started about 100 years ago and is still accumulating.Sharp differences in soil development indicate that dune formation was discontinuous and much more rapid at some periods than others. The two youngest phases are considered to have been triggered off by the destruction of vegetation on the stabilised dunes near the coast and in the inland river valleys that followed the arrival of the Maori and European. This led to renewed wind erosion of the dunes and to accelerated erosion in the valleys, which caused more sand to be brought to the beaches. The causes of the two earliest phases are unknown.In an appendix, the pollen floras in a peaty layer associated with the Koputaroa Dune-sand are described and discussed. The pollen results indicate a climate considerably cooler than at present, which is attributed to a late phase of the Last Glaciation.

A distinctive ash, named the Aokautere Ash, is a useful marker bed for correlating late Quaternary terraces and deposits in the Manawatu and adjoining districts. The ash occurs on terraces older than the Ohakea Terrace, in dune sands at Koputaroa, and on the gently rolling tops of the Tararua Range at an altitude of 900 to 1,300 ft. Its exact age is uncertain, but its covering of loess that probably came from the growing Ohakea Terrace (the youngest extensive aggradational terrace in the Manawatu district), its absence from the Ohakea Terrace itself, and its association with a peat that contains a cool-climate pollen flora, suggest that it was erupted during a late stage of the Last Glaciation. The ash has proved to have considerable indirect pedological importance by showing that the parent material of the terrace soils is loess and not alluvial or marine sediment.

The taxonomic units proposed by Gibbs for the sequence of soils from andesitic tephra on Tongatapu have been redefined. The Lapaha series is defined as formed almost wholly from the older more weathered tephra, and the Vaini series as from moderately thick to thick younger tephra overlying the older tephra. Two new series are proposed-Fahefa series for soils from very thick deposits of the younger tephra, and Fatai series for soils with impeded drainage and evidence of gleying. Using the large number of profile observations that have been made on Tongatapu, percentage frequencies of the taxonomic units have been plotted for the mapping units shown on the original soil map of Gibbs, and on a revised map which is being prepared. These have shown that most of the mapping units are very variable and that some of them contain up to four taxonomic units. However, this present study has shown that predictions can be made for any one area on Tongatapu on the range of soils likely, the percentage frequency of occurrence of individual soils, and the dominant soil. Differences between most of the soils are due to variations in the thickness of the younger of the two contrasting tephras. The broad regional pattern of soils is related to the eastward thinning of the younger tephra. Superimposed on this regional pattern there is considerable variability related to local thinning and thickening of the younger tephra. This is partly related to present-day topography, which may have led to erosional redistribution of the younger tephra on sloping land and partly to some other factor unrelated to the present-day topography. This factor is probably related to irregularities in the underlying coral surface.

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Loess covers most of the terrace and rolling lands of the Manawatu district.