Dune-building phases in the Manawatu district, New Zealand

Abstract

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.

The source, age, and stabilisation of the Koputaroa dunes, Otaki‐Te Horo, New Zealand

“…Within the Manawatu-Horowhenua area, North Island, New Zealand, a broad chronological sequence of landscape evolution has been postulated. This sequence explains the relative stratigraphy, the Holocene dune phases, the fluvial terraces and loess deposits, and the present interglacial highstand seacliff (Cowie 1963;Palmer et al 1988;Muckersie & Shepherd 1995 Many of these same landscape elements (including the Koputaroa dunes), although significantly smaller, are also present farther south at Otaki-Te Horo (Fig. 1).…”

“…In the Horowhenua-Manawatu area, the Koputaroa dunes are no closer than 5 km from the coast and extend up to 25 km inland. Using radiocarbon, thermoluminescence (TL), and infrared stimulated luminescence dating, and sedimentological analysis, their relative stratigraphic position, origin, and age have been postulated (Cowie 1963;Shepherd 1985;Shepherd & Price 1990;Duller 1996). Pollen analysis of these dunes shows they formed during cool climatic conditions, most likely during a late stage of 5 18 O stage 2 (Mclntyre 1963).…”

“…Pollen analysis of these dunes shows they formed during cool climatic conditions, most likely during a late stage of 5 18 O stage 2 (Mclntyre 1963). The degree of soil development led Cowie (1963) to conclude that they were between 10 000 and 20 000 yr old. Shepherd & Price (1990) obtained a TL date of 24 000 ± 3700 yr for a sample of Koputaroa dune sand taken from Paiaka Road, Horowhenua (Fig.…”

“…These dunes were subsequently remobilised about the time of the Kawakawa Tephra deposition. Cowie (1963) andFleming (1972) argued that the Koputaroa dune sand was of fluvial origin. However, Shepherd (1985) concluded that some, if not all, of the sand in these dunes in Manawatu-Horowhenua was of coastal origin.…”

Some aspects of the late Quaternary geomorphology of the lower Manawatu Valley, New Zealand

“…1) : (1) The Tokomaru Marine Terrace (Cowie 1961) borders the western flanks of the Tararua Range, rising from 30-40 m above mean sea level in the vicinity of Levin to approximately 90 m near Palmerston North. The terrace is underlain by soft sandstones, siltstones, and gravels with a surface cover of loess (1-4 m in thickness), Aokautere Ash (Cowie 1964a;1964b), and, in places, Pleistocene dune sand (Cowie 1963) and gravel fans. The terrace formation has been described in detail by Oliver (1948) and Rich (1959), and the upper beds have been tentatively placed in the Oturian (Interglacial) Stage by Fleming (1971).…”