Named tephras and tephra formations occurring in the Central North Island, with notes on derived soils and buried paleosols

Abstract

Published names of tephra formations and members are arranged in chronological order, with estimated ages, distribution, and a statement of their mineralogical composition. The clay minerals in surface soils and in buried paleosols derived from them are listed, and the surface soils are classified.The sources of the tephras are mapped, with the 30 em isopachs of tephras that occur within 45 em of the surface and the 15 em isopachs of tephras found between 45 and 100 em from the surface also shown.The sequence of tephras that are likely to be found within 45 em from the surface is indicated, also, areas of recent soils from volcanic ash, and a suggested boundary between yellow-brown pumice soils and yellow-brown loams.

Identification and correlation of thinly bedded tephra: The Tirau and Mairoa Ashes

“…Pullar (1967), describing a profile near Tirau, suggested that Tirau Ash comprised Taupo Pumice and the Rotorua and Rotoma Ashes. The ages of these tephra (Pullar et al 1973) are younger than the Egmont Ash, which suggests that Mairoa Ash would underlie Tiran Ash. Alternatively the two deposits may interdigitate or be indistinguishable.…”

Tephra distribution and sedimentation rates m the Bay of Plenty, New Zealand

“…1), c. 1000 yrs B.P. (Pullar et al 1973) was found in any of the cores examined. This confirms the strong westerly fallout pattern of this tephra (Gibbs 1968;Pullar et al 1973).…”

Palynology, age and environmental significance of some peat beds in the upper Pleistocene Hinuera formation, South Auckland, New Zealand

“…The maximum age ot the Hinuera Formation is presently uncertain, although Hume et al (1975) suggested Hinuera-l aggradation may have commenced following emplacement of the ash-flow deposits and tephra.~ of the Rotoiti Breccia Formation in the Central Volcanic Region of the North Island, erupted between about 45000 and 40000 yr BP (Pullar et al 1973;Howorth and Vucetich 1976). During the sinking of bridge piles to carry sewerage pipes across the Waikato River at Te Rapa, Hamilton (N56j754530) , peat samples were collected from about 25 m below the bed of the river within a sequence of alluvial volcaniclastic silts, sands and gravels, correlated with the Hinuera Formation and presumed to represent mainly Hinuera-l sediments.…”