RECORD OF CLIMATIC FLUCTUATIONS FROM CA 500 KA LOESS DEPOSITS AND PALEOSOLS NEAR WANGANUI, NEW-ZEALAND

In the Wanganui region of North Island, New Zealand, a record of clima te change for the last ca. 500 ka is preserved in a terrestrial cover bed sequence. Eleven loess layers from five major glacial cycles are s eparated by paleosols and punctuated by both rhyolitic and andesitic t ephra layers. The dated rhyolitic tephras, thermoluminescence dates fr om the loess, and dated marine terraces on which the sequence rests, p rovide good chronological control. A detailed stratigraphy and the use of four physical and chemical parameters enables a climatic interpret ation, and a correlation with the marine oxygen isotope record, to be made. Variations in dry bulk density and potassium content have result ed from weathering of the upper part of each loess unit during a warme r climate than that responsible for generation of the loess. Fluctuati ons in quartz content and magnetic susceptibility are of sedimentary o rigin and represent alternating quartzo-feldspathic and andesitic prov enance. Fluctuations in potassium content and dry bulk density are cau sed by weathering of the accumulating sediment. Glacial periods were t imes of environmental destabilization, loess accumulation, and least w eathering, while warm periods saw soil formation and gentle accession of andesitic tephra. The main periods of environmental destabilization were during marine Oxygen Isotope Stages 2, 3 (upper part), 6, 8, 10, and 12, while stages 1, 3 (lower part), 5, 7, 9, 11, and 13 provided most stable conditions and soil formation. Copyright (C) 1996 INQUA/El sevier Science Ltd