Details

Autor(en) / Beteiligte

• Shulmeister, James
• Shane, Phil
• Lian, Olav B
• Okuda, Masaaki
• Carter, John A
• Harper, Margaret
• Dickinson, Warren
• Augustinus, Paul
• Heijnis, Henk

Titel

A long late-Quaternary record from Lake Poukawa, Hawke’s Bay, New Zealand

Ist Teil von

• Palaeogeography, palaeoclimatology, palaeoecology, 2001-12, Vol.176 (1-4), p.81-107

Erscheinungsjahr

2001

Link zum Volltext

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• The Lake Poukawa Basin is a large co-seismic depression located at 20 m above mean sea level in Hawke's Bay in eastern North Island, New Zealand. We present a detailed environmental history of the basin for the last c. 60 ka based on analyses of the top 105 m of a 200-m core record. Dating control is provided by radiocarbon, optically stimulated luminescence (OSL) and U/Th disequilibrium ages. The chronology is supported by nine tephras of inferred age including marker tephras, Kawakawa (22590 plus or minus 230 yr BP at -18.25 m core datum), Tahuna (c. 35-43 ka) at -33.1 m core datum, and Rotoehu (45-50 ka) at -39.1 m core datum. Disagreements between some of the older tephra ages and the numerical ages from the OSL and U/Th dating mean that more than one age model can be applied. Three major lithostratigraphic units are identified: a basal calcareous silt with lignitic peats between 105.28 and 98.58 m of marine oxygen isotope stage (MIS) 3 age; an extended sequence of detrital shelly sands and silts, between 98.58 and 8 m of MIS 3 and 2 age; and a Holocene peat unit (MIS 1) from 8 to 0 m. Alternatively, but less likely, the basal unit may represent stage MIS 5a and the detrital shelly sands would then contain an amalgam of MIS 4, 3, and 2 deposits. We propose a notably moist phase represented by the peat which our numerical dating model places near the start of isotope stage 3. This suggests the existence of mild conditions during an interstadial in central New Zealand at c. 55-50 ka when a podocarp-beech-broadleaf forest of near-interglacial affinity surrounded the basin. The interstadial is marked by both lake and peat formation in the basin. After 50 ka a thermal decline set in, though the climate remained moist initially. Under these conditions, the Poukawa Basin was rapidly infilled by alluvial fan deposits from the surrounding hills.