Last Glacial loess and early Last Glacial vegetation history of Wairarapa Valley, New Zealand

Abstract

The upper Quaternary stratigraphic and physiographic record of Wairarapa Valley, southern North Island, is one of the most complete sequences for this time period in New Zealand. Wairarapa Valley is situated within an active tectonic belt, and opens to the south on a coastline that has been rapidly deformed during the Quaternary. Warm climate and high eustatic sea level are reflected by a sequence of five well-preserved marine benches, and by lacustrine environments in Wairarapa Valley. Cold climate (and low eustatic sea level) are reflected by erosion, fluvial aggradation, and loess production.

Three loess units deposited on Last Interglacial marine benches are widely preserved around the coastal part of the valley, and on fluvial aggradation gravels older than the Last Interglacial, further inland. At several other sites, the three loess units are preserved conformably on lacustrine sediments containing pollen and diatoms. At one site, Bidwill Hill, a well-preserved pollen and diatom flora record the cooling transition from the Last Interglacial to the first stadial of the Last Glacial.

Keywords:

• Wairarapa Valley
• upper Quaternary
• loess
• vegetation
• diatoms
• Ohakea
• Rata
• Porewa
• Last Interglacial
• marine benches
• aggradation terraces