Stratigraphy and sedimentology of Late-Pleistocene Lacustrine to alluvial deposits from the Waipaoa river catchment, North Island, New Zealand

Two stratigraphic sections of sediment were extracted on the Redpath Farm within the Waipaoa River Catchment, approximately 48 km northwest of Gisborne on the North Island of New Zealand. A 10-m drill core (Redpath 3) and a ~8 m stratigraphic section from a nearby stream-bank outcrop (Redpath 1A) were measured, described, and photographed. The Redpath 3 and 1A sections were sub-sampled at 2 and 1 cm contiguous intervals, respectively, for laboratory analyses that included mass magnetic susceptibility (CHI), loss on ignition at 550°C for percent total organic matter (TOM), and loss on ignition at 950°C for percent total carbonate (TC). Lacustrine and non-lacustrine (fluvial/alluvial) deposits were identified at each location, the former being characterized by laminations, numerous organic layers, and olive grayish color and the latter by very coarse, alluvial sediment, cobble beds, and massive sediment. Both Redpath 3 and Redpath 1A sections show similar ranges and mean values for CHI and TOM, as well as similar 14C ages (maximum of ~14,300 calendar years before present and minimum of ~13,300 calendar years before present). Values for TC, however, differ in their mean values and overall downsection patterns. Distinctive patterns in sedimentation and structure are observed at each location, such that the sections do not directly correlate despite their close proximity (~67 m) to one another. Such rapid facies changes are characteristic of small lake basins where sandy ‘storm pulses’, as defined at nearby (~300 km southwest) modern Lake Tutira, are found throughout both Redpath sections, indicating a rather dynamic climate during the time of deposition.