ABSTRACT

A recently discovered upland paleolake (Redpath Lake) provides evidence of the expansion of lowland podocarp temperate forest to higher elevations within the tectonically active Waipaoa Sedimentary System (WSS), eastern North Island, New Zealand, during the Last Glacial-Holocene Transition. Interpreted as a localised landslide-dammed lake, lithofacies analyses indicate deposition and preservation in a low energy, sub-aqueous, lacustrine environment. Robust Bayesian-derived age-depth models constrained by key tephra fall beds and independent ¹⁴C dating (n = 7) indicate storm-bed frequency of c. 226 yrs on average. The absence of extensive soft-sediment deformation or lake-bed tilting implies that seismic shaking was insignificant during the Lake’s c. 12 ka yr (17.3–5.5 cal ka BP) existence. Pollen spectra extracted from lacustrine deposits include a mix of montane shrubland and lowland podocarp species spanning a well-dated c. 2200-year (c. 16.3–14.1 cal ka BP) period coeval with a phase of significant climate amelioration (late NZCe–5/NZce-4 mild episode), based on biotic proxies during the latter part of the climatically variable Last Glacial-Interglacial Transition (LGIT) (c. 18.2–11.8 cal ka BP). These pollen spectra represent the first New Zealand record of replacement of montane shrublands in terrestrial uplands of the WSS were replaced by lowland podocarp forest.

摘要

最近发现的一个高地古湖（Redpath Lake）提供了证据，证明在最后一次冰河-全新世过渡期间，新西兰北岛东部的构造活跃的 Waipaoa 沉积系统 (WSS) 内的低地罗汉松温带森林向更高海拔地区扩张。岩相分析被解释为一个局部的滑坡堰塞湖，表明沉积和保存在低能量、水下、湖泊环境中。受关键火山灰层和独立¹⁴ C 测年（n = 7) 表示 c 的风暴床频率。平均226岁。没有广泛的软沉积物变形或湖床倾斜意味着在湖的 c 期间地震震动是微不足道的。12 ka yr (17.3–5.5 cal ka BP) 存在。从湖泊沉积物中提取的花粉光谱包括山地灌木丛和低地罗汉松物种的混合物，这些物种跨越了一个年代久远的 c。2200 年 (c. 16.3–14.1 cal ka BP) 时期与显着气候改善阶段（晚期 NZCe-5/NZce-4 温和事件），基于气候变量末次冰期后期的生物代理-间冰期过渡 (LGIT) (c. 18.2–11.8 cal ka BP)。这些花粉光谱代表了新西兰第一个将 WSS 陆地高地中的山地灌木丛替换为低地罗汉松林的记录。