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A multi-proxy paleoenvironmental interpretation spanning the last glacial cycle (ca. 117 ± 8.5 ka BP) from a lake sediment stratigraphy from Lake Kai Iwi, Northland, New Zealand
Journal of Paleolimnology ( IF 2.1 ) Pub Date : 2020-09-09 , DOI: 10.1007/s10933-020-00151-z
Gianna Evans , Paul Augustinus , Patricia Gadd , Atun Zawadzki , Amber Ditchfield , Jenni Hopkins

A 9.3-m-long lake sediment core from dune-impounded Lake Kai Iwi in Northland, New Zealand provides a nearly continuous record of environmental changes from multi-proxy organic, physical index, and µ-XRF elemental data sets. The chronology for the upper 3 m of the core was established by 210 Pb, 14 C and tephrochronology and includes Marine Isotope Stage (MIS) 1 (Holocene), MIS 2 and late MIS 3. From this well-dated section of the core stratigraphy we were able to infer the environmental proxies that respond to wind and/or precipitation during cool periods (MIS 2 and 4) and with the warm periods (MIS 1 and 5). Principal component analysis (PCA) and cluster analysis were performed on the µ-XRF elemental data set including elements common in lake sediments (P, S, Fe, Ti, K, Ca, and Si) and five ratios (Sr/Ca, Br/Cl, Mn/Fe, Ti/K, and Inc/coh) to identify patterns in the µ-XRF proxy data associated with environmental change manifesting as changes in precipitation and wind deposition. The PCA indicates that Component (PC)-1 represents detrital versus organic deposition, and PC-2 is associated with nutrient influx versus anoxic conditions in the lake. The cool periods of MIS 2 and 4 are apparent in the µ-XRF data as having increased detrital influx in the form of Sr/Ca from marine derived sediments from the exposed continental shelf during low sea level indicating cool and dry conditions. Warmer and wetter periods (MIS 1 and 5) are identified by increased Ti/K influx from precipitation runoff and increased organic productivity as shown by Inc/coh and total organic carbon. The Holocene warm equivalent conditions of MIS 5e are not represented in the lower part of the Lake Kai Iwi core stratigraphy consistent with an extrapolated basal age of 117 ± 8.5 ka BP.

中文翻译:

来自新西兰北地凯伊维湖的湖泊沉积地层的跨最后一次冰川周期(约 117 ± 8.5 ka BP)的多代理古环境解释

来自新西兰北地沙丘蓄水的凯艾维湖的一个 9.3 米长的湖泊沉积物核心通过多代理有机、物理指数和 µ-XRF 元素数据集提供了近乎连续的环境变化记录。岩心上部 3 m 的年代学由 210 Pb、14 C 和地质年代学确定,包括海洋同位素阶段 (MIS) 1(全新世)、MIS 2 和晚 MIS 3。我们能够推断出在凉爽时期(MIS 2 和 4)和温暖时期(MIS 1 和 5)对风和/或降水做出反应的环境代理。对 μ-XRF 元素数据集进行了主成分分析 (PCA) 和聚类分析,包括湖泊沉积物中常见的元素(P、S、Fe、Ti、K、Ca 和 Si)和五个比率(Sr/Ca、Br /Cl、Mn/Fe、Ti/K、和 Inc/coh) 来识别 μ-XRF 代理数据中与环境变化相关的模式,表现为降水和风沉积的变化。PCA 表明组分 (PC)-1 代表碎屑沉积与有机沉积,PC-2 与湖泊中营养物质流入与缺氧条件相关。MIS 2 和 4 的凉爽期在 μ-XRF 数据中很明显,因为在低海平面期间,来自暴露大陆架的海洋沉积物以 Sr/Ca 的形式增加了碎屑流入,表明凉爽和干燥的条件。更暖和更湿润的时期(MIS 1 和 5)通过降水径流中 Ti/K 流入的增加和有机生产力的增加来确定,如 Inc/coh 和总有机碳所示。
更新日期:2020-09-09
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