(ESH) Holocene Climatic Variations in the Midcontinent of North America: Analyses of Annually Laminated Sediments from Minnesota Lakes

每年来自湖泊的层状沉积物（varves）提供了一种独特的工具，可以获得具有安全年表的大陆古气候数据。该提案旨在分析来自明尼苏达州四个湖泊的不同沉积物，以获得一套地球化学、沉积学和生物学代用指标，以评估北美大陆中部全新世的气候变化。这些指标包括阀厚度、有机和无机碳、碎屑矿物、矿物组成、粒度、碳酸盐和介形虫壳的氧和碳同位素、介形虫壳的微量元素组成和花粉。研究目标是：(1)利用近100年的仪器气象数据对不同沉积物中的各种气候代用物进行校准，以评估每种代用物与气候因子的关系；(2)在校准结果的基础上，通过解释我们研究地点的代用物记录，评估全新世气候变化，特别是周期和突变；(4)将北美大陆中部与格陵兰岛、北大西洋和全球其他地区的气候波动模式进行比较，以评估全新世气候变化的机制。

Annually laminated sediments (varves) from lakes provide a unique vehicle to acquire continental paleoclimatic data with secure chronologies. This proposal seeks to analyze varved sediments from four Minnesota lakes for a suite of geochemical, sedimentological, and biological proxies to assess Holocene climatic variability in the midcontinent of North America. These proxies include varve thickness, organic and inorganic carbon, detrital minerals, mineralogical composition, grain size, oxygen and carbon isotopes of carbonates and ostracode shells, trace-element composition of ostracode shells, and pollen. The research objectives are: (1) Calibrate various climatic proxies in varved sediments with instrumental weather data for the last 100 years to evaluate how each proxy is related to climatic factors, (2) Assess Holocene climatic variations, particularly cyclic and abrupt changes, by interpreting proxy records from our study sites on the basis of calibration results, (3) Integrate new varved-sediment data with findings from other high-resolution paleoclimatic studies in adjacent areas to provide a regional synthesis of Holocene climatic variations, (4) Compare patterns of climatic fluctuations in the midcontinent of North America with those in Greenland, the North Atlantic, and other parts of the globe to evaluate mechanisms of Holocene climatic variability.