Collaborative Research: P2C2: A High Resolution Paleoclimate Archive of Termination I in Oneida Lake and Glacial Lake Iroquois Sediments

在最后一个冰河时代结束时，仍然覆盖着北美东北部大部分地区的巨大冰盖，在其南部边缘充当了融水池塘的水坝。当冰盖崩塌时，这些新鲜的湖水被释放到大西洋，并被认为扰乱了海洋环流，导致北半球，甚至可能是全球的突然寒冷。在安大略省南部和纽约州北部附近，巨大的易洛魁冰川湖含有大量的冷淡水，该湖的现代遗迹包括安大略湖和奥奈达湖。奥奈达湖位于古代冰川湖易洛魁的最东端附近，这个地区和莫霍克山谷是向哈德逊河和大西洋释放融水的关键阀门。奥奈达湖项目将研究这些融水释放期间沉积的古代沉积物，以确定它们的精确时间，然后将这些时间与格陵兰冰芯以及南部和大西洋沉积物中过去的气候记录进行比较。研究人员将使用地球物理（声纳）方法对奥奈达湖底下的沉积物进行成像，然后收集沉积物岩心进行详细分析。特殊的碳14测年技术将用于测定岩心沉积物的年代，并将分层沉积物与之前在新英格兰收集的类似记录联系起来。项目外展工作包括为湖边社区举办一系列公开讲座，与奥奈达国家高中科学课程合作，以及在湖上的州立公园安装科学信息亭。美国东部边缘。该项目通过分析新的地球物理数据和新的沉积物岩心，研究了纽约州北部奥奈达盆地的晚第四纪沉积物记录。异常丰富的地层档案将限制更新世末期劳伦泰德冰原东南缘的古气候演化。研究人员还将开发古代易洛魁冰川湖的能量平衡水文模型，以更好地约束该盆地的填水和排水事件。扰乱全球气候系统的非线性事件（例如，新仙女木时期的降温）包括与易洛魁冰川湖及其前身相关的主要融水脉冲和排水通道切换。研究人员将利用奥奈达湖和周围露头的丰富的变异沉积物记录，在几千年的季节分辨率下评估Termination I（末次冰期结束，约2万年前）。将盆地内新发现的湖泊沉积物露头观测与奥奈达湖岩心恢复的相关沉积序列相结合。通过古地磁法（交叉测年）与北美冰川期年代学对冰川期记录进行年代学约束，并通过选择性地使用有机质Ramped PyrOx放射性碳测年和单独的花粉14C测年进一步固定。初步的高分辨率地震数据揭示了一个显著的、高保真的地层学，并提供了溃决洪水事件、冰盖不稳定以及从冰川消融到全新世的连续时间序列的证据。整个湖泊将采用CHIRP（扫描信号地震）和多通道地震反射方法进行高空间分辨率的调查。校准后的事件时间序列将与三个成熟的全球档案进行比较：格陵兰冰芯记录、南极半岛帕尔默深和卡里亚科盆地海洋剖面。除了直接的科学成果和研究生培训之外，研究人员还将开展一项外展工作，包括：1)河岸社区系列讲座；2)在两个湖滨公园建设两个信息亭，描述易洛魁冰湖的地质演变和奥奈达湖的后续演变；3)在实地和实验室活动中吸引代表性不足的群体，包括来自奥奈达族的中学生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

At the end of the last ice age, the vast ice sheet still covering much of northeastern North America served as a dam for ponded meltwaters along its southern edge. When the ice sheet collapsed, those fresh lake waters were released to the Atlantic Ocean, and are thought to have disrupted ocean circulation, causing abrupt cold spells in the northern hemisphere, and perhaps globally. Near southern Ontario and northern New York State, enormous Glacial Lake Iroquois contained massive amounts of cold fresh water, and modern remnants of that lake include Lake Ontario and Oneida Lake. Oneida Lake is located near the easternmost part of ancient Glacial Lake Iroquois, and this area and the Mohawk Valley were a key valve for the release of meltwaters to the Hudson River and to the Atlantic. The Oneida Lake project will study the ancient sediments laid down during these meltwater releases, to determine their precise timing, and will then compare those timings to past climate records derived from Greenland ice cores and from sediments from the Southern and the Atlantic Oceans. The researchers will use geophysical (sonar) methods to image the sediments below the bottom of Oneida Lake, and then collect sediment cores for detailed analyses. Special Carbon-14 dating techniques will be used to date sediments in the cores and to correlate the layered sediments to similar records previously collected in New England. Project outreach efforts include a public lecture series for lake-side communities, engagements with Oneida Nation high school science classes, and the installation of science information kiosks at a State Park on the lake?s eastern edge.This project is examining the Late Quaternary sediment record from the Oneida Basin in Upstate New York, through analyses of new geophysical data and new sediment cores. The unusually rich stratigraphic archive will constrain the paleoclimate evolution along the SE margin of the Laurentide Ice Sheet in the terminal Pleistocene. The researchers will also develop an energy balance hydrologic model of ancient Glacial Lake Iroquois to better constrain fill and discharge events from this basin. Non-linear episodes that perturb the global climate system (e.g., the Younger Dryas cooling) include major meltwater pulses and drainage pathway switches associated with Glacial Lake Iroquois and its precursors. The researchers will evaluate Termination I (the end of the last glaciation, ~20,000 years ago) at seasonal resolution over several millennia, using the rich varved sediment record in Oneida Lake and surrounding outcrops. Outcrop observations of newly discovered lake sediment exposures (varves) in the basin will be integrated with correlative sedimentary sequences recovered by cores from Oneida Lake. The glacial varve record will be chronologically constrained via paleomagnetic methods (cross-dating) with the North American Varve Chronology and further fixed by selective use of Ramped PyrOx radiocarbon dating of organic matter and separately of pollen 14C dating. Preliminary high-resolution seismic data reveal a remarkable, high-fidelity stratigraphy with evidence for outburst flood events, ice sheet instabilities, and a continuous time series from deglaciation through the Holocene. The full lake will be surveyed at high spatial resolution using CHIRP (sweep signal seismic) and multichannel seismic reflection methods. The calibrated time series of events will be compared to three well-established global archives: the Greenland ice core record, the Antarctic Peninsula Palmer Deep and Cariaco Basin marine sections. Beyond the direct scientific outcomes and graduate student training, the researchers will mount an outreach effort including: 1) a riparian community lecture series; 2) construction of two information kiosks describing the geologic evolution of Glacial Lake Iroquois and subsequent evolution of Oneida Lake at two lakeside parks; and 3) engage under-represented groups including secondary school students from the Oneida Nation during both field and laboratory activities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.