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

在上一个冰河时代结束时，北美东北部大部分地区仍然覆盖着巨大的冰盖，充当了南部边缘积水融化的水坝。当冰盖崩塌时，这些淡水被释放到大西洋，被认为扰乱了海洋循环，在北半球乃至全球造成了突如其来的寒流。在安大略省南部和纽约州北部附近，巨大的冰川易洛魁湖含有大量冰冷的淡水，该湖的现代遗迹包括安大略湖和奥内达湖。奥内达湖位于古冰川湖易洛魁的最东端，这一地区和莫霍克山谷是向哈德逊河和大西洋排放融化水的关键阀门。奥奈达湖项目将研究这些融水释放过程中沉积的古代沉积物，以确定它们的准确时间，然后将这些时间与格陵兰冰芯以及来自南大洋和大西洋的沉积物得出的过去气候记录进行比较。研究人员将使用地球物理(声纳)方法对奥内达湖底部以下的沉积物进行成像，然后收集沉积物岩心进行详细分析。将使用特殊的碳14测年技术来确定岩心中的沉积物的年代，并将分层沉积物与以前在新英格兰收集的类似记录进行关联。项目外展工作包括为湖边社区举办一系列公开讲座，与Oneida Nation高中的科学课程接触，以及在S湖东缘的一个州立公园安装科学信息亭。该项目正在通过分析新的地球物理数据和新的沉积物岩心，研究纽约州北部Oneida盆地的第四纪晚期沉积物记录。异常丰富的地层档案将制约晚更新世Laurentide冰盖东南缘的古气候演化。研究人员还将开发古冰川湖易洛魁斯湖的能量平衡水文模型，以更好地约束该盆地的充填和排放事件。扰乱全球气候系统的非线性事件(例如，年轻的仙女座降温)包括与冰川易洛魁斯湖及其前体有关的主要融水脉冲和排水路径开关。研究人员将利用奥内达湖和周围露头的丰富多样沉积物记录，以季节性分辨率评估终止期I(约2万年前最后一次冰川的结束)，时间跨度超过数千年。对盆地新发现的湖泊沉积物暴露(VARVE)的露头观测将与奥内达湖岩心恢复的相关沉积序列相结合。冰川曲线记录将通过与北美Varve年代学的古地磁方法(交叉测年)进行年代学限制，并通过选择性地使用有机质的斜面PyrOx放射性碳测年和分开的花粉14C测年来进一步确定。初步的高分辨率地震数据显示了一个显著的、高保真的地层学，有证据表明洪水爆发、冰盖不稳定，以及从冰川消融到全新世的连续时间序列。将使用CHIRP(扫描信号地震)和多道地震反射方法以高空间分辨率调查整个湖泊。校准后的时间序列将与三个久负盛名的全球档案进行比较：格陵兰冰芯记录、南极半岛帕尔默深海和卡里亚科盆地海洋部分。除了直接的科学成果和研究生培训，研究人员还将开展外联活动，包括：1)河岸社区讲座系列；2)在两个湖边公园建造两个信息亭，描述冰川湖易洛魁的地质演变和随后的奥内达湖演变；以及3)在实地和实验室活动中接触到代表不足的群体，包括来自奥内达民族的中学生。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.