Was the Deepest Lake in North America a Subglacial Lake?

科学价值：这是一个为期一年的研究项目，旨在验证加拿大东北大奴湖克里斯蒂湾至少在末次冰期的部分时期是一个大型冰下湖的假设。过去的冰下湖泊代表了独特的、具有科学价值的古环境和古气候资料档案。它们也可以作为地球上的类似物，用于探索太阳系中冰冷的行星上过去的生命栖息地。2005年夏季在克里斯蒂湾的一个试验项目中收集的地震数据揭示了一个约150- 200米厚的解释（冰川）湖源沉积物序列。考虑到北美大型湖泊的冰期后线性沉积速率通常为0.1至1毫米/年，这样厚的层序可能潜在地保存了覆盖一个或多个冰期旋回的地面和冰下湖泊条件的记录。在对克里斯蒂湾序列进行采样和分析之前，需要收集更多的数据，以获得对克里斯蒂湾过去存在冰下湖的信心，并更好地规划未来对现有沉积记录的勘探。首席研究员将部署气枪和Chirp地震工具，以及多波束回波探测和短沉积物岩心，对覆盖600-800公里的地球物理湖泊进行调查。新的数据将阐明冰下和（冰川）湖相作用在克里斯蒂湾厚层序沉积中的相对重要性。它们还将对层序上部的线性沉积速率提供约束。对沉积速率的了解对于解释该沉积序列是否可能沉积起着关键作用：1)完全自消冰期~9,000-10,000年BP（即不需要冰下湖来解释观测结果），2)在一个冰期旋回（~100,000年）中，或3)在多个冰期旋回中。接受第一种后冰期模式将代表拒绝这一建议的指导假设。更广泛的影响对不同学科的贡献：项目结果将与许多学科相关，包括冰川地质学、地貌学、沉积学、地球物理学和气候动力学。人力资源发展：拟议的研究将代表UCSC首席研究员研究小组发展的重要阶段，因为它将继续参与北极研究，并将现代和过去冰下环境的两极研究联系起来。一名研究生将获得与沉积盆地勘探相关的最新地球物理技术应用方面的高级培训。一名非裔美国本科生将获得实验室和实地研究经验，并将在此基础上完成毕业论文。对课堂教学的影响：实地经验和研究成果将被纳入几个不同的课程，每年约有120名UCSC学生。社区和媒体外展：研究区域由第一民族控制，计划开展一些活动与当地社区接触（例如，在Lustelk'e的一所学校进行介绍，下午开放参观研究船，雇用第一民族成员担任两名船长和一名营地管理员）。当主要研究结果发表时，首席研究员将与加州大学圣迭戈分校的科学作家合作发布新闻稿。

ABSTRACTTulaczykOPP-0612385Scientific Merit: This is a one-year research project to test the hypothesis that Christie Bay, NE Great Slave Lake, Canada, was a large subglacial lake during at least part of the last glacial period. Past subglacial lakes represent unique and scientifically valuable archives of paleoenvironmental and paleoclimatic data. They may also serve as terrestrial analogs for exploration of past life habitats on icy planetary bodies in our Solar System. Seismic data collected in Christie Bay in summer 2005, during a pilot project, revealed a ~150-to-200-meter-thick sequence of sediments of interpreted (glacio) lacustrine origin. Given that postglacial linear sedimentation rates in large lakes in North America are typically of the order of 0.1 and 1 mm/yr, such a thick sequence may potentially hold a record of subaerial and subglacial lacustrine conditions covering one or more glacial cycles. Before sampling and analyses of the Christie Bay sequence will be warranted, there is need to collect more data to gain confidence in the past presence of a subglacial lake in Christie Bay and to better plan future exploration of the existing sedimentary record. The Principal Investigator will deploy air gun and Chirp seismic tools, together with multibeam echo sounding, and short sediment cores on a geophysical lake survey covering total of 600-800 km. The new data will elucidate the relative importance of subglacial and (glacio) lacustrine processes in deposition of the thick sedimentary sequence found in Christie Bay. They will also provide constraints on linear sedimentation rates within the upper part of the sequence. Understanding of sedimentation rates plays a key role in interpreting whether this sedimentary sequence may have been deposited: 1) entirely since deglaciation ~9,000-10,000 years BP (i.e., no subglacial lake needed to explain observations), 2) in one glacial cycle (~100,000 years), or 3) in multiple glacial cycles. Acceptance of the first, postglacial model will represent rejection of the guiding hypothesis of this proposal.Broader ImpactsContribution to Different Disciplines: Project results will be relevant to a number of disciplines, including glacial geology, geomorphology, sedimentology, geophysics, and climate dynamics.Human Resource Development: The proposed research will represent an important stage in the evolution of Principal Investigator's research group at UCSC because it will enable continuing involvement in Arctic research and will connect bi-polar studies of modern and past subglacial environments. One graduate student will obtain advanced training in application of state-of-the-art geophysical techniques relevant to exploration of sedimentary basins. One African-American undergraduate student will gain laboratory and field research experience and will complete senior thesis based on this work.Impact on Classroom Teaching: Field experience and research results will be incorporated in several different courses reaching annually ~120 students at UCSC. Community and Media Outreach: The study area is under control of First Nations and a number of activities are planned to interface with the local community (e.g., presentation at a school in Lustelk'e, open afternoon for visits to the research vessel, hiring of First Nation members in position of two skippers and one camp manager). The Principal Investigator will work with UCSC science writers to issue press releases when major findings are published.