Paleomagnetism and Magnetostratigraphy of the James Ross Basin, Antarctica

南极洲詹姆斯罗斯盆地的古地磁学和磁性地层学

• 批准号: 1341729
• 负责人: Joseph Kirschvink
• 金额: $ 41.51万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1341729&HistoricalAwards=false
• 关键词: Paleomagnetism; Magnetostratigraphy; James; Ross; Basin

Non-Technical Summary: About 80 million years ago, the tip of the Antarctic Peninsula in the vicinity of what is now James Ross Island experienced an episode of rapid subsidence, creating a broad depositional basin that collected sediments eroding from the high mountains to the West. This depression accumulated a thick sequence of fossil-rich, organic-rich sediments of the sort that are known to preserve hydrocarbons, and for which Argentina, Chile, and the United Kingdom have overlapping territorial claims. The rocks preserve one of the highest resolution records of the biological and climatic events that led to the eventual death of the dinosaurs at the Cretaceous-Tertiary boundary (about 66 million years ago). A previous collaboration between scientists from the Instituto Antártico Argentino (IAA) and NSF-supported teams from Caltech and the University of Washington were able to show that this mass extinction event started nearly 50,000 years before the sudden impact of an asteroid. The asteroid obviously hit the biosphere hard, but something else knocked it off balance well before the asteroid hit. A critical component of the previous work was the use of reversals in the polarity of the Earth?s magnetic field as a dating tool ? magnetostratigraphy. This allowed the teams to correlate the pattern of magnetic reversals from Antarctica with elsewhere on the planet. This includes data from a major volcanic eruption (a flood basalt province) that covered much of India 65 million years ago. The magnetic patterns indicate that the Antarctic extinction started with the first pulse of this massive eruption, which was also coincident with a rapid spike in polar temperature. The Argentinian and US collaborative teams will extend this magnetic polarity record back another ~ 20 million years in time, and expand it laterally to provide magnetic reversal time lines across the depositional basin. They hope to recover the end of the Cretaceous Long Normal interval, which is one of the most distinctive events in the history of Earth?s magnetic field. The new data should refine depositional models of the basin, allow better estimates of potential hydrocarbon reserves, and allow biotic events in the Southern hemisphere to be compared more precisely with those elsewhere on Earth. Other potential benefits of this work include exposing several US students and postdoctoral fellows to field based research in Antarctica, expanding the international aspects of this collaborative work via joint IAA/US field deployments, and follow-up laboratory investigations and personnel exchange of the Junior scientists. Technical Description of Project The proposed research will extend the stratigraphic record in the late Cretaceous and early Tertiary sediments (~ 83 to 65 Ma before present) of the James Ross Basin, Antarctica, using paleo-magnetic methods. Recent efforts provided new methods to analyze these rocks, yielding their primary magnetization, and producing both magnetic polarity patterns and paleomagnetic pole positions. This provided the first reliable age constraints for the younger sediments on Seymour Island, and quantified the sedimentation rate in this part of the basin. The new data will allow resolution of the stable, remnant magnetization of the sediments from the high deposition rate James Ross basin (Tobin et al., 2012), yielding precise chronology/stratigraphy. This approach will be extended to the re-maining portions of this sedimentary basin, and will allow quantitative estimates for tectonic and sedimentary processes between Cretaceous and Early Tertiary time. The proposed field work will refine the position of several geomagnetic reversals that occurred be-tween the end of the Cretaceous long normal period (Chron 34N, ~ 83 Ma), and the lower portion of Chron 31R (~ 71 Ma). Brandy Bay provides the best locality for calibrating the stratigraphic position of the top of the Cretaceous Long Normal Chron, C34N. Although the top of the Cretaceous long normal Chron is one of the most important correlation horizons in the entire geological timescale, it is not properly correlated to the southern hemisphere biostratigraphy. Locating this event, as well as the other reversals, will be a major addition to understanding of the geological history of the Antarctic Peninsula. These data will also help refine tectonic models for the evolution of the Southern continents, which will be of use across the board for workers in Cretaceous stratigraphy (including those involved in oil exploration).This research is a collaborative effort with Dr. Edward Olivero of the Centro Austral de Investigaciones Cientificas (CADIC/CONICET) and Prof. Augusto Rapalini of the University of Buenos Aires. The collaboration will include collection of samples on their future field excursions to important targets on and around James Ross Island, supported by the Argentinian Antarctic Program (IAA). Argentinian scientists and students will also be involved in the US Antarctic program deployments, proposed here for the R/V Laurence Gould, and will continue the pattern of joint international publication of the results.

非技术摘要：大约8000万年前，现在詹姆斯·罗斯岛（James Ross Island）附近的南极半岛的尖端经历了快速沉降的一集，创造了一个广泛的定义盆地，该盆地收集了从高山向西部侵蚀的沉积物。这种抑郁症积累了一系列厚实的化石，有机丰富的沉积物，这些沉积物已知可以保存碳氢化合物，而阿根廷，智利和英国为此具有重叠的领土主张。岩石保留了生物和气候事件的最高分辨率记录之一，导致恐龙最终在白垩纪 - 距离边界（大约6600万年前）死亡。来自加州理工学院和华盛顿大学的NSF支持的Argentino学院（IAA）和NSF支持的团队的科学家之间的先前合作能够证明，这一群众扩展事件始于小行星突然影响之前将近50，000年。小行星显然很难击中生物圈，但在小行星命中率之前，其他有些事情使得它触及了平衡。先前工作的一个关键组成部分是在地球磁场的极性中使用逆转作为约会工具？磁学。这使团队可以将南极的磁反转与地球上的其他地方相关联。这包括来自6500万年前大部分印度大部分地区的大型火山喷发（洪水盆地省）的数据。磁性模式表明，南极延伸始于这种巨大喷发的第一个脉冲，这也与极性温度的快速升高相吻合。阿根廷和美国的合作团队将及时扩展这一磁性极性记录，并及时延伸约2000万年，并横向扩展，以在整个沉积盆地提供磁反转时间线。他们希望恢复白垩纪长正常间隔的末端，这是地球历史上最独特的事件之一。新数据应改进盆地的沉积模型，允许更好地估计潜在的碳氢化合物储量，并允许将南半球的生物事件与地球其他地方的其他数据进行比较。这项工作的其他潜在好处包括将几名美国学生和博士后研究员暴露于南极洲的基于现场的研究，通过联合IAA/美国现场部署扩大了这项合作工作的国际方面，以及对初级科学家的后续实验室调查和人员交流。项目的技术描述拟议的研究将使用古磁方法在南极洲的詹姆斯·罗斯盆地（James Ross Basin）的晚白垩统和早期第三纪沉积物（现在〜83至65 mA）中扩展地层记录。最近的努力提供了分析这些岩石，产生其主要磁化以及产生磁极性模式和古磁极位置的新方法。这为西摩岛上的年轻沉积物提供了第一个可靠的年龄限制，并量化了盆地这一部分的沉积率。新数据将允许从高沉积速率James Ross Basin（Tobin等，2012）中解析出稳定的残留磁化，从而得出精度年代学/地层。这种方法将扩展到该沉积盆地的重新介绍部分，并将允许对白垩纪和早期第三纪时间之间的构造和沉积过程进行定量估计。所提出的现场工作将完善白垩纪长正常末端（Chron 34n，〜83 Ma）和Chron 31r（〜71 MA）的几种地磁逆转的位置。白兰地湾（Brandy Bay）提供了校准白垩纪长正常Chron（C34N）顶部的地层位置的最佳地方。尽管白垩纪长的正常纪录的顶部是整个地质时间尺度中最重要的相关范围之一，但它与南半球生物学学没有正确的相关性。在理解南极半岛的地质历史上，定位此事件以及其他逆转将是一个主要的补充。 These data will also help refine tectonic models for the evolution of the Southern continents, which will be of use across the board for workers in Cretaceous stratiography (including those involved in oil exploration).This research is a collaborative effort with Dr. Edward Olivero of the Centro Austral de Investigaciones Cientificas (CADIC/CONICET) and Prof. Augusto Rapalini of the University of Buenos Aires.该合作将包括在阿根廷南极计划（IAA）支持的詹姆斯·罗斯岛（James Ross Island）及其周围的重要目标的未来现场旅行中收集样本。阿根廷科学家和学生还将参与美国南极计划的部署，并在这里为R/V劳伦斯·古尔德（R/V Laurence Gould）提议，并将继续以国际联合发布结果的模式。