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.

非技术概要：大约8000万年前，现在詹姆斯罗斯岛附近的南极半岛尖端经历了一次快速下沉，形成了一个广阔的沉积盆地，收集了从高山向西侵蚀的沉积物这个洼地积累了一系列富含化石、富含有机物的沉积物，这些沉积物已知可以保存碳氢化合物，阿根廷、智利和英国对其拥有重叠的领土主张。这些岩石保留了最高分辨率的沉积物之一。导致白垩纪-第三纪边界（大约 6600 万年前）恐龙最终死亡的生物和气候事件的记录是阿根廷南极研究所 (IAA) 和美国国家科学基金会支持的加州理工学院团队之前的合作成果。华盛顿大学能够证明，这场大规模灭绝事件在小行星突然撞击生物圈之前就开始了近 5 万年。很难，但早在小行星撞击之前，其他东西就使其失去了平衡，之前的工作的一个关键组成部分是利用地球磁场的极性反转作为磁地层学工具。南极洲与地球其他地方的磁反转模式这包括 6500 万年前覆盖印度大部分地区的一次主要火山喷发（洪水玄武岩省）的数据。南极洲的灭绝始于这次大规模喷发的第一次脉冲，这也与极地温度的迅速上升同时发生。阿根廷和美国的合作团队将把这一磁极性记录再向后推延约 2000 万年，并将其横向扩展至 2000 万年前。他们希望能够恢复整个沉积盆地的磁反转时间线，这是地球磁场历史上最独特的事件之一。新数据应该可以完善沉积模型。这项工作的其他潜在好处包括让几名美国学生和博士后研究员能够进行实地研究。南极洲，通过 IAA/美国联合实地部署以及后续实验室调查和初级科学家的人员交流，扩大了这项合作工作的国际范围。 项目技术说明 拟议的研究将扩展白垩纪晚期和早期的地层记录。南极洲詹姆斯罗斯盆地的第三纪沉积物（距今约 83 至 65 Ma）最近的研究成果为分析这些岩石提供了新方法，产生了它们的初级磁化强度，并产生了磁极性模式和古地磁极位置。这为西摩岛较年轻的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速率，这将有助于解决稳定的残余磁化强度问题。来自高沉积率 James Ross 盆地的沉积物（Tobin 等，2012），产生精确的年代学/地层学，这种方法将扩展到该沉积盆地的其余部分，并将允许对构造和沉积进行定量估计。白垩纪和早第三纪之间的过程。拟议的实地工作将完善白垩纪长正常时期（Chron）结束期间发生的几次地磁反转的位置。 34N, ~ 83 Ma) 和 Chron 31R (~ 71 Ma) 的下部提供了校准白垩纪长正常年代 (C34N.) 顶部地层位置的最佳地点。正常时间是整个地理时间尺度中最重要的相关层位之一，它与南半球生物地层学没有正确的相关性。事件以及其他逆转将有助于了解南极半岛的地质历史，这些数据还将有助于完善南部大陆演化的构造模型，这将全面用于研究。这项研究是与 Centro Austral de Investigaciones Cientificas (CADIC/CONICET) 的 Edward Olivero 博士和 Prof.布宜诺斯艾利斯大学的奥古斯托·拉帕里尼 (Augusto Rapalini) 的合作将包括在阿根廷南极计划 (IAA) 的支持下，在未来前往詹姆斯罗斯岛及其周围的重要目标进行实地​​考察时收集样本，阿根廷科学家和学生也将参与其中。美国南极计划的部署，在这里提出了劳伦斯·古尔德号R/V，并将延续国际联合发布结果的模式。