Collaborative Research: Exhumation History of the Indian Lesser Himalaya: Discriminating Tectonic Models with Implications for the Neogene Isotopic Composition of Seawater

合作研究：印度小喜马拉雅山的发掘历史：区分构造模型及其对新近纪海水同位素组成的影响

• 批准号: 1450976
• 负责人: Neil 'Ryan' McKenzie
• 金额: $ 36.18万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1450976&HistoricalAwards=false
• 关键词: Collaborative; Research; Exhumation; History; Indian

The uplift of the Himalayan Mountains due to collision of the Indian and Eurasian plates is the textbook example of continental collision in plate tectonics. The effect that uplift of this orogenic belt has had on the Earth surface system processes and lithospheric dynamics has been dramatic and far-reaching. This project will use an integrative multidisciplinary approach to better understand timing and sequence of thrust fault deformation and exhumation of crustal rocks in the 'outer' Himalayan zone of the Lesser Himalaya of India. The research will greatly improve our understanding of compression-driven crustal deformation processes associated with mountain building. These results will provide a means to critically evaluate the potential relationship between monsoon intensity and thrust fault propagation, as well as document the importance of Himalayan uplift and exhumation and chemical weathering on ocean chemistry. The isotopic seawater record of the ratios of osmium (187Os/188Os) as recorded in sedimentary rocks has been used as a proxy for global chemical weathering, and the results of this study will provide data with profound influences on future global oceanographic and climate models. In addition to the scientific objectives of this study, potential benefits to society and national interests include providing support for an early career researcher at a major research institution; graduate and undergraduate student training in a science, technology, engineering, and mathematics (STEM) discipline; with international collaboration of a U.S. graduate student and post-doctoral researcher with Indian scientists; education and outreach activities aimed at U.S. and Indian K-12 equivalent students; and development of web-based informational contributions for the general public. The project will promote broadening of participation of underrepresented groups in science, and the results of the work will dissemination of research results through professional science presentations, the peer-reviewed scientific literature, and incorporation of research results in into publicly accessible community databases. The project involves a high-resolution geo/thermochronometric investigation of bedrock and foreland basin deposits of the Himalayan frontal system in north India to constrain exhumation timing for distinct zones in the Lesser Himalaya. This work will focus on a series of strike-perpendicular transects across major thrust sheets for (Uranium-Thorium)/Helium dating of zircon and apatite, coupled with detailed facies analysis and provenance studies via zircon Uranium-Lead-Helium (U-Pb-He) double dating of foreland basin deposits. Contrasting models have been proposed for the sequence of thrust propagation of Lesser Himalayan blocks, notably the time of exhumation and structural affinities of the 'outer' Lesser Himalayan zone. These models postulate structural emplacement ages for the 'outer' Lesser Himalayan zone that range from the late Eocene to less than about 14 million years ago--a potential 14 to 30 million-year discrepancy. However, recent studies of foreland basin provenance data suggested the 'outer' Lesser Himalayan zone was likely exhumed at approximately 16 Ma, which corresponds with a noted increase in monsoon intensity. The weathering of 'outer' Lesser Himalayan zone rocks enriched in radiogenic 187Os has been tied to a pronounced increase in Neogene seawater 187Os/188Os at 16 million years ago. Our comprehensive study will constrain the sequence of thrust propagation and exhumation timing of the 'outer' Lesser Himalayan zone, allowing us to: 1) differentiate between contrasting kinematic models for Himalayan thrust belt evolution, and 2) test the hypothesis that exhumation and weathering of distinct Himalayan tectonic zones was the principal driver of secular changes in Neogene seawater chemistry. Preliminary (U-Th)/He geochronologic data offers intriguing support for the hypotheses of a direct link between Himalayan weathering and seawater chemistry.This award is co-funded by NSF's International Science and Engineering Section.

印度板块和欧亚板块的碰撞导致喜马拉雅山脉的隆起是板块构造中大陆碰撞的典型例子。该造山带的隆升对地球表面系统过程和岩石圈动力学产生了巨大而深远的影响。该项目将使用综合的多学科方法，以更好地了解印度小喜马拉雅山脉外喜马拉雅带逆冲断层变形和地壳岩石折返的时间和序列。这项研究将极大地提高我们对与造山相关的挤压驱动的地壳变形过程的理解。这些结果将为批判性地评价季风强度与逆冲断层传播之间的潜在关系，以及证明喜马拉雅抬升折返和化学风化对海洋化学的重要性提供手段。沉积岩中所记录的Os(187Os/188Os)同位素海水记录已被用作全球化学风化的替代，这项研究的结果将为未来的全球海洋学和气候模型提供深刻的影响。除了这项研究的科学目标外，这项研究还可能对社会和国家利益产生重大影响，包括为一家大型研究机构的早期职业研究员提供支持；科学、技术、工程和数学(STEM)学科的研究生和本科生培训；一名美国研究生和博士后研究员与印度科学家的国际合作；针对美国和印度K-12等值学生的教育和外联活动；以及为普通公众开发基于网络的信息贡献。该项目将促进未被充分代表的群体更广泛地参与科学工作，工作成果将通过专业科学报告、同行评议的科学文献以及将研究成果纳入可供公众查阅的社区数据库来传播研究成果。该项目涉及对印度北部喜马拉雅前缘系统的基岩和前陆盆地沉积进行高分辨率地质/热年代学调查，以限制小喜马拉雅地区不同区域的挖掘时间。这项工作将集中在一系列主要逆冲断块的走向垂直剖面上，进行锆石和磷灰石的(铀-钍)/氦测年，并通过前陆盆地矿床的锆石-铀-铅-氦(U-Pb-He)双重测年进行详细的相分析和物源研究。对于小喜马拉雅地块的逆冲传播序列，特别是外喜马拉雅带的折返时间和构造亲和力，已经提出了不同的模型。这些模型假定小喜马拉雅山脉外围地带的构造侵位年龄从始新世晚期到不到1,400万年前--这可能存在1,400万到3,000万年的差异。然而，最近对前陆盆地物源数据的研究表明，小喜马拉雅带的“外部”可能在大约16 Ma时被挖掘出来，这与季风强度的显著增加相对应。富含放射性成因的187Os的“外部”小喜马拉雅带岩石的风化与1600万年前新近纪海水187Os/188Os的显著增加有关。我们的综合研究将约束小喜马拉雅带“外”的逆冲传播序列和折返时间，使我们能够：1)区分喜马拉雅冲断带演化的不同运动学模型；2)检验不同喜马拉雅构造带折返和风化是新近纪海水化学长期变化的主要驱动因素的假说。初步(U-Th)/He地质年代学数据为喜马拉雅风化和海水化学之间存在直接联系的假设提供了耐人寻味的支持。该奖项由美国国家科学基金会国际科学与工程部共同资助。