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

印度板块和欧亚板块碰撞导致的喜马拉雅山的隆升是板块构造学中大陆碰撞的典型例子。造山带隆升对地球表面系统过程和岩石圈动力学的影响是巨大而深远的。该项目将采用综合的多学科方法，以更好地了解印度小喜马拉雅山"外"喜马拉雅带逆冲断层变形和地壳岩石折返的时间和顺序。这项研究将大大提高我们对与造山运动有关的挤压驱动地壳变形过程的认识。这些结果将提供一种手段，严格评估季风强度和逆冲断层传播之间的潜在关系，以及喜马拉雅山脉的隆起和折返和化学风化对海洋化学的重要性文件。沉积岩中锇（187Os/188Os）比值的海水同位素记录已被用作全球化学风化的代用指标，其研究结果将为未来的全球海洋学和气候模式提供具有深远影响的数据。除了这项研究的科学目标，对社会和国家利益的潜在利益包括为主要研究机构的早期职业研究人员提供支持;在科学，技术，工程和数学（STEM）学科的研究生和本科生培训;与美国的国际合作研究生和博士后研究员与印度科学家;教育和推广活动，针对美国和印度的K-12相当于学生;和发展基于网络的信息贡献，为广大公众。该项目将促进扩大代表性不足群体对科学的参与，其工作成果将通过专业科学介绍、同行评审的科学文献以及将研究成果纳入公众可访问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锋面系统的基岩和前陆盆地沉积物进行高分辨率地质/热年代学调查，以限制小喜马拉雅不同地区的剥露时间。这项工作将重点关注跨越主要逆冲岩片的一系列走向垂直横断面，用于对锆石和磷灰石进行（铀-钍）/氦测年，并通过锆石铀-铅-氦（U-Pb-He）双测年进行详细的相分析和物源研究前陆盆地沉积物。对比模型已经提出了小喜马拉雅地块的逆冲传播序列，特别是折返的时间和结构的“外”小喜马拉雅带的亲和力。这些模型假设“外部”小喜马拉雅带的结构侵位年龄范围从始新世晚期到不到1400万年前-一个潜在的1400万至3000万年的差异。然而，最近的前陆盆地物源数据的研究表明，“外”小喜马拉雅地区可能在大约16马，这与季风强度的显着增加相对应的挖掘。富含放射成因187Os的"外"小喜马拉雅带岩石的风化作用与1600万年前新近纪海水187Os/188Os的显著增加有关。我们的全面研究将限制序列的逆冲传播和折返时间的“外”小喜马拉雅带，使我们能够：1）区分对比运动学模型喜马拉雅冲断带的演变，和2）测试的假设，折返和风化不同的喜马拉雅构造带的主要驱动力的长期变化在新近纪海水化学。初步（U-Th）/He地质年代学数据为喜马拉雅山风化和海水化学之间的直接联系的假设提供了有趣的支持。该奖项由NSF国际科学与工程部共同资助。

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.