The 87Sr/86Sr Record of Himalayan Paleorivers During the Neogene: Patterns and Causes

新近纪喜马拉雅古河的 87Sr/86Sr 记录：模式和原因

• 批准号: 9725607
• 负责人: Jay Quade
• 金额: $ 33.58万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-03-01 至 2000-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9725607&HistoricalAwards=false
• 关键词: 87Sr; 86Sr; Record; Himalayan; Paleorivers

9725607 Quade The Himalayas stand at the center of the debate on how mountain building can alter climate. One of the clearest proxies of the global effects of Himalayan uplift is the marine 87Sr/86Sr record. Yet the specific contribution that past and present Himalayan rivers make to the marine 87Sr/86Sr record, and how this contribution translates quantitatively into silicate weathering rates and therefore consumption of atmospheric CO2 is unclear. Our recent research demonstrates that the 87Sr/86Sr ratios of Himalayan paleorivers can be reconstructed from carbonates preserved in the Siwalik Group foreland basin deposits in the frontal part of the Himalayan fold-thrust belt. These data show 87Sr/86Sr ratios have increased markedly in the late Neogene, probably in response to unroofing of high 87Sr/86Sr (0.720-0.729) marble and dolostone in the Lesser Himalayan and frontal Himalayan nappes. We propose to (1) expand our Himalayan river 87Sr/86Sr record into easternmost Nepal, and back to the beginning of the Miocene, thereby completing the isotopic history for the paleo-Ganges river system, (2) quantify the contribution of carbonate versus silicate weathering in a modern Nepali river, and (3) combine the isotopic data with sedimentological, structural, and provenance data from the foreland basin deposits in order to document the entire record of erosional unroofing of the Nepal Himalayas since the beginning of the Miocene. The results of the proposed research will have major implications for our understanding of the relationships between collisional orogenesis, climate, and ocean water chemistry.

9725607 Quade 喜马拉雅山处于关于造山如何改变气候的争论的中心。 喜马拉雅隆升对全球影响最清晰的代表之一是海洋 87Sr/86Sr 记录。 然而，过去和现在的喜马拉雅河流对海洋 87Sr/86Sr 记录的具体贡献，以及这种贡献如何定量转化为硅酸盐风化速率以及大气二氧化碳的消耗尚不清楚。 我们最近的研究表明，喜马拉雅古河流的 87Sr/86Sr 比值可以根据喜马拉雅褶皱逆冲带前部 Siwalik 群前陆盆地沉积物中保存的碳酸盐来重建。 这些数据显示 87Sr/86Sr 比率在新近纪晚期显着增加，可能是由于小喜马拉雅山和喜马拉雅山正面推覆体中高 87Sr/86Sr (0.720-0.729) 大理石和白云岩的剥落所致。 我们建议 (1) 将喜马拉雅河 87Sr/86Sr 记录扩展到尼泊尔最东部，并追溯到中新世初期，从而完成古恒河系统的同位素历史，(2) 量化碳酸盐与硅酸盐的贡献现代尼泊尔河流中的风化作用，(3) 将同位素数据与前陆盆地沉积物的沉积学、结构和物源数据相结合，以记录侵蚀的完整记录自中新世开始以来，尼泊尔喜马拉雅山的屋顶被剥落。 拟议研究的结果将对我们理解碰撞造山作用、气候和海水化学之间的关系产生重大影响。