Collaborative Research: He and Os isotope investigation of Miocene marine sediments: particulate extraterrestrial matter as a paleoflux tracer

确定海洋沉积物的累积速率对于重建过去生产力和碳埋藏的变化至关重要，但在长地质时间尺度上重建这种通量速率的能力受到放射性衰变(例如230Thxs)和替代产生率或来源(例如4He)的变异性的限制。这个合作项目涉及夏威夷大学马诺阿分校和加州理工学院的研究人员，开发了将海洋沉积物中的外星颗粒用作助熔剂替代品的方法，这可能会扩大科学家的范围？能够重建从数万年到数亿年的不断变化的累积速率。通过将海洋沉积物中两种独立、稳定的颗粒外星物质示踪剂--氦(He)和Os(Os)同位素--结合在一起，研究人员将能够区分外星物质流向地球的变化和外星颗粒在向海底运输过程中的地面聚焦。该方法将在距今1000万至400万年的时间窗口内应用，已知的时间段包括小行星带碰撞导致的外星人流向地球的大幅增加。研究人员将比较来自太平洋盆地的几个不同沉积岩芯的记录，这些岩心的累积速率相差超过20倍，以确定相对于Os，地外颗粒物是否优先关注高沉积速率的地点。最后，研究人员将测试是否可以为太平洋红粘土开发一个可靠的年龄模型，这将极大地提高这些沉积物作为古海洋档案的潜力。在更广泛的影响方面，资金支持博士后研究人员和本科生的教育和培训，并促进国际合作。这项研究还将开发一种潜在的重要新工具，为研究包括生产力和陆地干旱在内的重要环境参数在很长一段时间内如何变化提供新的潜力。

Determining the rates of marine sediment accumulation is critical in reconstructing past changes in productivity and carbon burial, but the ability to reconstruct such flux flux rates over long geologic timescales is been limited by radioactive decay (e.g., 230Thxs) and by variability in the proxy production rate or source (e.g., 4He). This collaborative project, involving researchers from the University of Hawaii at Manoa and the California Institute of Technology, develops the use of extraterrestrial particles in marine sediments as flux proxies, potentially extending scientists? ability to reconstruct changing accumulation rates from tens of thousands of years to hundreds of millions of years. By combining two independent, stable tracers of particulate extraterrestrial matter in marine sediments-- helium (He) and osmium (Os) isotopes-- the researchers will be able to distinguish between changing extraterrestrial flux to Earth and terrestrial focusing of extraterrestrial particles during transport to the seafloor. The method will be applied over a time window of 10 to 4 million years before present, a time period known to encompass an episode of greatly increased extraterrestrial flux to the Earth resulting from collisions in the asteroid belt. The researchers will compare records from a number of different sediment cores from the Pacific Basin, with accumulation rates varying by a factor of more than twenty, to determine whether or not particulate extraterrestrial He is preferentially focused to high sedimentation rate sites relative to Os. Lastly, the researchers will test whether a reliable age model can be developed for Pacific red clays, which would greatly improve the potential of these sediments as paleoceanographic archives. In terms of broader impact, funding supports education and training of a postdoctoral researcher and an undergraduate student and fosters international collaborations. The research will also develop a potentially important new tool that would unlock new potential for studying how important environmental parameters, including productivity and terrestrial aridity, change over long time periods.