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

确定海洋沉积物堆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通量速率的能力受到放射性衰变（例如，230Thxs）和代用产量或来源（例如，4He）的可变性的限制。夏威夷大学马诺阿分校和加州理工学院的研究人员参与了这个合作项目，开发了利用海洋沉积物中的外星粒子作为通量代用物的方法，可能会延长科学家的工作时间。能够重建从数万年到数亿年的变化积累率。通过结合海洋沉积物中两种独立的、稳定的外星物质颗粒示踪剂——氦（He）和锇（Os）同位素——研究人员将能够区分地球上不断变化的外星通量和地球上的外星粒子在运输到海底过程中的陆地聚焦。该方法将应用于距今1000万年至400万年的时间窗口，这段时间已知包含了小行星带碰撞导致地外通量大大增加的一段插曲。研究人员将比较来自太平洋盆地的许多不同沉积物岩心的记录，这些岩心的沉积速率变化超过20倍，以确定地球外的He颗粒是否优先集中在相对于Os的高沉积速率地点。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，这将大大提高这些沉积物作为古海洋学档案的潜力。就更广泛的影响而言，资金支持博士后研究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，它将为研究重要的环境参数（包括生产力和陆地干旱）在很长一段时间内的变化提供新的潜力。

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.