Collaborative Research: Th-230 as a Sediment Focusing Indicator: constraints from He-3 in Interplanetary Dust Particles

近年来，230Th等通量代理（CFP）剖面法计算泥沙累积速率（ARs）成为一个有重大争议的话题，特别是在泥沙聚焦及其量化问题上。在古海洋学研究中，使用年龄模型还是使用CFPs来推导ar会导致截然不同的解释。根据该合同，pi将调查沉积物再分配过程，以确定230 CFP的准确性。他们将测量另一个具有独立源项的CFP，即行星际尘埃粒子（IDPs），以及其中包含的外星3He。在北大西洋不同且研究充分的沉积环境中，230Th和3He变化之间的一致性将进一步支持使用两种CFPs进行通量归一化。在已知沉积物集中和筛选数量的地点产生的数据将有助于限制深海洋流对IDPs和携带吸附230Th的沉积物的影响，并将提供对这些颗粒的水动力分选程度的见解。当结合14C和配对的3He和230Th对沉积物细粒组分的各种分离组分的测量时，pi将验证以下假设：1)3He对沉积物聚焦的敏感性低于230Th，以及2)沉积物再分配过程从沉积物中含有230Th的部分中分离出含3He的IDPs的程度。在未来，支持者希望开发一种新的代理（3He/230Th比率），用于与过去气候变化相关的深海洋流强度变化。这个项目将让学生参与到他们的教学、培训和学习中来。

Recently, the 230Th constant-flux proxy (CFP) profiling method of calculating sediment accumulation rates (ARs) has become a topic of significant controversy, especially with respect to the issue of sediment focusing and its quantification. Depending on whether one derives ARs using age models or CFPs leads to vastly different interpretations in paleoceanographic studies. Under this award the PIs will investigate sediment redistribution processes to determine the veracity of the 230Th CFP. They will measure another CFP with an independent source term, namely interplanetary dust particles (IDPs), and the extraterrestrial 3He contained therein. Agreement between 230Th and 3He variations in varied and well-studied depositional environments in the North Atlantic would constitute further support for the use of both CFPs for flux normalization. The data generated on sites with known amounts of sediment focusing and winnowing will help constrain the influence of abyssal currents on IDPs and the sediments carrying adsorbed 230Th, and will provide insights into the extent of hydrodynamic sorting of these particles. When combined with 14C and paired 3He and 230Th measurement on various separated fractions of the fine-grained component of the sediment, the PIs will test the hypotheses that 1) 3He is less sensitive than 230Th to sediment focusing, and 2) the degree to which sediment redistribution processes fractionate 3He-containing IDPs from the 230Th containing portion of the sediment. In the future, the proponents hope to develop a new proxy (3He/230Th ratio) for changes in the strength of deep-sea currents in association with past climatic changes. This project will involve students in their teaching, training and learning.