Deposition and retention of meteoric Be-10 in Holocene Taiwan river terraces
Deposition and retention of meteoric Be-10 in Holocene Taiwan river terraces
复制标题
全新世台湾河流阶地流星Be-10的沉积与滞留
DOI：
10.1016/j.quascirev.2021.107048
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发表时间：
2021
影响因子：
4
通讯作者：
von Blanckenburg Friedhelm
中科院分区：
文献类型：
--
作者：
Deng Kai;Wittmann Hella;Hsieh Meng-Long;Yang Shouye;von Blanckenburg Friedhelm
在大气中产生并主要由降雨清除的宇宙成因陨石10Be是确定地球表面过程的日期和速率的宝贵工具。它的应用的一个关键前提是了解10Be到地球表面的长期沉积通量。以往获取10Be沉积通量的努力包括一般大气环流模型(GCM)、降雨10Be记录的经验拟合以及确定已知年龄的土壤剖面清单。在这里，我们从台湾山区全新世河流阶地的10Be清单中得到了10Be的沉积通量。我们测量了三个阶地的10Be和9Be浓度，~(14)C年龄在3.83~9.05千卡之间，采样深度高达6.2米。根据我们的河流阶地的10Be清单，计算出台湾造山带10Be的长期沉积通量在0.32~0.49×10~6at/cm~2/yr之间。我们认为，这些阶地中的部分铍保留、表面侵蚀、多相沉积物沉积和不完整的采样深度是通量低估的潜在原因。当考虑到这些因素及其不确定性时，由此产生的每个梯田的通量估计显示出0.66-0.88×106at/cm2/yr的重叠范围。因此，在快速侵蚀的台湾造山带，特别是在气候条件与所研究的阶地相似的地区，建议将这种新的具有千年时间尺度的约束通量范围应用于地球表面。与其他方法的通量估计相比，基于降雨量的拟合方程的通量超过我们新的梯田得出的通量的两倍多。我们认为台湾造山带不可能有如此高的通量，并认为降水对10Be通量的控制在降水数据拟合中可能被高估了。GCM得出的通量高估了10Be的沉积通量，高估程度较小(至少为23%)，这与之前全球10Be通量数据汇编的结果一致。
The cosmogenic meteoric10Be that is produced in the atmosphere and mainly scavenged by rainfall is a valuable tool for determining dates and rates of Earth surface processes. A key prerequisite for its applications is the knowledge of the long-term10Be depositional flux to Earth's surface. Previous efforts on obtaining10Be depositional fluxes include general atmospheric circulation modelling (GCM), empirical fitting of rainfall10Be records, and determining the inventory of soil profiles of known age. Here, we derive10Be depositional fluxes from Holocene river terrace10Be inventories across the Taiwan mountain belt. We measured10Be and9Be concentrations from three terrace profiles, with14C ages ranging between 3.83 and 9.05 cal. kyr BP and sampling depths of up to 6.2 m.Based on10Be inventories of our river terraces, the calculated long-term10Be depositional fluxes vary from 0.32 to 0.49 × 106at/cm2/yr in the Taiwan orogen. We identify partial Be retention, surface erosion, multi-phase sediment deposition, and incomplete sampling depth in these terraces as potential causes of flux underestimation. When accounting for each of these factors and their uncertainties, the resulting flux estimates of each terrace show an overlapping range of 0.66–0.88 × 106at/cm2/yr. This newly constrained flux range representative over millennial timescales is thus recommended for Earth surface applications in the fast-eroding Taiwan orogen, especially in regions with similar climatic conditions as the studied terraces. When comparing to flux estimates from other approaches, the flux from the rainfall-based fitting equation exceeds our new terrace-derived flux by more than a factor of two. We consider such high flux to be unlikely for the Taiwan orogen, and suggest that the control of precipitation on the10Be flux here may be overestimated in rainfall data fitting. The GCM-derived flux overestimates the10Be depositional flux in this setting to a smaller degree (at least 23%), which is in accordance with findings from previous global data compilation of10Be fluxes.