Extraction method for fossil pollen grains using a cell sorter suitable for routine 14C dating
Extraction method for fossil pollen grains using a cell sorter suitable for routine 14C dating
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DOI：
10.1016/j.quascirev.2021.107236
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发表时间：
2021-11
影响因子：
4
通讯作者：
Keitaro Yamada;T. Omori;I. Kitaba;Tatsuo Hori;T. Nakagawa
中科院分区：
文献类型：
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作者：
Keitaro Yamada;T. Omori;I. Kitaba;Tatsuo Hori;T. Nakagawa
化石花粉粒一直被认为是放射性碳测年的理想材料。近年来，细胞分选机技术的发展使化石花粉粒的测年成为可能。虽然已经提出了各种方法，但由于难以稳定有效地从各种沉积物中以足够高的纯度提取小的化石颗粒，因此没有一种方法被常规地实施。在这里，我们展示了一种新的方法，它允许常规提取和可靠的放射性碳测年的化石花粉粒，甚至从有机丰富的沉积物。改进的物理化学预处理能够在不使用氧化剂的情况下从大量富含有机物的沉积物中进行有效富集。我们还提出了新的分选标准组成的多步“门”，其中每一个是基于荧光特性和散射光的颗粒。分选方法与改进的物理化学预处理相结合，使得可以使用细胞分选器将小化石花粉粒与杂质如绿色藻类、微炭、孢子和植物碎片分离。特别是，相对较小的化石花粉粒，以前提出的方法往往遭受，可以提取有机丰富的湖泊沉积物和有机泥炭在一个非常高的纯度和速度，使用我们的方法。随后测量的放射性碳年龄的化石花粉浓缩物制备我们的方法表现出非常好的协议与陆地叶化石提取的同一沉积物的水月湖，直接记录大气14 C。提取方法提供了一个新的机会，定期确定年龄的沉积物，不包含同期的宏体化石遗骸，并允许我们通过战略性地选择地平线约会之前，纳入贝叶斯年代模型，以提高年龄模型的精度。
Fossil pollen grains have long been recognised as potentially ideal materials for radiocarbon dating. In recent years, the development of cell sorter technology has made it possible to date fossil pollen grains. Although various approaches have been proposed, none of them is being practiced routinely because of the difficulty in stably and efficiently extracting small fossil grains at high enough purity from a variety of sediments. Here we show a new method which allows routine extraction and reliable radiocarbon dating of fossil pollen grains, even from organic-rich sediments. The improved physicochemical pre-treatment enables efficient enrichment from large volume of organic-rich sediments without the use of an oxidant. We also propose new sorting criteria consisting of multi-step ‘gates’, each of which is based upon fluorescence characteristics and scattered light of the particles. The sorting method, combined with the improved physicochemical pre-treatments, makes it possible to separate small fossil pollen grains from impurities such as green algae, micro charcoal, spores and plant fragments using a cell sorter. In particular, relatively small fossil pollen grains, with which previously proposed methods tended to suffer, could be extracted from organic-rich lacustrine sediments and organic peats in a remarkably high purity and velocity using our method. Radiocarbon ages subsequently measured on fossil pollen concentrates prepared by our method show very good agreement with those of terrestrial leaf fossils extracted from the same sediments of Lake Suigetsu, which directly record atmospheric14C. The extraction method provides a new opportunity to routinely determine ages of sediments that do not contain contemporaneous macrofossil remains, and allow us to increase the precision of age models by strategically selecting horizons for dating prior to incorporation into Bayesian chronological modelling.