晚奥陶世灭绝的地理模式与天体物理电离辐射损害的模拟比较
Late Ordovician geographic patterns of extinction compared with simulations of astrophysical ionizing radiation damage
摘要：
根据超新星和伽马射线暴等各种强电离辐射事件的强度和速率，地球很可能在中生代遭受过一次或灭绝级事件。这些变化导致大气化学发生变化，因此，到达地表和近地表水的太阳紫外线B辐射水平可能会在长达十年的时间内增加一倍。从实验中得知，这种UVB水平足以杀死许多种生物，特别是浮游植物。它很容易导致海洋中以光合作用为基础的食物链崩溃。在大气变化的模拟中，损害的纬度分布有明显的规律。我们以前提出，晚奥陶纪灭绝是一个合理的候选人，从电离辐射事件的贡献，根据三叶虫的环境选择性。为了检验基于这一建议的零假设，我们面临的纬度差异灭绝率预测的模拟与数据发表的分析纬度梯度在奥陶纪灭绝。紫外线B的破坏模式总是在某些纬度显示出强烈的最大值，在最大值的北部和南部强度要低得多。我们发现，从我们的模拟预测的损害模式是一致的数据假设爆发大约在南极，并没有进一步北超过-75度。我们预测，任何大陆块（如中国北方的部分地区，劳伦提斯和新几内亚），然后躺在赤道以北应该是一个避难所，从UVB效应，并显示出不同的模式灭绝的第一次罢工的奥陶纪末灭绝，如果由这样的辐射事件。
英文摘要：
Based on the intensity and rates of various kinds of intense ionizing radiation events such as supernovae and gamma-ray bursts, it is likely that the Earth has been subjected to one or extinction level events during the Phanerozoic. These induce changes in atmospheric chemistry so that the level of Solar ultraviolet-B radiation reaching the surface and near-surface waters may be doubled for up to a decade. This UVB level is known from experiment to be more than enough to kill off many kinds of organisms, particularly phytoplankton. It could easily induce a crash of the photosynthetic-based food chain in the oceans. Regularities in the latitudinal distribution of damage are apparent in simulations of the atmospheric changes. We previously proposed that the late Ordovician extinction is a plausible candidate for a contribution from an ionizing radiation event, based on environmental selectivity in trilobites. To test a null hypothesis based on this proposal, we confront latitudinal differential extinction rates predicted from the simulations with data from a published analysis of latitudinal gradients in the Ordovician extinction. The pattern of UVB damage always shows a strong maximum at some latitude, with substantially lower intensity to the north and south of this maximum. We find that the pattern of damage predicted from our simulations is consistent with the data assuming a burst approximately over the South Pole, and no further north than -75 degrees. We predict that any land mass (such as parts of north China, Laurentia, and New Guinea) which then lay north of the equator should be a refuge from UVB effects, and show a different pattern of extinction in the first strike of the end-Ordovician extinction, if induced by such a radiation event.
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