Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact
Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact
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DOI：
10.1073/pnas.1905989116
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发表时间：
2019-11-05
影响因子：
11.1
通讯作者：
Hull, Pincelli M.
中科院分区：
文献类型：
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作者：
Henehan, Michael J.;Ridgwell, Andy;Hull, Pincelli M.
大规模灭绝在白垩纪-古近纪（K-Pg）边界与希克苏鲁布火流星的影响相吻合，也福尔斯在德干陷阱就位的更广泛的时间框架内。然而，至关重要的是，关于这些因素中的任何一个如何驱动观察到的灭绝模式和碳循环扰动的经验证据仍然缺乏。在这里，使用有孔虫中的硼同位素，我们记录了希克苏鲁布撞击后地质学上快速的表层海洋pH值下降，支持撞击引起的海洋酸化是海洋领域生态崩溃的一种机制。随后，随着海洋钙化生物的灭绝和全球碳循环的相关不平衡，地表水pH值急剧反弹。我们重建的水柱pH梯度，结合地球系统建模，表明全球海洋初级生产力减少了50%，足以解释在K-Pg观测到的海洋碳同位素模式，由于溶解度泵的基本作用。虽然初级生产力在数万年内恢复，但向深海输出碳的效率低下持续了更长时间。这种分阶段恢复的设想调和了先前提出的解释K-Pg碳同位素记录的相互竞争的假设，并解释了整个事件中海洋生产力变化的空间变化模式和深海海底缺乏灭绝。总之，我们提供了对上一次大规模灭绝的驱动因素，在灭绝后世界中海洋碳循环的恢复，以及海洋生物将其同位素信号印在地质记录上的方式的见解。
Mass extinction at the Cretaceous-Paleogene (K-Pg) boundary coincides with the Chicxulub bolide impact and also falls within the broader time frame of Deccan trap emplacement. Critically, though, empirical evidence as to how either of these factors could have driven observed extinction patterns and carbon cycle perturbations is still lacking. Here, using boron isotopes in foraminifera, we document a geologically rapid surface-ocean pH drop following the Chicxulub impact, supporting impact-induced ocean acidification as a mechanism for ecological collapse in the marine realm. Subsequently, surface water pH rebounded sharply with the extinction of marine calcifiers and the associated imbalance in the global carbon cycle. Our reconstructed water-column pH gradients, combined with Earth system modeling, indicate that a partial similar to 50% reduction in global marine primary productivity is sufficient to explain observed marine carbon isotope patterns at the K-Pg, due to the underlying action of the solubility pump. While primary productivity recovered within a few tens of thousands of years, inefficiency in carbon export to the deep sea lasted much longer. This phased recovery scenario reconciles competing hypotheses previously put forward to explain the K-Pg carbon isotope records, and explains both spatially variable patterns of change in marine productivity across the event and a lack of extinction at the deep sea floor. In sum, we provide insights into the drivers of the last mass extinction, the recovery of marine carbon cycling in a postextinction world, and the way in which marine life imprints its isotopic signal onto the geological record.