Delayed calcareous nannoplankton boom-bust successions in the earliest Paleocene Chicxulub (Mexico) impact crater
Delayed calcareous nannoplankton boom-bust successions in the earliest Paleocene Chicxulub (Mexico) impact crater
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DOI：
10.1130/g46143.1
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发表时间：
2019-08-01
期刊：
影响因子：
5.8
通讯作者：
Bralower, Timothy J.
中科院分区：
文献类型：
--
作者：
Jones, Heather L.;Lowery, Christopher M.;Bralower, Timothy J.
白垩纪-古近纪（K-Pg；66 Ma）大规模灭绝是由火流星撞击现代墨西哥希克苏鲁伯附近的尤卡坦平台引起的。钙质超微浮游生物作为初级生产者的主要群体，此时几乎被消灭。北半球地点的撞击后微浮游生物组合的特点是一系列短暂的高优势、低多样性的极端（“繁荣-萧条”演替），这可能代表了不稳定的撞击后环境。尽管这些繁荣-萧条演替是一个全球信号，但控制不同物种之间分类转换的机制目前尚不清楚。在这里，我们对希克苏鲁伯陨石坑峰环的新 K-Pg 剖面中的钙质超小型浮游生物和浮游有孔虫组合进行了详细分析。我们表明，尽管超微浮游生物组合类似于特提斯遗址的典型一系列顶点，但火山口中“灾难”顶点的终止至少延迟了 500 k.y。主要浮游有孔虫营养群的变化与超小型浮游生物繁荣-萧条类群的转换之间的重合表明，这一系列的极端可能代表了由生物泵效率的全球恢复驱动的逐渐向寡营养化的趋势。因此，全球繁荣-萧条演替的历时性可能反映了海洋盆地和环境之间生物泵恢复的不同节奏。
The Cretaceous-Paleogene (K-Pg; 66 Ma) mass extinction was caused by a bolide impact on the Yucatan platform near modern Chicxulub, Mexico. Calcareous nannoplankton, a dominant group of primary producers, were almost eradicated at this time. Post-impact nannoplankton assemblages from Northern Hemisphere sites were characterized by a short-lived series of high-dominance, low-diversity acmes ("boom-bust" successions), which likely represent an unstable post-impact environment. Although these boom-bust successions are a global signal, the mechanisms that controlled the taxonomic switchovers between acmes are currently unknown. Here, we present detailed analyses of calcareous nannoplankton and planktic foraminiferal assemblages in a new K-Pg section from the peak ring of the Chicxulub crater. We show that although nannoplankton assemblages resemble the typical series of acmes at Tethyan sites, the termination of the "disaster" acme in the crater is delayed by at least 500 k.y. The coincidence between shifts in the dominant planktic foraminiferal trophic group and switchovers in nannoplankton boom-bust taxa suggests that this series of acmes may represent a gradual trend toward oligotrophy driven by the global restoration of biological pump efficiency. Thus, the global diachroneity of boom-bust successions likely reflects the differential pacing of biological pump restoration between oceanic basins and settings.