The Habitat of the Nascent Chicxulub Crater
The Habitat of the Nascent Chicxulub Crater
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DOI：
10.1029/2020av000208
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发表时间：
2020-12-01
期刊：
影响因子：
8.4
通讯作者：
Tikoo, S. M.
中科院分区：
文献类型：
--
作者：
Bralower, T. J.;Cosmidis, J.;Tikoo, S. M.
扩大的沉积剖面提供了一个机会来阐明白垩纪-古近纪（K-Pg）边界撞击后数小时至数千年间新生希克苏鲁伯陨石坑的状况。随着火山口能量下降，海啸和塞赫波沉积了沉积物，最终形成了含有大气沉降物的薄薄的半远洋泥灰岩单元。 Seiche 沉积物主要由方解石组成，该方解石是由目标石灰石在撞击过程中脱碳，然后在水柱中碳化而形成的。这些碳酸盐的团块同位素记录的温度超过 70 摄氏度，热量可能来自中央冲击熔池。然而，尽管浑浊且炎热，新生火山口盆地内的水域很快就成为食物链中极其多样化的横截面的可行栖息地。撞击发生数天或数周后沉积的最早的塞克层包含最早的丹尼亚超微浮游生物和恐龙囊幸存者。代表随后几年到几千年的半远洋泥灰岩含有几乎单一的钙质甲藻休眠囊肿组合，表明环境条件不断恶化，其中一种解释涉及撞击后的低光照水平。在同一地平线上，微生物化石表明存在繁荣的细菌群落和独特的磷酸盐化石，包括远洋甲壳类动物的附属物、粪化石和细菌隧道鱼骨，这表明食物链基础的快速恢复可能支持了更大、更高营养级生物的生存。极其多样化的化石组合表明，该陨石坑在撞击后是一个独特的栖息地，可能是由于热液活动提供的热量和营养物质的结果。 简单语言摘要 新形成的希克苏鲁伯陨石坑迅速被海水填充，然后受到海啸和塞克波的干扰。随着波能下降而沉积的沉积层为了解撞击后数月、数年至数千年的新生陨石坑的环境提供了一个独特的窗口。地球化学数据显示，最初几年，火山口较热区域的温度超过 70 摄氏度，热量来自于下方的熔体片，通过热液循环产生热量。撞击后不久，陨石坑较冷的区域就成为了栖息地，一系列化石表明海底和海面存在着多种生命，从微生物到海洋节肢动物，可能还有鱼类。我们认为这个群落是靠热液系统的营养和热量维持的。希克苏鲁伯陨石坑和上方海洋的早期快速恢复表明生命在极其恶劣的条件下具有恢复能力，这对地球早期生命和其他行星上的生命具有重要影响。 70 摄氏度，热量可能来自中央撞击熔池 撞击后，火山口盆地内较冷的区域很快成为多种生物的栖息地，从微生物到海洋节肢动物，可能还有鱼类
An expanded sedimentary section provides an opportunity to elucidate conditions in the nascent Chicxulub crater during the hours to millennia after the Cretaceous-Paleogene (K-Pg) boundary impact. The sediments were deposited by tsunami followed by seiche waves as energy in the crater declined, culminating in a thin hemipelagic marlstone unit that contains atmospheric fallout. Seiche deposits are predominantly composed of calcite formed by decarbonation of the target limestone during impact followed by carbonation in the water column. Temperatures recorded by clumped isotopes of these carbonates are in excess of 70 degrees C, with heat likely derived from the central impact melt pool. Yet, despite the turbidity and heat, waters within the nascent crater basin soon became a viable habitat for a remarkably diverse cross section of the food chain. The earliest seiche layers deposited with days or weeks of the impact contain earliest Danian nannoplankton and dinocyst survivors. The hemipelagic marlstone representing the subsequent years to a few millennia contains a nearly monogeneric calcareous dinoflagellate resting cyst assemblage suggesting deteriorating environmental conditions, with one interpretation involving low light levels in the impact aftermath. At the same horizon, microbial fossils indicate a thriving bacterial community and unique phosphatic fossils including appendages of pelagic crustaceans, coprolites and bacteria-tunneled fish bone, suggesting that this rapid recovery of the base of the food chain may have supported the survival of larger, higher trophic-level organisms. The extraordinarily diverse fossil assemblage indicates that the crater was a unique habitat in the immediate impact aftermath, possibly as a result of heat and nutrients supplied by hydrothermal activity.Plain Language Summary The newly formed Chicxulub crater was rapidly filled by seawater then disturbed by tsunami and seiche waves. Sedimentary layers deposited as wave energy declined provide a unique window into the environment of the nascent crater in the months and years to millennia after the impact. Geochemical data show temperatures in hotter regions of the crater in excess of 70 degrees C for the first few years with heat derived from the underlying melt sheet via hydrothermal circulation. Cooler regions of the crater became habitats soon after impact with a suite of fossils indicating diverse life on the seafloor and sea surface, ranging from microbes to marine arthropods, and possibly fish. We suggest that this community was sustained by nutrients and heat from the hydrothermal system. The rapid early recovery in the Chicxulub crater and ocean above demonstrates the resiliency of life under extraordinarily harsh conditions, which has important ramifications for early life on Earth and life on other planets.Key PointsSediments derived from decarbonation of the Chicxulub impact target were deposited by tsunami and seiche waves over months to years followed by a layer with atmospheric fallout Temperatures in the ocean above the hotter regions of the crater were in excess of 70 degrees C, with heat likely derived from the central impact melt pool Cooler regions within the crater basin became habitats soon after impact with diverse life ranging from microbes to marine arthropods, and possibly fish