Global K-Pg Layer Deposited From a Dust Cloud
Global K-Pg Layer Deposited From a Dust Cloud
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DOI：
10.1029/2019gl086562
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发表时间：
2020-03-28
影响因子：
5.2
通讯作者：
Morg, Joanna
中科院分区：
文献类型：
--
作者：
Artemieva, Natalia;Morg, Joanna
虽然人们普遍认为，远侧K-Pg粘土层含有来自希克苏鲁布撞击地点的喷出物，但目前没有任何模型能够解释这些喷出物如何从撞击地点向地球仪周围移动。一个被广泛接受的假设是，撞击小球和层中的冲击矿物质从膨胀的撞击羽流中喷出，并沿着弹道路径行进到其最终目的地，然而，冲击矿物质以太低的速度喷出，无法到达远端位置，并且合理的弹道喷出模型无法解释观察到的喷出物分布。使用一套数值模拟，我们发现，喷出物幕和大气之间的强烈相互作用产生了一个快速移动的尘埃云，以每秒几公里的速度旅行，携带相当大一部分喷出物，包括冲击矿物质，远端网站。我们的结论是，喷出物幕材料必须作出重大贡献的形成远K-Pg层。简明语言摘要我们首次发现，地球已被一个大的小行星撞击6600万年前，当一个薄的粘土层被发现有外星化学。这一层在地质记录中是独一无二的，它可以在世界各地找到，包含来自小行星和希克苏鲁布撞击地点的物质。到目前为止，还没有模型能够充分解释这些撞击喷出物如何在世界各地旅行。在本文中，我们表明，高速喷出物和大气之间的强烈相互作用产生一个快速移动的尘埃云，这是能够运输这些喷出物远比以前认为的。
Although it is widely agreed that the distal K-Pg clay layer contains ejecta from the Chicxulub impact site, no current models can explain how these ejecta travel from the impact site around the globe. A widely accepted hypothesis is that impact spherules and shocked minerals in the layer were ejected from an expanding impact plume and traveled to their final destination on a ballistic path. Shocked minerals, however, are ejected at too low a velocity to reach distal sites, and plausible ballistic ejection models cannot explain the observed ejecta distribution. Using a suite of numerical simulations, we find that intense interactions between the ejecta curtain and atmosphere generate a fast-moving dust cloud traveling at speeds of a few kilometers per second, which carries a substantial fraction of ejecta, including shocked minerals, to distal sites. We conclude that ejecta curtain material must make a major contribution to the formation of the distal K-Pg layer.Plain Language Summary We first discovered that the Earth had been hit by a large asteroid 66 million years ago when a thin clay layer was found to have an extraterrestrial chemistry. This layer is unique in the geological record-it can be found all around the world and contains material that originated from the asteroid and Chicxulub impact site. To date, no models have been able to adequately explain how these impact ejecta traveled all around the world. In this paper we show that intense interactions between the high-velocity ejecta and atmosphere produce a fast-moving dust cloud, which is able to transport these ejecta much further than previously thought.