Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago

摘要

In this study, we tested the hypothesis by Firestone et al. (1) that fragments of an asteroid or comet collided with Earth 12,900 calendar years ago (12.9 ka), depositing an exotic assemblage of impact-related markers, such as microspherules and nano'diamonds, across parts of several continents. Our goals were to search for, analyze, and determine potential origins of the proposed impact proxies from 18 dated sites, spanning 12,000 km across three continents: North America, Europe, and Asia. We discovered that the 18 sites all display a 12.9-ka Younger Dryas boundary layer containing abundance peaks of microspherules. In addition, we discovered vesicular, high-temperature melt-glass, referred to as scoria-like objects, in the Younger Dryas boundary layer at three of those sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina). Our research indicates that these high-temperature materials support the hypothesis of a cosmic impact at 12.9 ka and are inconsistent with any other origin.