Preserved flora and organics in impact melt breccias

Abstract

Impact cratering can destroy life from local to global scales and result in sudden turnovers of dominant genera and/or species. Here we report that it can also preserve components of the local biology present at the time of impact. We have investigated floral matter encapsulated within Cenozoic Era impact glasses produced by separate bolide impacts into the loessoid sediments of Argentina that occurred between 9.2 Ma (Miocene) and 6 ka (Holocene). The encapsulation preserved not only macro-scale morphological biosignatures such as vascular bundles, veins, phytoliths, and papillae, but also structures down to the cellular level. In the best-preserved samples we also found evidence for organic matter. While fossilization typically occurs over an extended time period as minerals slowly replace organic matter and the host rock lithifies under pressure, the process documented here is instantaneous. Preservation of morphological and chemical biosignatures in impact events can provide snapshots of the ecology in environments that do not otherwise promote a diverse fossil record. We suggest that this would provide a new strategy for identifying signs of possible early life on ancient Mars, where similar target conditions once existed.