Shock-wave-induced fracturing of calcareous nannofossils from the Chesapeake Bay impact crater

摘要: Fractured calcareous nannofossils of the genus Discoaster from synimpact sediments within Chesapeake Bay impact crater demonstrate that other petrographic shock indicators exist for cratering process in addition to quartz minerals. Evidence shock-induced taphonomy includes marginal fracturing rosette-shaped species into pentagonal shapes and pressure- temperature-induced dissolution ray tips edges discoasters. Rotational deformation individual crystallites may be mechanism produces fracture pattern. Shock-wave–fractured were recovered matrix material representing tsunami or resurge sedimentation followed impact. Samples taken cohesive clasts rubble show no evidence fracturing. The data presented here support growing microfossils can used determine intensity timing wet-impact cratering.