Late Eocene impact craters and impactoclastic layers—An overview
Multiple bolide impact events, possibly related to a comet or asteroid shower over a duration of ~2–3 m.y., may have played an important role in the deterioration of the global climate at the end of the Eocene. Upper Eocene marine sediments around the world contain evidence for at least two closely spaced impactoclastic layers, i.e., layers containing impact debris such as tektites and microtektites, shocked minerals, and rock fragments. The upper layer correlates with the North American tektite strewn field (mostly on the eastern side of North America), and the 85-km-diameter Chesapeake Bay crater (USA) has been suggested as its source crater, whereas the lower, microkrystite layer (with clinopyroxene-bearing spherules) was most likely derived from the 100-km-diameter Popigai impact crater (Russia). In summary, at least five impact structures with late Eocene ages are known. Disturbances in the climate at that time are documented, and connection with the impact events is likely. This contribution provides a short review of late Eocene impact craters and ejecta layers.