Secondary cratering on Earth: The Wyoming impact crater field
Boulder, Colo., USA: Several dozen small impact craters, 10–70-m in size,
have been discovered in southeastern Wyoming. A team of U.S. and German
geoscientists found these ancient craters in exposed sedimentary layers
from the Permian period (280 million years ago). After discovering the
first craters, the team initially suspected that they are a crater-strewn
field, formed by the breakup of an asteroid that entered the atmosphere.
However, with the discovery of more and more craters over a wide area, this
interpretation was ruled out.
Many of the craters are clustered in groups and are aligned along rays.
Furthermore, several craters are elliptical, allowing the reconstruction of
the incoming paths of the impactors. The reconstructed trajectories have a
radial pattern.
“The trajectories indicate a single source and show that the craters were
formed by ejected blocks from a large primary crater,” said project leader
Thomas Kenkmann, professor of geology at the University of Freiburg,
Germany. “Secondary craters around larger craters are well known from other
planets and moons but have never been found on Earth,”
The team calculated the ballistic trajectories and used mathematical
simulations to model the formation of the craters. All of the craters found
so far are located 150–200 km from the presumed primary crater and were
formed by blocks that were 4–8-m in size that struck the Earth at speeds of
700–1000 m/s. The team estimate that the source crater is about 50–65 km in
diameter and should be deeply buried under younger sediments in the
northern Denver basin near the Wyoming-Nebraska border.
FEATURED ARTICLE
Secondary cratering on Earth: The Wyoming impact crater field
Thomas Kenkmann, Louis Mueller; Allan Fraser; Doug Cook; Kent Sundell;
Auriol Rae
Contact: thomas.kenkmann@geologie.uni-freiburg.de, Institut für Geo- und
Umweltnaturwissenschaften, Geologie, Freiburg, Germany
Article URL:
https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B36196.1/611743/Secondary-cratering-on-Earth-The-Wyoming-impact
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