Possible K-Pg tsunami deposit uncovered in North Dakota

[Halichoeres]

A newly described fossil site in North Dakota appears to be a mass death site, part of the Hell Creek formation. The authors of this study claim that a seismically-associated tsunami washed over the area, burying large numbers of fishes and some frogs in a death assemblage that would be hard to explain with a different mechanism. Here's a figure showing how a mass of sturgeons and paddlefishes were preserved.



The paddlefishes also had blobs in their gills that the authors say is ejecta (rock that was thrown up in the initial impact) that landed in the water column and then was strained out of the water by the filter-feeders.

Paper (open access): https://www.pnas.org/content/early/2019/03/27/1817407116

And some commentary on the controversy surrounding the site and the paper's lead author: https://science.sciencemag.org/content/364/6435/10