In the fossilized sedimentary deposits at the bottom of the former ocean, scientists noticed high folds that were left by the passage of a tsunami caused by an asteroid that crowned the Cretaceous-Paleogene extinction.
About 66 million years ago, a massive asteroid that fell to Earth near what is now Mexico drew a line under the long era of dinosaur dominance. The shock wave brought intense heat and led to global fires, powerful seismic waves passed through the thickness of the planet, and a tsunami swept across the ocean. Water waves hit North America, the most dangerous of which could reach 1,500 meters in height.
Scientists have found traces of such waves in fossilized sedimentary rocks, which captured their passage. At the height of the Cretaceous-Paleogene extinction, these rocks were located at the bottom of coastal shallow water, and today they are in the center of Louisiana, and they were noticed thanks to seismography. Geologists talk about their find in an article published in the journal Earth and Planetary Science Letters.
Gary Kinsland and his colleagues at the University of Louisiana used data collected by oil company Devon Energy, which was conducting exploration in the state. During such work, geologists collect data on the passage of seismic waves through the upper layers of the earth's crust, obtaining information about its internal density and structure.
This is how scientists noticed that at a depth of about 1,500 meters there is a series of petrified folds - similar to those that are formed at the bottom near the shore of the reservoir under the influence of waves. Only their dimensions were much more impressive - about 16 meters high, with the distance between the ridges reaching up to a kilometer.
The authors are confident that these are traces of a tsunami from the asteroid Chicxulub, which passed through shallow water. This is indicated by both the location of the folds and their orientation. According to Kinsland and his colleagues, the depth of the sea here at that time reached about 60 meters. Powerful waves could leave folds at the bottom, which then did not disturb the usual tides and storms for a long time, allowing them to remain in the geological record.