Friday, June 17, 2022

That Day 66 Million Years Ago

Just wanted to share this abstract of a paper detailing an outcrop from Baja California, Mexico, which preserves heterogeneous deposits resulting from the Chicxulub meteorite impact 66 million years ago. 

We report K-Pg-age deposits in Baja California, Mexico, consisting of terrestrial and shallow marine materials re-sedimented onto the continental slope, including corals, gastropods, bivalves, shocked quartz grains, an andesitic tuff with a SHRIMP U-Pb age (66.12 ± 0.65 Ma) indistinguishable from that of the K-Pg boundary, and charred tree trunks. The overlying mudstones show an iridium anomaly, and fungal and fern spores spikes. We interpret these heterogeneous deposits as a direct result of the Chicxulub impact, and a mega-tsunami in response to seismically-induced landsliding. The tsunami backwash carried the megaflora offshore in high-density flows, remobilizing shallow marine fauna and sediment en route. Charring of the trees at temperatures up to >1000°C took place in the interval between impact and arrival of the tsunami, which on the basis of seismic velocities and historic analogues amounted to only tens of minutes at most. This constrains the timing and causes of fires, and the minimum distance from the impact site over which fires may be ignited.

Raging forest fires, a tsunami and its backwash, hundreds of millions of tons of sediment mobilized as gigantic mixed debris flows, ecosystems laid waste.

What a catastrophic time! 

The paper is open access but be aware that it is a preprint, yet to be peer reviewed. 

Forest fire at the K-Pg boundary on the Pacific margin of Baja California, Mexico: timing and causes- Amanada Santa Catharina 2022.

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