05/19/2026
Way cool stuff
A new study has found geological evidence of a massive global fungal bloom that erupted in the aftermath of the Chicxulub asteroid impact 66 million years ago - the same event that ended the dinosaurs.
The impact, which hit the Yucatán Peninsula with a force of 100 million megatons, alongside simultaneous volcanic eruptions, blotted out the sun and plunged Earth into cold, dark, damp conditions.
Bad news for megafauna. Near-perfect conditions for fungi, which thrive as decomposers of dead and dying organic matter.
Baker and Casadevall sampled rock layers from two well-preserved geological sites - Denver Basin in Colorado and Williston Basin in North Dakota - looking for fossilised spores and other microfossils (called palynomorphs) across the Cretaceous, the K/Pg boundary, and the Paleocene.
At the K/Pg boundary clay layers, fungal forms made up 50% or more of the total fossil assemblage. They found corroborating fungal spikes at both sites, including evidence of fungal roots (hyphae) and multiple spore types.
Crucially, they only found this because they changed the method. Standard geological analysis uses a harsh sequence of acids and chemical treatments that, it turns out, dissolve fungal microfossils in the process.
By switching to sodium hexametaphosphate and skipping a standard filtration step that removes smaller particles, they preserved evidence that previous studies had been accidentally destroying for years.
This also explains why prior evidence for this phenomenon was so thin. Only one previous study, from Moody Creek Mine in New Zealand, had documented it.
The researchers also note that fungi may not have just fed on the dead. Ecological stress compromises immune defences, meaning living species could have faced surging fungal disease pressure at the same time as everything else was going wrong.
Source: R.P. Baker, & A. Casadevall, Fungal proliferation before and after the Cretaceous–Paleogene mass extinction event in North America, Proc. Natl. Acad. Sci. U.S.A. 123 (20) DOI: 2536899123