Thread by @rpancost

Final version of @ogu_bristol Research Fellow Claudia Sosa-Montes de Oca published. Once again, we find (as others have): "Minor changes in biomarker assemblages in the aftermath of the Cretaceous-Paleogene mass extinction event." Here in Spain.

Link here: …w-sciencedirect-com.bris.idm.oclc.org/science/articl…

But what does it mean?? It means.... that despite widespread extinction across all realms of life at the KPg, the organic markers for eukaryotic and bacterial life do not change much. 🤔

(You can stare at that figure a long time. Yes, there are a few wiggles across the KPg.... but nothing that is all that striking to an organic geochemist)

And this is consistent with a lot of other work. Other than studies like this lovely work directly from within the impact crater... pubs.geoscienceworld.org/gsa/geology/ar…

... most KPg Boundary investigagions have also shown minimal change. See especially this great paper led by @OGG_CUBoulder from 2009.

science.sciencemag.org/content/326/59…

Great work Claudia. And a pleasure to work on this with long-time friends and collaborators at Jaen and new ones in Granada. But where does this leave us???

Maybe these biomarkers are too generic and not sensitive to the specific biotic changes at the KPg Boundary? Maybe they document only minimal change amongst the simplest non-fossilising organisms? But you know what is weird?

We see huge perturbations in these biomarkers during biotic events in earlier Earth history. Saw this in my first palaeo-investigation of a mid to late-Ordovician biotic event that pales in magnitude to the KPg.

researchgate.net/profile/James-…

Perhaps our Palaeozoic investigations (for which few deep sea sites are preserved), are skewed by a focus on the great carbonate platforms that persist, remnants of Baltica and Laurentia, settings where biology was more sensitive to temperature or oxygen change? Or...

Or... perhaps algal populations have become more resilient over time? I find it fascinating that steranes (very common biomarkers for eukaryotes, derived from sterols) change dramatically throughout Earth history. But rarely in rocks from the past 100 million years.

So well done, Claudia. Some great findings. But lots of fascinating questions!

@threadreaderapp unroll

New link here:

https://twitter.com/rpancost/status/1379067264868233218?s=19

Better link for those of you not at @BristolUni!!

https://twitter.com/rpancost/status/1379067264868233218?s=19