New study finds evidence for a 'fast' dinosaur extinction | Howard Lee

New sediment data suggests the dinosaurs were rapidly done in, strengthening asteroid impact theory

Boring is beautiful when you’re studying a calamity, especially one as spectacular as the mass extinction that wiped out the dinosaurs. That’s because exciting sediments, full of variations and gaps, make it hard to disentangle the extinction signal from the noise of natural variability.

So you could say that James Witts, of the University of Leeds in the UK, lucked-out with an especially boring batch of sediments in Seymour Island on the Antarctic Peninsula (the part on the map that points up to South America). His study, recently published in the journal Nature Communications, catches the extinction of marine life in one of the most detailed records ever published for the end-Cretaceous. As Witts describes it:

The sedimentology is consistently, remarkably boring. More than 1,000 meters of sandy silt and silty sand!

It doesn’t look like the environmental setting over the extinction itself changed significantly, so we can discount any rapid changes in water depth having an effect on the pattern of extinction we see from the fossil record.

The anoxia story was a surprise to us. In such a shallow setting it appears unusual. I imagine a scenario like parts of the Gulf of Mexico today, with input of material from rivers driving changes in ocean oxygen on a rapid (maybe seasonal?) scale.

Ultimately, one of the problems with studies on the end-Cretaceous extinction is that we are pushing the limits of the resolution of many fossil records, as well as the proxies for environmental change.

The fact that the fossil disappearances occur directly below the interval containing the iridium anomaly suggests the link between impact and extinction is still the key to understanding the pattern we see in the fossil record. I would also argue that we still simply don’t know enough about whether the eruptions could have produced environmental change significant enough to cause the extinction.