Re: [dinosaur] Palacrodon from Arizona + from tracks from Korea + K-Pg seafloor eruptions + more

["David Marjanovic" <david.marjanovic@gmx.at>]

> John P Staub (2018)
> Paleozoic geomagnetism shapes vertebrate evolution.
> PeerJ Preprints 6:e26490v1
> [...]
>
> Background. Despite a fifty-year failure of paleontologists to find a viable 
> connection between geomagnetic polarity reversals and evolutionary patterns, 
> recent databases show that the early appearance, radiation, and 
> diversification of Paleozoic vertebrates tend to occur during periods having 
> frequent collapses of the Earthâs geomagnetic field. The transition time 
> during the collapse of the Earthâs protective magnetic shield can last 
> thousands of years, and the effects on biota are unknown. Solar and cosmic 
> radiation, volcanism, weather alteration, low-frequency electromagnetic 
> fields, depletion of ozone, and the stripping of atmospheric oxygen have been 
> proposed as possible causes, but previous studies have found no effects.
> [...]

It has been proposed that the multipolar geomagnetic field during a polarity 
reversal induces a magnetic field in the ionosphere which takes over the 
protective function. I'll have to read the preprint; the rest of the abstract 
promises several puzzling results.

> Joseph S. Byrnes & Leif Karlstrom (2018)
> Anomalous K-Pgâaged seafloor attributed to impact-induced mid-ocean ridge 
> magmatism.
> Science Advances 4(2): eaao2994
> [...]
>
> Eruptive phenomena at all scales, from hydrothermal geysers to flood basalts, 
> can potentially be initiated or modulated by external mechanical 
> perturbations. We present evidence for the triggering of magmatism on a 
> global scale by the Chicxulub meteorite impact at the Cretaceous-Paleogene 
> (K-Pg) boundary, recorded by transiently increased crustal production at 
> mid-ocean ridges. Concentrated positive free-air gravity and coincident 
> seafloor topographic anomalies, associated with seafloor created at 
> fast-spreading rates, suggest volumes of excess magmatism in the range of 
> ~105 to 106 km3.

10^5 to 10^6 of course, in case anyone is wondering.