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Re: Supernova link to Rancholabrean fauna extinction?



The lengths that people will go to in order to say "it was anything but
humans"...

This despite the great asynchrony of extinctions around the world, but
their close association with human arrivals; the fact that unlike all
other mass extinctions these are exclusively terrestrial macrofauna; etc.

On Thu, July 21, 2011 10:18 pm, bh480@scn.org wrote:
> From: Ben Creisler
> bh480@scn.org
>
> OK...this is not about dinosaurs, but it may interest people anyway. At
> least it might inspire some paleoartists...
>
>
> G. Robert Brakenridge (2011)
> Core-collapse Supernovae and The Younger Dryas/Terminal Rancholabrean
> Extinctions.
> Icarus (advance online publication)
> doi:10.1016/j.icarus.2011.06.043
> http://www.sciencedirect.com/science/article/pii/S0019103511002612
>
> Abstract
> Early predictions that some supernovae release large quantities of prompt
> high energy photons are now corroborated by optical identification of
> core-collapse supernovae associated with extragalactic GRBS (beamed
> gamma-ray bursts) and XRFS (beamed or unbeamed x-ray flashes). Given the
> in-galaxy supernova frequency and GRB and XRF recurrence statistics,
> significant Earth-incident events during the past several million years
> very likely occurred and nearby events should have affected the Earth and
> other planetary atmospheres, including terrestrial surface solar UV, the
> Earth?s climate, and its ecology. The Younger Dryas Stadial (12,900 to
> 11,550 calendar yr BP) began with sharply cooler temperatures in the
> Earth?s northern hemisphere, regional drought, paleoecological evidence
> compatible with increased UV, and abrupt increases in cosmogenic 14C and
> 10Be in ice and marine cores and tree rings. In North America,
> stratigraphic and faunal sequences indicate that a major pulse of
> mammalian
> extinctions (at least 23-31 genera) began very close to 12,830 calendar yr
> BP and was sudden: deposits one century younger are devoid of diverse
> extinct fauna remains. A 10 second beamed GRB within 2 kpc of the Earth
> delivers 100 kJ m-2 fluence to the Earth?s atmosphere, where it causes
> spallation and catalytic reactions depleting 35-50% O3, and producing
> excess NOx species (which favor cooling, drought, and surface fertility),
> 14C, and 10Be. An un-beamed, 1050 erg hard photon impulse at  250 pc
> produces similar terrestrial atmospheric effects. A well-characterized
> massive star supernova, the unusually close Vela event (d = 250 ± 30 pc;
> total energy of 1-2 x 1051 erg; age constrained from remnant nebula shock
> velocities considerations at 13,000-16,000 yr and from the pulsar
> characteristic age at 11,400 yr) may have initiated the Younger Dryas
> climate change, and caused the extinction of the terminal Rancholabrean
> fauna.
>
>
>
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Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA