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RE: K-Pg extinction sum of multiple events?



Cool paper! 

I am no expert on this subject but I have just been reading Nichols and 
Johnson's awesome book Plants and the K T Boundary (2008, Cambridge). It warns 
repeatedly that the Signor - Lipps effect has been ignored in investigations of 
the K T event. Signor-Lipps is an artifact of uneven fossil distribution that 
can cause apparent stepwise extinctions right before  a real extinction event. 
In other words, it can cause false signals of extinction events right below 
real ones.

I got the Tobin et al. paper as a pdf and searched it. They do not mention the 
Signor Lipps effect nor cite the work of Signor and Lipps 1982.

Nonetheless their data are interesting, their sample is said to be very 
complete, and it is interesting to see that Antarctic average temperatures in 
the Maastrichtian don't seem to go much above 9 or 10 degrees.

I have an open mind.
________________________________________
From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Ben Creisler 
[bcreisler@gmail.com]
Sent: Tuesday, July 10, 2012 12:05 PM
To: dinosaur@usc.edu
Subject: K-Pg extinction sum of multiple events?

From: Ben Creisler
bcreisler@gmail.com

A new online paper:

Thomas S. Tobin, Peter D. Ward, Eric J. Steig, Eduardo B. Olivero,
Isaac A. Hilburn, Ross N. Mitchell, Matthew R. Diamond, Timothy D.
Raub & Joseph L. Kirschvink (2012)
Extinction patterns, delta18O trends, and magnetostratigraphy from a
southern high-latitude Cretaceous – Paleogene section: Links with
Deccan volcanism.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
http://dx.doi.org/10.1016/j.palaeo.2012.06.029
http://www.sciencedirect.com/science/article/pii/S0031018212003847?v=s5


Although abundant evidence now exists for a massive bolide impact
coincident with the Cretaceous-Paleogene (K-Pg) mass extinction event
(~ 65.5 Ma), the relative importance of this impact as an extinction
mechanism is still the subject of debate. On Seymour Island, Antarctic
Peninsula, the López de Bertodano Formation yields one of the most
e
magnetostratigraphy, and isotopic data from carbonate-secreting
macrofauna, we present a high-resolution, high-latitude
paleotemperature record spanning this time interval. We find two
prominent warming events synchronous with the three main phases of
Deccan Traps flood volcanism, and the onset of the second is
contemporaneous with a local extinction that pre-dates the bolide
impact. What has been termed the K-Pg extinction is potentially the
sum of multiple, independent events, at least at high latitudes.