Re: Mesozoic Volcanoes?

[John Alroy <jack@homebrew.uchicago.edu>]

> From: Grant Harding <ad444@freenet.carleton.ca>
 > Hi,
 > 

 > Does anyone here know what periods of the Mesozoic there were  
volcanoes in?
 > Thanx,

Stan Friesen:

>> The simple answer - all of them.

>> If you want to know what periods had *more* volcanoes than
>> typically the case, that is a different question.

And a good one. A few months ago a fellow reader of this group turned  
me on to the following reference...

Stothers, R. B.  1993.  Flood basalts and extinction events.  
Geophysical Research Letters 20(13):1399-1402.

which included the following info...

Flood basalt    Age
Columbia River  17
Ethiopian       35
Brito-Arctic    61
Deccan Traps    66
Madagascar      90
Rajmahal        116
Serra Geral     133
Namibian        135
Antarctic       176
South African   190
West African    200
Eastern N.A.    201
Wrangellian     230
Siberian        247

I left out the analytical errors and references; the ages are in  
millions of years and are for the beginning of the volcanic phase,  
which may go on for several million years. The Deccan Traps are at  
the K-T boundary (end of the Mesozoic); the Siberian Traps are close  
to the P-T boundary (beginning of the Mesozoic). Stothers uses a  
semi-standard time series analysis method to show a marginally  
statistically significant correlation between these volcanic episodes  
and mass extinctions, but there is an error in his method (which I  
believed I discussed here before), so the results are questionable.