Ma vs myr

[Larry Bowlds <LBOWLDS@geosociety.org>]

The _Glossary of Geology_ defines Ma as millions of years before the 
present, and this is the usage GSA editors follow. Ma is not a 
substitute for millions of years.

I agree that myr is not a desirable abbreviation for millions of 
years, because it implies milliyears rather than megayears.
To avoid this problem, GSA uses m.y. for millions of years. I won't 
say this is the best solution, but it works well for us.

Larry
 
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