paleonet New time scale and biozones

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Brian Huber lately commented the new Gradstein & al. scale (Episodes, 27,
2, 83-100). Essentially, the ages of the Late Miocene are a bit older, the
ages of the Early Miocene significantly younger.
This however does not accounts for the changes in the placement of
biozones. Some biozones moved significantly with respect to the magnetic
chrons. Martin Head pointed the jump of  M3 (G insueta, close to the limit
C5Er/n) within C5Dn, which was later commented by Ogg & Gradstein here.
This change also resulted in a different Foram/Nanno calibration : the M3
used to encompass the NN3 and NN4 zones, and is now wholly and only within
NN4. This means that in the Berggren scale, G insueta occurred earlier than
(common) S heteromorphus, while in the Gradstein scale the relationship is
reversed.
Biozone M12 (N acostaensis), which belonged to chron C5r in Berggren & al.
(1995) lies in the upper part of chron C5n, which is more than a million
years move while chron C5 endures only minor change in age.
Biozone M6 (Orbulina datum, C5Bn in Berggren & al.) is now whithin C5AD.
The FAD of G sicanus (M5) lowers from C5Cn to C5Cr. The M13b base (FAD G
extremus) used to be within NN11 and chron C4r and is now in C4An and NN10,
implying a reversed order of the FADs of G extremus and D berggrenii.
All of this demands some argumentation. 
It is somewhat frustrating that the book that could be manipulated in
Florence by the end of august is now delayed until january !






Jean-Louis VOLAT
"L'Henric"
64350 LUC-ARMAU
05 59 68 24 08
jean-louis.volat@wanadoo.fr (pers.)
jean-louis.volat@total.com (prof.)