paleonet biostratigraphy: the relation between NN9, N13 and N14

["Van Heck, Shirley SIEP-EPT-DE" <Shirley.vanHeck@xxxxxxxxx>]

Title: biostratigraphy: the relation between NN9, N13 and N14

I am currently involved in a dispute about the sequence of the following biostratigraphic events: 1) the FAD of D. hamatus (defining base NN9), 2) the LAD of G. subquadratus (top N13) and 3) the LAD of G. mayeri / siakensis (top N14).  In literature (e.g. Bolli et al, 1985, Plankton stratigraphy) the base of NN9 is placed near the top of N14.

In the South China Sea, off NW Borneo, I have regularly observed an overlap of D. hamatus with G. mayeri / siakensis, and even, in a few cases, of D. hamatus with G. subquadratus (one sample only).  These observations were made in oil wells, based on sidewall samples. Hence in my opinion, base NN9 is at about the same level as top N13.

My question is: has anyone else observed this, and if so, where?

Shirley E. van Heck
Stratigrapher
Shell International Exploration and Production Inc.
Deepwater Services / BEAST
200 North Dairy Ashford, room 2230
Houston, Texas 77079, USA

Phone: +1 281 544 2638
Email: shirley.vanheck@shell.com