Paleonet: Biostratigraphic datums - a question

Martin J. Head mhead at
Tue Apr 17 22:27:27 UTC 2007

Dear Paleonetters,

I have a question concerning the nomenclature of a particular  
biostratigraphic datum.

Although highest occurrences often refer to the highest sample in  
which a taxon is found in a particular section, the real highest  
occurrence will likely be at some interpolated point (normally placed  
at the midpoint) between the highest observed occurrence and the next  
sample up.  The difference in position between the observed HO and  
the inferred HO will depend on the sample spacing.

Is there a term for this inferred/interpolated HO?

I'd wondered if HOD (highest occurrence datum) might be the  
appropriate term, but I believe this refers to a three-dimensional  
surface of HOs whereas my "inferred HO" could refer to a single  
stratigraphic section (i.e a point).

I hope the answer is not too obvious!  Thanks for any help or ideas.


Martin J. Head
Department of Earth Sciences
500 Glenridge Avenue
St. Catharines, Ontario L2S 3A1
Tel  905-688-5550 ext. 5216
Fax  905-682-9020
Email  mjhead at

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