Paleonet: Biostratigraphic datums - a question

Charles Marshall cmarshal at
Thu Apr 19 16:02:52 GMT 2007

Of course, if your taxon is not found in every sample within its 
range, then there is a significant probability that it was present 
but no preserved in the samples immediately beyond its last 
occurrences; in these cases you need graphic correlation (see Lucy's 
comments below), or something like the pilot method (see reference 
below) we developed to estimate how much further the taxon might have 
persisted undetected, given how frequently it was encountered in its 
known stratigraphic range:

Weiss, R.E., and Marshall, C.R.  1999.  The Uncertainty in the True 
End Point of a Fossil's Stratigraphic Range When Stratigraphic 
Sections are Sampled Discretely.  Mathematical Geology  31(4):435-453.

>For single-core comparison to a precise age model, I suggest graphic
>correlation with one-sided sample-interval bars or boxes (up to the next
>highest sample that could have contained the species but didn't for
>last/highest occurrences; down to the next lowest sample that  could have
>contained the species but didn't for first/lowest occurrences).
>I heartily suggest Gilinsky and Signor's 1991 Paleo Society shortcourse
>(#4) notes.
>Lucy E. Edwards
>U.S. Geological Survey
>926A National Center
>Reston, VA 20192
>phone: 703 648-5272
>leedward at
>Paleonet mailing list
>Paleonet at


Charles Marshall

Professor, Depts. of Organismic and Evolutionary Biology
	& Earth and Planetary Sciences
Curator, Dept. of Invertebrate Paleontology,
	Museum of Comparative Zoology

(617) 495-2572 office
(617) 496-5535 fax
cmarshal at
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