Chemical Geology 226 (2006) 73 www.elsevier.com/locate/chemgeo

Comment on bDetrital zircons as tracers of sedimentary provenance: Limiting conditions from statistics and numerical simulationQ by T. Andersen, Chemical Geology, vol. 216, pp. 249–270 Pieter Vermeesch Department of Geological and Environmental Sciences, Stanford University, United States Received 22 March 2005; received in revised form 13 September 2005; accepted 24 October 2005

Keywords: Clastic sediments; Provenance determination; U–Pb; Detritus; Zircon; Statistics

Andersen (2005) presents a welcome discussion of statistical issues that arise in provenance studies using U–Pb geochronology on detrital zircons. I agree with the main conclusions of this paper, although I am convinced that these conclusions could have been reached more elegantly, without the need for numerical simulations of the binomial distribution. With this comment, however, I would like to resolve an apparent misinterpretation of my paper on the subject (Vermeesch, 2004). On the third page of his paper, Andersen (2005) writes that Vermeesch (2004) makes strong bassumptions on the nature and distribution of the detected [age fractions]Q because bthe significance of an age fraction is reduced to that of the bin width in an abundance histogramQ. As a counterexample, Fig. 1 shows a detrital age distribution consisting of three age fractions (e.g., f 1: Cenozoic, f 2: Mesozoic, f 3: Paleozoic) of different duration, unrelated to the abundance histogram.

DOI of original article: 10.1016/j.chemgeo.2005.10.008. E-mail address: [email protected]. 0009-2541/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.chemgeo.2005.10.012

Fig. 1. The black and white boxes mark equally sized age fractions ( f 1, f 2 and f 3) corresponding to unequal time intervals (Cenozoic, Mesozoic and Paleozoic, respectively).

References Andersen, T., 2005. Detrital zircons as tracers of sedimentary provenance: limiting conditions from statistics and numerical simulation. Chemical Geology 216, 249 – 270. Vermeesch, P., 2004. How many grains are needed for a provenance study? Earth and Planetary Science Letters 224 (3–4), 441 – 451.