THE GLOBAL DETRITAL ZIRCON DATABASE: AN UPDATE

A flood of new detrital zircon U-Pb age data has allowed for a rapid growth of the Global Detrital Zircon Database (GDZD). The latest version of the database includes over 284,000 single age determinations from U-Pb dating of detrital zircons. These zircons represent ~5,600 detrital zircon age frequency distributions that come from all continents and range in age from modern sediment samples to Archean metasedimentary rocks. Host rock compositions are dominated by siliciclastics, though a small fraction of the samples are derived from carbonates and other chemical/biochemical sedimentary units. For all age frequency distributions, the GDZD also records a best estimate of the host sediment maximum and minimum age independent of the detrital zircon U-Pb ages.

The large amount of data has allowed us to empirically derive relationships between host sediment age and sample size of analyzed zircons. Detrital zircons are an excellent example of the principle of inclusions; they are always as old as, or older than, the host sediment. A simple quantitative metric can be used to measure the offset between the maximum host sediment age and the youngest detrital zircon age recorded. We have found that as a function of tectonic setting, relatively small sample sizes are required to best estimate the age of the host sediment with the smallest offset. Tectonic settings with syn-volcanism tend to require sample sizes of 40 grains or less in order to provide the best constraint on the age of the sample – a grain that is relatively contemporaneous with deposition of the unit. Passive margins and intracratonic basins tend to exhibit much greater offsets between the host sediment age and the youngest detrital zircon and require larger samples of dated zircons to find these young zircons.