Understanding ancient tectonic settings through detrital zircon analysis

The fertility and heterogeneity of source rocks play important roles in determining the age distribution of detrital zircon populations that accumulate in sedimentary basins. Detrital zircon samples in active convergent tectonic settings are typified by a dominance of well-defined young age modes associated with an arc/magmatic orogenic belt, while passive margins and extensional settings more commonly express dispersed polymodal age populations reflecting more extensive, geologically heterogeneous catchments and greater sediment recycling. Two newly defined metrics relating to (i) the temporal difference between the 10th and 50th percentiles of a detrital zircon age population, and (ii) a modified -distribution analysis of age population modality and dispersion, provide a powerful means of distinguishing between geologically active convergent systems and divergent/passive margin basins. Importantly, this tool does not require knowledge of depositional age. This “age distribution fingerprint” is assessed in three distinct Cenozoic to Proterozoic case-studies to demonstrate the tectonic resolution of the approach and potential in refining views of basin evolution. The age distribution fingerprint offers the ability to characterize sediment routing histories and investigate tectonic settings since the onset of subduction related plate tectonics, even where stratigraphic constraints are lacking.