Deciphering the sands of time: a zircon U-Pb age database for the Circum-Arctic region

How and when the Amerasia Basin opened are poorly understood but have significant implications for the geological histories and petroleum systems of sedimentary basins within the circum-Arctic region. This lack of understanding is in part due to the paucity of direct evidence and subsequent overprinting by the High Arctic Large Igneous Province. Uranium-lead detrital zircon geochronology, employed alone or in conjunction with Lu-Hf isotopes, is a widely employed tool for reconstructing sedimentary provenance. It can provide insights into the opening of the Amerasia Basin by constraining the pre-rift configuration of Arctic tectonic terranes and sediment transportation pathways.

Despite being comparatively remote, a large volume of published U-Pb age data exists from the onshore margins and offshore continental shelfs of the Arctic Ocean. Rigorous comparison of these data is, however, seldom straightforward. This is because of variations in the treatment and presentation of data used by different studies. Recalculation of data, using a common set of parameters and criteria, is often necessary; for example, using the same age system (²⁰⁶Pb/²³⁸U versus ²⁰⁷Pb/²⁰⁶Pb) and employing thresholds on analytical precision and U-Pb age discordance to remove imprecise and unreliable analyses. Such recalculation is a laborious endeavour, particularly when substantial volumes of data are involved.

In an attempt to elucidate the opening of the Amerasia Basin, a standardised dataset of published zircon U-Pb ages and Lu-Hf isotope data from the circum-Arctic region is being developed as a geographical information system (GIS) database using ArcGIS®. The database serves as both a repository for large volumes of U-Pb age and Lu-Hf isotope data, and as a platform from which to interrogate the dataset. Custom database tools have been developed within ArcGIS® using Microsoft Visual Studio®. These facilitate the searching of the database and visualisation of U-Pb age and Lu-Hf isotope data within the GIS environment as epsilon hafnium plots, conventional probability density and cumulative density plots, as well as novel probability density heat map barcodes. Furthermore, similarity measures, using multidimensional scaling, are being developed to enable data to be compared with statistical rigour.

Compilation of such a database is a considerable undertaking. So far we have focused predominantly on compiling zircon U-Pb age data from igneous and metamorphic rocks within the circum-Arctic region, although compilation of detrital zircon U-Pb age data is ongoing. The database presently contains over 2,500 individual samples, >60,000 U-Pb zircon analyses and >7,400 Lu-Hf zircon analyses.