DELIVERING GEOCHRONOLOGICAL INFORMATION AT A NATIONAL SCALE: THE CANADIAN GEOCHRONOLOGY KNOWLEDGEBASE

On the surface, a geochronometric age determination appears to be a quantitative measure and its capture in database format appears to be a straightforward capture of numerical results. In actuality, each age inherently contains significant amount of interpretation of measured data. This interpretation usually encompasses qualitative and quantitative application of collateral information, such as isotopic systematics, and external constraints such as geological relationships and other constraining age determinations. As such, any date must also capture the derived knowledge within a geochronological data set, if it is to be accurate and truly useful to end users. Of particular importance are the often overlooked needs to apply corrections to ensure conformity of reference standards (especially for methods that reference natural standards, such as HR-SIMS and ⁴⁰Ar-³⁹Ar) and the factors necessary to allow intercomparison of datasets derived from different isotopic systems. A relational data model has been developed in order to create a widely accessible Canadian Geochronology Knowledgebase (http://gdr.ess.nrcan.gc.ca/geochron/e/explorer.htm) that captures all publicly-available radiogenic isotope-based geochronological information. The knowledgebase is made up of tables containing sample location and general geological information, full bibliographic reference, age and complete details on the dating method and associated knowledge. In addition, data descriptions by trained experts highlight the qualitative factors inherent in each determination, allowing end-users to assess the suitability of each age to their application. Corrections derived from EARTHTIME-inspired, interlaboratory experiments on reference standards are integrated to ensure future compatibility with similar knowledgebases evolving elsewhere. To allow access to the knowledgebase, we have developed a web-based application with full search and retrieval capability. This database is centrally located and can be freely accessed by anyone. In order to maintain the integrity of the information, a panel of geochronological editors, each responsible for key geographic or geological locations, oversee submissions to knowledgebase. The knowledgebase provides non-experts with an efficient way of accessing fully-leveled geochronological information.