INVESTIGATING DEEP TIME: CHALLENGES AND POSSIBILITIES FOR RECONSTRUCTING EARTH HISTORY BACK TO THE ARCHAEAN (Invited Presentation)

Development of plate reconstruction models for broad application in deep time, potentially back to the Archean, is premised on a number of principals. Anything mapable at present day must be reconstuctable into the past, overlaid of suitably subdivided continental geodynamic units (GDU’s). The shape, extent and geometry of GDU’s relative to others has fundamental control on their motion since the Earth is approximately spherical. GDU’s must be represented in the model back to their interpreted age of formation. Palaeomagnetic constraints are fundamental to constraining motion of GDU’s but need to be supplemented by other geological information (geochronology, stratigraphy, LIPs, geochemistry, etc) because of the scarcity of palaeomagnetic data of ‘good’ quality. True polar wander is the most effective way to deal with unusually fast apparent plate motions during some critical time intervals. Longitude is modelled using the orthoversion approach. Continuity of kinematic motion is essential and needs to be implemented with high temporal resolution. Plate margins are derived from GDU kinematics, since there is no preserved, extensive oceanic crust prior to 160 Ma. The geometry and relative motion of adjacent plates is a fundamental test of the realism of the inferred model.

With a sufficiently detail model in place, it is possible to investigate many aspects of Earth history, including supercontinent cyclicity; the distribution of igneous activity; formation of sedimentary basins; the nature and distribution of ore deposits; influence of climate on lithostratigraphy, mineralization, etc. Available data suggest that simplistic climate bands are not good predictors of climate conditions and that the relative positions of different continental blocks and of topography also play important roles. The geographic distribution of suitable crust to preserve rock units, climate sensitive proxies and ore deposits appears to be just as important as global climate zonation.

The biggest challenges for effective model definition are the delineation of the GDU polygons and the availability of additional good quality geoscience information with both geographic and temporal constraints. Concerted efforts by the broader geoscience community to develop these additional attributed datasets will fundamentally improve future plate reconstruction models.