Authors

Maria Seton and Dietmar Müller (University of Sydney)

Abstract

In geosciences, we are often concerned with processes and events that have occurred in the past over geological timescales rather than an instantaneous snapshot of the present day. In order to understand the spatial and temporal framework of geological data and processes, an underlying plate kinematic model, which quantitatively describes how the Earth’s plates have moved through time is required. In addition, associated metadata must be assigned to features on the Earth’s surface, such as the present location (longitude, latitude), the age of formation and the tectonic plate on which the feature formed and now resides, to enable the linking of a feature to the plate kinematic model.

We have developed a global plate kinematic model describing the motions of the major tectonic plates from the early Jurassic (200 Ma) to the present day. We use a True Polar Wander corrected absolute reference frame for times prior to 100 Ma and a moving hotspot reference frame for all other times. This absolute reference frame is coupled with relative plate motions for all the major continental and oceanic plates, terranes and island arcs. Plate motions are primarily derived from the interpretation of potential field data, such as gravity and magnetic anomaly data, to create seafloor spreading isochrons and fracture zones, as well as using on-shore geological data and the rules of plate tectonics. The primary tool used to construct our plate motion model is the open source software package GPlates (www.gplates.org). GPlates enables a user to interactively import, interrogate, reconstruct, extract and visualise data for the whole world through geological time. Our plate kinematic model is distributed freely with GPlates giving researchers both in academia and industry as well as educators the ability to utilise this resource.

Our plate kinematic model has been successfully implemented in a number of studies, including:

• Computing long-term eustatic sea level and seafloor spreading rates from the Cretaceous to the present day by computing the age-area distribution of oceanic lithosphere through time [1-2].
• Examining the relative influence of topography, sea-surface temperature and CO2 to the Miocene Climate Optimum by using our plate kinematic derived palaeo-bathymetry grids as boundary layer input into palaeo-climate models [3-4].
• Understanding how surface processes are linked to mantle processes by deriving estimates for dynamic topography [5-6]. This involves converting our plate model into global plate velocity fields, which are used as surface boundary layer input into CitcomS. CitcomS is a finite element modelling software package which models mantle convection on a spherical earth. These models have also been used to make predictions on mantle structure [7-8].

In the future, our plate kinematic model will be formatted into GPML (GPlates Markup Language), allowing the seamless integration of spatially referenced geological data into GPlates and hence able to be implemented into various numerical modelling software tools.