Can high resolutuon plate tectonics models be used to assess sequence stratigraphy?

Category Paleontology and Stratigraphy
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Stampfli, Gérard; Hochard, Cyril
Holding Date 16 September 2008

To construct reliable palinspastic models of the Earth major geological elements, plate tectonics constraints must be taken into consideration, besides others elements such as faunal distribution or paleomagnetic data. Plate tectonic concepts allow to assess the kinematics of displacements of terranes and continents, keeping in mind that these continental entities are part of larger plates. For most continents/terranes, thousand km scale transport can be demonstrated, and used to construct paleogeographic models. These models usually consist in simple continental drift, and therefore, are poorly constrained in term of plate velocities. In such models it is not unusual to find velocities over 50 to 70 cm/y (usually based on paleomagnetic data) which are not acceptable in term of plate tectonics, mainly when they involve large continents like Gondwana. Plate tectonic concepts have been systematically applied to our global palinspastic models moving away from pure continental drift, not constrained by plate limits, to produce a model which finally is more and more self-constrained. In this approach inter-dependant reconstructions are created from the past to the present. Except during collisions, plates are moved step by step, as single rigid entities. Lithospheric plates are constructed by adding/removing oceanic material (symbolized by synthetic isochrones) to major continents and terranes. In the last years we changed our tools and moved into GIS softwares and built a geodynamic database to support the reconstructions, and the model was, and still is, extended to the whole globe, spanning the earth history from 600 Ma to 20 Ma, with average steps of 15 Ma.
The building up of this new approach is presented in a companion presentation by Hochard and Stampfli in GDP 04. Our high precision reconstructions allow to measure many geological features in time and space, starting with plate velocities. It is also possible to evaluate the changing space for the world oceanic volume, as oceans are reconstructed in time and their depth can be assessed in function of their age. It is also possible to measure the changing length of mid-ocean ridges and active margins, giving an insight into volcanic activity and thus potential climate changes. The areas of continental masses versus their position in latitude can also be measured. These figures can be confronted to existing paleoclimatic data and eustatic sea level curves, in order the assess the impact of plate tectonic versus short term climatic changes.