Reconstructing ocean basins through geological time
Channel: Paul Wessel
Date: 2020-02-05

Dr. Dietmar Müller (Sydney University, Australia) gave a guest lecture via Skype in Fall 2008 for a graduate class on Advanced Plate Tectonics in SOEST, University of Hawaii at Manoa.  The students recorded the lecture and produced video podcasts of the event.  This is one of 8 such lectures from the course which was taught by Prof. Paul Wessel.

ABSTRACT:

"Understanding the history of sea floor spreading and subduction requires the complete reconstruction of ocean floor through time, including the main ocean basins, back-arc basins, and now subducted ocean crust, and tying these kinematic models to geodynamic simulations. I will outline how to reconstruct paleo-oceans based on combining marine geophysical data with creating “synthetic plates”, the locations and geometry of which is established on the basis of preserved ocean crust (magnetic lineations and fracture zones), geological data, paleogeography, and the rules of plate tectonics. I will review Chang et al's plate reconstruction techniques and how to create a merged moving hotspot (Late Cretaceous-present) and palaeomagnetic/fixed hotspot (Early Cretaceous) reference frame. Based on this approach we have created a set of global oceanic paleo-isochrons and paleo-oceanic age grids.  The grids provide the first complete global set of paleo-basement depth maps, including now subducted ocean floor, for the last 130 million years based on a depth-age relationship. We show that the late-Cretaceous sealevel highstand and the subsequent long-term drop in sea level was primarily caused by the changing age-area distribution of Pacific ocean floor through time, and to a much lesser extent by the "supercontinent breakup effect", which resulted in the creation of the mid-Atlantic and Indian Ocean ridges at the expense of subducting old ocean floor in the Tethys.  Our kinematic models and age/depth grids provide constraints for subduction dynamics through time and represent a framework for the opening/closing of oceanic gateways for paleooceanographic models."