Preliminary global paleogeographic maps through the Greenhouse-Icehouse transition: forcing of the Drake Passage and Asian Monsoons.
Résumé
Paleogeographic maps are essential for understanding Earth dynamics. They provide the necessary boundary
conditions for climate and geodynamic modeling, surface processes and biotic interactions. In particular, the
opening and closing of ocean gateways and the growth of major mountain belts are major drivers of climate
changes and biotic interchange. However, the timing and spatial extent of such events are highly controversial and
regularly questioned by new data. As part of the ERC “MAGIC” project focusing on Asian Monsoons during the
Icehouse to Greenhouse transition we thus produced a set of worldwide Cenozoic paleogeographic maps in the
period time between 60 to 20 Ma, with a set of boundary conditions specific to the India-Asia collision zone and
the Drake Passage.
The creation of a paleogeographic map followed a rigorous and reproductively methodology that integrates paleo-
bathymetric, paleoshoreline and paleotopographic data into a coherent plate tectonic model using the open source
software GPlates. (1) We use the model provided by Seton et al. (2012) as a first order tectonic model modified
to integrate the full restoration of five regions: the Andes, the Scotia Arc, Africa, The Mediterranean Sea and the
Tibet-Himalayan collision zone. (2) The paleobathymetry was provided by Müller et al. (2008) using age-depth
relationships and assuming symmetric ridge spreading. (3) Paleoshoreline maps were modified according to the
fossil database from fossilworks.org and the geological record and were used to represent the boundary between
terrestrial and marine paleo-environments. (4) To reconstruct paleoelevations, the most controversial task, we
compiled a wide range of data including stable isotope, leaf physiognomy, and thermochronology combined with
regional fossil and geological records (tectonic setting) and geomorphological data. Finally, we use the open
source GMT software and a set of masks to modify the current Earth relief model (ETOPO) according to the
estimated paleoelevation for specific region at each period of time.
Our approach specifically takes into account the evolution of continental margins. Paleotopographic evolution is
coupled with the evolving shape of continents. Considering the constant addition of new data and models, the
value of this method is to generate a progressive paleorelief model of the Earth that can be easily compared and
updated with new data.