Intercomparison and Definition of Uncertainties of Deep-Time Global Earth Reconstructions: What’s the problem?

Global Earth reconstruction maps are used as baseline information for many studies, with high-level impacts and large implications. Yet, virtually no study fundamentally question the reliability of those reconstructions. In many cases, the model the study uses is not even credited. The reason for the absence of such discussion probably lies in the fact that none of the plate tectonic / palæogeographic modellers themselves have been able so far to assess the reliability of their own maps.

Why? First, because actually, there are ‘palæo-continental’, ‘plate tectonics’, ‘palæo-environmental’, and ‘palæogeographic’-types of reconstruction and it is difficult to compare apples and oranges. Second, because the workflow, definition, standard and vocabulary used to by the modellers can be quite different. And third and overall, because data, which reconstructions are based upon, may be contradictory and modellers must make choices.

If, for example, 4 data suggest a collision at a given time and a fifth does not, can we state that the model should display a collision zone at the 80% confidence level? What geological information is undoubtedly a proof of a collision? If among the 5 data, 2 corresponds to flysch-series, 1 corresponds to S-type granite, the 4th to tectonic unconformities and structural deformation, and the 5th is the definition of a retrograde path of metamorphic P – T conditions, is it sufficient to talk about collision, and do the 5 data have the same weight in terms of uncertainties? What about if the model does not display the collision zone at time the 4 first data suggest collision, but does display collision at the next time slice in agreement with the 5th information?

Contradictory data and debatable choices will always exist, and the existence of numerous global Earth reconstruction models is thus a wealth. However, in order to talk about uncertainties and to allow some intercomparison, the modellers of the Earth reconstruction community must collaborate, form an International Panel for Earth Reconstruction (IPER), and lay the foundation for shared definitions, concepts, vocabulary, and FAIR principles. A quantification of uncertainty on past reconstructions may then possibly be achieved by intercomparison between various models.