RECONSTRUCTING CRUSTAL PALAEOGEOGRAPHY: HOW MUCH CRUST WAS THERE, WHERE WAS IT AND HOW MUCH DOES PALAEOLATITUDE CONTROL CLIMATE?

Plate reconstruction models provide insight into the distribution of crust in deep time. Models which ensure that all known crust is represented in the model permit the calculation of the distribution of amalgamated crust through time. The fragmentation or combination of crustal blocks, here termed geodynamic units (GDU’s), has previously been calculated in a number of ways. We find that the automated calculation is most robustly determined as the area of the biggest amalgamation of GDU’s, which we refer to as SuperGDU’s. The area of the largest SuperGDU provides the best representation of super-continent and super-craton development. Approaches based on the perimeter length of SuperGDU’s have problems because of the complex shape of some SuperGDU boundaries, in part related to current Python toolboxes which are based on a Cartesian GIS view of the globe which causes splitting of boundaries for SuperGDUs at +/-180 degrees and near the poles.

It is often also thought that palaeolatide plays a fundamental role in the distribution of climate sensitive proxies like coals, bauxites and evaporites but it appears that the spatial distribution of crust, topography and oceanic connections which control oceanic currents have a greater control. Palaeolatitude has been used as a predictor for some styles of mineralization but the geographic distribution of available continental crust to host the mineralization seems to be fundamental. Changing availability and distribution of this crust needs to also be considered, particularly as it varies through time and may be concentrated in one hemisphere or the other. Variations which can be tested with compiled proxy data for the Phanerozoic will need to be extrapolated to Precambrian situations.