Getech’s Palaeo-Digital Elevation Models (Palaeo-DEMs) represent the palaeotopography and palaeobathymetry of the Earth’s surface through time. This is an explicit definition of the Earth’s surface in metres, but with stated uncertainties. These Palaeo-DEMs are hydrologically-correct (internally consistent with the mapped palaeodrainage), and provide the boundary conditions for Earth System Modelling and quantitative and qualitative assessments of surface processes that dictate sediment deposition, composition and flux.
Present Day topography has an intrinsic relationship with the underlying tectonic regimes. For example, areas of the Earth that are experiencing active tectonics tend to have the highest elevations. Conversely, areas of the Earth that have not seen any tectonic activity for prolonged periods of geological time and are predominantly depositional (or at least non-erosional) have the lowest elevations. This relationship is a direct consequence of the interaction between tectonic processes, and surface processes and forms the basis for Getech’s Palaeo-DEM Modelling.
The topography and bathymetry are modelled separately using different techniques. Getech’s model for palaeotopographic reconstruction generates elevations based on the defined tectonophysiographic terranes mapped in Getech’s palaeogeographies by analogy with modern elevation ranges for the same tectonic regime.
Once the elevation ranges for palaeoenvironments and tectonophysiographic terranes have been defined this is integrated with Getech’s global palaeodrainage networks to generate a hydrologically-correct DEM.
The palaeobathymetry of each timeslice is derived using several methods. The shelf break and intrashelf bathymetry are based on available seismic, lithological and palaeotontological information. These reconstructions are highly dependent on data availability.
The oceanic crust palaeobathymetry is calculated using the age-depth equations of Stein and Stein (1992) with corrections for sediment cover, sea-level changes and the intrusion history of oceanic seamounts. The modern ocean age grid is subset for only ocean crust of appropriate age and rotated into their palaeopositions using Getech’s Global Plate Model. The depth equations of Stein and Stein (1992) are then applied to this revised grid.
For areas of no well-dated ocean, or older time periods for which ocean crust is no longer preserved, age-depth calculations are applied to modelled synthetic isochrons based on the conceptual plate model for each area.