Palaeo-digital elevation models for use as boundary conditions in coupled ocean–atmosphere GCM experiments: a Maastrichtian (late Cretaceous) example

Palaeogeography (specifically palaeotopography and palaeobathymetry) provides an essential boundary condition for computer-based atmosphere and ocean modelling. It also provides the geographic context for understanding surface processes (palaeodrainage, palaeoweathering) and biotic interactions (palaeoecology, palaeobiogeography). With increased model resolution, coupled ocean–atmosphere general circulation models (GCMs) and the addition of vegetation, soil (weathering), ice and chemical modules, there is now a need for more robust, detailed palaeotopographies and palaeobathymetries that are fully integrated with the processes being modelled, especially the hydrological system. we present a new geographic information system (GIS)-based, hydrologically correct, palaeo-digital elevation model (DEM) for the Maastrichtian (late Cretaceous). We describe the methods and concepts used to construct the map, and draw attention to the limits imposed by scale and uncertainty, and how these factors must be considered as part of the error analysis of derived model results. The underlying palaeogeography is one of a series of 27 global maps that represent the stages of the Cretaceous and sub-epochs of the Cenozoic. Each map is generated at a scale of 1:30 million in ArcView® GIS and ArcInfo™, using data from the lead authorʹs own databases of lithologic, tectonic and fossil information, the lithologic databases of the Paleogeographic Atlas Project (The University of Chicago), a survey of published literature, and DSDP/ODP data. Interpretations of elevation are derived following the methods outlined in Ziegler et al. (Ziegler, A.M., Rowley, D.B., Lottes, A.L., Sahagian, D.L., Hulver, M.L., Gierlowski, T.C., 1985. Paleogeographic interpretation: with an example from the Mid-Cretaceous. Annual Review of Earth and Planetary Sciences, 13: 385–425), an understanding of the tectonic regime and evolution of each feature, and the age–depth relationship for the ocean. The global palaeo-DEM was derived using the elevation contours from the paleogeography and the suite of hydrological tools available in ArcInfo™ GRID. The palaeo-DEM has been constrained by defining areas of internal palaeodrainage, palaeoriver mouths and known palaeoriver courses. The Maastrichtian has been completed first to provide the boundary conditions for a series of coupled atmosphere–ocean experiments. ntegrated with the results of the coupled ocean–atmosphere model, the result is a powerful tool for understanding surface processes and an important step towards the development of a continuous series representing a fully evolving palaeolandscape.