Paleogeographic reconstructions using QGIS: Introducing Terra Antiqua plugin and its application to 30 and 50 Ma maps (2023)

Paleogeography describes the distribution of highlands, lowlands, shallow seas, and deep ocean basins on the Earth's surface during different geological periods. As such Paleogeography combines datasets and interpretations from widely different fields of Earth, Environment and Life sciences that are integrated in paleogeographic reconstruction maps produced since the early days of geology until today (e.g., Hunt, 1837; Scotese, 2021). Paleogeographic reconstructions provide fundamental constraints for climate and geodynamic models (e.g. Gurnis et al., 2012; Chandra et al., 2021), for the exploration of resources (e.g. Markwick, 2019; Dutkiewicz et al., 2020; Wrobel-Daveau et al., 2022) and are widely used to convey our understanding of Earth evolution in outreach and teaching at all levels (e.g. Seton et al., 2023). Paleogeographic reconstructions sharply developed in accuracy following the revolution of the plate tectonic theory and the growing demand in resources related to the industrial revolution, particularly oil and gas (Wegener, 1912, Du Toit, 1937; Wilson 1966; Dewey and Bird, 1970; Ziegler et al., 1985). In the current context of climate change, the interest in climate models aiming to predict future conditions by making hindcasts of the present day and pre-industrial climate is booming (e.g., Lunt et al., 2021). Paleoclimatic and palaeoceanography studies using numerical model simulations particularly depend on the geographic boundary conditions that are implemented in the form of paleo-Digital Elevation Models (paleo-DEMs), describing the land-sea and elevation distribution on the Earth's surface at a geological time under investigation (e.g., Tardif et al., 2021; Straume et al., 2022). The accuracy of these models has increased again tremendously in the last decade in relation to numerical power and the inclusion of complex physical processes, yet their reliability is still strongly dependent on the accuracy of paleogeographic reconstructions because land-sea distributions, bathymetric and topographic patterns considerably determine climatic and biotic evolution and their interactions (Fluteau and Sepulchre, 2021). Despite their importance for Earth System Sciences, paleogeographic reconstructions integrating a wide range of geophysical and geological data from various fields remain complex to do and therefore can hardly keep up with the growing amount of data and models available to update them.

The ongoing development of Geographic Information System (GIS) software that provides advanced utilities for storing and working with geospatial data has allowed scientists to not only visualize their discoveries and interpretations in past coordinates but also build precise models of the motion of tectonic plates, hence reconstructing their position in the geological past (Müller et al., 2016; Scotese, 2016; Stampfli and Borel, 2002; Vérard, 2021; Wrobel-Daveau et al., 2022). Today, the most advanced open-access software package for tectonic reconstruction is GPlates (Williams et al., 2012), which is fully featured to model tectonic plate motions and reconstruct the past position of continents. It also allows to model the deformation at plate boundaries and provide estimates on shortening of the Earth crust and uplift of mountain ranges and plateaux (Müller et al., 2019). GPlates has advanced input - output features that allow rapid integration of vast arrays of geological and geophysical data into a single tectonic model that enables users to explore past plate tectonic evolution that have resulted in complex present-day tectonic configuration. However, additional tools beyond reconstructing the past positions of tectonic blocks, are required to make paleographic reconstructions. The past topography on continents, the past shorelines, the gaps and overlaps arising between the rotated tectonic blocks or the parts of the Earth crust that once existed but were destroyed during geological processes (i.e., subduction, crustal shortening etc.) remain to be reconstructed in the final paleogeographic map. Different developing approaches have been recently described to reconstruct complete paleogeographic maps using the rotated tectonic blocks as an input (e.g., Baatsen et al., 2016; Golonka et al., 2006; Poblete et al., 2021; Scotese, 2014a, Scotese, 2016, Scotese, 2021; Seton et al., 2020; Stampfli and Borel, 2002; Torsvik et al., 2021; Vérard et al., 2011, Vérard et al., 2015, 2021; Wrobel-Daveau et al., 2022; Zahirovic et al., 2019). These excellent advanced approaches remain often difficult to access because they can require private licenses and rely on complex geologic and geophysical expertise in combination with different GIS, graphics software and scripting languages.

To make paleogeographic reconstructions more accessible to a growing community in various disciplines we have developed Terra Antiqua, a free user-friendly software for producing simple regional and global paleo-DEMs. Terra Antiqua takes as input the tectonic model reconstructed using GPlates to make paleogeographic reconstructions using a set of tools. These include combining various raster and vector files (e.g. continents, modern topography, bathymetry), defining shorelines or modifying and creating topo/bathymetric features. Terra Antiqua is a plugin for QGIS - a GIS software, that provides all utilities for input, output and manipulation of geospatial data. Within QGIS, it is possible to interactively add data, modify symbologies, arrange data into layers, and create and modify interpretations. Terra Antiqua is also geared with an intuitive Graphical User Interface (GUI) and guiding tips that make reconstruction easy and fast. The outcome of Terra Antiqua can then be saved in any GIS supported format, including NetCDF that is widely used in climate models to introduce boundary conditions. Terra Antiqua comes with guidelines, user manuals, downloads, video tutorials and a forum on www.paleoenvironment.eu/terra-antiqua and https://jaminzoda.github.io/terra-antiqua-documentation/.

Here we review paleogeographic methods, concepts and software that provide a framework for the user-driven approach used in Terra Antiqua. We then describe the workflow of the Terra Antiqua software for paleogeographic reconstructions and map creation. This is then illustrated by an example application to the global paleogeographic reconstructions at 30 and 50 Ma. Finally, we review the potential developments of paleogeographic reconstructions with GIS in general and for Terra Antiqua in particular.