Palaeogeographic Mapping

Palaeogeographic reconstructions represent the Earth’s surface through time. This includes the underlying tectonics, depositional environments, climate, vegetation, rivers and landscape. Getech has considerable expertise in palaeogeographic analysis and mapping, with a large team of over 12 geologists working full time on the next generation of atlases, which currently include reconstructions for every stratigraphic Stage back to the Permian.

Palaeogeography, put simply, represents the geography of the Earth’s past. At Getech palaeogeography is central to showing how the complex elements of the Geological Record fit together spatially and temporally. Nowhere is this more important than in exploration: the past juxtaposition and distribution of source, reservoir and seal deposition;  how these relate to and are dictated by the underlying tectonics; the source to sink relationships that map the transport pathways for clastics, and the degree of structuralisation in a basin.

Getech’s digital Atlases of Palaeogeography now comprise ArcGIS™-based maps for every one of the 59 Stages from the Permian to Present Day, and include reconstructions of the following: structural and tectonic elements; gross depositional environments (GDEs); tectonophysiographic terranes (the tectonic regime as classified according to the last thermo-mechanical event to affect the area); shoreline positions (both maximum transgression and lowstand); lithology; palaeorivers and palaeodrainage basins; PalaeoDEMS (bathymetry and topography), together with representations of the underlying data. These maps then form the boundary conditions for state-of-the-art Earth System Modelling experiments, which provide results for the contemporary climatology, oceanography, tides, waves and vegetation.

Building these maps is an iterative and highly-skilled process. Getech’s Palaeogeographic Mapping Teams currently comprise 15 full-time staff with a combined mapping experience of over 40 years.

Getech has been responsible for developing new mapping techniques, and especially for refining the concept of Tectonophysiographic Terranes (Markwick & Valdes, 2004) and building the extensive attribution and audit trails accompanying the Getech maps. The mapping concepts themselves build on the seminal research of Professor Fred Ziegler at the University of Chicago, whose Paleogeographic Atlas Project (PGAP) published some of the earliest palaeotopographic atlases back in the late 1970s and 1980s and were responsible for many of the methods still used by numerous palaeogeographers today (see Ziegler et al. 1985).

An example from Getech’s 2012 Atlas of Cretaceous Global Palaeogeography showing the reconstruction of gross depositional environments, structural elements and tectonics (left) and related landscape (right) for the middle Cretaceous of southern Gondwana

An example from Getech’s 2012 Atlas of Cretaceous Global Palaeogeography showing the reconstruction of gross depositional environments, structural elements and tectonics (left) and related landscape (right) for the middle Cretaceous of southern Gondwana

Interpretations are drawn onto basemaps, which are generated using the results of the plate modelling, structural mapping and analysis, and rotated ‘observational’ and other primary data from our extensive wells and outcrop database, digital geology and other third party databases. These are used to constrain the depositional environments, lithologies (together grouped as GDEs) and tectonics.

Our underlying paradigm is that the maps represent contemporary base-level with areas of deposition (below base-level) and areas subjected to erosion (areas above base-level or tectonophysiographic terranes). This allows the maps to show the dynamics of the landscape and related depositional systems, whilst also providing a direct conceptual link to accommodation space and sequence stratigraphy.

This is an iterative process because insights learned from the mapping are fed back into both the plate model and structural datasets for further refining. The resulting maps are then used as the basis for constructing palaeodrainage and PalaeoDEMs. The reconstructed palaeodrainage is the result of a comprehensive analysis of Present Day morphometrics constrained by provenance, stratigraphic and sedimentological observations. Other data, such as fish DNA and palaeobiogeography, provide further tests of hypotheses. The PalaeoDEMs follow the methodologies outlined in Markwick and Valdes (2004), and are based on an analysis of elevational distributions for different tectonic settings then refined using palaeoaltimetry and denudation information.  Combined these explicitly show source to sink relationships across the globe, which is key for understanding reservoir quality and composition.

The palaeobathymetric and palaeotopographic grids, and defined palaeo-river systems, provide the key boundary conditions for a coupled ocean-atmosphere climate model, which is used to generate quantitative oceanographic, climatic and vegetation results. The paleobathymetric models also provide the necessary input for detailed, variable mesh tidal modelling, which is used to reconstruct transport capacity and the probable nature of coastal bedforms.

All our work can be easily implemented into regional studies, both by ourselves and our clients, including, amongst others, refined high resolution structural datasets, CRS mapping and landscape analysis studies.

References Cited

Markwick, P.J. & Valdes, P.J.(2004). “Palaeo-digital elevation models for use as boundary conditions in coupled ocean-atmosphere GCM experiments: a Maastrichtian (late Cretaceous) example” Palaeogeography, Palaeoclimatology, Palaeoecology, v.213 (1–2), p.37–63
Ziegler, A.M., D.B. Rowley, A.L. Lottes, D.L. Sahagian, M. L. Hulver, and T.C. Gierlowski (1985). “Paleogeographic Interpretation: with an example from the Mid-Cretaceous”. Annual Reviews of Earth and Planetary Sciences v. 13, p. 385–425.

To find out more about Getech’s Palaeogeographic Mappinclick to get in touch