3.6.1. Background

The East-European Platform (EEP) provides a unique natural laboratory to study the links between the sedimentary record, the crust and mantle structure, and the tectonic evolution of continental lithosphere over a time span of ca. 3 Gy. Past analogues are keys for understanding modern geodynamic processes. 4D models of the lithospheric structure based on integration of already available data, deployment of seismic and magnetotelluric networks, and process-orientated modelling will provide the database for ancient analogues of modern tectonic processes and for validation of process modelling in the TOPO-EUROPE target areas of Phanerozoic Europe.

Three Archean continents (Baltia, Sarmatia, and Volga-Uralia) form the basement of the EEP. These are separated by roughly linear, several thousand kilometres long, trans-cratonic sutures zones. These zones, consisting of a tectonic mixture of high-grade metamorphic, volcanic, and sedimentary rocks, are interpreted as paleo-collision zones. Most of the EEP crust underwent intense tectonic reworking during the Paleoproterozoic. However, as most of Volga-Uralia is covered by a thick sedimentary cover (typically 2 to 3 km, with ca. 4 km in the Proterozoic trans-cratonic sutures zones, and as much as 25 km of sediments in the Peri-Caspian Basin), the paleotectonic evolution of the north-western part of the EEP (Baltia, Sarmatia) is better known. Baltia is characterized by Archean granulate-gneiss and greenstone terranes, surrounded by Paleoproterozoic mobile belts with high-grade metamorphic rocks. Largely Paleoproterozoic in age, Baltia is separated from Sarmatia by WSW-ENE trending continental arcs that were accreted during Paleoproterozoic large-scale tectonic collisions (e.g. Bogdanova et al., 2006). Further south, within the Sarmatian paleocontinent, the orientation of the paleoterranes becomes largely N-S. This part of the EEP, which consists of a collage of Archean low-grade and high-grade metamorphic terranes, includes the oldest rocks of the European continent that are also among the oldest ones on the planet (ca. 3.6 Ga).

Studies on the evolution of the East-European Craton have shown that processes occurring along its margin exerted a strong control on the development of its internal parts (e.g. Poprawa et al., 1999; Nikishin et al., 2001). It can be argued that this linkage is one of the major factors controlling the neotectonic and related surface processes of the EEP. But it is also clear that intracratonic heterogeneities are of primary importance. For example, the response of the intracratonic lithosphere to tectonic forces applied to its margins is strongly influenced by its rheological structure. This ‘crustal memory’ is a basic concept that explains the neotectonic reactivation of ancient tectonic features, thus linking processes that took place 1-2 billion years ago during crustal accretionary phases with present-day processes.

The lithosphere of the EEP is essentially strong and, though the intensity of ongoing tectonic processes is rather low, neotectonic activity has a significant impact on the recent relief and surface processes. Because relief is dominantly low, even small changes in vertical motions of the crust may lead to significant changes of the surface system. A recent example is the shallowing of the harbours in the Scandinavian part of the Baltic Sea due to on-going crustal uplift while the lowlands along the southern shores of the Baltic Sea are subject to progressive flooding.

Indeed, much of the Phanerozoic tectonic activity within the EEP is reflected in the thickness of its sedimentary cover, which increases eastwards from 1-3 in the central part of the EEP to 4-7 km along the Urals. Rapid subsidence of the eastern part of the EEP during the Paleozoic was, at least partly, related to the development of the Uralian Orogen. Late Paleozoic peri- and intracratonic rifting on the southern parts of the EEP led to the development of the Pripyat-Dniepr-Donets rift, which contains more than 20 km of Devonian and younger sediments in its deepest parts and which cuts across the Archean-Paleoproterozoic terranes of Sarmatia into the Ukrainian Shield and the Voronezh Massif (e.g. Stephenson et al., 2001). Rifting may have been driven by Late Devonian mantle plume activity (Stephenson et al., 2006), which may have caused a substantial thermo-mechanical and compositional reworking of the cratonic lithosphere (Fig. 66). Paleozoic subsidence of the contiguous Peri-Caspian Basin, which contains one of the thickest known sedimentary sequences (25+ km) and has a huge hydrocarbon potential, could be related to similar lithospheric processes, but large-scale mechanisms to explain the subsidence of the entire southern part of the EEP have not yet been thoroughly examined (cf. Saintot et al., 2006; Stephenson et al., 2006).