Pre-Devonian landscape of the Baltic Oil-Shale Basin, NW of the Russian Platform

Abstract

The erosional relief of Ordovician and Silurian deposits in Estonia was developed during the continental period in late Silurian and early middle Devonian times. The uplift of the area and marine regression were induced by compressional tectonics in the continental interior related to the closure of the Iapetus and Tornqvist Oceans.In the northern part of the Baltic sedimentary basin (Estonia), on the gentle southerly dipping slope between the Fennoscandian Shield (Finland) and Baltic Syneclise (Latvia), a pre-Devonian, slightly rugged erosional relief with few cuesta was developed. The pre-Devonian erosional landforms -hills, depressions and escarpments reaching 150m in height -were probably buried under the Devonian deposits and then partly re-exposed by pre-Quaternary erosion. These landforms are described in detail using data from several thousands of cores drilled in the course of oil-shale and phosphorite exploration and mining.

Chapter 6 Phanerozoic palaeoenvironment and palaeolithofacies maps of the Arctic region

“…It was a large but rather shallow basin where quartz and glauconitic sand, graptolite ooze and detrital limestone with a total thickness of a few tens of metres (no more than 100 m) were deposited. In the Baltic republics, in Estonia and Lithuania, formations of black diktyonite schists were found (Kaljo et al 1988;Zdanavȋciuté & Bojesen-Koefoed 1997;Puura et al 1999;Modliński et al 2007;Raudsep 2008). Similar shallow marine conditions were in the Scandinavian part of the basin; however the sediments had another composition.…”

“…Stratified argillaceous and calcareous sediments up to 180 m thick were accumulated in the central part of the basin. Carbonates dominated in the deposits of the Baltic republics and Scandinavia (Jaanusson 1973;Kaljo et al 1988;Zdanavi˘ciuté & Bojesen-Koefoed 1997;Puura et al 1999;Tuuling & Flodén 2000;Lewandowski & Abrahamsen 2002;Ainsaar et al 2004;Modliński et al 2007;Pedersen et al 2007;Raudsep 2008). Subsidence of the Peri-Urals zone continued along the entire eastern margin of the craton.…”

Multiphase Silurian bentonites in the Baltic Palaeobasin

“…The lower Silurian complex reached its maximum burial depth (less than 1.5 km) during Middle or Late Devonian, after which the sequence remained at peak burial throughout Carboniferous (Kirsimäe et al, 1999). Its slow uplift started presumably in the Permian simultaneously with the extensional tectonic movements (Puura et al, 1999). This suggests that the lower Palaeozoic sediments, at least in the northern part of the basin, stayed at maximum burial depth for at least 150 million years at temperatures well below 100°C.…”

Paleozoic rocks structure versus Cenozoic cuesta relief along the Baltic Shield–East European Platform transect

“…Be sides the vari able and rapidly chang ing li thol ogy, the con ti nu ity of the seafloor-form ing Silu rian rocks is dis mem bered by nu mer ous smaller or larger erosional cuts (Tuuling and Flodén, 2009a, b, 2011, 2016 Seis mic stud ies have proved that the gen eral tec tonic setting along side the plat form Pre cam brian base ment and Pa leozoic ve neer re la tions de scribed in Es to nia (Puura and Vaher, 1997) con tin ues be low the cen tral Bal tic Sea area . Thus, at a gen tle an gle (6-13') un der the platform cover, the south ern slope of the Bal tic Shield forms an exten sive pe ne plain that is eroded into Pre cam brian crys tal line rocks (Winterhalter et al, 1981;Puura et al, 1996Puura et al, , 1999.…”