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

Abstract

1 Uni ver sity of Tartu, In sti tute of Ecol ogy and Earth Sci ences, Ravila 14A, 50411 Tartu, Es to nia Tuuling, I., 2017. Pa leo zoic rocks struc ture ver sus Ce no zoic cuesta re lief along the Bal tic Shield-East Eu ro pean Plat form transect. Geo log i cal Quar terly, 61 (2): 396-412, doi: 10.7306/gq.1342Based on struc tural maps, the bed rock struc ture on the south ern slope of the Bal tic Shield is ana lysed. Gently south erly dipping (0.1-0.2°) Paleozoic lay ers from Es to nia to the Swed ish east coast form the Bal tic Homocline (BH). Nu mer ous monoclinal folds, forced by base ment fault ing, in duce slight vari a tions in bed rock at ti tude across the BH. Stud ies on faults ex posed in South ern Fin land sug gest that many monoclinal folds in duc ing base ment faults within the BH are of Pre cam brian or i gin and have been ac tive in pulses. The pres ent mono clines were shaped by the Cal edo nian Orog eny. Submeridional tectonic hinge-lines in duce mi nor re gional-scale changes in the struc tural set ting and con trol trends/styles of the forced folds. From the west, the BH bounds with the Bal tic-Bothnian mo bile zone that has been in ter mit tently ac tive since Mesoproterozoic times. The evolv ing Bal tic Syneclise in the Si lu rian re ar ranged the struc tural set ting typ i cal for the Or do vician Bal tic Ba sin. The Ce no zoic up lift of Scan di na via cre ated a SE-to-E-dip ping bed rock se quence around the Gotland-Öland area. As the lat ter area had a dif fer ent at ti tude than the BH, two Ce no zoic cuesta-sets started to evolve around the north ern Bal tic Proper. They both had an out let to the N-S-flow ing Eridanos River around the Gotska Sandön area, cre at ing thus two in de pend ent sec tions of the Bal tic Klint.

Origin of the Baltic Sea basin by Pleistocene glacial erosion

“…3). Differential erosion of sequences of Early Palaeozoic sedimentary rocks, with unconsolidated Cambrian clays, fissile shales and more massive Ordovician and Silurian limestones, that dip gently southwards (Tuuling 2017) likely led to development of north-facing homoclinal scarps along the receding edge of the sedimentary cover. A cuesta may have existed on the thick chalk at the site of the present Darss Sill.…”

The outlines of the bedrock relief and the Quaternary cover between the Estonian mainland and the islands of Muhu and Saaremaa in the West Estonian Archipelago

“…So far, almost nothing has been known about the bedrock relief, its features beneath the Väinameri. Still, many authors have supported the hypothesis of a deep preglacial buried valley running beneath the Bay of Matsalu and between Hiiumaa and Saaremaa, a westerly continuation of the present valley of the Kasari River (Kvasov 1975;Tavast and Raukas 1982, fig 42;Tuuling 2017). One of the main reasons for such a prediction were the cliffs of the Silurian Klint that occasionally emerge around the Suur Strait and along the northern coast of Saaremaa.…”

“…One of the main reasons for such a prediction were the cliffs of the Silurian Klint that occasionally emerge around the Suur Strait and along the northern coast of Saaremaa. The continuation of the Silurian Klint beneath the central part of the Baltic Sea, where it represents a steeper bank of an asymmetrical cuesta valley, suggests that the river passing through the Väinameri is only a section of a large tributary of the Eridanos, which once ran along the Swedish east coast (Overeem et al 2001;Tuuling and Flodén 2016;Tuuling 2017). For verifying this concept, the Suur Strait along with the adjacent Väinameri section is one of the critical areas, and the knowledge about the nature of its bedrock relief is of paramount importance.…”

“…The most prominent feature is undoubtedly the bedrock depression concealed beneath the Baltic Sea, with its branching northern gulf sections (Bothnia, Finland and Riga). The most eyecatching relief entities onshore are obviously the preglacial terraced escarpments emerging in the platform cover, the Baltic and the Silurian klints, which besides picturesque coastal sections in Estonia and Sweden exhibit an excellent cuesta-relief on the seafloor beneath the central Baltic Sea Flodén 2001, 2016;Tuuling 2017).…”

The role of the Leba Ridge–Riga–Pskov Fault Zone in the tectonic evolution of the deep-facies Livonian Tongue within the Baltic Ordovician–Silurian sedimentary basin: a review

“…The Caledonian orogeny with intensive faulting activity reached its peak in the latest Silurian to the earliest Devonian period, while the NW EEC interior has been considered as a tectonically relatively stable basinal area with only rare fault movements for most of Ordovician-Silurian time (Šliaupa & Hoth 2011;Tuuling 2017).…”