Ciechocinek Formation
Jurassic geologic formation in Europe / From Wikipedia, the free encyclopedia
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The Ciechocinek Formation (also known as the Gryfice Formation at Suliszewo[3]), known in Germany as the Green Series/Grimmen Formation[4] (German: Grüne Serie) is a Jurassic (lower Toarcian) geologic formation that extends across the Baltic coast, from Grimmen, Germany, to Lithuania, with its major sequence in Poland and a few boreholes in Kaliningrad.[5][6] It represents the largest continental area defined as deltaic in the fossil record, estimated to cover ~7.1 × 100,000 km2 (39,000 sq mi) only in the Polish realm.[7] It is mostly known for its diverse entomofauna, composed of more than 150 species of different groups of insects, as well as its marine vertebrate fossils, including remains of sharks, actinopterygians and marine reptiles, along with terrestrial remains of dinosaurs, including the early thyreophoran Emausaurus and others not yet assigned to a definite genus.[8] Its exposures are mostly derived from active clay mining of a dislocated glacial raft with exposed Upper Pliensbachian to late Toarcian shallow-marine sediments.[9] Starting with coarse and fine sand deposits with concretions, the pure clay of the Ciechocinek Formation, after the falciferum zone, was deposited in a restricted basin south of the Fennoscandian mainland. It hosts a layer full of carbonate concretions, where a great entomofauna is recovered.[10]
Ciechocinek Formation | |
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Stratigraphic range: Lower Toarcian ~182–179 Ma Tenuicostatum-Bifrons | |
Type | Geological formation |
Unit of |
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Sub-units | |
Underlies |
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Overlies |
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Area | Polish Basin-North German Basin |
Thickness | 140 m (460 ft) |
Lithology | |
Primary | Claystone & abundant Clay Pits[1] |
Other | Sandy-clayey sediments deposited with traces of breaks and weathering. Grey heteroliths, Mudstones, Claystones, Siltstones and fine-grained Sandstones[1] |
Location | |
Country |
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Extent | Approx. 205,000 km2 (79,000 sq mi) |
Type section | |
Named for | Ciechocinek, Poland |
Named by | Stefan Zbigniew Różycki (as an informal unit)[1][2] |
Year defined | 1958 |
The Ciechocinek Formation is the sister unit of the Sorthat Formation of Bornholm, being its frontal brackish system (measured thanks to the presence of phyllopods and absence of Echinoderms and other stenohaline invertebrates), and the Lava Formation of Lithuania (that represents a more brackish setting at the east), a foreshore setting of the deltaic/lagoonar depositions of the Sorthat, located at the south of this last one, and sharing material between both due to the presence of a measured deltaic system that developed between the two units.[11][5] The Ciechocinek Formation was, in the late Toarcian a depositional area located north-eastern margin of the North German Basin, where the Sorthat Formation (Bornholm high, Fennoscandinavian coast) and the northern part of the island of Rügen (Ringkøbing-Fyn High), both to the north, provided the terrestrial elements of the Ciechocinek Formation taphocoenosis.[12] The Posidonia Shale, deposited mostly on nearby deeper parts of this basin interfinger with the Ciechocinek Fm in the western parts of the states of Mecklenburg-Western Pomerania and Brandenburg.[12][13] Its main equivalents are the Posidonia Shale, upper part of the Rydeback Member, Rya Formation (Southern Sweden), the Fjerritslev Formation (Danish Basin), the Sorthat Formation (Bornholm) or the Lava Formation (Lithuania).[1] There are also coeval abandoned informal units in Poland: Gryfice Beds (Now fused with the Ciechocinek, Pomerania region), Lower Łysiec beds (Częstochowa region), or the "Estheria series".[1]