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Paleozoic Evolution of the Eastern European Platform in Poland and Shale Gas Potential

Abstract

The Eastern European Platform (EEG) belonged to the Paleozoic Baltica plate, which originated as a result of disintegration of supercontinent Pannotia during Early Cambrian. Baltica included part of Poland and adjacent areas northeast of line, which ran from Scania through Western Pomerania, Central Poland, Holy Cross Mountains Fault to the Black Sea. This plate was located in the Southern hemisphere and drifting northward. Silurian was a time of Caledonian orogeny, closing of Early Paleozoic oceans, collision of Baltica with Avalonia and Laurentia and origin of supercontinent Laurussia. The Pomeranian segment of EEG reflects the Caledonian collision. The system of NW-SE striking normal and strike slip faults cutting Precambrian basement as well as Cambrian, Ordovictian and Silurian deposits developed during these times. The Variscan Orogeny was caused by the collision of Bohemian Massif plates and Protocarpathian terrane with Laurussia. The Protocarpathian terrane acted as an indentor, which caused thrust tectonics of EEG in Holy Cross Mountains and Lublin areas. Paleoclimate modeling indicate positions of ancient upwelling systems This process stimulated high marine productivity, forming the organic-rich shales, target for unconventional hydrocarbon exploration in Poland. The coastal upwelling provided favorable condition during Silurian-Early Devonian times. The equatorial upwelling was active during Early Carboniferous. The Upper Ordovician (mainly Caradocian) and Lower Silurian (mainly Llandovery) graptolitic shales display the highest shale gas. This shales are characterized by relatively high total organic carbon (TOC) contents within intervals of considerable thickness, as well as by thermal maturity high enough for hydrocarbon generation. The thickness of the Ordovician and Silurian complexes increases southwestward from the central zone EEG toward its margins. Hydrocarbon generation and expulsion developed during Late Silurian- Devonian times. The Variscan uplift ended these processes during the Carboniferous times. This research has been financially supported by the Polish National Centre for Research and Development (NCRD) grant under the BLUE GAS – Polish Shale Gas program – BG1/GAZGEOLMOD/13.