Kreda górna w niecce mogileńsko-łódzkiej

Maria Jaskowiak-Schoeneichowa




The Mogilno and Lódź troughs were invaded by the sea at; the Albian time. The Middle-Polish swell represented then the deepest part of the basin and within the monocline area the sea shore corresponded to the present-day boundary of the deposits. The transgression can be investigated in neritic sands, covered with marls deposited after a deepening of the sea bottom beneath wave base. Some anticlines lack here any Albian deposits; most probably, these were shallow sea areas. In the south, the Albian deposits are arenaceous only, mainly due to an intense erosion of the Świętokrzyskie Mountains.
At the Lower Cenomanian time, the transportation of terrigene material decreased due to the deepening and widening of the sea. Limestones, with traces of synsedimentary dissolution, were laid dawn, proving thus approach to the depth of the critical saturation with carbon dioxide. Above some anticlines sedimentary gaps may be observed. The area of the Middle-Polish swell was, as formerly, the deepest part of the sea; on the monocline, the sea-shore was somewhat behind the contemporaneous range of the deposits.
At the Lower Turonian time the deposits were laid down in a deep sea. In the Upper Turonian, some anticlines were being denuded more and more, and this process changed the deposits from limestones into marls and opokas. The uplift of the remaining anticlines was responsible for the thinning of the deposits, going from synclines to anticlines. The process proceeded at the Coniacian time, too. At that time the Pomeranian swell emerged above the sea level. In the Coniacian, Santonian, Campanian, and Maastrichtian the sea became shallow, in the trough local structures were intensely formed and, as a result of the denudation process on summits of some anticlines and swells, such rocks like opokas, mads, and gaizes were deposited. The sea withdrew at the Maastrichtian time, or somewhat later.


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