Utwory cechsztyńskie w okolicach Niwnic

Wojciech Śliwiński



Zechstein deposits in the Niwnice area are represented by PZ1 (Werra), PZ3 (Leine) as well as one of the higher cyclothems (PZ4?, Aller). Zechstein Limestone (Cal) is developed in two facies - clay-carbonate-sulphate deposited in a mud plain environment and the carbonate one related to shallow marine zones. Upper Anhydrite (A1g) consists of isolated lenses of sulphates, often interlayered with clay shales. These sediments were deposited in narrow depressions located parallelly (?) to the supposed coast line, in the conditions of an evaporated basin. Stratigraphic position of tripartite clay sequence overlaying the Upper Anhydrite. is still controversial. Probably its uppermost part represents the bottom of the PZ3 cyclothem. Platy Dolomite (Ca3) is composed of bipartite dolostones. Its lower part deposited in low energetic conditions while increasing salinity, favoured development of Calcinema (?) algae. Its upper part was formed under inflow of fresh water and considerable water motion. Diagenetically consolidated dolostones were cut by fluvial (?) channels, part of them are infilled by sandstones. The uppermost part of Zechstein sequence (PZ4?) comprises clay-dolomitic deposits of shallow lagoon origin.

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