Skład izotopowy tlenu i węgla w górnojurajskich skałach węglanowych z Niecki Nidziańskiej

Zygmunt Heliasz, Bożena Jasińska

Abstrakt


ISOTOPIC COMPOSITION OF OXYGEN AND CARBON IN THE UPPER JURASSIC COMPONATE ROCKS IN THE NIDA TROUGH

Summary
The Nida Trough is a crucial region among the Upper Jurassic rocks outcropping within the Mesozoic margin of the Holy Cross Mts. and Cracow- Częstochowa Upland. In the Upper Jurassic the Trough was a part of a broad epicontinental basin situated between the boreal sea in the north and the geosynclinal basin in the south. Over l000 m thick suite of carbonate rocks was formed due to permanent, considerable subsidence of the basin.
The isotopic composition of oxygen and carbon comprised in carbonate deposits reflects physical and chemical conditions of the Upper Jurassic sedimentary basin as well as properties of diagenetic waters. Four boreholes located along the axis of the Nida Trough were examined.
The analysis of δ values for O18 and C13 indicates that the final redistribution of isotopes took place after the recent structural pattern of the Nida Trough had been formed due to the Laramide phase. Moreover the relation of oxygen isotopic composition and lithologic type of rock has been found. The highest δ values for O18 were recorded in marls and marly limestones.
This dependence can be interpreted as a result either of different diagenetic system (open one) or lower temperature of waters in the sedimentary basin. In top and bottom parts the recorded isotopic composition for oxygen and carbon were influenced by chemically different waters, connected with cover and substrate of the Upper Jurassic suite.

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