Utwory tufonośne antykliny zbrzańskiej (Góry Świętokrzyskie)

Zdzisław Migaszewski

Abstrakt


TUFFITE-BEARING STRATA IN THE ZBRZA ANTICLINE (THE ŚWIĘTOKRZYSKIE MTS.)

Summary
The paper deals with problem of cooccurrence of tuffites, bentonites and tuffite-bearing dolomites within the "Eifelian" lithostratigraphic unit in the Zbrza Anticline (SW part of the Holy Cross Mts). The issue has not been raised as yet in many scientific publications on stratigraphy of the Devonian in the Holy Cross Mts, although pyroclastic material coming from eruptions of unspecified volcanoes seems to have been widely spread. The main feature of the rocks mentioned above is presence in their mineralogical compos1t10n such constituents as volcanic glass, pyroclastic quartz and montmorillonites (mixed layer montmorillonite-illites M/I), apart from illites, zeolithes, light/dark micas and occasionally kaolinites. Transitional petrographic members are composed additionally of "floating" sub- and euhedral dolomite crystals.
Dolomite rocks forming this stratigraphic unit often embrace microinserts and intercalations of tuffite as well as admixtures of pyroclastic quartz. It has been assumed that the presence of tuffite was likely to affect the origin of ankerite during diagenetic phase (borehole IV-1 ). Other diagenetic processes such as formation of stylolites or solution stringers (flasers) might have been partially stimulated by occurrence of the tuffite in question. Further studies should be continued in the aspect of chemical and mineralogical composition, genesis, source of pyroclastic material and possible correlation of tuffite and bentonite horizons alike. Nonetherless, the displayed results force to new interpretation of the Middle Devonian in the area of the Holy Cross Mts from the point of view of lithology, diagenetic processes including dolomitization.

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