Sedimentary record of eustatic changes on the Givetian (Devonian) carbonate platform of Małopolska Massif, southern Poland

Małgorzata Sobstel

Abstract


The Givetian carbonate succession of the Mzurów 49-BN borehole, SW part of the Małopolska Massif, has been divided into three lithological units: set A (Amphipora limestones), set B (micritic limestones; subdivided into subsets B1 and B2), and set C (peritidal dolomites with evaporites). The sets represent three main depositional facies identified throughout the studied section. The succession corresponds to transgressive-regressive cycles identified in the Kielce region of the Holy Cross Mts, i.e. the northern part of MaΠopolska Massif. The event correlation is supported by biostratigraphy, based on conodonts and benthic faunas. These data indicate that the studied interval probably belongs to the latest part of the middle and late Givetian (Klaperina disparilis Zone to early Mesotaxis falsiovalis Zone). Set A represents largely shallow subtidal sediments deposited on an extensive shallow carbonate platform; its facies development shows many similarities to the youngest part of the Stringocephalus Beds and Dziewki Limestones. After a transgression in the late Givetian, open-marine micritic limestones (subset B1) were deposited. Their facies equivalent easily is readily identified as the Jaźwica Member in the southern part of the Holy Cross Mts. A regressive trend is recognized from the beginning of subset B2. Sea-level fall finally resulted in salinity increase in an isolated shallow-water basin of the Małopolska Massif. In mostly hypersaline conditions, cyclic deposition was developed. Three upward-shallowing metre-scale cycles within set C are recognised, each of them starting with thin calcareous mudstone beds with open marine biota and capped by grey dolomudstone with beds and nodules of gypsum or anhydrite.


Keywords


Givetian, Stratigraphy, Conodonts, MaΠopolska Massif, Eustasy, Carbonate complex

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