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Abstract
Calpionellid stratigraphy, magnetic susceptibility (MS) and gamma-ray spectrometry (GRS) have been investigated in the Berriasian pelagic limestones of ca. 21 m thick interval from the Lipse-tető section (Mecsek Mts, southern Hungary, Tisza Mega-unit). The section covers the lower and upper Berriasian (Calpionella and Calpionellopsis Zones respectively), however due to a thrust fault, the upper part of the Calpionella elliptica Subzone and the lower part of the Calpionellopsis simplex Subzone (lower/upper Berriasian boundary interval) were not documented. Reslults of GRS measurements reveal contrasting trends, with low detrital input (K, Th) and elevated Th/K ratio through the lower Berriasian, as well as relatively high detrital input and decreased Th/K ratio within the upper Berriasian. The differences occur also in the calpionellid frequencies and species richness: assemblages rich in Calpionella alpina dominate in the lower Berriasian, whilst more diversified yet less abundant associations characterize the upper Berriasian. Trends in palaeoenvironmental proxies correspond well with data from the Lower Sub-Tatric succession (Pośrednie-Rówienka composite section, Tatra Mts, Poland). The palaeoenvironmental change between the early and late Berriasian is most probably related to palaeoclimate (arid to humid transition), and fertility (from oligo- to mesotrophic regime). Trends documented in Th/K ratio might have been controlled by the intensity of aeolian transportation. As revealed by previous studies, the consistent record of palaeoenvironmental changes in both the Tisza Mega-unit and the Central Western Carpathians might be observed also in the middle Jurassic sediments.
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