The Langhian–Serravallian Transition in the Eastern Carpathians: Integrated Biostratigraphic, Mineralogical and Stable Isotope Evidence From Muntele Piatra Verde

ABSTRACT

The Middle Miocene Climatic Optimum (MCO) was followed by the Middle Miocene Climatic Transition (MMCT), a major Cenozoic cooling event that triggered evaporite deposition in the Carpathian realm. At Muntele Piatra Verde (MPV), Eastern Carpathians, Romania, this interval offers a rare opportunity to examine the interplay between global climate change, regional salinity crises and volcanic activity. The present study investigates how marine conditions at MPV evolved from the peak warmth of the MCO into the cooling of the MMCT, as recorded in lithology, foraminiferal assemblages and stable isotope data. We integrate mineralogical analyses, detailed biozonation and δ ¹³ C and δ ¹⁸ O measurements of Orbulina spp. across two stratigraphic successions. In Section 1 (S1), volcanic‐influenced sandstones in the lower sector with low‐diversity foraminifera give way to carbonate‐rich marls with diversified assemblages, culminating in the first occurrence (FO) of Globoturborotalia druryi and Globorotalia transsylvanica at the Langhian–Serravallian boundary (~13.82 Ma). Tuffs interbedded with gypsum mark the onset of the Badenian Salinity Crisis (~13.8 Ma), followed by Section 2 (S2) represented by brecciated gypsum and overlying shales. Biostratigraphy and radiometric dating indicate evaporite deposition lasted ~200 kyr (13.8–13.6 Ma). In this time interval, δ ¹⁸ O‐derived sea‐surface temperatures (SSTs) dropped from ~26°C below the tuff (S1) to temperatures less than 14°C above the gypsum (S2), while δ ¹³ C values capture the CM6 positive excursion above the boundary. This multiproxy record documents a ~10°C cooling across the MMCT, firmly linking regional evaporitic and volcanic phases to global climate change. These findings apply to various sedimentary settings, enabling both regional and global correlations of events.