Hydroclimatic events in the Carpathian karst during MIS 3–2: Evidence from sedimentary records in two Romanian caves

Abstract

Cave sediments are well-preserved terrestrial archives of Quaternary hydroclimatic variability, often recording changes at high temporal resolution. Urșilor and Muierilor caves in the Romanian Carpathians contain extensive paleoflood deposits that provide insight into past hydrological dynamics. Here, we integrate new and previously published data to reconstruct palaeohydrological activity during Marine Isotope Stages (MIS) 3–2, a period marked by rapid climate fluctuations. Our approach combines detailed stratigraphic logging, granulometric and clast-shape analyses, and chronological constraints derived from radiocarbon dating of fossil remains and Usingle bondTh dating of speleothems. The results indicate that both cave systems record recurrent high-magnitude flash floods, particularly during MIS 3 and the post–Last Glacial Maximum (LGM) phase of MIS 2, suggesting episodic intensification of hydrological extremes in the Carpathian region. Cave sediments are subdivided into allostratigraphic units, with paleoflood sequences represented by diamicton and thalweg facies, locally exhibiting channelized structures, and underlain by either backswamp (Muierilor) or slackwater deposits (Urșilor). Microstratigraphic variability within stalagmite PM163 further documents rapid environmental changes affecting the local hydrology at Muierilor. Three coeval hydrological events are identified in both caves, with deposition occurring after: ∼46 ka, ∼34.5 ka, and ∼29 ka. These results demonstrate that integrating sedimentological, microstratigraphic, and chronological data provides a robust framework for paleoenvironmental reconstruction. The sedimentary record indicates that flooding was modulated by large-scale hydroclimatic variability, although the relative contributions of precipitation and glacial meltwater remain unresolved. Overall, the studied cave deposits represent valuable archives of high-energy paleofloods during MIS 3–2 in the Romanian Carpathians, offering new constraints on the timing of hydrological extremes and suggesting regional synchronicity across karst systems with contrasting geomorphological settings.