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Abstract We examined a Late Holocene sea-level stillstand using phreatic overgrowths on speleothems (POS) recovered from Medvjeđa Špilja [Bear Cave] (northern Adriatic Sea) from −1.28 ± 0.15 m below present mean sea level. Different mineralogical analyses were performed to characterize the POS and better understand the mechanisms of their formation. Results reveal that the fibrous overgrowth is formed of calcite and that both the supporting soda straw and the overgrowth have very similar trace element compositions. This suggests that the drip-water and groundwater pool from which the POS formed have similar chemical compositions. Four subsamples were dated by means of uranium-series. We found that ca. 2800 years ago, the relative sea level was stable for about 300 years at a depth of approximately −1.28 ± 0.15 m below the current mean sea level. This finding roughly corresponds with the end of a relatively stable sea-level period, between 3250 and 2800 cal yr BP, previously noted in the southern Adriatic. Our research confirms the presence of POS in the Adriatic region and establishes the Medvjeđa Špilja pool as a conducive environment for calcite POS formation, which encourages further investigations at this study site. 

Cryogenic cave carbonates have been described from several formerly or presently glaciated karst caves. In most of these occurrences, they precipitated as loose grains or aggregates with various morphologies and sizes. Here, we report on a new speleothem type (cryogenic ridges) identified in Sohodoalele Mici Cave (SW Romania) within a large chamber near the entrance shaft. This study was motivated by the presence of a network of calcite ridges over the stalactites’ surface and by the observation that during winter, these speleothems are covered by a thin ice layer. The higher δ18O (−3.5 to –1‰) and δ13C (0 to 7‰) values found in the calcite ridges relative to δ18O (–7.5 to –4‰) and δ13C (–9 to –2‰) values of calcite from the inner stalactite indicate that the ridges are of cryogenic origin and formed during relatively rapid carbonate precipitation associated with evaporative cooling and freezing of the water. Four U-series ages suggest that the stalactites with ridges formed during cold winters of the Holocene, when cave air temperatures dropped below freezing. 

Modern global sea-level rise is anomalous relative to any natural variability over the past 4000 years. 

Abstract Water availability for Native Americans in the southwestern United States during periods of prolonged droughts is poorly understood as regional hydroclimate records are scant or contradicting. Here, we show that radiocarbon-dated charcoal recovered from an ice deposit accumulated in Cave 29, western New Mexico, provide unambiguous evidence for five drought events that impacted the Ancestral Puebloan society between ~ AD 150 and 950. The presence of abundant charred material in this cave indicates that they periodically obtained drinking water by using fire to melt cave ice, and sheds light on one of many human–environment interactions in the Southwest in a context when climate change forced growing Ancestral Puebloan populations to exploit water resources in unexpected locations. The melting of cave ice under current climate conditions is both uncovering and threatening a fragile source of paleoenvironmental and archaeological evidence of human adaptations to a seemingly marginal environment.