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The area around the town of Mangalia in Southern Dobrogea (Romania) hosts a unique karst landscape represented mostly by large collapse dolines. Around one of these collapse dolines, named Obanul Mare, there is a peculiar morphology of hillocks that resemble the tropical labyrinth-cone karst but on a much-reduced scale. This peculiar relief was hypothesized to be residual, resulting from the ceiling collapse of a two-dimensional maze cave. This type of maze caves form when the water table remains stable for long periods of time, allowing groundwater to dissolve the carbonate host rock along all available discontinuities. The Obanul Mare structure contains a 200 m long cave (Movile cave), whereas a few kilometers away we can find Limanu maze cave, whose passages sum up to more than 3,500 m. Because the existence of a former maze cave is difficult to demonstrate, in this study we took an indirect approach to this issue. We hypothesize that if there was a maze cave and its ceiling collapsed, then the inner walls would be left standing as pillars. Subsequent subaerial evolution of these pillars would create slopes that would incline towards the former cave passages. By quantifying the slope aspect from a high-resolution digital surface model, we would be able to identify the direction of the original passages, hence the main hypothetical fracture lines along which those passages formed. By comparing these orientations to those of local fractures (deduced from the nearby valley and doline axes), as well as with the orientations of the Movile Cave passages, we found that they are well correlated. This strengthens the hypothesis that the hillocky terrain is tectonically conditioned and that it might be the result of cave ceiling collapse, bringing more information on the existence of maze caves in the region. La zone autour de la ville de Mangalia dans le sud de la Dobrogea (Roumanie) abrite un paysage karstique unique représenté principalement par de grandes dolines effondrées. Autour de l'une de ces dolines d'effondrement, appelée Obanul Mare, il existe une morphologie particulière de buttes qui ressemble aux karsts à cône labyrinthiques tropicaux, mais à une échelle très réduite. Au sein de ce travail, nous proposons l'hypothèse que ce relief particulier était résiduel, résultant de l'effondrement du plafond d'une grotte labyrinthe bidimensionnelle. Ce type de grottes labyrinthiques se forme lorsque la nappe phréatique reste stable pendant de longues périodes, permettant aux eaux souterraines de dissoudre la roche carbonatée hôte le long de toutes les discontinuités disponibles. La structure Obanul Mare contient une grotte de 200 m de long (grotte Movile), tandis qu'à quelques kilomètres de là se trouve la grotte Limanu, dont les passages totalisent plus de 3 500 m. Parce qu'il est difficile de démontrer l'existence d’une ancienne grotte-labyrinthe, dans cette étude, nous avons adopté une approche indirecte de la question. Nous émettons l'hypothèse que s'il y avait une grotte-labyrinthe et que son plafond s'effondrait, alors les murs intérieurs resteraient debout tels des piliers. Les phases d’érosion subaérienne postérieures de ces piliers créeraient des pentes qui s'inclineraient vers les anciens passages de la grotte. En quantifiant l'aspect de la pente à partir d'un modèle de surface numérique à haute résolution, nous pourrions identifier la direction des passages d'origine, d'où les principales lignes de fracture hypothétiques le long desquelles ces passages se sont formés. En comparant ces orientations à celles des fractures locales (déduites des axes de vallées voisines et dolines), ainsi qu'avec les orientations des passages de Movile Cave, nous avons trouvé qu'elles sont bien corrélées. Cela renforce l'hypothèse selon laquelle le terrain vallonné est conditionné tectoniquement et qu'il pourrait être le résultat de l'effondrement du plafond de la grotte, apportant plus d'informations sur l'existence de grottes labyrinthiques dans la région.

The Early Pleistocene of Eurasia is marked by significant climatic, environmental, and faunal shifts and is the time during which Homo first appears in the Eurasian fossil record. To better characterize the environments that were available to these hominins, accurate data regarding the faunal composition of eastern European sites are necessary, as this is the region through which Homo is hypothesized to have dispersed into Europe. Here we present updated and revised taxonomy and biochronology for sites in the Olteţ River Valley (ORV) of central Romania. The site of Graunceanu is one of the most fossiliferous deposits from this time. Excavations and descriptions of the ORV sites took place during the 1960–1980s, but since that time many taxonomic revisions have been published. Here, we present a reassessment and update of the fauna from the ORV sites. We report several new taxa (e.g., Pachystruthio, Smutsia) and expand the known biogeographic range for other taxa (e.g., Puma pardoides). Our biochronological assessment of this updated taxonomy is consistent with previous reports, though with some refinement. We suggest Graunceanu is Late Villafranchian (~2.2–1.9 Ma) and compositionally similar to the sites of Saint-Vallier (France) and Vatera (Greece). Similarly, the La Pietris assemblage was likely deposited >1.7 Ma. The younger site of Fântâna lui Mitilan was deposited after 1.8 Ma, and perhaps as recently as 1.1 Ma. Thus, the ORV faunal assemblages provide an excellent record of nearly the entire span of the Late Villafranchian for both central Romania and eastern Europe.

When calcite precipitates in caves, its carbon stable isotope signature can be modified by the CO2 outgassing gradient between drip water and cave atmosphere. This effect is modulated by the water residence time in the cave, from its emergence in the cave until the deposition of calcite. Moreover, CO2 solubility, calcite precipitation rate, and isotopic fractionation are controlled by temperature. Here, we present up to date results of an ongoing monitoring study at Ascunsa Cave (Romania), exploring the relationship between farmed calcite δ13C, drip rate, and CO2 outgassing. In addition to measuring CO2 concentration in cave air, we also measured the CO2 concentration in the headspace of a water-air equilibrator that collects drip water without exposing it to cave atmosphere, preventing outgassing. δ13C from calcite farmed at two neighboring stalagmites with different drip rates was also measured. Although caves have generally stable temperatures, we show here that temperature inside Ascunsa and Isverna caves has risen by more than 2°C over the course of a year, bearing important implications for stable isotopic fractionation equations and CO2 dynamics. Our results show that δ13C of farmed calcite has a strong relationship with drip rate at the slow dripping site, but no correlation at the faster dripping site. These two sites are also different when δ13C is compared to the outgassing gradient. At the slower drip site, δ13C and the outgassing gradient are directly correlated, whereas at the faster drip site their correlation is inverse. Our study brings new light onto speleothem δ13C behavior in general, and at Ascunsa Cave in particular, which is crucial for understanding the paleoclimate information captured by speleothems from this cave or elsewhere.

In this study, we describe a sedimentary deposit situated above Ascunsă Cave (SW Romania) that should be in depositional connection with coeval stalagmites from the cave. We excavated a 2.5 m deep soil profile and took contiguous bulk samples every 5 cm. Soil samples were analyzed for clay mineralogy, grain size, chemical composition, magnetic susceptibility, and stable carbon isotopes. Radiocarbon dating revealed that the soil is of Holocene age, and presents a depositional hiatus between 5.4 and 2.3 thousand years before the present. Due to the open system behavior of soils and the mobility of organic matter, a few hundred years of uncertainty should be considered for the duration of this hiatus. The fine fraction is dominated by silt, while the clay mineralogical association is made of illite, chlorite, kaolinite, vermiculite, and illite–vermiculite and illite–chlorite mixed layered minerals. The sediment source of this soil is represented by a nearby mélange complex, as well as by an underlying terra rossa-type soil. As this latter type of soil is widespread in our study area, we performed luminescence dating on two samples from a representative location close to our site and it appears that this type of Mediterranean soil was formed during the Last Interglacial period. δ13C variability in soil organic matter and a stalagmite from the cave are compared well, and could help future studies identify modifications in isotopic fractionation processes within the cave.

The Asiatic wild dog (Cuon alpinus), restricted today largely to South and Southeast Asia, was widespread throughout Eurasia and even reached North America during the Pleistocene. Like many other species, it suffered from a huge range loss towards the end of the Pleistocene and went extinct in most of its former distribution. The fossil record of the dhole is scattered and the identification of fossils can be complicated by an overlap in size and a high morphological similarity between dholes and other canid species. We generated almost complete mitochondrial genomes for six putative dhole fossils from Europe. By using three lines of evidence, i.e., the number of reads mapping to various canid mitochondrial genomes, the evaluation and quantification of the mapping evenness along the reference genomes and phylogenetic analysis, we were able to identify two out of six samples as dhole, whereas four samples represent wolf fossils. This highlights the contribution genetic data can make when trying to identify the species affiliation of fossil specimens. The ancient dhole sequences are highly divergent when compared to modern dhole sequences, but the scarcity of dhole data for comparison impedes a more extensive analysis.

The Olteț River Valley in southern Romania hosts a large number of fossiliferous sites, the richest of which is Valea Grăunceanului. Based on biochronological estimations, these sites were assigned to the Late Villafranchian (MN17/MNQ1), at ~2.0-1.8 Ma. As yet, no other dating methods were employed and our present study aims to provide the geological and geomorphological background for radiometric and trapped charge dating, as well as for the stratigraphic correlation of these sites. These deposits are represented by fluvial-lacustrine sediments belonging to the Dacian Basin, a part of the Eastern Paratethys domain. Our approach is to create a regional stratigraphic column onto which to place the fossil sites. We first created a high-resolution 3D model of the surface using UAV technology. Further, we sampled sediments from several sections and determined their grain size and mineralogy. We also sampled pedogenic carbonates and fossil teeth for preliminary geochemical analysis, in preparation for uranium series dating. Although no human fossils have been found so far in the Olteț River Valley, the site is important for understanding the environment used by early humans to migrate out of Africa. These sites are close both in time and space to important anthropological sites such as Dmanisi, Khapry or Kozarnika, while being part of an area dominated by large water bodies that included the Pannonian, Dacian and Euxinic lakes.

The Carpathian island-type glaciokarst has a great potential of preserving signals of past environments, archived in cave deposits like speleothems and clastic infills.Wepresent here the geomorphology and structural control of several relict alpine caves and the surrounding glaciated marble karst in the Făgăraș Mountains. Four truncated and partially unroofed caves remained on the ridge-top of Mușeteica Mountain, above the glacial cirque, while a ponor cave that developed on the cirque bottom could be related to the Last Glacial Period. Structuralmeasurements and cave morphology showed that the conduits formed at the intersection of foliation planes and tectonic fractures on the NE-SWand NW-SE directions. Cave development reflects three speleogenetic stages: 1) textureand fabric-controlled dissolution and distension; 2) structurally-controlled breakdown; and 3) truncation, unroofing, and cave infillingwith sediments. Slowdiffuse dissolutionwas typical for the ridge-top caves,whereas M1 Cave developed by pressure flow. Further, we report the first U\\Th speleothem ages, related to the evolution of alpine caves and island glaciokarst in the South Carpathians during the Middle and Late Pleistocene. Dating results show a minimum estimated age of ~560 ka for the ridge-top caves, and that speleothem deposition met optimal conditions only during warmer periods, largely corresponding to interglacials. Stable carbon isotope values in speleothems range between−9.96‰and−4.11‰, indicating the presence of plant and soil organic activity at the time of deposition. In total, five speleothem growth phases were distinguished during the last ~560 ka. We excavated the sediment infill of a ridge-top doline down to a 2-mdepth. Radiocarbon dating revealed that it was deposited during the Late Holocene, and preliminary pollen analysis identified a plant assemblage dominated by grasses. Using the relationships between karst development, glaciation, and cave sedimentary archives,we present a time slice chronology of alpine landscape evolution at N560 ka, ~400 ka, ~330 ka, the Last Glacial Period (70–12 ka), and the Late Holocene. Our geomorphological, isotopic, and geochronological results also support the existinghypothesis that the South Carpathians may have experienced at least two glacial phases during the Pleistocene. Glacial erosion rate during the Last Glacial Period, and most likely during the penultimate glaciation, averages around 0.6 mm yr−1.

The Early Pleistocene is recognized as a time of major global climatic and environmental change, including increasing aridity, significant spread of grasslands, and substantial faunal turnovers and dispersals. Importantly, this is the first time hominins are found in Eurasia. Reconstructing the types of environments that existed during this time is imperative for understanding mammalian, including hominin, dispersal patterns relative to climatic change. One proposed dispersal corridor across Europe is the Danube River. Here we characterize the 2.2 to ~1.1 million years ago (Ma) paleoenvironments surrounding one of the tributaries to the Danube, the Olteţ River, in southern Romania using a multiproxy approach, including taxonomic uniformitarianism, dental mesowear, dental microwear, enamel stable isotope (carbon and oxygen), and coprolite/palynology analyses, and compare our results to other penecontemporaneous Eurasian sites. Older sites from this region, Graunceanu and La Pietris, both dating to 2.2–1.9 Ma, are reconstructed as being primarily open, though with some nearby woodlands and significant water resources. Fântâna lui Mitilan, which is younger (1.8–1.1 Ma), is reconstructed as slightly more closed, though still relatively open in nature. These results are similar to reconstructions for other Early Pleistocene Eurasian sites, including ones with and without hominins, suggesting that hominins were likely not inhibited from dispersing across Eurasia due to environmental constraints at this time.

Two speleothem stable isotope records from East-Central Europe demonstrate that Greenland Stadial 12 (GS12) and GS10—at 44.3–43.3 and 40.8–40.2 ka—were prominent intervals of cold and arid conditions. GS12, GS11, and GS10 are coeval with a regional pattern of culturally (near-)sterile layers within Europe’s diachronous archeologic transition from Neanderthals to modern human Aurignacian. Sterile layers coeval with GS12 precede the Aurignacian throughout the middle and upper Danube region. In some records from the northern Iberian Peninsula, such layers are coeval with GS11 and separate the Châtelperronian from the Aurignacian. Sterile layers preceding the Aurignacian in the remaining Châtelperronian domain are coeval with GS10 and the previously reported 40.0- to 40.8-ka cal BP [calendar years before present (1950)] time range of Neanderthals’ disappearance from most of Europe. This suggests that ecologic stress during stadial expansion of steppe landscape caused a diachronous pattern of depopulation of Neanderthals, which facilitated repopulation by modern humans who appear to have been better adapted to this environment. Consecutive depopulation–repopulation cycles during severe stadials of the middle pleniglacial may principally explain the repeated replacement of Europe’s population and its genetic composition.

Izvorul Taușoarelor Cave, which held for many years the record for the deepest cave in Romania, is renowned for its steeply descending galleries, tectonic-controlled speleogenesis, and a rich assemblage of sulfate minerals (gypsum, mirabilite, arcanite, bassanite, epsomite, konyaite, leonite, and syngenite) that form a variety of speleothems. The enigmatic spherical concretions, known as “Taușoare balls,” formed simultaneously with the limestone bedrock during its early diagenesis. The existence of hundreds of bones of cave bear (Ursus spelaeus) and brown bear (Ursus arctos) suggests the two species cohabited during the Quaternary in this part of the country. The cave represents the hibernation site for four bat species.

Limanu Cave is a network maze situated in the southern part of the Dobrogea Plateau (SE Romania), close to the Black Sea coast. It is hosted in Sarmatian (Kersonian) lumashelic and oolithic limestones, interbedded with marls. The total length of its passages is close to 3.5 km, and it preserves evidences of important human impact on its wall morphology. Throughout the cave, human intervention can be identified in the form of carving of walls and ceiling, as well as the buildup of walls made of stacked limestone slabs. Mineralogical data reveal an important presence of magnesian calcite and dolomite. The cave is a Site of Community Importance (ROSCI0191) and hosts the last colony of Rhinolophus mehelyi in Romania, which gathers ~100 individuals, in a steep decline from ~5000 individuals reported from Dobrogea in the 1960s.

The Fagaraș Mountains consisting mostly of impervious metamorphic rocks are an unlikely location for karst development. Yet, due to the occurrence of a series of marble stripes interbedded within the metamorphic rocks, several caves developed in two areas in the central part of the mountains: Piscu Negru (at ~1200 m) and Mușeteica-Râiosu (between ~2100 and ~2400 m). Average air temperature is around 6.5 °C inside the Piscu Negru caves and 3.3 °C in Mușeteica. Cave No. 1 from the Piscu Negru Mine is the longest cavity in the massif (804 m), whereas M3-R2 Cave contains the speleothems from the highest altitude in Romania. Cave fauna is poor, and some bat species were found at the highest elevations of their habitat. The caves preserve reliable speleothem records for future studies on past climate variability and interactions between glaciations and karst.

Isverna Cave is situated on the eastern slope of the Mehedinți Mountains, at an altitude of 450 m. It is over 4 km long, and it functions as the water collector for a karst area of over 20 km2. It is traversed by a river with very clear water except during flood conditions. A series of sumps, of which the longest is the Black Sump (~700 m), are spread along the underground river. This makes the cave an excellent destination for cave diving activities. The first few hundred meters of galleries host hibernation and maternity bat colonies.

As part of a microclimate study at Ascunsa Cave, Romania, we used Gemini Tinytag Plus 2 data loggers to record cave air temperature variability. At one of the monitoring points we recognized the presence of semidiurnal cycles on the order of a few thousands of a degree Celsius that could be produced under the influence of the semidiurnal tidal components of the Sun (S2) or the Moon (M2). Using a Gemini Tinytag Plus 2 data logger with an external probe we measured core rock temperature and showed that it does not influence the cave air temperature on such short time scales. We thus rejected the possibility that Earth tides, mostly produced by the lunar tidal influence on the Earth’s crust, would have had a semidiurnal influence on cave air temperature. Moreover, time series analysis revealed a 12.00-hour periodicity in temperature data, specific for the S2, allowing us to assign these variations to the influence of the thermo-tidal action of the Sun. Using the Ideal Gas Law and assuming a constant volume and amount of air, we calculated that a theoretical change in atmospheric pressure of around 40 Pa was needed to produce the temperature changes we observed. This agrees with published values of atmospheric pressure changes induced by the semidiurnal solar component of the thermal tides (S2(t)). We thus can assign the observed temperature changes to semidiurnal atmospheric pressure changes (S2(p)) induced by the thermal excitation of the Sun. Our study signals the possibility that readily available data from cave monitoring studies around the world could be used in the study of atmospheric tides. Moreover, it appears that Ascunsa Cave acts as a natural meteorological filter on a short time scale, removing the direct thermal influences of the Sun (especially night and day differences) and preserving only the barometric information from the surface.

We present here the results of a four year environmental monitoring program at Ascunsă Cave, Romania, intended to understand how climate information is transferred through the karst system and archived in speleothems. The air temperature inside the cave is around 7 °C, with slight differences between the upper and lower parts of the main passage. Relative humidity measurements were hampered by condensation on the capacitive sensors we used, thus we consider it to be close to 100 %. The local meteoric water line (δ2H = 7.7 δ18O + 10.1), constructed using monthly aggregated rainfall samples, is similar to the global one, revealing the Atlantic as the strongly dominant vapor source. The δ2H excess values, as high as 17 ‰, indicate that precipitation has an important evaporative component, possibly given by moisture recycling over the European continent. CO2 concentrations in cave air have a seasonal signal, with summer minima and winter maxima. This might be indicative of an organic matter reservoir deep within the epikarst that continues to decompose over the winter, possibly modulated by seasonal differences in cave ventilation. The maximum values of CO2 show a rise after the summer of 2014, from around 2000 ppm to about 3500 ppm. An analogous rise is seen in drip water stable isotopes and chemical elements such as Sr and Mg. The variability of stable isotopes and chemical elements is similar at all points inside the cave, indicating that they are draining a homogenous reservoir. Using two newly designed types of water/air equilibrators we were able to determine drip water dissolved CO2, by measuring its concentration in the equilibrator headspace and then using Henry's law to calculate its concentration in water. This opens the possibility of continuous data logging using infrared technology without the need of costly and less reliable chemical determinations.

Few caves exist in Romania that have provided clear evidences of their hypogene origin; these were described mainly in connection with investigations conducted on ore deposits or thermal water resources used in spas. Genetically, they are grouped in three categories: (1) caves related to upwelling of H2S-rich thermal waters along Cerna Valley (SW Romania) and around the town of Mangalia (SE Romania), (2) voids created in skarns and limestones during ascending flow of hot metasomatic and hydrothermal ore fluids (caves located mainly in the northern and western part of the country), and (3) mixing of salt and fresh water near the present Black Sea shore (e.g., Piatra Cave). Among all caves in these categories, Movile, a world-renowned biospeleological hot spot, the skarn-hosted caves from Baița, and Valea Rea, an underground mineralogical treasure, are the most representative.

We present here a speleothem δ13C-δ18O record from the Last Interglacial period that was retrieved from a small cave in the Făgăraş Mountains (2435 m asl). Current monitoring work shows that the average temperature inside the cave is ~3°C. Stalagmite M3-R2/1 is only 5 cm long and its growth model was calculated using six U-Th ages. According to this, the stalagmite formed between 125.5 (±1.3) and 123 (±1.3) ka, during the warmest stage of the Last Interglacial