We present new stable oxygen and carbon isotope composite records (δ18O, δ13C) of speleothems from Sandkraal Cave 1 (SK1) on the South African south coast for the time interval between 104 and 18 ka (with a hiatus between 48 and 41 ka). Statistical comparisons using kernel-based correlation analyses and semblance analyses based on continuous wavelet transforms inform the relationships of the new speleothem records to other proxies and their changes through time. Between 105 and ~70 ka, changes of speleothem δ18O values at SK1 are likely related to rainfall seasonality. Variations of δ13C values are associated with changes of vegetation density, prior carbonate precipitation (PCP), CO2 degassing in the cave, and possibly variations of the abundance of C3 and C4 grasses in the vegetation. The relationships of δ18O with other proxies shift between ~70 and 48 ka (Marine Isotope Stages 4–3) so that both stable isotope records now reflect CO2 degassing, evaporation, and PCP. Similar relationships also continue after the hiatus for the deposition phase between 42 and 18 ka. Our findings support modeling results suggesting drier conditions in the study area when the Southern Hemisphere westerlies are shifted north and the paleo–Agulhas Plain is exposed.

Lamalunga Cave (Altamura, Southern Italy) is renowned for the discovery in 1993 of an excellently preserved Neanderthal skeleton. Given the importance of the findings and the potential use of Lamalunga speleothems for paleoclimate reconstructions, a detailed monitoring program was undertaken to investigate the connections between microclimate parameters and speleothem growth. The cave air temperature is characterized by annual sinusoidal cycles with increasing phase shift and decreasing thermal amplitude from ± 2.1°C to ± 0.04°C as a function of increasing rock overburden, and daily to sub-daily cycles induced by surface air pressure (SAP) variations characterized by strong 24-hour and 12-hour solar harmonic frequencies, with thermal amplitude decreasing from 0.0054°C to 0.0021°C in the deeper parts of the cave. The ventilation regime is mainly controlled by SAP fluctuations. Fast SAP rises can trigger “emptying events” during which most of the cave air is replaced and the CO2 concentration falls towards near-atmospheric values. The steady and gentle ventilation created by SAP fluctuations also influences the growth and morphology of calcite coralloids, with larger popcorn assemblages concentrated in the northern galleries and delicate branching morphologies prevailing along the South Gallery where stable temperature and relative humidity conditions occur. The study is a seminal example of how high-precision measurements of cave air temperature can provide a wealth of information on cave ventilation and thermal regime and provide valuable support for robust paleoclimate reconstruction from speleothems.

The occurrence of kerolite in association with various secondary Ca-Mg carbonate mineral deposits (speleothems) was identified in basaltic sea caves on the island of Kauai, Hawaii. Kerolite is the dominant clay mineral in the deposits. X-ray diffraction (XRD) peaks of the kerolite are characteristically broadened indicating its extremely poor crystallinity. Few changes were observed in the XRD patterns of this kerolite when it was subjected to various humidity, temperature and ethylene-glycol treatments. The crystals appear as flaky masses with irregular or jagged edges in scanning (SEM) and transmission electron microscopy (TEM). Electron probe and energy dispersive X-ray (EDX) microanalysis show that the clay material is dominated by Mg-Si-O, with minor amounts of Al and Ca in some samples. The chemical composition, thermal analysis and TEM observations suggest that smaller amounts of an amorphous serpentine-like phase are mixed with the kerolite. Kerolite is often the only mineral associated with poorly mineralized, actively-growing microbial mats in these caves and it is common in completely lithified microbial mats. The latter commonly have microstromatolitic structures with kerolite as a dominant phase. These features suggest that kerolite formation is at least in part a result of microbial activity. The abundant extracellular polymers of the mat-forming bacteria bind and concentrate ions (Mg2+, silica) from solution and serve as nucleation sites for kerolite precipitation. Conditions within the mats also probably lead to formation of Mg-Si-gels, amorphous Mg-silicate precursors and ultimately kerolite. Evaporation of the cave solutions may also contribute to kerolite formation.

This study focuses on characterizing a discontinuity within the Seán stalagmite (4.75–7.75 cm) by means of two nondestructive techniques: (1) high-resolution micro-computed tomography (micro-CT) and (2) X-ray fluorescence (XRF) core scanning (XRFCS). Micro-CT was used to study the stalagmite density, and XRFCS was applied to obtain the qualitative elemental composition and colour measurements. The new data obtained from nondestructive techniques have been combined with previously published geochemical data and fabric determinations from the same stalagmite found in Sa Balma des Quartó cave in Mallorca. The two methodologies applied in the present study have improved the characterization of the distinctive horizon. The micro-CT images identified the layer as a minor event due the high air content. The distinctive horizon is characterized by a high Ti-content, indicating the arrival of terrigenous particles. Based on those observations, together with the fact that the micrite layer appears filling the gaps between the older columnar fabric, we argue that the micrite layer may represent a major flooding event inside the cave after the year 1616 ± 23 CE and before the year 1623 ± 28 CE, which can be related to an extreme rainfall event. This hypothesis is further supported by the observed cave flooding during the autumn of 2018.

We present the ‘SISAL webApp’—a web-based tool to query the Speleothem Isotope Synthesis and AnaLysis (SISAL) database. The software provides an easy-to-use front-end interface to mine data from the SISAL database while providing the SQL code alongside as a learning tool. It allows for simple and increasingly complex querying of the SISAL database based on various data and metadata fields. The SISAL webApp version currently hosts SISALv2 of the database with 691 records from 294 sites, 512 of which have standardized chronologies. The SISAL webApp has sufficient flexibility to host future versions of the SISAL database, which may include allied speleothem information such as trace elements and cave-monitoring records. The SISAL webApp will increase accessibility to the SISAL database while also functioning as a learning tool for more advanced ways of querying paleoclimate databases. The SISAL webApp is available at http://geochem.hu/SISAL_webApp.

New stalagmites from Qadisha Cave (Lebanon) located at 1720 m above sea level provide a high-resolution and well-dated record for northern Mount Lebanon. The stalagmites grew discontinuously from 9.2 to 5.7 and at 3.5 ka, and they show a tendency to move from a more negative oxygen isotope signal at ~9.1 ka to a more positive signal at ~5.8 ka. Such a trend reflects a change from a wetter to a drier climate at high altitudes. The δ13C signal shows rapid shifts throughout the record and a decreasing trend toward more negative values in the mid-Holocene, suggesting enhanced soil activity. In the short-term trend, Qadisha stalagmites record rapid dry/wet changes on centennial scales, with a tendency to more rapid dry events toward the mid-Holocene. Such changes are characterized by overall good agreement between both geochemical proxies and stalagmite growth and might be affected by the seasonal variations in snow cover. The Qadisha record is in good agreement with other Levantine records, showing more humid conditions from 9 to 7 ka. After 7 ka, a drier climate seems to affect sites at both low- and high-altitude areas. The Qadisha record reflects uniquely mountainous climate characteristics compared with other records, specifically the effect of snow cover and its duration regulating the effective infiltration.

In urban environments, diachronic evolution of water quality can be reconstructed using geochemical analysis of urban secondary carbonate deposits (USCDs), from urban underground structures, similar to speleothems from natural caves. The use of the radiocarbon bomb peak to build their precise chronology was recently tested in two Paris-area urban sites (France). In this study, new samples from contrasted environments in the Paris region were sampled in order to test the sites’ effects on the radiocarbon signal recorded: under wood, under a fountain, in underground aqueducts, in the south and north of Paris. We compared the post-bomb atmospheric radiocarbon record with the one measured at the top of USCDs, and estimated the dead carbon proportion (DCP), between 0 and 40%. USCDs fed by water with a rapid transfer through thin soil (Versailles fountain) had the lowest DCP (14C very close to atmospheric one). Highest DCP were found for USCD from deep underground quarry under urban wood, and intermediate ones for USCDs fed by the waters of perched aquifers. These data support the use of radiocarbon as chronometer for USCDs in contrasted urban contexts, and show that it can be used to determine carbon transport and sources, an important parameter for pollution reconstruction.

Ancient environmental DNA retrieved from sedimentary records (sedaDNA) can complement fossil-morphological approaches for characterizing Quaternary biodiversity changes. PCR-based DNA metabarcoding is so far the most widely used method in environmental DNA studies, including sedaDNA. However, degradation of ancient DNA and potential contamination, together with the PCR amplification drawbacks, have to be carefully considered. Here we tested this approach on speleothems from an Alpine cave that, according to a previous palynomorphological study, have shown to contain abundant pollen grains. This offers a unique opportunity for comparing the two methods and, indirectly, trying to validate DNA-based results. The plant taxa identified by sedaDNA are fewer than those by pollen analysis, and success rate of PCR replicates is low. Despite extensive work performed following best practice for sedaDNA, our results are suboptimal and accompanied by a non-negligible uncertainty. Our preliminary data seem to indicate that paleoenvironmental DNA may be isolated from speleothems, but the intrinsic weakness of PCR-based metabarcoding poses a challenge to its exploitation. We suggest that newly developed methods such as hybridization capture, being free from PCR drawbacks and offering the opportunity to directly assess aDNA authenticity, may overcome these limitations, allowing a proper exploitation of speleothems as biological archives.

Recent fieldwork and archival sedimentary materials from southern Iraq have revealed new insights into the environment that shaped southern Mesopotamia from the pre-Ubaid (early Holocene) until the early Islamic period. These data have been combined with northern Iraqi speleothem, or stalagmite, data that have revealed relevant palaeoclimate information. The new results are investigated in light of textual sources and satellite remote sensing work. It is evident that areas south of Baghdad, and to the region of Uruk, were already potentially habitable between the eleventh and early eighth millennia B.C., suggesting there were settlements in southern Iraq prior to the Ubaid. Date palms, the earliest recorded for Iraq, are evident before 10,000 B.C., and oak trees are evident south of Baghdad in the early Holocene but disappeared after the mid-sixth millennium B.C. New climate results suggest increased aridity after the end of the fourth millennium B.C. For the third millennium B.C. to first millennium A.D., a negative relationship between grain and date palm cultivation in Nippur is evident, suggesting shifting cultivation emphasising one of these crops at any given time in parts of the city. The Shatt en-Nil was also likely used as a channel for most of Nippur's historical occupation from the third millennium B.C. to the first millennium A.D. In the early to mid-first millennium A.D., around the time of the Sasanian period, a major increase in irrigation is evident in plant remains, likely reflecting large-scale irrigation expansion in the Nippur region. The first millennium B.C. to first millennium A.D. reflects a relatively dry period with periodic increased rainfall. Sedimentary results suggest the Nahrawan, prior to it becoming a well-known canal, formed an ancient branch of the Tigris, while the region just south of Baghdad, around Dalmaj, was near or part of an ancient confluence of the Tigris and Euphrates.

Archaeological reconnaissance and test excavation conducted in south-central Ethiopia reveal the region's rich Stone Age and Holocene archaeology. Ongoing lithic, faunal and dating analyses aim to understand chronological and behavioural contexts of prioritised rockshelters as part of a newly launched project. Speleothems in some of the caves promise high-resolution palaeoclimatic reconstruction.

Secondary carbonate deposits (similar to speleothems) in urban undergrounds, have been recently highlighted as powerful archives for reconstruction of the historical anthropogenic imprint on the environment. The precise chronology of these secondary carbonate deposits is a key issue for the accurate time reconstruction of environmental conditions. We present three 14C data sets for urban speleothem-like deposits that developed in contrasted man made environments. The first one was sampled in an underground technical gallery of the Palace of Versailles (France), and the other two in a manhole (Saint-Martin spring) of a historical underground aqueduct in Paris (France). The comparison of these records with the bomb peak and relative chronology (laminae counting) allowed us to identify: i) fast carbon transfer from the atmosphere to the urban underground; ii) a high proportion of dead carbon and a high damping effect in relation to possible old carbon stored within urban soils and/or the influence of local fossil carbon burning. This study also shows that the lamination of these deposits is bi-annual in these highly urbanized sites.

So-called annual banding has been identified in a number of speleothems in which the number of bands approximates the time interval between successive U-series dates. The apparent annual resolution of speleothem records, however, remains largely untested. Here we statistically compare variations in band thickness from a late Holocene stalagmite in Carlsbad Cavern, Southern New Mexico, USA, with three independent tree-ring chronologies form the same region. We found no correspondence. Although there may be various explanations for the discordance, this limited exercise suggests that banded stalagmites should be held to the same rigorous standards in chronology building and climatic inference as annually resolved tree rings, corals, and ice cores.

Fossil travertine and subaqueous speleothems in presently dry caves suggest periods of enhanced ground-water recharge during the Quaternary Period in semiarid northeastern Brazil. Travertine deposits and water-table speleothems were dated by the 230Th/234U technique, yielding new evidence for the timing of past periods of increased rainfall. The travertine was deposited in two distinct phases, extensive in situ deposits during marine isotope stage 2 and fragmentary, indurated deposits dating to ca. 400,000 yr B.P. (possibly marine isotope stage 10 or 12). Dating of water-table speleothems showed that the regional water table was 13±1 m above the present level at the last glacial maximum. A second site yielded ages suggesting a still higher water table during marine isotope stage 6. These new data demonstrate that northeastern Brazil did not follow the general pattern of a dry last glacial maximum, as suggested by other continental records in Amazonia and southeastern Brazil, and as depicted in recent General Circulation Model (GCM) simulations. Our results thus indicate that significant variability in regional rainfall patterns occurred in the area during glaciations and caution against overgeneralization of paleoclimate patterns.

The scarcity of numerical dates of the arid areas in southern Africa is a challenge for reconstructing paleoclimate. This paper presents a chronological reconstruction in the central part of the Namib Desert, Namibia, for the last 420,000 yr. It is based on 230Th/U dates (TIMS) from a large stalagmite and a thick flowstone layer in a small cave located in the hyper-arid central Namib Desert. The results provide for the first time evidence of three or possibly four succeeding wet periods of decreasing intensity since 420 ka through which speleothem deposited at approximately 420–385 ka, 230–207 ka and 120–117 ka following the 100-ka Milankovitch cycle. Speleothem growth was not recorded for the Holocene. These wet periods interrupted the predominantly dry climate of the Namib Desert and coincided with wet phases in deserts of the northern hemisphere in the Murzuq Basin, Sahara, the Negev, Israel, the Nafud Desert, Saudi Arabia, and the arid northern Oman, Arabian Peninsula.

High-resolution 230Th/234U ages and δ18O and δ13C compositions of speleothems in Ma’ale Efrayim Cave located to the east of the central mountain ridge of Israel enable us to examine the nature of the rain shadow aridity during glacial and interglacial intervals. Speleothem growth occurred during marine glacial isotopic periods, with no growth during the two last marine isotope interglacial intervals and during the peak of the Last Glacial Maximum. This contrasts with speleothem growth in caves located on the western flank of the central mountain ridge, in the Eastern Mediterranean semiarid climatic zone, which continued throughout the last 240,000 yr. Thus, during glacial periods water reached both sides of the central mountain ridge. A comparison of the present-day rain and cave water isotopic compositions and amounts at the Ma’ale Efrayim Cave site with those on the western flank shows that evaporation and higher temperatures on the eastern flank are major influences on isotopic composition and the lack of rainfall. The δ18O and δ13C profiles of the speleothems deposited between 67,000 and 25,000 yr B.P. match the general trends of the isotopic profiles of Soreq Cave speleothems, suggesting a similar source (eastern Mediterranean Sea) and similar climatic conditions. Thus, during glacial periods the desert boundary effectively migrated further south or east from its present-day location on the eastern flank, whereas interglacial periods appear to have been similar to the present, with the desert boundary at the same position. The decrease in overall temperature and a consequent reduction in the evaporation to precipitation ratios on the eastern flank are viewed as the major factors controlling the decay of the rain shadow effect during glacial periods.

U–Th ages have been obtained by TIMS on the growth periods of a stalagmite from the “Grotte des Puits de Pierre-la-Treiche” (northeastern France), during the middle part of the “Weichselian glaciation” (Marine Isotope Stage 3), between 55.36 ± 0.95 and 53.34 ± 0.49 ka and around 45.85 ± 0.49 ka. These episodes are contemporaneous with abrupt climatic variations recorded in Greenland ice cores (Greenland interstadials 12, 14 and 15) that have been previously recognized in European speleothems. They also coincide with two interstadials, known as “Goulotte” and “Pile” in the Grande Pile pollen sequence (eastern France), which have been correlated with the Moershoofd complex in the Netherlands. Such evidence of speleothem deposition related to temperate episodes gives a strong indication of the absence of continuous shallow permafrost during the middle part of MIS 3 in northeastern France.

Wet climatic episodes are known to have prevailed in the Egyptian Sahara several times during the late Quaternary, most recently during the Holocene 8000 yr ago. Earlier wet episodes have been recognized as having occurred during the past 300,000 yr and have been dated by U-series methods in speleothems and in lake travertines. We show here that the times of enhanced groundwater movement can also be determined by 230Th/234U dating of secondary U in ores of uranium, iron, and phosphate. We also present evidence that such acceleration of groundwater movements is indicated by relatively low 234U/238U activity ratios in the secondary uranium. Our new data show that pluvial periods in Egypt occurred during marine oxygen isotope stages 4, 5, 6, and 7 and therefore are consistent with the view that the wet episodes are the results of migration of the tropical monsoonal belt driven primarily by the 23,000-yr precession cycle of the Milankovich curve, modulated by the 100,000-yr eccentricity cycle.

Dated oxygen and carbon isotopic profiles from a Holocene stalagmite (11.9–1.1 ka) from the Jeita cave, Lebanon, are compared to variations in crystallographic habit, stalagmite diameter and growth rate. The profiles show generally high δ18O and δ13C values during the late-glacial period, low values during the early Holocene, and again high values after 5.8 ka. On the basis of the good correlation between the morphological and crystallographic aspect of the stalagmite and its isotopic records, as well as the isotopic response of speleothems from central and northern Israel, we relate high δ18O and δ13C values to drier conditions. Between 6.5 and 5.8 ka an increase in isotopic values, a decrease in growth rate and stalagmite diameter suggest a transition from wet conditions in the early Holocene towards drier conditions in the mid-Holocene. The transition occurred in two steps, first a progressive change to drier conditions started at 6.5 ka but was interrupted by a short (∼ 100 years) return to wetter conditions, followed by an equally rapid (< 200 years) change to drier conditions.

A stalagmite from Rana, northern Norway, dated by the TIMS uranium-series technique, yields records of stable oxygen and carbon isotopes covering the period from late marine oxygen isotope substages (MIS) 5e to 5a, that is, 123,350 to 73,300 yr ago. Rapid growth (∼46 μm/yr) between 123,350 and 119,500 yr ago reflects climatic conditions favorable for speleothem growth. This period is characterized by century- to millennial-scale oscillations in both stable isotope records, where both the absolute values and the isotope ranges are similar to Holocene and older samples from the region. From 119,500 to 107,700 yr ago, speleothem growth was slow (∼0.7 μm/yr), and between 107,700 and 73,300 yr ago growth is barely noticeable (0.07 μm/yr). During the period of slow growth the stable isotope records show an overall enrichment trend. The transition between rapid and slow growth rate occurring sometime between 119,500 and 107,700 yr ago is believed to reflect the termination of interglacial climate in this region. The absence of detritus and corrosion features in the slowly deposited calcite suggests that the valley outside the cave remained sufficiently ice free for speleothem growth to occur until at least 73,300 yr ago.

Deciphering pollen assemblages from alpine speleothems holds potential to provide unique information about past vegetation in rapidly changing environments. Here, we reconstruct subsurface aerosol transport at Milchbach cave (Switzerland, 1840 m asl) based on the pollen content of two Holocene stalagmites. We demonstrate that pollen is chiefly associated with bacterially mediated calcite fabrics, typical of a well-ventilated cave system. In contrast, pollen is absent from columnar calcite fabrics confirming that hydrological transport is not a significant process for the incorporation of pollen into speleothems at Milchbach cave. Our results support significant changes in the subsurface ventilation regime, which can be associated with the waxing and waning of Upper Grindelwald glacier. Pollen assemblages obtained from six carbonate sub-samples attest the presence of a mixed deciduous forest in the Grindelwald valley during the early and middle Holocene, in agreement with coeval regional pollen records. This study demonstrates that even small amounts of calcite (0.3–2.8 cm3) are capable of delivering pollen spectra representative of the original vegetation if sufficiently elevated deposition fluxes are provided.