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The sedimentary sequence in Scladina Cave (Belgium) is well-known for its rich Middle Paleolithic assemblages and its numerous faunal remains. Of particular interest is the presence of a nearly complete mandible of a Neandertal child. To place all these finds in the correct chronostratigraphic context, various dating techniques have been applied over the past decades. This resulted in a reasonably well-constrained age model, roughly spanning the last glacial cycle. Age constraints of the lower part of the Scladina sequence as well as from the underlying Sous-Saint-Paul Cave were however absent until now. Previous attempts to date several speleothem layers in Scladina Cave, using U-Th dating were only partly successful, presumably because diagenetic alteration of speleothem material compromised the ages. In the present study we re-assessed U-Th dating of various speleothem levels in Scladina Cave, applying state-of-the-art U-Th dating, and carefully selecting material that experienced little to no diagenetic alteration. The new results constitute a robust age framework for the Scladina sequence, which provides precisely dated stratigraphic anchor points that improve the previous age model. Furthermore, new U-Th analyses, for speleothems from the lower part of the Scladina sequence and from the Sous-Saint-Paul sequence, document Middle Pleistocene ages, making this one of the longer fossil-rich cave sedimentary sequences in NW Europe. The new data confirm that speleothem deposition predominantly took place in periods of warmer climate, while siliciclastic sediments characterize the colder intervals. New speleothem ages further suggest that the Neandertal mandible found in the sequence, and previously placed in Marine Isotope Stage 5a or 5b, could potentially be as old as Marine Isotope Stage 5d. [ABSTRACT FROM AUTHOR]

A speleothem collected from Palco Cave (Puerto Rico) spans the 8.2 ka event, a time interval associated with fluctuations of Atlantic Ocean circulation and possible drying in the Caribbean region. While stalagmite δ18O, δ13C, and Mg/Ca data do not show a sustained change in mean state over the 8.2 ka event, the proxies provide robust evidence for three abrupt fluctuations toward drier conditions in rapid succession, each lasting less than two decades, occurring at 8.20, 8.14, and 8.02 ka BP. A cave monitoring program at Palco Cave supports the interpretation of the speleothem proxy records. Because changes in the position of the Intertropical Convergence Zone (ITCZ) are directly coupled to sea-surface temperature variations in the North Atlantic, we hypothesize that cold events in the North Atlantic temporarily limited the northward migration of the ITCZ and tropical rain belt in boreal summer during these abrupt drying periods. The speleothem record suggests that the 8.2 ka event was associated with rapid rainfall fluctuations in the northern Caribbean followed by a comparably warm and wet phase after the 8.2 ka event. This enhanced variability during the transitional period of the deglaciation appears to be linked to a fast coupling between interacting oceanic and atmospheric processes. This involves, in particular, the Atlantic Meridional Overturning Circulation in modulating interhemispheric heat transport. [ABSTRACT FROM AUTHOR]

On glacial‐interglacial time scales, changes in the Earth's orbital configuration control climate seasonality and mean conditions. Tropical coral skeletons can be sampled at a sufficient resolution to reconstruct past seasonality. Here, last deglacial Porites skeletons from Integrated Ocean Drilling Program Expedition 310 to Tahiti are investigated and, supported by a modern calibration, monthly resolved time series in geochemical proxies (Sr/Ca, δ18O, δ13C) are constructed. For most of the deglaciation, Sr/Ca seasonality was similar to modern (0.139 ± 0.010 mmol mol−1; 2.8 ± 0.2°C) reflecting the small change in insolation seasonality. However, during the Younger Dryas, high values in Sr/Ca seasonality (0.171 ± 0.017 mmol mol−1; 3.4 ± 0.3°C) suggest a reduced mixed layer depth and enhanced influence of the South Pacific Subtropical Gyre due to South Pacific Convergence Zone (SPCZ) inactivity. Furthermore, high amplitudes in Younger Dryas skeletal δ18O (0.40 ± 0.22 ‰) and δ13C (0.86 ± 0.22 ‰) seasonality compared to modern (δ18O = 0.29 ± 0.08 ‰; δ13C = 0.27 ± 0.08 ‰) point to elevated winter‐summer discrepancies in rainfall and runoff. Mean coral Sr/Ca variability suggests an influence of Northern Hemisphere climate events, such as the Younger Dryas cooling (+0.134 ± 0.012 mmol mol−1;−2.6 ± 0.2°C), or the Bølling–Allerød warming (+0.032 ± 0.040 mmol mol−1; −0.6 ± 0.4°C). Deglacial mean coral Δδ18O (δ18Oseawater contribution to skeletal δ18O), corrected for the ice volume effect, was elevated pointing to more saline, thus dryer conditions, likely due to a northward migration of the SPCZ. Seasonal cycles in coral δ13C were likely caused by variations in linear extension rates that were reduced during the last deglaciation (1.00 ± 0.6 cm year−1) compared to today (1.6 ± 0.3 cm year−1). Plain Language Summary: Changes in the Earth's movement around the sun are the primary cause of changes in the annual cycle and annual mean of environmental conditions during the last glacial‐interglacial periods. Distinct from most climate archives, the annual bands of coral skeletons can be sampled at a monthly resolution that allows for reconstructions of past seasonal cycles. In this study, the chemical composition of coral skeletons from the genus Porites that grew during the last deglaciation at Tahiti (∼15,000–9,000 years ago) was analyzed to infer seasonal variations and mean conditions in past sea surface temperature and salinity. Prior to application, the methods were successfully calibrated using modern coral skeletons from Tahiti. Results showed that sea surface temperature seasonality was similar to today during most of the deglaciation. However, for the Younger Dryas, a particular cold interval, a marked increase in sea surface temperature seasonality suggests that Tahiti was at that time located outside the South Pacific Convergence Zone, a rain band extending across the tropical Southwest Pacific. Furthermore, coral reconstructions revealed that, although distant, North Atlantic last deglacial climate events influenced mean climate conditions at Tahiti. In addition, we show that last‐deglacial coral growth rates were reduced compared to today. Key Points: Last deglacial changes in Tahiti coral Sr/Ca suggest an influence of Northern‐Hemisphere climate events on the tropical South PacificVariations in last deglacial Tahitian climate were modulated by meridional migrations of the South Pacific Convergence ZoneLast deglacial Porites corals revealed reduced linear extension rates (1.0 ± 0.6 cm year−1) compared to today (1.6 ± 0.3 cm year−1) [ABSTRACT FROM AUTHOR]

The Kurai Fault Zone (KFZ) is one of the most hazardous seismogenic structures in the Gorny Altai (Russia), which bounds the largest Kurai and Chuya intermontane basins from the north. Trenching studies, radiocarbon dating of colluvial wedge deposits, and 230Th-U dating of seismogenic travertine of the Meshtuyaryk field showed that the fault scarp in the northwestern part of the Chuya Depression was formed by earthquakes that occurred ca. 9.5, 7.7, 5.8, and 4.8–3.4 ka BP. The last two palaeoearthquakes are younger than 3.2 ka BP. The parameters of seismogenic ruptures, as well as the distances between coeval seismogenic travertines along the KFZ, yielded estimates of the Mw of the four oldest palaeoearthquakes as 6.8–7.6 and ESI 2007 shaking intensities of VIII–XI. The results of 230Th-U dating suggest that deposition of the Meshtuyaryk travertines was triggered by three strong palaeoearthquakes at ca. 9.5, 7.7, and 4.8–3.4 ka BP, which activated faults and caused a rapid rise along them of ambient-temperature bicarbonate groundwaters previously sealed in deep-seated limestone aquifers. [ABSTRACT FROM AUTHOR]

Hells Bells are underwater secondary carbonates discovered in sinkholes (cenotes) southeast of Cancun on the north-eastern Yucatán peninsula, Mexico. These authigenic calcite precipitates, reaching a length of up to 4 m, most likely grow in the pelagic redoxcline. Here we report on detailed 230Th/U-dating and in-depth geochemical and stable isotope analyses of specimens from cenotes El Zapote, Maravilla and Tortugas. Hells Bells developed since at least ~ 8000 years ago, with active growth until present day. Initial (234U/238U) activity ratios (δ234U0) in Hells Bells calcite decreas from 55 to 15‰ as sea level converges toward its present state. The temporal evolution of the geochemistry and isotope composition of Hells Bells calcites thus appears to be closely linked to sea-level rise and reflects changing hydrological conditions (desalinization) of the aquifer. We suggest that decelerated leaching of excess 234U from the previously unsaturated bedrock traces Holocene relative sea-level rise. Considering this proxy, the resulting mean sea-level reconstruction contains half as much scatter, i.e. improves by a factor of two, when compared to previously published work for the period between 8 and 4 ky BP. [ABSTRACT FROM AUTHOR]

The carbon isotopic signature inherited from soil/epikarst processes may be modified by degassing and prior calcite precipitation (PCP) before its imprint on speleothem calcite. Despite laboratory demonstration of PCP effects on carbon isotopes and increasingly sophisticated models of the governing processes, to date, there has been limited effort to deconvolve the dual PCP and soil/epikarst components in measured speleothem isotopic time series. In this contribution, we explore the feasibility, advantages, and disadvantages of using trace element ratios and δ44Ca to remove the overprinting effect of PCP on measured δ13C to infer the temporal variations in the initial δ13C of dripwater. In 8 examined stalagmites, the most widely utilized PCP indicators Mg/Ca and δ44Ca covary as expected. However, Sr/Ca does not show consistent relationships with δ44Ca so PCP is not universally the dominant control on Sr/Ca. From δ44Ca and Mg/Ca, our calculation of PCP as fCa, fraction of initial Ca remaining at the deposition of the stalagmite layer, yields multiple viable solutions depending on the assumed δ44Ca fractionation factor and inferred variation in DMg. Uncertainty in the effective fractionation of δ13C during degassing and precipitation contributes to uncertainty in the absolute value of estimated initial δ13C. Nonetheless, the trends in initial δ13C are less sensitive to these uncertainties. In coeval stalagmites from the same cave spanning 94 to 82 ka interval, trends in calculated initial δ13C are more similar than those in measured δ13C, and reveal a common positive anomaly initial δ13C during a stadial cooling event. During deglaciations, the trend of greater respiration rates and higher soil CO2 is captured in the calculated initial δ13C, despite the tendency of higher interglacial dripwater situation to favor more extensive PCP. [ABSTRACT FROM AUTHOR]

Here, we report on the first radiometric dating of pre-Quaternary sinters covering the ENE–WSW striking vertical faults filled with Upper Badenian sands (neptunian dykes) in Mesozoic carbonates of the Devín quarry in the Malé Karpaty Mountains. The 238U/206Pb age of 13.98±0.56 Ma fits well with the former age prediction based on biostratigraphic evidence. Our results provide fault opening age, refine the age of sediments and fossils preserved in the neptunian dykes, and constrain the onset of Badenian sea transgression. [ABSTRACT FROM AUTHOR]

We present speleothem fluid inclusion δ18 O f and δ2 H f values from Larga Cave, Puerto Rico, that cover the interval between 46.2 and 15.3 ka on the millennial scale, including the Last Glacial Maximum (LGM) and several stadial and interstadial cycles. The data set can be divided in two main clusters of stable isotope compositions of the fluid inclusion water with respect to the global meteoric water line (GMWL), which coincide with strong variations in the water content of the stalagmite. In particular, this clustering is found to be climate related, where one cluster comprises samples from cold and dry periods, such as the Heinrich and Greenland stadials (HSs and GSs), as well as parts of the LGM, which exhibit very high δ18 O f and δ2 H f values. We interpret this enrichment as being caused by evaporation inside the cave due to enhanced cave ventilation during these colder and drier times. In contrast, in most samples corresponding to warmer and wetter Greenland interstadials (GIs), but also for some from HS 2 and 3, the δ18 O f and δ2 H f values plot on the meteoric water line and modification of fluid inclusion water due to "in-cave" evaporation are found to be negligible. Consequently, variations of recent glacial hydro-climate and temperatures in the western tropical Atlantic can be constrained. In general, δ18 O f values from fluid inclusions are up to 3 ‰ higher than those of modern drip water, which is interpreted as a weaker atmospheric convective activity during the last glacial period. In addition, reconstructed temperatures suggest an average cooling of 2–3 ∘ C during the LGM compared to modern cave temperatures. Reconstructed cave temperatures yield an average cooling of - 1.4 ± 2.8 ∘ C for HS 2 and - 3.6 ± 2.2 ∘ C for HS 3. Higher δ18 O f values of these samples further suggest that the drip water was dominated by orographic rainfall and/or cold fronts, along with weak or even absent convective activity. In contrast, during interstadial phases, reconstructed temperatures reached nearly modern values, and convective activity was comparable to or only slightly weaker than today. [ABSTRACT FROM AUTHOR]