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Long-range atmospheric dust transport affects the climate by impacting radiative transfer, cloud formation and the global carbon cycle. Furthermore, dust plays an important role in pedogenesis, whereas Fe-rich dust in particular influences the primary productivity of the ocean. Transport of Saharan dust via the westerlies to the Caribbean is well recorded, even under present conditions, however, its variability over Quaternary glacial-interglacial cycles is less well understood. Here, we present initial investigations into the speleothem record of long-range Saharan dust transport to the Bahamas. A stalagmite collected from -25.6 m below sea level from Abaco Island, Bahamas, macroscopically displays a tripartite structure beginning and ending with opaque crystalline calcite, but with a middle section containing striking insoluble Fe-rich layers several mm thick that alternate with finer opaque layers. The red layers are interpreted to be formed under vadose conditions and not due to precipitation of an Fe-rich crust in an unsaturated mixing zone. U-Th dating reveals that the opaque calcite sections were deposited during Marine Isotope Stage (MIS) 10 and late MIS 8, with the intervening Fe-rich section being deposited during early MIS 8. Dripstone speleothem deposition during MIS 10 and 8 therefore places an upper constraint on relative sea-level elevation of -25.6 m during those glacial periods, with the interglacial MIS 9 hiatus considered to be sea-level controlled. The Fe-rich section indicates atmospheric dust transport to Abaco Island increased during early MIS 8 synchronous with an episode of cooler sea surface temperatures in the sub-tropical Atlantic. On the other hand, the decline in dust transport during late MIS 8 is associated with higher sea surface temperatures.

Investigating the precise timing of regional-scale climate changes during glacial terminations and the interglacial periods that follow is key to unraveling the mechanisms behind these global climate shifts. Here, we present a high-precision time series of climate changes in the Austrian Alps that coincide with the later portion of Termination III (TIII), the entire penultimate interglacial (Marine Isotope Stage (MIS) 7), Termination IIIa (TIIIa), and the penultimate glacial inception (MIS 7–6 transition). Using state-of-the-art mass spectrometry techniques, we have constructed a uranium-series chronology with relative age uncertainties averaging 1.7 ‰ (2σ) for our study period (247 to 191 thousand years before present, ka). Results reveal the onset of warming in the Austrian Alps associated with TIII at 242.5 ± 0.2 ka and the duration of MIS 7e warming between 241.8 and 236.7 (±0.6) ka. An abrupt shift towards higher δ18O values at 216.8 ka marks the onset of regional warming associated with TIIIa. Two periods of high δ18O values (greater than −10 ‰ Vienna Pee Dee Belemnite (VPDB)) between 215.9–213.3 and 204.3–197.5 (±0.4) ka coincide with interglacial substages MIS 7c and 7a, respectively. Multiple fluorescent inclusions suggest a partial retreat of the local Alpine glacier during peak obliquity forcings at 214.3 ± 0.4 ka. Two newly collected stalagmites from Spannagel Cave (SPA146 and 183) provide high-resolution replications of the latter portion of the MIS 7a-to-6e transition. The resulting multi-stalagmite record reveals important chronological constraints on climate shifts in the Austrian Alps associated with MIS 7 while offering new insight into the timing of millennial-scale changes in the North Atlantic realm leading up to TIII and TIIIa.

Speleothems are important timekeepers of Earth’s climate history. A key advantage of speleothems is that they can be dated using U–Th techniques. Mass spectrometric methods for measuring U and Th isotopes has led to vast improvements in measurement precision and a dramatic reduction in sample size. As a result, the timing of past climate, environment, and Earth system changes can be investigated at exceptional temporal precision. In this review, we summarize the principles and history of U–Th dating of speleothems. Finally, we highlight three studies that use U–Th dated speleothems to investigate past changes to the Asian monsoon, constrain the timing of sociopolitical change in ancient civilizations, and develop a speleothem-based calibration of the 14C timescale.

Parental depressive symptoms are associated with greater variability and inconsistency in parenting behavior as well as children's emotional and behavioral dysregulation. The present study explored whether such relations extended to dyadic processes, examining whether maternal and paternal depressive symptoms at child age 3½ interacted with concurrent higher dyadic behavioral variability (DBV) in mother-child free play to heighten children's emotional and behavioral dysregulation at age 4 (N = 100). Child dysregulation was measured as mother-reported emotional lability-negativity and externalizing problems, and DBV was measured as the number of transitions among dyadic behavioral states using state space grids. Parent behaviors included parent directives, positive reinforcement, and disengagement, and child behaviors included child compliance, persistence, and noncompliance, among others. Analyses also accounted for the degree of positive (compared to negative) behavioral content. Moderation analyses showed that DBV predicted greater child dysregulation only when maternal or paternal depressive symptoms were higher. Further, DBV was detrimental only when dyadic positive interaction content was low. Findings suggest DBV combined with low positive content in parent-child interactions is a particular risk factor for children's regulatory development. Fostering positive, predictable interaction patterns may be an important target for family interventions with a depressed parent. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Uranium–uranium ( 234 U– 238 U) disequilibrium dating can determine the age of secondary carbonates over greater time intervals than the well-established 230 Th– 234 U dating method. Yet it is rarely applied due to unknowns in the initial δ234 U ( δ234 U i ) value, which result in significant age uncertainties. In order to understand the δ234 U i in Devils Hole 2 cave, Nevada, we have determined 110 δ234 U i values from phreatic calcite using 230 Th– 234 U disequilibrium dating. The sampled calcite was deposited in Devils Hole 2 between 4 and 590 ka, providing a long-term look at δ234 U i variability over time. We then performed multi-linear regression among the δ234 U i values and correlative δ18 O and δ13 C values. The regression can be used to estimate the δ234 U i value of Devils Hole calcite based upon its measured δ18 O and δ13 C values. Using this approach and the measured present-day δ234 U values of Devils Hole 2 calcite, we calculated 110 independent 234 U– 238 U ages. In addition, we used newly measured δ18 O, δ13 C, and present-day δ234 U values to calculate 10 234 U– 238 U ages that range between 676 and 731 ka, thus allowing us to extend the Devils Hole chronology beyond the 230 Th– 234 U-dated chronology while maintaining an age precision of ∼ 2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 ± 11 kyr ago. The novel method presented here may be applied to future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

The growth intervals of stalagmites from Northeast (NE) Brazil provide precise information on the timing of pluvial periods associated with the southward shift of the Intertropical Convergence Zone (ITCZ) during Heinrich Stadials (HS). Using 230 Th dating and annual band counting, we constrained the timing of the pluvial period associated with HS4 to occur between 40.06 ± 0.11 and 38.38 ± 0.10 thousand years before present (kyr B.P.), coinciding with the interval between the end of Greenland Interstadial (GIS)/Chinese Interstadial (CIS) 9 and GIS/CIS 8. Oxygen isotope analysis shows a close anti-correlation between NE Brazil wet periods and East Asian monsoon intensity recorded in Hulu Cave, supporting the hypothesis of a southerly migration of the global ITCZ during HS4. The pluvial anomaly can be divided into three phases, starting with a precursor, less intense pluvial interval (phase 1) between 40.06 ± 0.11 and 39.59±0.10 kyr B.P., likely correlative to the cool phase of the North Atlantic immediately before the partial collapse of the Laurentide Ice Sheet (LIS). This phase ends abruptly (

Determining the precise timing of glacial terminations and the interglacials that follow is key to addressing questions surrounding future warming. Here, we present a high-precision record of Termination III (TIII), Termination IIIa (TIIIa), the penultimate interglacial (MIS 7), and the penultimate glacial inception (MIS 7/6 transition) from Spannagel Cave in the Austrian Alps. Using state-of-the-art mass spectrometry techniques, we have constructed a uranium-series dated chronology with relative age uncertainties averaging 1.7 ‰ (2σ) during our study period (247 to 191 thousand years before present). Results reveal the onset of TIII at 242.5 ± 0.2 ka and the duration of MIS 7e between 241.8 to 236.7 (±0.6) ka. Depleted δ18O values indicating MIS 7b center at 229.5 ± 2.3 ka. An abrupt shift towards higher δ18O values at 217.1 ± 0.5 ka marks the beginning of TIIIa. Two periods of high δ18O values (greater than −10 ‰) between 215.9–213.3 and 204.3–197.5 (±0.4) ka coincide with interglacial substages MIS 7c and 7a, respectively. Two newly collected stalagmites from Spannagel Cave (SPA146 & 183) provide high-resolution replications of the latter portion of the MIS 7a/6e transition, which occurred between approximately 197.1 and 191.4 (±0.3) ka. The resulting multi-stalagmite timeseries provides important chronological constraints on climate shifts in Europe and the North Atlantic during MIS 7. This study also provides a clear answer to the exact timing of TIIIa, which has been previously debated.

Uranium-uranium (234U-238U) dating can determine the age of secondary carbonates over greater time intervals than the well-established 230Th-234U dating method. Yet it is rarely applied due to unknowns surrounding the initial δ234U (δ234Ui) value, which result in significant age uncertainties. In order to understand the δ234Ui in Devils Hole 2 cave, we have precisely determined 110 δ234Ui values from phreatic calcite crusts using a 230Th-234U chronology. The sampled calcite crusts were deposited in Devils Hole 2 between 4 and 590 thousand years, providing a long-term look at δ234Ui variability over time. We then performed multi-linear regressions among the δ234Ui values and correlative δ18O and δ13C values. These regressions allow us to predict the δ234Ui value of Devils Hole calcite based upon its δ18O and δ13C. Using this approach and measured present-day &felta;234U values, we calculate 110 independent 234U-238U ages of Devils Hole 2 cave deposits. In addition, we used newly measured δ18O, δ13C, and present-day δ234U values to calculate 10 234U-238U ages that range between 676 and 731 thousand years, thus allowing us to extend the Devils Hole chronology beyond the 230Th-234U-dated chronology while maintaining an age precision of ~2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 ± 11 thousand years ago. The novel method presented here may be used in future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

We present a high-precision record of the Penultimate Interglacial (MIS 7) and the Penultimate Glacial inception (MIS 7–6 transition) from Spannagel Cave in the central European Alps (southern Austria). Drip waters in this high-elevation cave are largely sourced from the overlying low-permeability gneiss, giving rise to unusually high uranium concentrations in secondary calcite deposits (up to 200 ppm). The large quantities of 234U and 230Th incorporated in samples can be measured using high-precision spectrometry, resulting in relative age uncertainties as low as 1‰ (2σ) during our study period (~250 to 197 thousand years ago [ka]). Using this unprecedented age control, we revisit Spannagel stalagmite SPA121 that grew continuously throughout MIS 7 and the MIS 7–6 transition. Previous work by Spötl et al. (EPSL 2008) revealed that SPA 121 δ18O displays similar timing and structure to global benthic marine δ18O during MIS 7, including distinct sub-stages. New dating allows us to constrain the exact timing and duration of MIS 7 sub-stages in the European Alps, including the timing of Terminations (T) III and IIIa. Preliminary results show the onset of MIS 7e at 241.4 ± 0.3 ka, the δ18O minima during MIS 7b at 224.5 ± 0.3 ka, and the mid point of TIIIa at ~216.2 ± 0.3 ka. The onset of decreasing δ18O associated with the MIS 7a–6e transition occurred no later than 193.0 ± 0.2 ka. Two newly collected stalagmites from this cave (SPA146 & 183) provide two high-resolution replications of the MIS 7a–6e transition. The resulting multi-stalagmite record will provide important chronological constraints on climate shifts in the European Alps during the Penultimate Interglacial and subsequent glacial inception.

Processes active within buoyant hydrothermal plumes are expected to modulate the flux of elements, such as Fe, to the deep ocean; however, they are yet to be described in a comprehensive manner through observations or models. In this study, we compare observed particulate Fe (pFe) speciation with thermodynamic (equilibrium) reaction path modeling for three vent fields in the Eastern Lau Spreading Center (ELSC). At each site, particles were collected from the buoyant rising portion of hydrothermal plumes using in situ filtration with a Remotely Operated Vehicle. Filter bound particles were analyzed by synchrotron micro-probe X-ray fluorescence mapping (XRF), X-ray diffraction (XRD), XRF spectroscopy, and X-ray absorption near edge structure (XANES) spectroscopy at the Fe 1 s edge, as well as XRF-based chemical speciation mapping for Fe. For buoyant plumes of the ELSC, diversity in solid-state chemistry was high, and poorly crystalline, meta-stable phases were common. We demonstrate that to fully describe the crystalline-to-noncrystalline character of plume pFe, a multi-modal XRD-XANES analytical approach is needed. We found that an equilibrium modeling approach worked well for pyrite but performed poorly for important families of meta-stable pFe, namely Fe (oxyhydr)oxides and monosulfides. Based on our findings, we recommend future field expeditions strategically explore sites representing a diversity of site-specific conditions to better capture the full range of processes active in plumes. We also recommend development of kinetic models, as well as expansion of thermodynamic databases to better reflect the solid-state composition of plumes. These steps should allow oceanographers to understand the processes controlling Fe speciation in plumes well enough to create realistic models of hydrothermal fluxes to the ocean.

The difference is all in the water Glacial cycles are in part controlled by the pattern of incident solar energy determined by the geometry of Earth's orbit around the Sun. The classic record of the penultimate deglaciation from Devils Hole, Nevada, did not reconcile the presumption of so-called orbital forcing, however, suggesting that deglaciation began ~10,000 years too early. Moseley et al. present analyses of a new set of data from Devils Hole that show that the deglaciation indeed occurred at the time expected on the basis of orbital forcing. The age offset displayed by the older samples apparently was caused by interaction with groundwater, which preferentially affected the deeper original samples but not the new shallower samples. Science , this issue p. 165

Winograd and Coplen question the thorium-230 distribution model proposed to explain the age bias observed with increasing depth during Termination II. We have evaluated both criticisms and find that all samples display virtually identical fabrics, argue that the modern setting is not analogous to the conditions during Termination II, and reiterate the robustness of our age models. Our conclusions remain unchanged.

Virus-Enhanced Sulfur Oxidation How do microbial viruses affect subsurface microbial communities? Anantharaman et al. (p. 757 , published online 1 May) investigated the interactions between ubiquitous marine lithotrophs found at hydrothermal vents and their viruses. The genes for sulfur oxidation in viruses that infect abundant marine chemosynthetic sulfur-oxidizing bacteria enhanced sulfur oxidation, thereby influencing the biogeochemical sulfur cycle.