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Paleoclimate records from lakes of the southwestern USA have been limited by a lack of independent paleothermometers, resulting in conflicting characterizations of millennial-scale variability in temperature and moisture. Here a novel method called Brillouin thermometry is applied to halite-bearing dry intervals of the late Pleistocene/Holocene (45–0 ka) core record of Searles Lake, California. Halite from the sediment-water interface records lake bottom temperatures during dry, high salinity periods. Analysis of modern saline lakes of various chemistries, depths, climate zones, and mixing regimes shows that: 1) average bottom water temperature is approximately equal to mean annual air temperature, and 2) annual range of bottom water temperature is inversely proportional to lake depth. Brillouin temperatures for eight halite intervals 30.6 ka to 8.5 ka range from 11.8 ± 3.6 to 22.4 ± 3.2 °C. Bottom water temperature variability indicates paleolake depths of ~10 m during halite precipitation. Brillouin thermometric results are then assessed in comparison with two additional temperature proxy records from the same Searles Lake sediment core: 1) branched glycerol dialkyl glycerol tetraethers (brGDGTs) extracted from wet mud intervals, and 2) thermodynamic constraints from evaporite minerals and mineral sequences. Temperatures from brGDGTs for mud intervals 44.7 ka to 3.6 ka range from 13.4 ± 2.8 to 23.9 ± 3.0 °C. Comparisons of Brillouin/brGDGT temperatures with predicted equilibrium temperatures of salt crystallization indicate intervals where seasonal temperature variability forced the dissolution and/or recrystallization of existing temperature-sensitive evaporites. The multiproxy temperature record of Searles Lake agrees with other regional records at glacial/interglacial timescales but displays a wider degree of millennial-scale variability, with temperatures during the last glacial ranging from 8.3 °C below modern mean annual temperatures to 3.8 °C above.

The Salinas del Bebedero occupies an isolated basin in the foreland of central Argentina at 33°S and was flooded repeatedly over past 25 ka. Isotopic evidence demonstrates that this flooding was due to overflow of the nearby Río Desaguadero with waters derived from the distant (≥300 km) central Andes between 28–34°S. Stratigraphic and shoreline evidence shows that floods occurred most frequently from 14.3 to 11.4 ka, followed by lesser events between 14.3 to 11.4 ka, and during the late Holocene from 2.6 to ca. 0.2 ka. Hydraulic modeling (2D HEC-RAS) shows that these floods could have originated from repeated subglacial drainage or sudden outbursts with a volume of >100 × 106m3and a peak discharge of >1,000 m3s-1each. The absence of flood deposits from 11 to 3 ka points to exceptionally dry and virtually ice-free conditions in the Andes between 28–34°S. The floods were probably caused by major rainfall or dammed-lake outbursts clustered largely during wet pluvial periods in the otherwise moisture-limited central Andes and Atacama Desert, such as when the Intertropical Convergence Zone was shifted southward. These include Central Andean pluvial events (CAPE) I (17–14.5 ka) and II (12.5–9 ka), and the Neoglacial/Formative archeological period 2500 ka to near-present.

Speleothem oxygen isotope (δ18O) records provide key insight into the rate and timing of terrestrial paleoclimate changes during the late Quaternary. However, it can be difficult to deconvolve the δ18O signal into individual components, which include processes related to moisture source, moisture transport, temperature, precipitation amount, infiltration, and the cave environment. We developed a framework that uses triple oxygen isotope distributions in speleothems to refine interpretations of δ18O speleothem records. This framework identifies the influence of dominant processes on δ18O values through time by their characteristic (although not necessarily unique) trends in δ’18O vs. Δ’17O space, where Δ′17O = δ’17O – 0.528δ’18O and δ’xO = ln(δxO+1). Following Guo and Zhou (2019a), we expect that ‘cave kinetic’ processes (e.g., fast degassing at the drip site, prior calcite precipitation) will drive positive trends between δ’18O and Δ′17O. In contrast, we can identify hydrologic processes from near–horizontal trends that reflect Rayleigh–type meteoric water processes and negative trends driven by changes in evaporation processes at the moisture source region or at the cave site, mineralization temperature, and seasonality in precipitation/infiltration amount. We applied this framework to four western USA speleothems from Cave of the Bells (Arizona), Leviathan Cave (Nevada), and Lehman Caves (Nevada). The Cave of the Bells and Leviathan data have near–horizontal to negative trends indicating δ18O variability was driven largely by changes in Rayleigh distillation of atmospheric moisture and moisture source conditions, supporting prior interpretations. We analyzed two Lehman Caves records because they were likely influenced by non-equilibrium processes and the data show weak to moderate negative trends. For sample LMC–12b, chosen for its extreme 7.5 ‰ δ18O range, the trend is statistically distinct from the near–horizontal Rayleigh–process trend and most consistent with changes in local evaporation intensity and infiltration seasonality as primary drivers. None of these records displays a positive covariation slope between δ’18O and Δ′17O, suggesting limited variability in cave kinetic processes through time or unknown limitations to the kinetic model of Guo and Zhou (2019a). Additionally, reconstructed formation waters for all sites fall near the δ’18O vs. Δ′17O Local Meteoric Water Line, a correlation we suggest as a novel test of the absolute magnitude of isotopic offset due to cave kinetic processes. More broadly, our framework adds context to the only other study of carbonate speleothem triple oxygen isotope composition (Sha et al., 2020). We find that positive to negative δ’18O vs. Δ′17O trends likely exist in speleothem data that may reasonably be expected from regional climate processes and that, combined with other proxy data, triple oxygen isotope data will be useful in constraining interpretations of δ18Ospeleothem records.

This article describes the recent identification, documentation, and preservation of a large wooden lattice-work panel recovered from a wet-site trap complex located in Comox Harbour on the east coast of Vancouver Island, British Columbia. This project was the result of Indigenous community members proactively taking control of their heritage for protection and conservation. Based on the research of the contributors, this panel appears to be the largest and most intact example of a fish trap panel from an archaeological context on the Northwest Coast. This paper provides data and interpretations to better understand Indigenous fisheries and the technology of the extensive systems of wooden fish traps that once spanned most of Comox Harbour.

Lake Chalco lies south of the Basin of Mexico and has been the subject of studies related to Late Quaternary climate variability. In 2016, the International Continental Scientific Drilling Program “MexiDrill Project” recovered a 520-m sediment record from Lake Chalco. Magnetic susceptibility measurements revealed substantial changes in sediment physical properties between 343 and 285 m depth, suggesting changes in composition associated with fluctuations in the depositional environment. We targeted sediments in the 343–285 m interval for high-resolution facies analysis, to develop a model of Lake Chalco formation. We identified three facies associations, using sediment composition, texture, mineralogy and micro-morphological characteristics: (1) detrital facies, consisting of laminated silt, massive sand, stratified silty sand, clast-supported gravel and matrix-supported gravel; (2) biogenic facies, which include diatom ooze and bivalve coquina; and (3) volcaniclastic facies, represented by clast-supported pumice deposits. We propose that formation of Lake Chalco occurred in four stages, which we identified by changes in sediment characteristics. The first stage was an alluvial delta environment, in which debris and hyper-concentrated flows were the main sediment transport agents. The second was characterized by turbulent flows in a fluvial deltaic environment, which alternated with laminar flows associated with floodplains. The third stage was a time of fluvio-lacustrine transition in the basin, with formation of the previously identified Paleo-Chalco-I Lake, in response to wet conditions. During the fourth stage, a deep eutrophic lake formed (Paleo-Chalco-II), with an origin that appears to have been related to regional volcanism. Our working age-depth model indicates establishment of the lake at ca. 400 ± 46 ka. This paper presents the only available record of the transition from alluvial to lacustrine sedimentation of Lake Chalco. Our results allow us to establish (1) how the lake was formed and what the phases of its development were, (2) how a major volcanic event altered and transformed the lacustrine sedimentation, and (3) which climatic conditions dominated during the lake formation. The age for the onset of the lacustrine sedimentation in Chalco is for the first time constrained to around 400 ka. This enables to expand our knowledge of the climate for a time for which there is no information from terrestrial records of tropical North America.

A group of four amphoras found in the anchialine cave of Vodeni Rat in the Croatian island of Sveti Klement, on a rocky ledge at 24 m water depth, indicates that a freshwater source was exploited at the bottom of this karstic pit by islanders and/or passing-by sailors from the late Roman Republican Period to the Early Medieval Period. In other words, prior to the 4th–7th century CE, Vodeni Rat was not an anchialine cave but a Pleistocene karstic pit with a freshwater pool at the bottom. Seawater started to infiltrate this cavity via newly opened fissures in the surrounding limestone after the 4th–7th century CE, as the archeometric age of the youngest intact amphora found down in the pit suggests. At present, the 29-m-deep water body is stratified, with a saline water layer at the bottom, a freshwater layer at the surface, and a transitional brackish water layer in the middle. Our study of the physical and biological characteristics of the cave water column revealed diversified and highly partitioned populations of stygobitic crustaceans including ostracods, copepods, amphipods, and thermosbaenaceans. Some species known to be exclusively endemic of highly saline habitats were collected from the bottom saline layer, whereas others known to be of freshwater origin were found in the upper water layer. This suggests that the freshwater dwellers were already present in this cave prior to the early medieval event that caused seepage of seawater into this karstic pit., SCOPUS: ar.j, info:eu-repo/semantics/published

In this paper, we present old and new data about our integrated interdisciplinary stratigraphic study of sedimentary deposits preserved in the Grotta dei Baffoni Cave of the Frasassi hypogenic cave complex, including sedimentological, paleontological, archaeometric, and radiometric analyses. This research work allowed us to reconstruct the geologic, environmental, and human history of this part of the northeastern Apennines of Italy for the past 200,000 years, from the late Middle Pleistocene to the Present. Accumulation of alluvial sediment began in this cave ~200,000 years ago, when an entrance was breached by the Sentino River during its process of incision and deepening of the Frasassi Gorge coupled with regional tectonic uplift. Flooding of the cave went on until the entrance sill of the cave was lifted up to an elevation that could no longer be reached by the river, sometime in the mid–Late Pleistocene. After this, windblown dust (i.e., loess) and coarser carbonate clasts derived from the disintegration of the vaults due to cryogenic processes and/or seismically induced collapses of the limestone vaults, accumulated on this now-dry underground environment. The stratigraphy of an ~4-m-thick sedimentary deposit accumulated in the vast atrium room of the cave was measured, sampled, and documented in two excavation trenches in 1952 by archaeologist Anton Mario Radmilli. By collecting a dozen stratigraphically located osteological finds for 14C dating, and revisiting artifacts collected by Radmilli, which are archived respectively in the Museum of Natural History of Verona and in the National Museum of Archaeology of Ancona, we assessed that the cave was frequented by wild animals, such as cave bear and ibex, starting in the mid–Late Pleistocene. Dating of charcoal particles from subsurface sediments in the inner part of the cave suggested that fires were lit in this cave by Epigravettian visitors during the Younger Dryas cold period. Scarce archaeological evidence nevertheless suggests that man began using this underground environment for worship practices probably in the early Neolithic. Human bones in the lower part of one of Radmilli's excavations yielded early Eneolithic ages. No other human bones were found in overlying levels of this excavation, but the typology of animal bones and associated ceramic artifacts, corroborated by our 14C dates, suggest that this cave was utilized as a worship or ritual place until the early Middle Bronze Age. After that, the cave was sporadically used as a shelter for herders until recent times.

In the late fall of 1986, a team of cavers from the Gruppo Speleologico Marchigiano of Ancona reported to the regional Archeological Superintendence their discovery in a room of the Grotta del Fiume Cave (Marche region of central Italy) of archeological finds such as the charcoal remains of a bonfire, a number of ibex bones, and four chert artifacts. However, since the discovery and archival of all this material, no further research or focused studies were carried out about this important archeological site. Therefore, we engaged in a thorough re-examination of this site by mapping this part of the Grotta del Fiume Cave with modern surveying approaches, including terrestrial laser scanner and ground penetrating radar. Moreover, we have radiocarbon dated a few ibex bones and also charcoal samples from the main fireplace and other smaller charcoal deposits we found scattered around the room’s floor. The chert artifacts were examined in detail and their typology classified accordingly. U-Th dating of calcite from speleothems helped us reconstruct this hypogeal environment at the time it was frequented by man. We also studied a puzzling deposit of speleothem crust slabs piled up in a corner of the cave, which may represent a funeral earthen mound. All in all, the absence of artifacts other than the four chert blades, the few ibex bones, the one main fireplace and three other minor charcoal deposits in the room, and the probable earthen mound located tens of meters underground from a now debris-sealed entrance, lead us to hypothesize that this cave room does not represent a residential dwelling but rather a worship place sporadically utilized by few representatives of a local Epigravettian hunter community.

Glacial–interglacial cycles have constituted a primary mode of climate variability over the last 2.6 million years of Earth's history. While glacial periods cannot be seen simply as a reverse analogue of future warming, they offer an opportunity to test our understanding of the response of precipitation patterns to a much wider range of conditions than we have been able to directly observe. This review explores key features of precipitation patterns associated with glacial climates, which include drying in large regions of the tropics and wetter conditions in substantial parts of the subtropics and midlatitudes. I describe the evidence for these changes and examine the potential causes of hydrological changes during glacial periods. Central themes that emerge include the importance of atmospheric circulation changes in determining glacial–interglacial precipitation changes at the regional scale, the need to take into account climatic factors beyond local precipitation amount when interpreting proxy data, and the role of glacial conditions in suppressing the strength of Northern Hemisphere monsoon systems.

Reconstructions of aeolian dust flux to West African margin sediments can be used to explore changing atmospheric circulation and hydroclimate over North Africa on millennial to orbital timescales. Here, we extend West African margin dust flux records back to 37 ka in a transect of sites from 19° to 27°N, and back to 67 ka at Ocean Drilling Program (ODP) Hole 658C, in order to explore the interplay of orbital and high-latitude forcings on North African climate and make quantitative estimates of dust flux during the core of the Last Glacial Maximum (LGM). The ODP 658C record shows a Green Sahara interval from 60 to 50 ka during a time of high Northern Hemisphere summer insolation, with dust fluxes similar to levels during the early Holocene African Humid Period, and an abrupt peak in flux during Heinrich event 5a (H5a). Dust fluxes increase from 50 to 35 ka while the high-latitude Northern Hemisphere cools, with peaks in dust flux associated with North Atlantic cool events. From 35 ka through the LGM dust deposition decreases in all cores, and little response is observed to low-latitude insolation changes. Dust fluxes at sites from 21° to 27°N were near late Holocene levels during the LGM time slice, suggesting a more muted LGM response than observed from mid-latitude dust sources. Records along the northwest African margin suggest important differences in wind responses during different stadials, with maximum dust flux anomalies centered south of 20°N during H1 and north of 20°N during the Younger Dryas.