This article reviews key data and debates focused on relative sea-level changes since the Last Interglacial (approximately the last 132,000 years) in the Mediterranean Basin, and their implications ...for past human populations. Geological and geomorphological landscape studies are critical to archaeology. Coastal regions provide a wide range of resources to the populations that inhabit them. Coastal landscapes are increasingly the focus of scholarly discussions from the earliest exploitation of littoral resources and early hominin cognition, to the inundation of the earliest permanently settled fishing villages and eventually, formative centres of urbanisation. In the Mediterranean, these would become hubs of maritime transportation that gave rise to the roots of modern seaborne trade. As such, this article represents an original review of both the geo-scientific and archaeological data that specifically relate to sea-level changes and resulting impacts on both physical and cultural landscapes from the Palaeolithic until the emergence of the Classical periods. Our review highlights that the interdisciplinary links between coastal archaeology, geomorphology and sea-level changes are important to explain environmental impacts on coastal human societies and human migration. We review geological indicators of sea level and outline how archaeological features are commonly used as proxies for measuring past sea levels, both gradual changes and catastrophic events. We argue that coastal archaeologists should, as a part of their analyses, incorporate important sea-level concepts, such as indicative meaning. The interpretation of the indicative meaning of Roman fishtanks, for example, plays a critical role in reconstructions of late Holocene Mediterranean sea levels. We identify avenues for future work, which include the consideration of glacial isostatic adjustment (GIA) in addition to coastal tectonics to explain vertical movements of coastlines, more research on Palaeolithic island colonisation, broadening of Palaeolithic studies to include materials from the entire coastal landscape and not just coastal resources, a focus on rescue of archaeological sites under threat by coastal change, and expansion of underwater archaeological explorations in combination with submarine geomorphology. This article presents a collaborative synthesis of data, some of which have been collected and analysed by the authors, as the MEDFLOOD (MEDiterranean sea-level change and projection for future FLOODing) community, and highlights key sites, data, concepts and ongoing debates.
The halite-encrusted salt pans (salars) present at low elevations in the hyperarid core of the Atacama Desert in northern Chile are unique features of one of the driest and possibly oldest deserts on ...Earth. Here we show that these landscapes were shallow freshwater lakes and wetlands during the last glacial period and formed periodically between ∼46.9 ka and 7.7 ka. The moisture appears to have been sourced from increased Andean runoff and most of our chronologies for these deposits were coeval with the Central Andean Pluvial Event (17.5–14.2 ka and 13.8–9.7 ka), but we also find evidence for older as well as slightly younger wet phases. These environments supported a diverse hygrophytic-halophytic vegetation, as well as an array of diatoms and gastropods. Using a regional hydrological model, we estimate that recharge rates from 1.5 to 4 times present were required to activate and maintain these wetlands in the past. Activation in the late Pleistocene was part of a regional enhancement of water resources, extending from the Andes, downstream and through riparian corridors, to the lowest and most arid portions of the desert itself. This fundamentally unique environment was encountered by the earliest human explorers in the region, and most likely facilitated migration and encampments on a landscape that at present lacks macroscopic life on its surface.
•Lakes and wetlands formed in the hyperarid core of the Atacama during the late Quaternary.•Groundwater highstands formed a network of wetlands and paleolakes from the Andes to the Pacific.•Most of our findings are coeval with the Central Andean Pluvial Event (CAPE) 17.5–9.7 ka.•Pre-CAPE enhanced periods of recharge have occurred since ∼46.9 ka.
Chronostratigraphic records in the drylands of north China provide essential archives to reveal the dynamic connections between climate changes and behaviours of aeolian systems. This study presents ...a detailed investigation of aeolian sediment accumulation around the Tengger Desert during the late Quaternary, comprising of grain-size characteristics and sources, sediment types and burial ages, and potential responses to external and localised forces. A combination of previously published chronostratigraphic records and 91 newly dated optically stimulated luminescence (OSL) samples collected from multiple sites covering a wide region of the south margin of the desert are used to constrain the accumulation of aeolian sediments during the late Quaternary. The prevailing strong near-surface winds at 22–19 ka, 18–14 ka, 13–10 ka, and 3–0 ka are found to be in anti-phase relation with the strength of the East Asia summer monsoon (EASM). The widespread attenuation of aeolian activity occurred between 7 and 3 ka. The accumulation of aeolian sediments during the past 250 ka has been controlled by multiple factors, including wind, aridity, sediment availability, and preservation capacity. We demonstrate that the interpretation of chronostratigraphic records is significantly affected by the number of available records, which emphasises the importance of sampling at multiple sites. The synchronous accumulation of aeolian sand and sandy loess at certain periods and the significant overlapping of volume percentage distributions at certain grain-size intervals between the two types of sediments indicate that their responses to external forces may not be independent and that the palaeoclimatic significance of sandy loess accumulated in the desert-loess transition zone requires a reassessment.
•Grain-size analysis and sources of aeolian sediments of the Tengger Desert.•Enrichment of radionuclides in sandy loess containing more clay and silt fractions.•Parallel accumulations of aeolian sand and sandy loess.•Multiple factors control the accumulation of aeolian sediments.
Quaternary ammonium compounds (QACs), commonly used in cleaning, disinfecting, and personal care products, have recently gained worldwide attention due to the massive use of disinfectants during the ...COVID-19 pandemic. However, despite extensive use of these chemicals, no studies have focused on the analysis of QACs in human milk, a major route of exposure for infants.
Our objectives were to identify and measure QACs in breast milk and evaluate early-life exposure to this group of compounds for nursing infants.
Eighteen QACs, including 6 benzylalkyldimethyl ammonium compounds (BACs, with alkyl chain lengths of C8-C18), 6 dialkyldimethyl ammonium compounds (DDACs, C8-C18), and 6 alkyltrimethyl ammonium compounds (ATMACs, C8-C18), were measured in breast milk samples collected from U.S. mothers. Daily lactational intake was estimated based on the determined concentrations for 0-12 month old nursing infants.
Thirteen of the 18 QACs were detected in breast milk and 7 of them were found in more than half of the samples. The total QAC concentrations (ΣQAC) ranged from 0.33 to 7.4 ng/mL (median 1.5 ng/mL). The most abundant QAC was C14-BAC with a median concentration of 0.45 ng/mL. The highest median ΣQAC estimated daily intake (EDI) was determined for <1-month old infants based on the average (using the median concentration) and high (using the 95
percentile concentration) exposure scenarios (230 and 750 ng/kg body weight/day, respectively).
Our findings provide the first evidence of the detection of several QACs in breast milk and identify breastfeeding as an exposure pathway to QACs for nursing infants.
Our findings provide the first evidence of QAC occurrence in breast milk and identify breastfeeding as one of the exposure pathways to QACs for nursing infants.
To address the Arctic Ocean response to the Quaternary climate change, three sediment cores from the Alpha Ridge, central Arctic Ocean, were analyzed for proxies of sediment transport and ...depositional mechanisms. The identified end-member grain-size components - clayey EM1, fine-silty EM2, and silty-sandy EM3 - are interpreted as proxies of sea ice transport, near-bottom current, and iceberg inputs, respectively. The sea-ice and iceberg transport proxies, EM1 and EM3, have opposing patterns peaking in the interglacials/interstadials and glacials/stadials, respectively. The near-bottom current proxy EM2 shows an overall gradual decrease with secondary variations indicating current slow-down during intervals of enhanced iceberg discharge. EM3 peaks during Marine Isotope Stages (MIS) 12, 10, 8, and MIS 7 stadials co-occur with high Ca content indicative of iceberg inputs from the Laurentide ice sheet via the Beaufort Gyre. Other EM3 peaks, notably during MIS 6 and MIS 4/3 likely originated from the Siberian margin based on elevated Zr content, thus indicating expanded Eurasian ice sheet and the Transpolar Drift extension towards the central Arctic Ocean. High coherences in the spectral analysis between the sea ice and iceberg proxies versus the global ice volume and orbital parameters on the 100-kyr and 23-kyr time bands illustrate the strong responses of sea ice and glaciations to eccentricity and precessional cycles. A persistent precessional impact of low latitude processes on high Arctic environment indicates a potential link to the low latitudes via atmospheric moisture and heat transport.
•Grain-size proxies reveals Quaternary paleoclimate changes in central Arctic Ocean.•Sea-ice transport increased and decreased in the interglacials and glacials, respectively.•Iceberg transport peaks occurred in the glacials and stadials.•Sea-ice and iceberg rafting were controlled by the 100- and 23-kyr orbital cycles.•Deep current transport slowed down through the Mid-Late Quaternary.
The Middle and Late Pleistocene glaciations of northern Eurasia had a great impact on the evolution of the modern drainage system. This paper presents a review and synthesis on the palaeogeography of ...glacial lakes, their drainage and impact on the re-organization of the drainage systems during the last two glacial-interglacial cycles. We will focus on four regions: (1) northern Central Europe and Fennoscandia, (2) the central part of the East European Plain, (3) the west Siberian Plain and (4) the Aral – Caspian – Black Sea area. The main findings of the last decade(s) include the improved chronology of some major river system formation and of meltwater overflows across the continental drainage divides. Major drainage systems of the north-central and west-central part of the East European Plain (upper Volga, upper Dnieper) formed due to overspill of glacial lakes in late MIS 6 with a partial re-organization (upper Dnieper) in MIS 2. The Aral – Caspian – Black Sea cascade acted as a sink for glacial meltwater from the north. The major meltwater yield to the Aral and Caspian seas occurred in MIS 6 and late MIS 5. In MIS 2, the meltwater delivery via the Volga valley into the Caspian Sea was low and therefore had only a minor influence on the sea level. Considerable meltwater discharge to the Black Sea through the Dnieper River system occurred around the maximal stage of the MIS 2 glaciation and ceased very quickly after the onset of deglaciation.
A novel sugar-functionalized amphiphilic pillar5arene containing galactose groups as the hydrophlic part and alkyl chains as the hydrophobic part was designed and synthesized. It self-assembles in ...water to produce nanotubes as confirmed by TEM, SEM, and fluorescence microscopy. These nanotubes, showing low toxicity to both cancer and normal cells, can be utilized as excellent cell glues to agglutinate E. coli. The existence of galactoses on these nanotubes provides multivalent ligands that have high affinity for carbohydrate receptors on E. coli.
Reconstructing the dynamics and drivers of late Quaternary megafaunal extinctions requires direct radiometric date series that are assessed within probabilistic statistical frameworks. Extinction ...chronologies are poorly understood for many tropical regions, including Madagascar, which had a diverse, now-extinct Holocene large vertebrate fauna including a “megaherbivore” guild of endemic hippopotami and elephant birds. Madagascar's megaherbivores likely played vital roles in regulating ecosystem structure and nutrient cycling, but few direct dates are available for megaherbivore specimens identified to species level, with uncertainty over when and why different representatives of this guild disappeared. Here, we conduct a new investigation into Malagasy megaherbivore extinction dynamics, including 30 new AMS dates and 63 audited published dates. We use Gaussian-resampled inverse-weighted McInerny (GRIWM) analysis to estimate species-specific extinction dates for three elephant bird species (Aepyornis hildebrandti, Mullerornis modestus, Vorombe titan), eggshell representing Aepyornis or Vorombe, and two hippo species (Hippopotamus lemerlei, H. madagascariensis), and to estimate extinction dates for megaherbivore communities in different biomes. Megaherbivores persisted for millennia after first human arrival. Extinction date estimates vary significantly between biomes, with disappearance from dry deciduous forest over a millennium earlier than other biomes, possibly reflecting local variation in megaherbivore population densities or human pressures. However, megaherbivore communities including all elephant bird and hippo species persisted elsewhere across Madagascar until ∼1200-900 bp, when they collapsed suddenly. Extinctions are closely correlated in time with intensive conversion of forests to grassland at ∼1100-1000 bp, probably associated with a shift to agro-pastoralism and representing a radical change in sustainability of prehistoric human interactions with biodiversity.
•First study to observe extinction chronologies of Madagascars megaherbivores at the species resolution.•Large expansion of radiocarbon data available for Holocene Magadagascar's megafauna.•Simultaneous disappearance of all of Madagascar's megaherbivores species observed.•Taxonomic review of Malagasy Hippopotamus taxa.
The South China Sea offers an excellent case for studying source-to-sink transport processes of fluvial sediments among the global marginal seas. This study synthesizes existing clay mineralogical ...and geochemical data from ~1500 samples from the seafloor and surrounding rivers, deepwater mooring observation results, and high-resolution glacial–cyclic clay mineralogy records from six high-quality sediment cores. Source-to-sink sediment transport from the river mouth to the continental shelf and then to the abyssal basin is investigated at two time scales: modern process and Late Quaternary glacial cycles. The results firstly show the high diversity of clay mineralogical and geochemical compositions in riverbed surface sediments surrounding the South China Sea, e.g., dominant illite and chlorite in Taiwan, overwhelming majority of smectite in Luzon, dominant kaolinite in South China, and similar amounts of the four clay mineral species in Red and Mekong river systems. The formation of these fluvial sediments through chemical weathering in surrounding drainage systems is controlled principally by the East Asian monsoon climate with warm temperature and high precipitation, and subordinately by tectonic activity and specific lithological character. The basin-wide distribution of clay mineral assemblages combined with neodymium and strontium isotopic compositions reflects strong provenance control and differential settling effects. The differential settling of kaolinite in slightly saline and proximal regions relative to smectite in more saline and distal regions is well demonstrated in the South China Sea. Through combining clay mineralogical distributions on the seafloor with observed oceanic current systems, the modern transport pathways can be well established, e.g., in the northern South China Sea, illite and chlorite from Taiwan are mainly carried by contour currents with the strong influence of mesoscale eddies.
High-resolution sediment dynamic analysis for the Late Quaternary reveals different sediment transport patterns in the northern, western, and southern South China Sea when the land–sea configuration dramatically changed during glacial conditions. In the north, the terrigenous dispersal is mainly controlled by provenance supply and oceanic current transport. In the west, the clay mineral assemblage reflects variations of the prevailing surface current influenced by monsoon winds. In the south, the clay mineral input indicates intensive chemical weathering during interglacial periods and strengthened physical erosion during glacial periods. The transport of terrigenous sediments since the last glaciation is quantitatively reconstructed through studying two deepwater sediment cores located in the northern South China Sea. The relative contributions from three provenances (South China, Luzon, and Taiwan) highlight their distinct variability over the last 28ka, implying that the southward shift of the inter-tropical convergence zone (ITCZ) at 16ka BP caused an increased sediment contribution from South China, the intensified influence of the Kuroshio Current intrusion controls more efficient westward transport of Luzon sediments, and the stronger deepwater current transports Taiwan-sourced sediments further westward from the last glaciation to the Holocene.
Quaternary ammonium compounds (QACs), a large class of chemicals that includes high production volume substances, have been used for decades as antimicrobials, preservatives, and antistatic agents ...and for other functions in cleaning, disinfecting, personal care products, and durable consumer goods. QAC use has accelerated in response to the COVID-19 pandemic and the banning of 19 antimicrobials from several personal care products by the US Food and Drug Administration in 2016. Studies conducted before and after the onset of the pandemic indicate increased human exposure to QACs. Environmental releases of these chemicals have also increased. Emerging information on adverse environmental and human health impacts of QACs is motivating a reconsideration of the risks and benefits across the life cycle of their production, use, and disposal. This work presents a critical review of the literature and scientific perspective developed by a multidisciplinary, multi-institutional team of authors from academia, governmental, and nonprofit organizations. The review evaluates currently available information on the ecological and human health profile of QACs and identifies multiple areas of potential concern. Adverse ecological effects include acute and chronic toxicity to susceptible aquatic organisms, with concentrations of some QACs approaching levels of concern. Suspected or known adverse health outcomes include dermal and respiratory effects, developmental and reproductive toxicity, disruption of metabolic function such as lipid homeostasis, and impairment of mitochondrial function. QACs’ role in antimicrobial resistance has also been demonstrated. In the US regulatory system, how a QAC is managed depends on how it is used, for example in pesticides or personal care products. This can result in the same QACs receiving different degrees of scrutiny depending on the use and the agency regulating it. Further, the US Environmental Protection Agency’s current method of grouping QACs based on structure, first proposed in 1988, is insufficient to address the wide range of QAC chemistries, potential toxicities, and exposure scenarios. Consequently, exposures to common mixtures of QACs and from multiple sources remain largely unassessed. Some restrictions on the use of QACs have been implemented in the US and elsewhere, primarily focused on personal care products. Assessing the risks posed by QACs is hampered by their vast structural diversity and a lack of quantitative data on exposure and toxicity for the majority of these compounds. This review identifies important data gaps and provides research and policy recommendations for preserving the utility of QAC chemistries while also seeking to limit adverse environmental and human health effects.
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