The characterization of modern pollen rain assemblages along environmental gradients is an essential prerequisite for reliable interpretations of fossil pollen records. In this study, we identify pollen-vegetation relationships using modern pollen rain assemblages in moss polsters (n = 13) and lake sediment surface samples (n = 11) along a steep temperature gradient of 7°C (3100–4200 m above sea level) on the western Andean Cordillera, Ecuador. The pollen rain is correlated to vascular plant abundance data recorded in vegetation relevées (n = 13). Results show that pollen spectra from both moss polsters and sediment surface samples reflect changes in species composition along the temperature gradient, despite overrepresentation of upper montane forest taxa in the latter. Estimated pollen transport distance for a lake (Laguna Llaviucu) situated in a steep upper montane forest valley is 1–2 km, while a lake (Laguna Pallcacocha) in the páramo captures pollen input from a distance of up to 10–40 km. Weinmannia spp., Podocarpus spp., and Hedyosmum sp. are indicators of local upper montane forest vegetation, while Phlegmariurus spp. and Plantago spp. are indicators for local páramo vegetation.

Sediments that accumulate in high-latitude lakes serve as valuable environmental archives of changing conditions in a region currently undergoing rapid change. A previously unexplored sedimentary sequence reaching back 16,000 years from Lakes Peters and Schrader (Neruokpuk Lakes) in the northeastern Brooks Range (69°N), Alaska, shows distinct changes in accumulation rates and biophysical properties including bulk density (BD), organic matter (OM) content, and grain-size distribution at five widely distributed core sites. The oldest sediments contain little OM and accumulated rapidly as glaciers retreated around 15 ka. OM peaked between 12 and 10 ka along with Northern Hemisphere summer insolation. BD increased and OM decreased until around 5 ka, possibly reflecting a decrease in river-transported terrestrial OM. From 5–2 ka, OM consistently increased, suggesting a rise in river discharge, or a rise in summer temperatures, which led to higher productivity, or both. After 2 ka, sediments increased in BD and decreased in OM, suggesting glacier growth. Evidence for glacier expansion late during the Little Ice Age is weak, but increased sedimentation rates may reflect glacier retreat during the last century. This study provides a framework for future paleoenvironmental research of a rare archive in a relatively pristine Arctic setting.

Through the last millennium, Patagonia has been affected by changing climate conditions and successive volcanic eruptions. Lake Tonček is a high-altitude lake in the Southern Volcanic Zone in the northern Patagonian Andes. We documented the responses of the subfossil chironomid community to the effects of successive volcanic and different conditions in a sedimentary sequence from this lake comprising the last 900 years. The community composition and structure (abundance, diversity, and richness) and the development of morphological anomalies in the chironomid mouthparts were evaluated throughout the core. Both climatic conditions and volcanism affected the chironomid community differentially. The chironomid community changed following short-term climate change patterns, being affecting not only by temperature changes but also by variations in the regional precipitation regime. Decreases in abundance and diversity were only observed in coarse volcanic layers. In these samples, we recorded a high percentage of damaged chironomid mouthparts caused by mechanical wear, breakage or abrasion, possibly due to the increase of mineral particles. Our results represent important baseline data about the responses of chironomid communities to environmental disturbances in high-altitude lakes over long time frames.

More than 130 late Pleistocene trackway sites from the coastal eolianites and beach deposits of the Cape south coast, South Africa, have previously mostly yielded tracks of large mammals and birds. However, two sites east of Still Bay, and a third near Garden Route National Park, yield distinctive trackways of hatchling sea turtles, made during the short posthatching (postemergence) interval when the trackmakers headed for the sea. One assemblage of approximately parallel trackways indicates smaller loggerhead turtle hatchlings, with alternating gaits, and contrasts with a wider trackway indicating a leatherback turtle hatchling. These are the world's first reports of fossil traces that document this brief “run-for the-sea” phenomenon. They help delineate late Pleistocene sea turtle breeding ranges and indicate climatic conditions along the Cape south coast. Ichnotaxonomically defined swim tracks of large adult sea turtles are known from a few Mesozoic sites. Likewise, walking and swim traces of terrestrial freshwater turtles are also known from the Mesozoic and Cenozoic. However, as no ichnotaxonomy exists for these diagnostic hatchling trails, we assign the trackways of the inferred loggerheads to the new ichnotaxon Australochelichnus agulhasii ichnogen. et ichnosp. nov., and the inferred leatherback trackway to Marinerichnus latus ichnogen. et ichnosp. nov.

Central Asia is highly vulnerable to large earthquakes, yet existing records of past seismic activity in this area are still insufficient to reliably assess regional earthquake hazard on longer timescales. Within this study, the sediments of Sary Chelek, a mountain lake in the western Kyrgyz Tian Shan, were investigated to explore its potential as a natural paleoseismic archive. The lacustrine deposits are characterized by a succession of annually laminated (varved) sediments overlying event deposits that consist of large-scale turbidites and distorted lake sediments, similar to earthquake-related deposits described from other lake sediment records. Microscopic sediment analysis furthermore revealed distorted varves in the laminated sequence that closely resemble earthquake-related soft-sediment deformation structures. Varve counting and radiometric dating determine the formation of the distorted varves and the emplacement of the large-scale event deposits to the early 1990s and mid-1940s, respectively. This is in good temporal agreement with the occurrence of two large earthquakes that struck western Kyrgyzstan in AD 1992 and AD 1946. These results and particularly the precise age control of the Sary Chelek sediment record highlight its potential for establishing a long and precisely dated record of regional earthquake activity.

We investigated the ecology and paleoecology of testate amoebae in peatlands of the Colombian páramo to assess the use of testate amoebae as paleoenvironmental indicators. Objectives were to (1) identify environmental controls on testate amoebae, (2) develop transfer functions for paleoenvironmental inference, and (3) examine testate amoebae in a Holocene peat core and compare our findings with other proxy records. Results from 96 modern samples indicate that testate amoebae are sensitive to pH and surface moisture, and cross-validation of transfer functions indicates potential for paleoenvironmental applications. Testate amoebae from the Triunfo Peatland in the Central Cordillera provided a proxy record of pH and water-table depth for the late Holocene, and inferred changes were correlated with peat C/N measurements during most of the record. Comparison with a lake-level reconstruction suggests that at least the major testate amoeba–inferred changes were driven by climate. Our work indicates that testate amoebae are useful paleoenvironmental indicators in high-elevation tropical peatlands.

Schmidt-hammer exposure-age dating (SHD) of boulders on cryoplanation terrace treads and associated bedrock cliff faces revealed Holocene ages ranging from 0 ± 825 to 8890 ± 1185 yr. The cliffs were significantly younger than the inner treads, which tended to be younger than the outer treads. Radiocarbon dates from the regolith of 3854 to 4821 cal yr BP (2σ range) indicated maximum rates of cliff recession of ~0.1 mm/yr, which suggests the onset of terrace formation before the last glacial maximum. Age, angularity, and size of clasts, together with planation across bedrock structures and the seepage of groundwater from the cliff foot, all support a process-based conceptual model of cryoplanation terrace development in which frost weathering leads to parallel cliff recession and, hence, terrace extension. The availability of groundwater during autumn freezeback is viewed as critical for frost wedging and/or the growth of segregation ice during prolonged winter frost penetration. Permafrost promotes cryoplanation by providing an impermeable frost table beneath the active layer, focusing groundwater flow, and supplying water for sediment transport by solifluction across the tread. Snow beds are considered an effect rather than a cause of cryoplanation terraces, and cryoplanation is seen as distinct from nivation.

A previously undocumented type of wetland is described from the Atacama Desert in northern Chile (3000 m above sea level), sustained exclusively by direct precipitation and perched above the regional water table. Geomorphological mapping, pedostratigraphy, geochemistry, and analysis of contemporary vegetation is used to understand wetland formation and dynamics during historical and present time periods. The paleowetland deposits overlie a Miocene tuff that acts as an impermeable barrier to water transfer and creates conditions for local shallow ground water. These deposits include several paleosols that were formed during periods when precipitation increased regionally at 7755–7300, 1270, 545, and 400–300 cal yr BP. The similarity in timing with other palaeohydrological records for the Atacama implies that paleosols from this wetland are proxies for reconstructing past changes in local and regional hydrological cycle. Archaeological investigations have revealed the presence of two small farms from the Late Intermediate period, i.e., during the earliest wetter phase represented by the paleosols. Both farms are located near the paleowetland deposits, which suggests that local inhabitants exploited these water sources during late pre-Hispanic times. Results of this study improve knowledge of settlement patterns during this and earlier cultural periods.

This contribution discusses possible relationships between human populations and Holocene environmental deterioration phenomena (cold/arid pulses and volcanic eruptions) in the Fuegian Archipelago (South America), based on summed probability distributions of archaeological dates, paleoenvironmental information, geospatial data, and archaeological evidence. During the first millennia after peopling, only the Hudson (ca. 7700 cal yr BP) and the first Monte Burney (ca. 8600 cal yr BP) eruptions might have played a role in human dispersion. Particularly, a more intense human occupation around the Beagle Channel and long-distance interactions are proposed as risk-buffer strategies related to the Hudson eruption. A cooling phase and a demographic growth at ca. 5500 cal yr BP might have favored more dispersed spatial occupations and a subsistence diversification in the Beagle Channel. In the northern steppes, the second Monte Burney eruption (ca. 4300 cal yr BP) and an arid episode (ca. 2600 cal yr BP) are proposed as the main triggers for changes in land-use patterns, long-network interactions, and subsistence strategies. Even though occupation changes in the Fuegian Archipelago coexist with environmental deterioration episodes after 1500 cal yr BP, demographic processes and the European colonization most likely explain this trend. Similarities between the steppe/ecotone and forest occupation curves suggest common behavioral patterns across the Holocene.

Aspects of paleoclimatic and paleoceanographic evolution of the north Aegean Sea through the Holocene are revealed by the study of quantitative variations in planktonic foraminiferal, pteropodal, and palynomorph assemblages; the isotopic composition of planktonic foraminifera; and hydrographic-related indices, extracted from two high-sedimentation rate cores from the North Aegean Trough. Focusing on the last ~10 cal ka BP, the current Holocene subdivision (Greenlandian, Northgrippian, and Meghalayan) confirms the traditional understanding of an evolution from wetter (Greenlandian) to gradually drier (Northgrippian and Meghalayan) climatic conditions and further highlights the role of changing seasonality during this time. The most warm and humid phase corresponds to the time of the sapropel S1 deposition (9.6–6.1 cal ka BP). The Holocene climatic instability of the study area is further supported by six episodes of brief cooling (North Aegean cooling; NAEGC6–NAEGC1) centered at 9.30, 8.05, 7.05, 4.55, 3.55, and 2.05 cal ka BP, reflected by significant faunal changes and oxygen isotope enrichments. These cold/arid events are coeval with equivalent cooling events that have been described in different basins of the Mediterranean Sea, while signal similarities with equivalent changes in the intensity of the Siberian high suggest a climatic link between the studied area and the high-latitude areas.

A current goal among many scientific disciplines is to incorporate data on past human land use and climate change into current global climate and vegetation models. Here, we used existing archaeological and paleoecological data to provide a spatiotemporal reconstruction of human history in Greater Amazonia over the Holocene. We used an ensemble distribution model based on a database of georeferenced 14C-dated material and environmental factors to predict the changes in spatial distributions of past human occupation sites. We ran these models for the precultivation (13,000–6000 yr ago), early cultivation (6000–2500 yr ago), and late cultivation (2500–500 yr ago) periods. The ensemble models suggest that people mostly inhabited the peripheral areas of Greater Amazonia and the eastern sections of the main Amazon River and its larger tributaries during the precultivation period. Human populations began growing exponentially through the early cultivation period, and people spread and expanded into the interior forests and along river channels in western Amazonia. Populations continued growing through the late cultivation period in these same regions. Our results suggest that many forests, particularly in the peripheral regions and riverine locations, may still be in recovery from disturbances that have occurred repeatedly through the Holocene.

The introduction of agriculture is known to have profoundly affected the ecological complexion of landscapes. In this study, a rapid transition from C3 to C4 vegetation is inferred from a shift to higher stable carbon (13C/12C) isotope ratios of soils and sediments in the Benoué River Valley and upland Fali Mountains in northern Cameroon. Landscape change is viewed from the perspective of two settlement mounds and adjacent floodplains, as well as a rock terrace agricultural field dating from 1100 cal yr BP to the recent past (<400 cal yr BP). Nitrogen (15N/14N) isotope ratios and soil micromorphology demonstrate variable uses of land adjacent to the mound sites. These results indicate that Early Iron Age settlement practices involved exploitation of C3 plants on soils with low δ15N values, indicating wetter soils. Conversely, from the Late Iron Age (>700 cal yr BP) until recent times, high soil and sediment δ13C and δ15N values reflect more C4 biomass and anthropogenic organic matter in open, dry environments. The results suggest that Iron Age settlement practices profoundly changed landscapes in this part of West Africa through land clearance and/or utilization of C4 plants.

The focus of this paper is the Neolithic of northwest Europe, where a rapid growth in population between ~5950 and ~5550 cal yr BP is followed by a decline that lasted until ~4950 cal yr BP. The timing of the increase in population density correlates with the local appearance of farming and is attributed to the advantageous effects of agriculture. However, the subsequent population decline has yet to be satisfactorily explained. One possible explanation is the reduction in yields in Neolithic cereal-based agriculture due to worsening climatic conditions. The suggestion of a correlation between Neolithic climate deterioration, agricultural productivity, and a decrease in population requires testing for northwestern Europe. Data for our analyses were collected during the Cultural Evolution of Neolithic Europe project. We assess the correlation between agricultural productivity and population densities in the Neolithic of northwest Europe by examining the changing frequencies of crop and weed taxa before, during and after the population “boom and bust.” We show that the period of population decline is coincidental with a decrease in cereal production linked to a shift towards less fertile soils.

High-resolution climate archives of the Late Holocene are essential in the study of paleoclimatic dynamics and for understanding the importance of natural and anthropogenic influences on past and future climate changes. Here, we present well-dated X-ray fluorescence scanning records retrieved from a varved sediment core from Lake Kusai. These records show the decadal- to centennial-scale paleoclimatic variability of the northern Qinghai-Tibetan Plateau over the last 2000 yr. Ca is mainly related to the precipitation of authigenic carbonates and is a proxy for temperature changes. The Ca record of Lake Kusai is well-correlated with the variations and periodicities of solar activity. Therefore, solar output can be suggested as being the predominant forcing mechanism of decadal- to centennial-scale temperature fluctuations over the last 2000 yr. The evolution of effective moisture was inferred from the log-ratios of Rb/Sr, which demonstrated synchronous changes with the typical Indian summer monsoon record from Dongge Cave. These results indicate that the decadal- to centennial-scale effective moisture evolution of the northern Qinghai-Tibetan Plateau is mainly influenced by the Indian summer monsoon. Additionally, we have not found the evident periodicities of solar activity in our effective moisture record over the last 2000 yr.

This paper presents new excavation data on the Chinchihuapi I (CH-I) locality within the Monte Verde site complex, located along Chinchihuapi Creek in the cool, temperate Valdivian rain forest of south-central Chile. The 2017 and 2018 archaeological excavations carried out in this open-air locality reveal further that CH-I is an intermittently occupied site dating from the Early Holocene (~10,000 cal yr BP) to the late Pleistocene (at least ~14,500 cal yr BP) and probably earlier. A new series of radiocarbon dates refines the chronology of human use of the site during this period. In this paper, we describe the archaeological and stratigraphic contexts of the recent excavations and analyze the recovered artifact assemblages. A fragmented Monte Verde II point type on an exotic quartz newly recovered from excavations at CH-I indicates that this biface design existed in at least two areas of the wider site complex ~14,500 cal yr BP. In addition, associated with the early Holocene component at CH-I are later Paijan-like points recovered with lithic tools and debris and other materials. We discuss the geographic distribution of diagnostic artifacts from the site and their probable relationship to other early sites in South America.

We report comprehensive rock-magnetic and archaeointensity investigations from 21 well-constrained pottery fragments from the Catamarca province of northwest Argentina. The absolute ages of the studied sites are ascertained by several high-quality radiometric ages and range between 1940 to 114014C yr BP. Magnetic mineralogy experiments indicates that the remanence is carried by thermally stable Ti-poor titanomagnetites. Forty-seven samples belonging to 11 out of 98 studied potsherds yielded reliable absolute intensity determinations judging from the quality parameters associated with the Thellier double-heating experiments. Moreover, we analyzed the available absolute geomagnetic intensities associated with the radiometric ages to construct the first intensity paleosecular variation curve (PSVC) for South America using thermoremanent magnetization carried by burned archaeological artifacts obtained in the present investigation and 79 other selected archaeointensities (out of 213 published in the literature). The dataset is used to build the PSVC reference curve by combined bootstrap and temporal P-spline methods. The variation curve shows significant differences with the global prediction model SHA.DIF.14k mainly based on the GEOMAGIA database. This intensity PSVC curve shows reasonably good agreement with paleosecular variation curves for Europe between 850 through 1150 BC and for Asia between 1000 and 1500 BC. This regional curve may be used as most reliable archaeomagnetic dating tool for the major part of South America (Peru, Brazil, Argentina, Chile, and Bolivia) for the last two millennia.

The geomorphology and stratigraphy of the South Fork Hoh River (SF Hoh), Olympic Mountains, Washington, allow for greater understanding of Marine Oxygen Isotope Stage 2 (MIS 2) ice fluctuations, glacial dynamics, and sedimentation. Age control from optically stimulated luminescence and radiocarbon dating constrains deposited sediments associated with four Late Pleistocene ice-marginal positions that formed under reduced ice volume conditions compared with MIS 3–5 glaciers in the same drainage. The earliest MIS 2 ice margin extended into the main Hoh River valley (pre–SF 1, 28 ka to >23.0 ka). After retreat, the ice occupied three closely spaced ice-marginal positions (SF 1–3) that range in age from 22.0 ka to shortly after 18.7 ka. While the SF 1 and SF 3 positions were previously identified as the Twin Creeks I and II positions, the intermediate SF 2 position had not been recognized. Moraines are composed of poorly sorted, but stratified, sediment and few tills. Diamicton units show evidence of water reworking. This research documents a detailed record of MIS 2 glaciation in a maritime setting in western North America and provides evidence of rapid MIS 2 ice-marginal fluctuations that likely reflect responses to millennial-scale climatic fluctuations and may be relevant to understanding other complex MIS 2 moraine sequences.

We present a continuous, sediment core-based record of paleohydroclimate spanning ~5800 cal yr BP to recent from Lower Pahranagat Lake (LPAH), a shallow, alkaline lake in southern Nevada. We apply stable isotopes (δ18O and δ13C) from fine-fraction authigenic carbonate, which are sensitive recorders of hydroclimatic variability in this highly evaporative region. Additional geochemical proxies (total organic carbon, C/N, and total inorganic carbon) provide supporting information on paleoecological change in and around the lake. Our data suggest progressively wetter conditions starting at the later part of the middle Holocene and extending into the late Holocene (~5500–3350 cal yr BP) followed by a millennial-scale dry period from ~3150 to 1700 cal yr BP. This latter interval encompasses the ‘Late Holocene dry period’ (LHDP) reported by other investigators, and our data help refine the area affected in this episode. Our data also show evidence for a series of century-scale fluctuations in regional hydroclimate, including wet and dry intervals between 2350 and 1600 cal yr BP, and drier conditions over the past few centuries. Paleohydroclimate trends in the LPAH record show correspondence with those from the central Great Basin to the north, suggesting that both areas were subject to similar climatic forcings.

A 230Th/U-dated stalagmite from Hulu Cave was analyzed for δ18O, δ13C, and trace elements. A ~10-yr-resolution δ18O record, spanning 51.7–42.6 ka, revealed Dansgaard-Oeschger (DO) events 14 to 11. A similar rapid transition and synchronous timing of the onset of DO 12 is evident between the Greenland and Hulu Cave records, which suggests a common forcing mechanism of DO cycles in the North Atlantic and monsoonal region of Asia. Centennial-scale monsoonal oscillations in the cave δ18O record are indicative of hydroclimatic instability during interstadials. After removing the signals of remote moisture sources, the proportion of moisture from nearby sources is found to be higher during stadials than during interstadials. To explain this, we propose that the movement of the westerly jet is an important control on the balance of nearby and distant moisture sources in East Asia. In addition, the records of δ13C and trace element ratios, which are proxies of local environmental changes, resemble the δ18O record on the scale of DO cycles, as well as on even shorter timescales. This suggests that hydrological processes and biological activity at the cave site respond sensitively to the monsoonal changes.

We present a multiproxy record using pollen, magnetic susceptibility, carbon isotopic composition, carbon/nitrogen ratio, and particle size of mid- to late Holocene environmental changes based on a sediment core from the Pomaeho lagoon on the east coast of Korea. The records indicate that climate deteriorations around 6400 cal yr BP and 4000 cal yr BP caused rapid vegetation changes in the study area, which were presumably attributable to low sunspot activity and strong El Niño–like conditions, respectively. These two cooling events were likely modulated by different climate mechanisms, as El Niño–Southern Oscillation activity began to strengthen around 5000 cal yr BP. These events may have had a substantial impact on ancient societies in the study area. Combining our results with archaeological findings indicated that climate deterioration led to drastic declines in local populations around 6400 cal yr BP, 4400 cal yr BP, and 4000 cal yr BP. Because of its high population, coastal East Asia (e.g., eastern China, Japan, and Korea) is particularly vulnerable to potential cooling events in the future. Therefore, there is a strong need for detailed paleoclimate information in this region.