593 results
Search Results
2. Approximate Bayesian computation and ecological niche models elucidate the demographic history and current fragmented population distribution of a Korean endemic shrub.
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Ong, Homervergel G., Kim, Yong‐In, Lee, Jung‐Hoon, Kim, Bo‐Yun, Kang, Dae‐Hyun, Jung, Eui‐Kwon, Shin, Jae‐Seo, and Kim, Young‐Dong
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ECOLOGICAL models ,ECOLOGICAL niche ,ENDANGERED plants ,CLIMATE change ,HOLOCENE Epoch ,PHYTOGEOGRAPHY - Abstract
Climatic fluctuations and geological events since the LGM are believed to have significantly impacted the population size, distribution, and mobility of many species that we observe today. In this paper, we determined the processes driving the phylogeographic structure of the Korean endemic white forsythia by combining the use of genome‐wide SNPs and predicting paleoclimatic habitats during the LGM (21 kya), Early Holocene (10 kya), Mid‐Holocene (6 kya), and Late Holocene (3 kya). Using a maximum of 1897 SNPs retrieved from 124 samples across nine wild populations, five environmental predictors, and the species' natural occurrence records, we aimed to infer the species' demographic history and reconstruct its possible paleodistributions with the use of approximate Bayesian computation and ecological niche models, respectively. Under this integrated framework, we found strong evidence for patterns of range shift and expansion, and population divergence events from the onset of the Holocene, resulting in the formation of its five distinct genetic units. The most highly supported model inferred that after the split of an ancestral population into the southern group and a larger central metapopulation lineage, the latter gave rise to the eastern and northern clusters, before finally dividing into two sub‐central groups. While the use of molecular data allowed us to identify and refine the (phylo)genetic relationships of the species' lineages and populations, the use of ecological data helped us infer a past LGM refugium and the directions of post‐glacial range dynamics. The time frames of these demographic events were shown to be congruent with climatic and geological events that affected the central Korean Peninsula during these periods. These findings gave us a better understanding of the consequences of past spatiotemporal factors that may have resulted in the current fragmented population distribution of this endangered plant. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
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3. Accelerating the Renewable Energy Revolution to Get Back to the Holocene.
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Abbott, Benjamin W., Abrahamian, Chelsea, Newbold, Nicholas, Smith, Peter, Merritt, Marina, Sayedi, Sayedeh Sara, Bekker, Jeremy, Greenhalgh, Mitchell, Gilbert, Sophie, King, Michalea, Lopez, Gabriel, Zimmermann, Nils, and Breyer, Christian
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RENEWABLE energy sources ,ENVIRONMENTAL health ,HOLOCENE Epoch ,RENEWABLE energy costs ,STANDARD of living ,INDUSTRIAL energy consumption ,ENERGY consumption - Abstract
The UN's Paris Agreement goal of keeping global warming between 1.5 and 2°C is dangerously obsolete and needs to be replaced by a commitment to restore Earth's climate. We now know that continued use of fossil fuels associated with 1.5–2°C scenarios would result in hundreds of millions of pollution deaths and likely trigger multiple tipping elements in the Earth system. Unexpected advances in renewable power production and storage have radically expanded our climate response capacity. The cost of renewable technologies has plummeted at least 30‐year faster than projected, and renewables now dominate energy investment and growth. This renewable revolution creates an opportunity and responsibility to raise our climate ambitions. Rather than aiming for climate mitigation—making things less bad—we should commit to climate restoration—a rapid return to Holocene‐like climate conditions where we know humanity and life on Earth can thrive. Based on observed and projected energy system trends, we estimate that the global economy could reach zero emissions by 2040 and potentially return atmospheric CO2 to pre‐industrial levels by 2100–2150. However, this would require an intense and sustained rollout of renewable energy and negative emissions technologies on very large scales. We describe these clean electrification scenarios and outline technical and socioeconomic strategies that would increase the likelihood of restoring a Holocene‐like climate in the next 100 years. We invite researchers, policymakers, regulators, educators, and citizens in all countries to share and promote this positive message of climate restoration for human wellbeing and planetary stability. Plain Language Summary: New research in global ecology and public health shows that the consequences of burning fossil fuels are much more severe than previously understood. Current global warming targets are not enough to protect us from sea level rise, ecosystem collapse, and hundreds of millions of human deaths from fossil fuel pollution. Thankfully, the cost of renewable energy technologies has dropped below the cost of fossil fuels decades faster than predicted. This has triggered a renewable revolution that is transforming the global energy system. Our paper considers the feasibility of accelerating this transition through policy, investment, and strategic research. We conclude that there is a viable pathway to restoring Earth's climate through clean electrification and carbon capture. We call for a global commitment to restore pre‐industrial climate conditions within a century and describe what approaches would increase our chances of success. Accelerating the renewable revolution would move us toward a sustainable civilization by eliminating air pollution, stabilizing climate, reducing energy costs, and enhancing living standards worldwide. Because there is no safe level of climate disruption or pollution death, we believe it is our responsibility to restore a Holocene‐like climate, which we know can support human civilization and other life on Earth. Key Points: Goals of 1.5–2°C are not safe given current understanding of ecosystem climate sensitivity and high social costs of fossil fuel pollutionClimate restoration‐rapidly reestablishing Holocene‐like conditions‐has not been fully considered because of socioeconomic obstaclesStrategic financing and prioritization of clean electrification could create pathways back to the Holocene within a century [ABSTRACT FROM AUTHOR]
- Published
- 2023
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4. Observations of the incipient and penultimate stages of Holocene marine terrace development.
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Dickson, Mark E., Omidiji, Jokotola, Litchfield, Nicola J., Norton, Kevin P., Matsumoto, Hironori, Krier‐Mariani, Raphael L., Horton, Sophie L., Acharya‐Chowdhury, Lovleen, McLean, Aidan D., Hurst, Martin D., and Stephenson, Wayne J.
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EROSION ,HOLOCENE Epoch ,TERRACING ,EARTHQUAKE magnitude ,COASTAL changes ,CONCEPTUAL models - Abstract
Flights of Holocene marine terraces are useful for reconstructing past earthquakes, but coastal erosion can remove terraces from the landscape, potentially leading to incorrect estimates of earthquake magnitude and frequency. Relatively little effort has been afforded to studying terrace erosion processes, and this paper presents the first field evidence that we are aware of documenting terrace erosion rates. Two case studies from New Zealand provide a unique opportunity to observe the beginning and end phases of terrace development. We present downwear and backwear erosion measurements, showing that both sets of processes are important. Micro‐erosion meter measurements from Kaikōura Peninsula, South Island, confirm that downwear processes are modifying new marine terraces that were created when the peninsula was uplifted about 1 m during the 2016 earthquake. Erosion rates were high immediately following uplift as the relatively barren intertidal rock shore platform rapidly transformed into an incipient marine terrace with cover deposits. However, the Kaikōura earthquake uplifted shore platforms only a small distance above the upper tidal limit and ongoing downwear and backwear erosion may begin to remove parts of this terrace in future decades. We explored this prospect with a case study at Māhia Peninsula, North Island, where 100–300 years have elapsed since the last terrace‐forming earthquake. Historical photographs were used to document about 80 years of backwear erosion. Terrace erosion rates have been nearly constant through this period, and extrapolation implies that the terrace will be removed in places by 2030. The erosion data in this paper provide new insights into how terraces can be removed from the landscape, but there are many complicating factors. To help understand these factors we present a new conceptual model of marine terrace creation and destruction for soft‐rock coasts. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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5. Herpetofauna diversity from late Holocene wetlands of northeastern Argentina.
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Escobar, Guillermo, Zaracho, Víctor, Cuaranta, Pedro, Barboza, Carolina, Píccoli, Carolina, Luna, Carlos A., Gallego, Oscar F., and Monferran, Mateo D.
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HERPETOFAUNA , *FOSSIL reptiles , *HOLOCENE Epoch , *VIPERIDAE , *FOSSILS , *WETLANDS , *ANURA - Abstract
The palaeofauna of the Quaternary is mostly known from the mammals' record, while the herpetofauna is less represented. In the same way, in northeastern Argentina reptile fossils records are scarce, usually represented by preliminary communications. This paper focuses on the study of herpetofauna remains from the Isla El Disparito archaeological site. The faunal materials collected at the site revealed an increase in taxonomic diversity related to the Quaternary herpetofauna in the IED site, with over 50% of the bone remains represented by anurans and at least six recognized squamates taxa. The purpose of this study is to properly identify these new records of herpetofauna remains from northeastern Argentina during the Holocene as well as to provide a dichotomous key of postcranial remains for identifying extant squamates taxa in other Quaternary sites from Argentina. The identified squamate assemblage includes the lizard Ophiodes sp., the snake families Typhlopidae, Dipsadidae, Viperidae and undetermined colubroids, along with anuran bone remains (Anura indet. and ?Hylidae). Additionally, the findings contribute to a better understanding of the herpetological assemblage in Argentina, providing insights into the composition of South American squamates during the Quaternary. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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6. Differing local‐scale responses of Bolivian Amazon forest ecotones to middle Holocene drought based upon multiproxy soil data.
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Hill, James, Black, Stuart, Soto, Daniel, Chavez, Ezequiel, Vos, Vincent, and Mayle, Francis
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DROUGHTS ,ECOTONES ,HOLOCENE Epoch ,TROPICAL dry forests ,ENVIRONMENTAL engineering ,PALEOECOLOGY ,BOGS ,FOREST soils - Abstract
Uncertainty remains over local‐scale responses of ecotonal Amazonian forests to middle Holocene drying due to the scarcity, and coarse spatial resolution, of lacustrine pollen records. This paper examines the palaeoecological potential of soil phytoliths, stable carbon isotopes and charcoal for capturing local‐scale ecotonal responses of different types of Bolivian Amazonian forest to middle Holocene climate change. Soil pits 1 m deep were dug at ecotones between rainforest, dry forest, Chaco woodland and savannah, and sampled at 5–10 cm resolution. Both phytolith and stable carbon isotope records indicate stability of dry forest–savannah ecotones over the last ca. 6000 years, despite middle Holocene drought, revealing the dominance of edaphic factors over climate in controlling this type of ecotone. In contrast, δ13C data reveal that rainforest–savannah ecotones were more responsive to climate change, with rainforest likely replaced by drought‐tolerant dry forest or savannah vegetation during the mid‐Holocene, consistent with regional‐scale lacustrine pollen records. However, such shifts are not apparent in most of our phytolith records due to insufficient taxonomic resolution in differentiating rainforest from dry forest. Charcoal data show that ecotonal dry forests experienced greater fire activity than rainforests and that recent high fire activity at all forest sites is unprecedented since at least the middle Holocene. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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7. Comparison and Renormalization of Holocene Paleointensity Records From Central North America (17°N–51°N, 205°E–295°E).
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Lund, Steve P., Richardson, Marci, Verosub, Ken, King, John, Champion, Duane, and St‐Onge, Guillame
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HOLOCENE Epoch ,GEOMAGNETISM ,LAVA flows ,ELECTRIC generators ,OSCILLATIONS - Abstract
This paper develops a composite absolute paleointensity record for Holocene paleomagnetic secular variation (PSV) from central North America. Twelve full‐vector (inclination, declination, paleointensity) PSV records were assessed in order to build the composite record. Nine of the paleointensity records come from sediment paleomagnetic studies and are considered relative in intensity. Three of the paleointensity records come from absolute paleointensity measurements of archeological materials and lava flows. This paper develops a new method to normalize the sediment relative paleointensity records to the absolute intensity records. The final composite paleointensity record describes intensity variability over a region of Central North America delineated by 35°–48.6°N and 240.4–291.4°E (∼14° × 50°). This composite record shows a distinctive long‐duration (∼104 year) oscillation and a series of millennial‐scale intensity oscillations that are consistent over our study region. Plain Language Summary: This study develops a composite record of geomagnetic field intensity for the central North America for the last 8,000 years. This record is important for considering the total geomagnetic field variability I this region and its dynamo source(s). Key Points: We develop a new composite absolute paleointensity record for Holocene Central North AmericaWe develop a new renormalization technique to combine absolute paleointensity records and sediment relative paleointensity recordsThe final composite absolute paleointensity record has a distinctive long‐term trend and millennial‐scale variability [ABSTRACT FROM AUTHOR]
- Published
- 2021
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8. Variations in Spring Atmospheric Circulation on the Southwestern Tibetan Plateau During Holocene Linked to High‐ and Low‐Latitude Forcing.
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Ma, Qingfeng, Zhu, Liping, Wang, Junbo, Ju, Jianting, and Wang, Yong
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SPRING ,CLIMATE change ,HOLOCENE Epoch ,TIMBERLINE ,POLLEN ,PLANT phenology ,ATMOSPHERIC circulation - Abstract
Recent climate and environment over the Tibetan Plateau (TP) have undergone significant changes, dominated by variations in the Westerlies and the Indian summer monsoon. However, long‐term shifts in atmospheric circulation during the transitional seasons are still lacking. Here we investigate the modern distribution of Tsuga pollen over the central‐western TP and confirm it as an indicator of variable atmospheric circulation in spring. By combining our Tsuga record from Taro Co with existing records in the Tsuga pollen source area, we suggest that a potential particle transport pathway from the southern slope of the Himalayas to the interior of the plateau appeared in the spring of the late Holocene. Our results show that the springtime atmospheric circulation over the southwestern TP during the early and late Holocene is closely related to the substantial remnants of ice sheets at northern high latitudes and the frequency of El Niño events, respectively. Plain Language Summary: The spring climate over the Tibetan Plateau (TP) is undergoing significant changes that yield profound impacts on environmental changes such as variations in vegetation phenology and alpine treeline. Knowledge of long‐term variations in atmospheric circulation during spring can improve the understanding of current climatic and environmental change and the projection of future variability. In this paper, we use an exotic pollen grain, which can be transported long distances in the air, as an indicator to trace the variability of spring atmospheric circulation over the TP. The results indicate that the spring meridional atmospheric circulation from the southern slope of the TP to its interior has been enhanced in the last four thousand years, which is mainly influenced by the frequency of El Niño events. Key Points: Spring atmospheric circulation change over the southwestern Tibetan Plateau (TP) during Holocene is reconstructedMeridional atmospheric circulation in spring over the southwestern TP is strengthened in the late HoloceneHigh‐(low‐) latitude forcing mainly influence the variations in spring atmospheric circulation during the early (late) Holocene [ABSTRACT FROM AUTHOR]
- Published
- 2023
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9. Disasters in the Anthropocene: a storm in a teacup?
- Author
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Hollis, Simon
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HOLOCENE Epoch ,DISASTERS ,EMERGENCY management ,HUMAN ecology - Abstract
Copyright of Disasters is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2023
- Full Text
- View/download PDF
10. Was the termination of the Jizera River meandering during the Late Holocene caused by anthropogenic or climatic forcing?
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Elznicová, Jitka, Kiss, Timea, von Suchodoletz, Hans, Bartyik, Tamás, Sipos, György, Lenďáková, Zuzana, Fačevicová, Kamila, Pavlů, Ivana, Kovárník, Jaromír, and Matys Grygar, Tomáš
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MEANDERING rivers ,OPTICALLY stimulated luminescence ,GROUND penetrating radar ,HOLOCENE Epoch ,CLIMATE extremes ,FLUVIAL geomorphology ,AGGRADATION & degradation - Abstract
The Jizera River in Czechia is a typical mid‐sized Central European watercourse. Its floodplain shows a morphological contrast between the laterally stable low‐sinuous current channel and preserved palaeomeanders. The aim of this paper was to date and explain the obvious metamorphosis of the channel pattern from meandering to low‐sinuous. We analysed the morphology of the lower river reach using a digital terrain model (DTM) and historical maps from the 1840s. Furthermore, the floodplain architecture was described based on the DTM, geophysical imaging (ground penetrating radar, GPR), sediment lithology and anthropogenic contamination using geochemical proxies, and optically stimulated luminescence (OSL) dating. The geochemical proxies were processed using log‐ratio methods from the compositional data analysis toolbox. According to our results the Jizera River showed signs of systematic lateral floodplain reworking during the Late Holocene with only minor aggradation, although parts of the catchment are covered by easily erodible loess. Interestingly, vertical aggradation did not show a significant increase during the last millennium. In the main study area, this limited vertical aggradation resulted in the preservation of palaeomeander fragments and palaeochannel belts with 100–200 m mean width in the 300–600 m wide floodplain, which are recognisable in the topography and in subsurface GPR imaging. This channel meandering took place between around 4 and 1.2 ka, and the transition towards the laterally stable modern channel with low sinuosity occurred around 1.2 ka. This timing indicates a climatic rather than anthropogenic impact, which was rather weak around that time. One likely cause for this transition was the influx of material from ravines incised into the sandstone valley edges during past climatic extremes. Subsequently, the re‐establishment of a meandering pattern was possibly prevented by a combination of low fluvial activity and the construction of weirs that reduced stream power. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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11. Nonadult vertebral maturation in Late Holocene hunter‐gatherers from Patagonia (Salitroso Lake, Argentina).
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Morlesin, Milena C., Guichón Fernández, Rocío, and García Guraieb, Solana
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HUNTER-gatherer societies ,HOLOCENE Epoch ,STATURE ,BONE growth ,SEXUAL dimorphism ,LAKES - Abstract
Bioarchaeological research of bone growth patterns provides information on the health status and disease of past populations. Recent studies have pointed out the potential of metric analysis of nonadult vertebrae as indicators of stress during different stages of ontogeny, highlighting that most vertebral measurements present low sexual dimorphism, a stable and known pattern of growth and give useful information even in incomplete spines. The aims of this paper are first, to construct a vertebral growth profile for nonadults of a skeletal series of Patagonian Late Holocene hunter‐gatherers from Salitroso Lake (SAC); second, to compare it to the ones obtained in other archaeological and modern populations with different stress experiences; and third, building on this, to assess whether individuals with evidence of stress experienced in early development demonstrate different patterns in vertebral growth than those without. Two spinal dimensions are used: vertebral body height (VBH) and transverse diameter of the neural canal (TDNC) in a sample of 23 nonadult skeletons with ages previously estimated from dental and bone indicators. The vertebral dimensions of 20 adults between 18 and 35 years of age were also measured as reference information. Results show that the growth of the VBH is steady over the years and reaches adulthood size by approximately 16 years of age whereas TDNC dimensions do not experience marked fluctuations in size throughout life and adult dimensions are reached at approximately 4 years of age as expected. The vertebral growth pattern observed in SAC is similar to that obtained in other archaeological samples from very different settings but experiencing relatively high nutritional or pathological stress in early stages of life. However, it is markedly different, and systematically smaller, to the 20th century sample pattern, probably responding to a secular trend in the modern population with a more stable access to resources and medical treatment. Finally, SAC individuals with systemic stress markers do not tend to exhibit smaller vertebral dimensions than those without them. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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12. An Energetic Perspective on the Holocene North American Monsoon.
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HOLOCENE Epoch ,HYDROLOGIC cycle ,LONG-Term Evolution (Telecommunications) ,MONSOONS ,RAINFALL ,CORE & periphery (Economic theory) - Abstract
The North American Monsoon (NAM) is a critical component of the hydrologic cycle in southwestern North America. However, our understanding of the long‐term evolution of this monsoon system is incomplete due to a paucity of long‐term paleoclimatic records from the core and periphery of the NAM domain. C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) leverage a new compilation of Holocene proxy records to generate a new composite index of NAM evolution over the Holocene. They identify a relationship between NAM strength and the latitudinal temperature gradient over the Holocene. The authors suggest that shifts in the strength of the westerlies altered NAM convection via ventilation, a process whereby the large‐scale circulation imports low moist entropy air into the monsoon domain. These results highlight the importance of paleoclimatic records, especially from past "warm" intervals, for generating new insights about the evolution of regional monsoons. Plain Language Summary: The North American Monsoon is a circulation that brings summer rain to regions of the US southwest and western Mexico. Despite the fact that this circulation provides a majority of the precipitation in many parts of the arid southwest, we do not fully understand the factors that govern long‐term changes in this monsoon. A new paper by C. Routson et al. (2022, https://doi.org/10.1029/2022gl099772) uses proxy indicators of past summer rainfall, stretching from Central America to Arizona, to reconstruct changes in the monsoon over the geologic epoch known as the Holocene, or the last 11,000 years of Earth history. The results of this study suggest that Holocene changes in the temperature difference between the equator to pole, known as the "latitudinal temperature gradient," exerted an important influence over monsoon strength in the southwest. This has implications for the future of the summer monsoon, especially as the high latitudes of the northern hemisphere are expected to warm in the future. Key Point: The strength North American Monsoon tracks changes in the position of the midlatitude westerlies over the Holocene [ABSTRACT FROM AUTHOR]
- Published
- 2022
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13. High Latitude Modulation of the Holocene North American Monsoon.
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Routson, Cody C., Erb, Michael P., and McKay, Nicholas P.
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HOLOCENE Epoch ,ATMOSPHERIC models ,JET streams ,RAINFALL ,WESTERLIES ,LATITUDE ,MONSOONS - Abstract
The North American monsoon (NAM) is an important source of rainfall to much of Mexico and southwestern United States. Westerly winds (westerlies) can suppress monsoon circulation and impact monsoon timing, intensity, and extent. Recent Arctic warming is reducing the temperature gradient between the equator and the pole, which could weaken the westerlies; however, the implications of these changes on the NAM are uncertain. Here we present a new composite index of the Holocene NAM. We find monsoon strength reached a maximum circa 7,000 years ago and has weakened since then. Proxy observations of temperature, hydroclimate and upwelling, along with model simulations, show that the NAM was modulated by the westerlies over the Holocene. If the observed Holocene pattern holds for current warming, a weaker meridional temperature gradient and weaker westerlies could lead to a stronger future NAM. Plain Language Summary: The North American monsoon (NAM) is a main source of summertime rain in Mexico and southwestern North America. Here we explore how the NAM rainfall has changed over the past 11,000 years using information from natural archives of past climate (called "proxies") as well as climate models. We find that monsoon was strongest around 7,000 years ago and has weakened since then. This weakening of the monsoon appears to be caused by a strengthening of the mid‐latitude jet stream, which was influenced by changes in high‐latitude versus low‐latitude temperatures over that period. This paper explores the relationship between temperatures, the jet stream, and the NAM in data and models, which is relevant to future climate in the region. Key Points: A new multi‐proxy‐based estimate of the Holocene North American monsoon (NAM) is presentedProxy and modeled evidence show westerly winds were a dominant control on the Holocene NAMHigh‐latitude temperature drove changes in the Holocene westerly winds and thus the NAM [ABSTRACT FROM AUTHOR]
- Published
- 2022
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14. Holocene environments on the west‐central Kola Peninsula (north‐west Russia): lithology, chronology and biostratigraphy records from Lake Tikozero and a neighbouring bog.
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Korsakova, Olga, Kolka, Vasily, Tolstobrov, Dmitry, Savelieva, Larisa, Kosova, Anna, Petrov, Alexei, and Semyonova, Lyudmila
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HOLOCENE Epoch ,PETROLOGY ,BIOSTRATIGRAPHY ,LAKES ,LAKE sediments ,BOGS ,FOSSIL diatoms - Abstract
The paper studies sediments from Lake Tikozero that have accumulated successively in the littoral of Lake pre‐Imandra, Imandra lagoon, and an open lake isolated from a parental freshwater body. The 'Apatity' bog was concurrently formed on the Lake Imandra coast. Lithological, 14C, pollen and diatom data and findings of previous investigations provide the regional Holocene stratigraphy, which is subdivided into the early (c. 11 550–8200 cal a bp), middle (c. 8200–4000 cal a bp) and late (last 4000 cal a bp) Holocene sub‐stages. In the early Holocene, environments became favourable for diatoms after c. 9700 cal a bp. Birch phytocoenoses and pine forests with birch flourished in the area. In the middle Holocene, the west‐central Kola Peninsula was covered by a pine‐birch forest with alders. Lake Tikozero became shallow and desiccated in a warm and dry climate between c. 6300 and 4000 cal a bp; and a Sphagnum raised bog developed in the adjacent area, provoked by lowering of the water table. Spruce appeared in a pine‐birch forest and indicates a colder and wetter climate in the late Holocene. The flooding of Lake Imandra created a number of new small lakes; and fens occurred along the wet shores. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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15. Holocene evolution and depositional model of a bayhead delta, Lake Illawarra, Australia.
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Hopley, Carl A., Jones, Brian G., and Pontén, Anna
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RELATIVE sea level change ,SEDIMENTARY facies (Geology) ,SEDIMENTARY structures ,HOLOCENE Epoch ,RIVER sediments ,ABSOLUTE sea level change - Abstract
Extensive research into the evolution of wave‐dominated estuaries has been documented since the 1960s. However, there has only been limited research on the prograding bay‐head deltas that are the primary drivers for the rate and stage of estuary evolution. This paper presents the findings of a high‐resolution spatial study into the evolution of the Macquarie Rivulet bayhead delta in the Lake Illawarra barrier estuary. The delta's evolution has been established based on sedimentological analysis of 74 cores, two 14C ages and 45 amino acid racemization ages. This study intersected two Pleistocene and 10 Holocene sedimentary facies associations representing both the retrogradational and progradational phases of delta development. The distribution of bayhead delta facies associations in shallow barrier estuaries is initially controlled by the antecedent morphology, but, in contrast to deeper estuaries, this influence decreases as sedimentation proceeds. Changing relative sea level also has a major control on facies distribution with transgressive facies deposited as relative sea‐level rises being replaced by prograding deltaic facies during the highstand and subsequent minor relative sea‐level fall. Fluvial sediment supply and river flood events affect the rate of delta progradation, and produce low and high flow sediment deposits within the overall deltaic sequence. The low tidal flux in barrier estuaries, the muddy cohesive nature of the sediments and the prevalence of bioturbation means that primary sedimentary structures are rarely preserved in these bayhead delta facies. The depositional model of bayhead delta evolution shown by the Macquarie Rivulet delta would be widely applicable to other similar barrier estuary settings. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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16. Holocene fluvial depositional regimes of the Huab River, Skeleton Coast, Namibia.
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Walsh, Ella, Caracciolo, Luca, Ravidà, Domenico, Burrough, Sallie, and Thomas, David
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FLUVIAL geomorphology ,HOLOCENE Epoch ,OPTICALLY stimulated luminescence ,LASER spectroscopy ,HEAVY minerals ,RAMAN lasers ,SKELETON ,ACCELERATOR mass spectrometry - Abstract
Dryland fluvial systems respond to hydroclimate changes on Quaternary timescales, yet deciphering the palaeoenvironmental histories they preserve is often complex. Whilst hydrological signals are preserved in sediment stores as variations in sediment amount, character, and composition, studies in dryland settings such as Namibia that link sedimentological and compositional changes to palaeoflow are limited. Focusing on the Huab River, Skeleton Coast, this paper presents the first integrated study of textural, compositional, and stratigraphic features from a Namibian fluvial archive. Petrographic and heavy mineral assemblages from Raman laser spectroscopy are combined with lithostratigraphic and particle size analysis. Together with a chronology established through 42 optically stimulated luminescence ages, we reconstruct provenance, changes in river style, and fluvial response to climate. The Huab lithostratigraphic record details periods of flashy ephemeral flow interbedded with flow within well‐defined channels. Compositional assemblages indicate that humid conditions during the early to mid‐Holocene resulted in activation of sediment stores across the catchment. Episodic discharge within an ephemeral river from 12 to 9 ka was followed by a more sustained river flow in a channelized system from 7 to 5 ka. During the late Holocene, better hydraulic sorting, increased mechanical breakdown of polycrystalline grains, and flash flood lithofacies suggest that flow occurred within a more arid climate. This fine‐scaled analysis of an ephemeral fluvial system indicates the utility of assessing compositional changes to distinguish between depositional regimes. This is an important approach for reconstructing fluvial response to climate and for obtaining palaeoenvironmental records from complex sedimentary archives in dryland river settings. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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17. Alluvial fan development during the Holocene in the Qu'Appelle Valley, Saskatchewan.
- Author
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Hardenbicker, Ulrike Maria, Kelly, Christina L., Watanabe, Makiko, and Kotowich, Roberta
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ALLUVIAL fans ,FOSSIL microorganisms ,HOLOCENE Epoch ,SURFACE stability ,SEDIMENT transport ,DRILL core analysis - Abstract
Copyright of Canadian Geographer is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2022
- Full Text
- View/download PDF
18. Petrographic study of the pottery of hunter–gatherers from the lower basin of the Colorado river (Argentina) during the Late Holocene.
- Author
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Borges Vaz, Erika and Pereyra Domingorena, Lucas
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HOLOCENE Epoch ,POTTERY ,WATERSHEDS ,HUNTER-gatherer societies ,GEOLOGICAL research - Abstract
This paper presents the first petrographic study of pottery made by hunter–gatherer societies that inhabited the eastern Pampa–Patagonia transition regions (Buenos Aires province, Argentina), between c.1900 and 400 radiocarbon‐years bp. The data show that the potters maintained technical choices during this period as part of a technological tradition. With this common knowledge, local fabric recipes coexisted linked to the regularity of the use of raw materials in accordance with the geology of the research area. Furthermore, the finding of archaeological clay doughs would indicate the in situ production of vessels in the residential contexts of these pre‐Hispanic populations. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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19. Investigating hafting and composite tool repair as factors creating variability in backed artefacts: Evidence from Ngungara (Weereewa/Lake George), south‐eastern Australia.
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Way, Amy Mosig, Koungoulos, Loukas, Wyatt‐Spratt, Simon, and Hiscock, Peter
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LAKES ,HOLOCENE Epoch ,CONTINENTS ,REGIONAL differences ,IMPORTS - Abstract
Copyright of Archaeology in Oceania is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2023
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20. Late Pleistocene to Holocene vegetation and climate changes in northwestern Chukotka (Far East Russia) deduced from lakes Ilirney and Rauchuagytgyn pollen records.
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Andreev, Andrei A., Raschke, Elena, Biskaborn, Boris K., Vyse, Stuart A., Courtin, Jeremy, Böhmer, Thomas, Stoof‐Leichsenring, Kathleen, Kruse, Stefan, Pestryakova, Lyudmila A., and Herzschuh, Ulrike
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VEGETATION dynamics ,CLIMATE change ,PLEISTOCENE Epoch ,HOLOCENE Epoch ,POLLEN ,CYPERUS ,POTAMOGETON - Abstract
This paper presents two new pollen records and quantitative climate reconstructions from northern Chukotka documenting environmental changes over the last 27.9 ka. Open tundra‐ and steppe‐like habitats dominated between 27.9 and 18.7 cal. ka BP. Betula and Alnus shrubs might have grown in sheltered microhabitats but disappeared after 18.7 cal. ka BP. Although the climate was rather harsh, local herb‐dominated communities supported herbivores as is evident by the presence of coprophilous spores in the sediments. The increase in Salix and Cyperaceae ~16.1 cal. ka BP suggests climate amelioration. Shrub Betula appeared ~15.9 cal. ka BP, and became dominant after ~15.52 cal. ka BP, whilst typical steppe communities drastically reduced. Very high presence of Botryococcus in the Lateglacial sediments reflects widespread shallow habitats, probably due to lake level increase. Shrub Alnus became common after ~13 cal. ka BP reflecting further climate amelioration. Simultaneously, herb communities gradually decreased in the vegetation reaching a minimum ~11.8 cal. ka BP. A gradual decrease of algae remains suggests a reduction of shallow‐water habitats. Shrubby and graminoid tundra was dominant ~11.8–11.1 cal. ka BP, later Salix stands significantly decreased. The forest‐tundra ecotone established in the Early Holocene, shortly after 11.1 cal. ka BP. Low contents of green algae in the Early Holocene sediments likely reflect deeper aquatic conditions. The most favourable climate conditions were between ~10.6 and 7 cal. ka BP. Vegetation became similar to the modern after ~7 cal. ka BP but Pinus pumila came to the Ilirney area at about 1.2 cal. ka BP. It is important to emphasize that the study area provided refugia for Betula and Alnus during MIS 2. It is also notable that our records do not reflect evidence of Younger Dryas cooling, which is inconsistent with some regional environmental records but in good accordance with some others. [ABSTRACT FROM AUTHOR]
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- 2021
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21. Impact of climate change on sedimentation processes in the eastern Gulf of Finland during the Middle to Late Holocene.
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Ryabchuk, Daria V., Sergeev, Alexander Yu., Prishchepenko, Diana V., Zhamoida, Vladimir A., Elkina, Daria V., Piskarev, Alexey L., Bashirova, Leyla D., Ponomarenko, Ekaterina P., Budanov, Leonid M., Grigoriev, Andrey G., and Evdokimenko, Anton V.
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HOLOCENE Epoch ,SEDIMENTARY basins ,CLIMATE change ,SEDIMENTATION & deposition ,LAKES ,HYPOXIA (Water) ,CLAY - Abstract
This paper presents the results of high‐resolution sedimentological analyses of sediment cores from the eastern Gulf of Finland (Baltic Sea). Sampling sites in the periphery of sedimentary basins were selected on the basis of acoustic profiling analyses. The research allowed tracing of the transition from the freshwater Ancylus Lake to the Littorina Sea. A specific transitional layer of 'blue clays', indicating the first stage of brackish water inflow into the Gulf of Finland, was dated to 9.1 ka BP. The date of first appearance of Littorina silty clay sedimentation was as follows: from 8.0 ka BP near Gogland Island, from 7.0 ka BP near Moshchny Island and from 5.9 ka BP near the Berezovye Islands. Holocene cycles of hypoxia, associated with periods of warming, were identified and cycles of 'warming – transgression – anoxic conditions' and 'cooling – regression – oxygen‐rich conditions' were revealed. During the first stage of Littorina transgression (8.0–7.0 ka BP), the near‐bottom environment in the deepest sedimentary basin of the eastern Gulf of Finland was characterized by oxygen deficiency. In contrast, 7.0–6.0 ka BP was dominated by oxygen‐rich conditions and active processes of bioturbation. Anoxic conditions occurred again from 6.0–4.8 ka BP (Holocene Climatic Optimum), resulting in the accumulation of undisturbed silty clays with subhorizontal lamination. The interval from 4.8–2.0 ka was then characterized by oxygen‐rich near‐bottom conditions favourable for benthic organisms. The grain‐size distributions throughout the sediment cores from the easternmost sedimentary basins suggest a relative lowering of the sea level from 3.5–1.8 ka and a rise after 1.8 ka BP. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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22. The Anthropocene and Geography III: Future Directions.
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Castree, Noel
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EARTH sciences ,GEOGRAPHICAL research ,ANTHROPOCENE Epoch ,GEOGRAPHERS ,HOLOCENE Epoch ,DEBATE - Abstract
This is the last of three papers that explore the relevance of 'the Anthropocene' (and the related idea of 'planetary boundaries') to present and future research in Geography. The first paper (The Anthropocene and Geography I: The back story) summarised the origins and evolution of the proposition that the Holocene has ended. The second paper (The Anthropocene and Geography II: Current contributions) then mapped-out the relatively few, but varied, contributions that geographers have so far made to assessing or advancing this proposition. This final instalment looks ahead. It offers readers informed speculation on how future discussions of the Anthropocene might take shape in Geography. These discussions may matter for a great many others besides geographers in the years ahead. Given their epochal meanings and enormous implications for humans, the Anthropocene and planetary boundaries ideas stand to become societal keywords that, along with some other collateral terms, might organise debate and action about one of the greatest human questions, namely: 'how should we live?'. [ABSTRACT FROM AUTHOR]
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- 2014
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23. Late Quaternary record of Indian summer monsoon‐induced stratification and productivity collapse in the Andaman Sea.
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Sijinkumar, A. V., Nath, B. Nagender, Clemens, Steven, Gayathri, N. M., and Miriyala, P.
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YOUNGER Dryas ,SUMMER ,HOLOCENE Epoch - Abstract
During each summer monsoon, the northeastern Indian Ocean receives a huge amount of rain and river discharge, resulting in strong stratification and prevalence of oligotrophic conditions. These water column changes impact upper ocean productivity which is reflected in the planktonic foraminifera distribution, providing an opportunity to study the effect of monsoon forcing and stratification history. Analogous to modern‐day stratification, very intense water column stratification and productivity collapse were observed associated with Indian summer monsoon (ISM) evolution. This paper reports significant stratification events during MIS 3 (37.0 to 33 and 27 to 24 cal ka), Bølling/Allerød (B/A), early Holocene (10.0 to 8.0 cal ka) and mid‐Holocene (7.0 to 5.0 cal ka) which slowly muted upwelling and productivity. The deglacial intensification of the ISM started in the early stages of the Bølling/Allerød (B/A) followed by slight weakening during the Younger Dryas and regained strength during the early Holocene, coinciding with the highest summer insolation at 30°N. A progressive decline in the abundances of productivity and salinity proxies from 4.2 to 2.0 cal ka suggests a gradual weakening of the ISM. The late Quaternary productivity variations in the Bay of Bengal and the Andaman Sea are primarily controlled by salinity‐related stratification. [ABSTRACT FROM AUTHOR]
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- 2021
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24. The missing Myopus: plugging the gaps in Late Pleistocene small mammal identification in western Europe with geometric morphometrics.
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Arbez, Louis, Royer, Aurelien, Schreve, Danielle, Laffont, Remi, David, Serge, and Montuire, Sophie
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PLEISTOCENE Epoch ,MORPHOMETRICS ,FOSSIL teeth ,FOSSILS ,HOLOCENE Epoch ,ARCHAEOLOGICAL geology - Abstract
Lemmus and Myopus are two lemming species with distinct habitat requirements but which show very similar dental morphologies. They are thus extremely difficult to distinguish from one another in the fossil record on the basis of their dental remains, leading to poor understanding of the palaeobiogeographical evolution of Myopus as well as inaccurate palaeoenvrionmental reconstructions. Currently, the presence of Myopus in the fossil register from the Pleistocene is still debated and no firm occurrence of this lemming in western Europe has yet been confirmed for the Late Pleistocene. In this paper, we used geometric morphometrics on modern material to establish morphological differences between Lemmus and Myopus teeth (first lower and third upper molars). Morphological data were then used to build a robust linear discriminant model able to confidently classify isolated teeth of these two genera, and finally, linear discriminant models were used on fossil remains of Lemmus/Myopus from two Late Pleistocene archaeological/palaeontological sites (Grotte des Gorges and Gully Cave). This study demonstrates, for the first time, the presence of Myopus schisticolor in west European Late Pleistocene sites between the end of Marine Isotope Stage 3 and the beginning of the Holocene, during climatic events that favoured the development of taiga forest of birch and pine in these regions. [ABSTRACT FROM AUTHOR]
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- 2021
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25. Loess deposits in the Tajik Basin, Central Asia: chronology, provenance and palaeoclimatic implications since the Last Glacial.
- Author
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Tian, Shengchen, Sun, Jimin, Zhang, Zhiliang, Abdulov, Sherzod, Cao, Mengmeng, Gadoev, Mustafo, and Oimahmadov, Ilhomjon
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LOESS ,OPTICALLY stimulated luminescence ,WESTERLIES ,HOLOCENE Epoch ,GLACIATION ,PROVENANCE (Geology) - Abstract
The thick loess deposits in Tajikistan are important archives for palaeoclimatic reconstruction in Central Asia during the Quaternary. To date however, adequate high‐resolution studies of chronology and climatic evolution of the Tajik loess have still not been carried out. In this paper, chronology, dust provenance, and palaeoclimatic significance of a loess section in the centre of the Tajik Basin has been studied. Optically stimulated luminescence (OSL) dating yields ages ranging from ~60.8 to 0.8 ka, indicating that this loess section accumulated during the Last Glacial period and the Holocene. The provenance of the Tajik loess includes dust transported by westerly winds from the upwind deserts in Turkmenistan, and minor proximal particles derived from alluvial sediments of the nearby mountains and fluvial/glacifluvial deposits on the river flood‐plains. Multiple palaeoclimatic proxies including colour, particle size, environmental magnetic parameters, and element concentrations together with their correlation with the deep‐sea δ18O record suggest that the Tajik loess accumulated during cold and dry stadial periods, while palaeosols formed during warm and moist interglacials or interstadials, which is similar to the Chinese Loess Plateau. Although the two regions have different dust provenances and wind systems, such similarity indicates that the palaeoclimatic variations in both regions might be forced by a common global factor, e.g. the global ice volume. Variations in global ice volume influenced the climate in Tajikistan and the Loess Plateau through affecting the westerlies and the East Asian Monsoon, respectively. [ABSTRACT FROM AUTHOR]
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- 2021
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26. Inherited periglacial geomorphology of a basalt hill in the Sudetes, Central Europe: Insights from LiDAR‐aided landform mapping.
- Author
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Migoń, Piotr, Jancewicz, Kacper, and Kasprzak, Marek
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SOLIFLUCTION ,GEOMORPHOLOGY ,BASALT ,DIGITAL elevation models ,SEDIMENT transport ,LANDFORMS ,HOLOCENE Epoch - Abstract
This paper presents the results of mapping inherited cold‐climate landforms and deposits at the Muchów Hills site in the Sudetes, Central Europe (51°N). Bedrock supporting the upper slopes is basalt, with well‐developed columnar jointing, and local relief is of the order of 100 m, whereas the middle and lower slopes are underlain by glacigenic deposits. Characteristic cold‐climate landforms include rock cliffs, talus aprons, mid‐slope benches, solifluction sheets and lobes, and are integrated into sediment transport systems linking bedrock elevations with the adjacent plain. Ground identification of these features may be ambiguous, but the interpretation of high‐resolution LiDAR Digital Terrain Modeling data helped to provide a comprehensive spatial picture. Reasons for partial remodeling of inherited periglacial landforms in the Muchów Hills include biogeomorphological activity throughout the Holocene, mainly tree uprooting and resultant regolith mixing. [ABSTRACT FROM AUTHOR]
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- 2020
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27. Revision of the occurrence of muskox (Ovibos moschatus Zimmermann 1780) from the Gravettian of Arbreda Cave (Serinyà, northeastern Iberian Peninsula): new insights for the study of Iberian cold‐adapted faunas.
- Author
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Rufí, Isaac, Drucker, Dorothée G., Bocherens, Hervé, Lloveras, Lluís, Madurell‐Malapeira, Joan, Maroto, Julià, Soler, Joaquim, and Soler, Narcís
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PENINSULAS ,COLD adaptation ,MOUNTAINS ,CAVES ,HOLOCENE Epoch ,STEPPES ,HERBIVORES - Abstract
During the Last Glacial cycle (MIS 4 to MIS 2), the isthmic Pyrenees mountain range acted as a biogeographical barrier, effectively restricting faunal exchanges to its western and eastern terminations. The study of the composition of megaherbivore communities has revealed the transitional character of the Cantabrian region (northwest Iberian Peninsula) during the MIS 3, between western European cold faunas and southern Iberian temperate faunas. In the Catalan area (northeastern Iberian Peninsula), cold‐adapted faunas are frequently recorded during the cold pulses of MIS 3 and MIS 2, albeit to a lesser extent. In the present paper, we provide the first direct evidence of a muskox record in the Iberian Peninsula, together with a morphometric study and the results of collagen δ13C and δ15N analysis. The results reveal that the Arbreda specimen fits biometrically within the Late Holocene Umingmak specimens (Banks Island, Canada). Moreover, its isotopic values fall into the range of Late Pleistocene Mammoth steppe muskoxen, which indicates a typical ecological behaviour for muskox. Indeed, it suggests a niche partitioning of this cold‐adapted specimen in relation to other Gravettian Iberian fauna. Chronologically, this occurrence is interpreted as an isolated southward expansion of the biogeographical limits of muskox during the Greenland Stadial 4, in the latest MIS 3. [ABSTRACT FROM AUTHOR]
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- 2020
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28. Holocene relative shore level changes and Stone Age hunter‐gatherers in Hiiumaa Island, eastern Baltic Sea.
- Author
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Rosentau, Alar, Nirgi, Triine, Muru, Merle, Bjursäter, Stefan, Hang, Tiit, Preusser, Frank, Risberg, Jan, Sohar, Kadri, Tõnisson, Hannes, and Kriiska, Aivar
- Subjects
STONE Age ,HOLOCENE Epoch ,GLACIAL isostasy ,HUNTER-gatherer societies ,LANDSCAPES ,SHORELINES - Abstract
Holocene relative shore level (RSL) changes and Stone Age palaeogeography of Hiiumaa Island are reconstructed using airborne LiDAR elevation data, sedimentological and archaeological proxies as well as GIS‐based landscape modelling. Altogether, 38 RSL index and limiting points are used in modelling and presented in the current paper. The highest raised shorelines of the Ancylus Lake and Litorina Sea, mapped at the elevations of 47 and 26 m a.s.l., formed around 10.3 and 7.4 cal. ka BP, respectively. The reconstructed RSL curve reveals a 20‐m drainage of Ancylus Lake followed by a land‐uplift‐driven 3‐m regression during the Initial Litorina Sea period. RSL rise during the Litorina Sea transgression remained below 4 m and its maximum was reached later than proposed previously, discarding therefore the idea of highly diachronous Litorina culmination in the eastern Baltic Sea. During the period 7.4–6.0 cal. ka BP,RSL fall was about 4.3 mm a−1, and afterwards in average at about 1 mm‐1 less suggesting deceleration in isostatic rebound. suggesting deceleration in isostatic rebound. Palaeogeographical reconstructions show that during its earliest occupation at about 7.6 cal. ka BP less than 1% of the terrain of Hiiumaa was above the sea level and that wind‐protected SE exposed shores were the most preferred campsite locations of Late Mesolithic and Neolithic settlers. These campsites are located successively at lower elevations following the shoreline retreat and show repeated use of this coastal area between 7.6 and 4.6 cal. ka BP. Due to the spread of the Corded Ware culture around 4.8–4.0 cal. ka BP the settlements of Hiiumaa Island and many other coastal areas of the eastern Baltic moved from the coast to more suitable places for agriculture and animal husbandry. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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29. The natural history of the fallow deer, Dama dama (Linnaeus, 1758) in Bulgaria in prehistory and new evidence for the existence of an autochthonous Holocene population in the Balkans.
- Author
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Karastoyanova, Nadezhda, Gorczyk, John, and Spassov, Nikolai
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FALLOW deer ,HOLOCENE Epoch ,NATURAL history ,PREHISTORIC peoples ,IRON Age ,ANIMAL wintering - Abstract
The fallow deer (Dama dama Linnaeus, 1758) has a long history of interaction with prehistoric humans. Beginning in the Neolithic, humans introduced fallow deer to several areas of the eastern Mediterranean and mainland Europe, with later additional importing happening in the Bronze and Iron Ages. However, in some parts of southeastern Europe, autochthonous populations of extant fallow deer may have survived through the end of the Pleistocene and into the early Holocene, making them available for exploitation by Neolithic and Chalcolithic communities. Climatic and vegetational regimes favourable to fallow deer covered nearly all of Bulgaria during this period; yet, the heavy use of the species by human communities was restricted to a very small area around southeastern Bulgaria. Eventually, climate deterioration, habitat change and overhunting led to the decline of fallow deer in later prehistory in Bulgaria. This paper offers a discussion of the environmental and cultural background of human‐fallow deer interactions from the sixth to fourth millennium BCE in Bulgaria. Using bivariate scatterplots and log ratio techniques, we demonstrate that Neolithic and Chalcolithic communities exploited a large extant fallow‐deer population, appearing to target both males and females equally. Our results are the first step in a larger archaeological investigation of human‐fallow deer relations that unfolded over several millennia, touching upon issues of settlement, migration and perhaps even taming or domestication. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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30. Statistical modeling of changes in relative sea level in Maine during the Holocene Era Statistical modeling of changes in relative sea level in Maine during the Holocene Era.
- Author
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Altman, N. S., Balco, G., Crainiceanu, C., Gehrels, W. R., Qiu, J., Staudenmayer, J., and Sullivan, P.
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SEA level ,HOLOCENE Epoch ,STATISTICAL models (Nuclear physics) ,LAND use planning - Abstract
Understanding past relative sea-level changes is important to a number of social and scientific questions, including the effects of global climate change and future land-use planning under scenarios of accelerated sea-level rise with a concomitant increased threat to coastal areas around the world. In particular, accurately characterizing millennial sea-level changes is important in evaluating vertical movements of the Earth's crust that happen in response to the advances and retreats of ice sheets during long-term climatic cycles. In this paper, we analyze sea-level data from several Maine salt marshes previously reported in a paper from the geological literature. We address these data and questions of geological interest with a 'smooth transition' model. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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31. 'Holocene history of the eastern side of Novaya Zemlya from glaciomarine sediment records in the Tsivol'ki Fjord': Comments.
- Author
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Taldenkova, Ekaterina
- Subjects
FJORDS ,HOLOCENE Epoch ,SEA ice drift ,FOSSIL microorganisms ,GLACIERS ,SEDIMENTS ,ICE calving - Abstract
Similar to planktic foraminifers, findings of bivalves in core sediments are occasional, in this case, largely owing to the small core diameter (sample size) and the relatively large size of valves in comparison with foraminifers and ostracods. ([8]) mix the terms "total abundance" and "species diversity", as is evident from this sentence on p. 10: 'The number of species is on average 22 specimens per g of sediment, and the number of their species is on average 11 species in sample'. ([8]) that the drop in the total abundance and diversity of benthic foraminifers during I c i . 3.6 to 4.6 cal. ka BP probably corresponds to the growing discharge of glacier suspended load and the dilution of microfossils with this material. Korsun & Hald ([4]) studied modern benthic foraminifers and sediments of the northern Novaya Zemlya fjords with tidewater glaciers. [Extracted from the article]
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- 2023
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32. Recent advances in paleoclimatological studies of Arctic wedge‐ and pore‐ice stable‐water isotope records.
- Author
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Porter, Trevor J. and Opel, Thomas
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SEA ice ,CLIMATOLOGY ,ISOTOPES ,STABLE isotopes ,ATMOSPHERIC temperature ,HOLOCENE Epoch ,ICE cores ,ICE - Abstract
Late Pleistocene and Holocene ground ice are common throughout the Arctic. Some forms of relict ground ice preserve local meteoric water, and their stable oxygen‐ and hydrogen‐isotope ratios can be used to reconstruct past air temperatures. In this paper, we review the formation and sampling of two forms of relict ground ice—wedge ice and pore ice—and recent (2010–2019) advances in paleoclimatological studies of ground‐ice stable isotope records in the Arctic. Recent advances are attributed to better chronological constraints and refined understandings of the systematics and seasonality of relict wedge ice and pore ice. A rich network of ice‐wedge records has emerged, primarily from the Siberian Arctic, whereas pore‐ice records are less common. The ice‐wedge network depicts a robust pattern of late Pleistocene cooling, and remarkably similar temperature depressions during Marine Isotope Stages 3 and 2. Very high‐resolution wedge‐ and pore‐ice stable isotope chronologies have been established recently and used to reconstruct winter and summer climate histories and to assess seasonal dependencies in insolation‐forced climate. Reports of ancient (>125 ka BP) ground ice demonstrate its long‐term persistence, and its potential to expand our knowledge of Quaternary climate dynamics in the terrestrial Arctic. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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33. Great Basin Paleoclimate and Aridity Linked to Arctic Warming and Tropical Pacific Sea Surface Temperatures.
- Author
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Lachniet, Matthew S., Asmerom, Yemane, Polyak, Victor, and Denniston, Rhawn
- Subjects
OCEAN temperature ,PALEOCLIMATOLOGY ,HOLOCENE Epoch ,YOUNGER Dryas ,INTERGLACIALS ,TREE-rings ,SEA ice - Abstract
The arid southwestern United States is susceptible to sustained droughts that impact water resources and economic activity for millions of residents. Previous work has not systematically investigated the structure, timing, and possible forcings of Holocene Great Basin sub‐orbital hydroclimate changes, impeding our ability to understand the potential future controls on Southwestern aridity. The objective of this paper is to constrain the potential forcings on Holocene aridity and temperature, via comparison of new high‐resolution speleothem data, an Aridity Index synthesizing hydroclimate records, and linkages of Southwestern paleoclimate to other regions. The high‐resolution data from Leviathan Cave provide a paleoclimate record since 13,400 yr ago: A cool Younger Dryas was followed by two pronounced Middle Holocene aridity intervals between 9,850 and 5,310 yr B2k characterized by low growth rates and high δ18O and δ13C values. Subsequently, stalagmite δ18O values show near‐modern levels for the last four millennia during which time growth rates were high and δ13C values were low in response to wetter conditions. The regional Aridity Index documents that Middle Holocene drying coincided with a warm Arctic and decreased sea ice extent, a warm western tropical Pacific, and a large sea surface temperature gradient across the tropical Pacific, all of which likely responded to northern hemisphere summer insolation forcing. Our data suggest that extreme Middle Holocene aridity is more severe than the short medieval droughts evident in the tree ring record, and such extreme aridity may represent a worst‐case analog for future climate. Key Point: We show from a high‐resolution speleothem record from Nevada and a regional Aridity Index that early to Middle Holocene aridity was associated with reduced arctic sea ice extent and a warm tropical Pacific Ocean driven by northern hemisphere summer insolation [ABSTRACT FROM AUTHOR]
- Published
- 2020
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34. Seasonal precipitation variability on Svalbard inferred from Holocene sedimentary leaf wax δ2H.
- Author
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Kjellman, Sofia E., Thomas, Elizabeth K., Farnsworth, Wesley R., Cowling, Owen C., Allaart, Lis, Brynjólfsson, Skafti, and Schomacker, Anders
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PRECIPITATION variability ,HOLOCENE Epoch ,ATMOSPHERIC circulation ,LAKE hydrology ,SEASONS - Abstract
Svalbard spans large climate gradients, associated with atmospheric circulation patterns and variations in ocean heat content and sea ice cover. Future precipitation increases are projected to peak in the northeast and to mainly occur in winter, but uncertainties underscore the need for reconstructions of long‐term spatial and temporal variations in precipitation amounts and seasonality. We use lipid biomarkers from four sedimentary lake records along a climatic gradient from western to northeastern Svalbard to reconstruct Holocene water cycle changes. We measured the leaf wax hydrogen isotopic composition of long‐chain (terrestrial) and mid‐chain (aquatic) n‐alkanoic acids, reflecting δ2H of precipitation (δ2Hprecip) and lake water (δ2Hlake), respectively. δ2Hprecip values mainly reflect summer precipitation δ2H and evapotranspiration, whereas δ2Hlake values can reflect various precipitation seasonality due to varying lake hydrology. For one lake, we used the difference between δ2Hprecip and δ2Hlake (εprecip‐lake) to infer summer evapotranspiration changes. Relatively 2H‐enriched δ2Hprecip values and higher εprecip‐lake in the Early and Middle Holocene suggest warm summers with higher evapotranspiration, and/or more proximal summer moisture. After c. 6 cal. ka BP, 2H‐depleted δ2Hprecip values and lower εprecip‐lake indicate summer cooling, less evapotranspiration, or more distally derived moisture. Early to Middle Holocene decrease in δ2Hlake values in two northern Spitsbergen lakes reflects an increase in the proportion of winter relative to summer precipitation, associated with regional warming and increased moisture supply, which may be due to increased distal moisture supply and/or reduced sea ice cover. Our northern Svalbard δ2Hlake records suggest great Late Holocene climate variability with periodic winter precipitation increases or decreases in summer precipitation inflow to the lakes. We find that Holocene summer precipitation δ2H values mainly follow changes in summer insolation and temperature, whereas the seasonal distribution of precipitation is sensitive to catchment hydrology, regional ocean surface conditions, and moisture source changes. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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35. Younger Dryas and Early Holocene ice‐margin dynamics in northwest Russia.
- Author
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Boyes, Benjamin M., Pearce, Danni M., Linch, Lorna D., and Nash, David J.
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YOUNGER Dryas ,HOLOCENE Epoch ,ICE sheets ,LANDFORMS ,CLIMATE change ,MELTWATER ,SUBGLACIAL lakes - Abstract
The dynamics of the last Fennoscandian Ice Sheet (FIS) are relatively well constrained in the Nordic countries. Ice‐sheet dynamics in NW Russia, however, are comparatively less well understood owing to the scale and resolution of existing studies. New large‐scale glacial geomorphological datasets from NW Russia based on high‐resolution remotely sensed imagery allow for an independent reassessment of the extent and dynamics of the FIS during the Younger Dryas and Early Holocene (c. 12.9–10 ka) in NW Russia. The reconstruction provides a more detailed link between geomorphological expressions of palaeoglaciation than previous proposals. Rather than a continuous Younger Dryas ice marginal zone (IMZ) stretching from Finland to northern Norway, the geomorphological signature of NW Russia reveals 14 IMZs that document discrete stationary ice‐margin positions (possibly standstill and/or readvance events) during the overall retreat. The relative age sequence of the IMZs, supported by an updated numerical age database, suggests that they formed time‐transgressively during the Younger Dryas and Early Holocene rather than contemporaneously. Moreover, specific landform assemblages reveal contrasting glacial landsystems in NW Russia: (i) a northern subpolar glacial landsystem; and (ii) a southern temperate glacial landsystem. The model presented herein provides robust empirical constraints for testing and validating numerical ice‐sheet models and understanding ice‐sheet responses to rapid climate change. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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36. Multi‐proxy palaeoenvironmental reconstruction of the Skagerrak from the Lateglacial to Middle Holocene.
- Author
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Ownsworth, Emma, Moros, Matthias, Lloyd, Jeremy, Bennike, Ole, Jensen, Jørn Bo, Blanz, Thomas, and Selby, David
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HOLOCENE Epoch ,X-ray fluorescence ,RADIOCARBON dating ,GRAIN size ,ACCELERATOR mass spectrometry ,FORAMINIFERA ,FOSSIL microorganisms - Abstract
This study uses a multiproxy approach including the first use of 187Os/188Os, %C37:4 biomarkers, carbonate content, sedimentological grain size, geochemical X‐ray fluorescence and microfossil benthic foraminifera species combined with radiocarbon dating, measured on six cores from across the Skagerrak, in order to study the Lateglacial to Middle Holocene history of the area. A new chronostratigraphic framework is developed based on the appearance of specific benthic foraminifera species along with changes in carbonate/X‐ray fluorescence and grain size data. This allowed the correlation of cores based on a series of radiocarbon dated tie points. Analysing the cores together reveals several events recorded in the Skagerrak including: (i) an increased freshwater input (bracketed between 13.3 and 11.3 cal. ka BP) signified by radiogenic 187Os/188Os values, high %C37:4 values and an increase in sand content; (ii) the Glomma drainage event, signified by a sudden appearance of Valvulineria as well as higher %C37:4; and (iii) the opening of the Danish Straits and English Channel leading to the development of modern‐day conditions and circulation patterns in the Skagerrak, signified by the appearance of Hyalinea balthica and a fall in %C37:4. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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- View/download PDF
37. Late Quaternary meltwater pulses and sea level change.
- Author
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Harrison, Stephan, Smith, David E., and Glasser, Neil F.
- Subjects
MELTWATER ,ABSOLUTE sea level change ,LAST Glacial Maximum ,ENVIRONMENTAL sciences ,HOLOCENE Epoch - Abstract
After the Last Glacial Maximum (LGM) global mean sea level (GMSL) rise was characterized by rapid increases over short (decadal to centennial) timescales superimposed on a longer term secular rise and these have been termed meltwater pulses (MWPs). In this paper we review the timing, impact and nature of these and the effects of rapid drainage of large post‐glacial MWPs into the world's oceans. We identify nine MWPs, four of which occurred in three periods of rapid sea level rise (19.5–18.8, 14.8–13.0 and 11.5–11.1 ka BP). The rest are dated to the period during the Early Holocene sea level rise after 11 ka BP. We show that drainage of the known post‐glacial lakes in total produced less than around 1.2 m of the 125 m of GMSLR since the LGM. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
38. Holocene climate vs. catchment forcing on a shallow, eutrophic lake in eastern Poland.
- Author
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Zawiska, Izabela, Apolinarska, Karina, and Woszczyk, Michał
- Subjects
CLIMATE change ,HOLOCENE Epoch ,FOSSIL cladocera ,EUTROPHICATION - Abstract
This paper presents a sedimentary record from Lake Łukie located in the southeastern part of the Central European Plain, beyond the reach of the maximum extent of the last glaciation. The lake has thermokarstic origin and developed during the last glacial termination due to subsidence of the sub‐Quaternary carbonate basement triggered by permafrost thawing. A sediment core was investigated to reconstruct water trophic state and lake depth changes during the Holocene. We aimed at showing the relationship between ecological and geochemical changes in the lake and regional/supraregional climatic and hydrological trends throughout the Holocene. Results of subfossil Cladocera analysis were combined with data on the geochemistry and stable C and O isotopes in sedimentary carbonates. Isotopic and geochemical proxies helped to detect sources of sedimentary particles in the lake and thus to reconstruct changes in the intensity of atmospheric and catchment processes (e.g. precipitation and surface runoff). The Cladocera analysis results indicated endogenic processes in the lake such as trophic changes. Our data revealed that Lake Łukie has always been a rather eutrophic water body and the periods of particularly high productivity were in the lower Preboreal and upper Subatlantic. Periods of increased water depth were recorded in the lower Preboreal, lower Boreal and upper Subboreal, whereas low water stands were obtained during the late Preboreal, late Boreal, late Atlantic and Atlantic/Subboreal transition as well as during the lower Subboreal. The sediment succession from Lake Łukie provides the first full Holocene record of carbon and oxygen stable isotopes in lacustrine carbonates from the eastern part of the Central European Lowland. The record is characterized by uncommonly high δ13C and δ18O values of the carbonates resulting from a combination of within‐lake processes and dissolution of the carbonate bedrock of Cretaceous age. The impact of the old carbonates on isotope values was helpful in the reconstruction of the catchment forcing on the lake. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
39. Human biogeography and faunal exploitation in Diamante River basin, central western Argentina.
- Author
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Otaola, Clara, Giardina, Miguel A., and Franchetti, Fernando R.
- Subjects
WATERSHEDS ,HOLOCENE Epoch ,HUNTER-gatherer societies ,BIOGEOGRAPHY ,ZOOARCHAEOLOGY - Abstract
A biogeographic model used to describe human peopling of southern Mendoza, central western Argentina, proposed an intensification process activated by an increase in population growth rate during the Late Holocene. During this process, high‐ranked resources at the surroundings of residential camps were depleted, and hunter–gatherers broadened their diet by incorporating a larger number of low‐ranked prey and domesticated plant resources. In this paper, we evaluate an alternative hypothesis, focusing on zooarchaeological data from the Diamante River basin. The results show that faunal resource intensification does not appear to have occurred in the Diamante River basin during the Late Holocene. Faunal consumption in Diamante River basin mainly reflects the local fauna in each ecological zone. The data do not show a lack of higher ranked resources. We suggest it is more likely that the demographic increase was not significant enough to cause an impact on the faunal resources. The archaeological evidence should be improved and analysed in smaller scales to continue with the intensification debate. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
40. First archaeogenetic results verify the mid-Holocene occurrence of Dalmatian pelican Pelecanus crispus far out of present range.
- Author
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Nikulina, Elena A. and Schmölcke, Ulrich
- Subjects
DALMATIAN pelican ,HOLOCENE Epoch ,PELICANS ,GENETIC barcoding ,CLIMATE change - Abstract
The paper presents an evaluation of subfossil bird bones from archaeological and geological sites in Europe that shows that birds of the genus Pelecanus occurred far out of their present range between 7.4 and 5.0 ka BP in the Danish archipelago. Additionally, from other northwestern European regions mid-Holocene records of pelicans are known. However, due to morphological similarities there are difficulties in species identification. In this paper ancient DNA barcoding techniques were used to clarify the species assignment of one of these records for the first time. Our results show that the bone derives from Dalmatian pelican Pelecanus crispus, a species that today breeds in 15 colonies in the eastern Mediterranean. This species identification is especially remarkable since the Dalmatian pelican is known to be less migratory. We demonstrate that the appearance and disappearance of pelicans in northwestern Europe coincide with climate parameters, since all records fall within warm periods. This applies for the larger group of Danish records during the Holocene thermal maximum in northern Europe as well as for two more groups of records from central Europe and Britain dating to 1.9 and 0.8 ka ago. Recent ecological research on the Dalmatian pelican shows that the species seems to profit from the modern climate changes and is starting to expand its range. Our paper documents that under special circumstances short-distance migrant birds are also able to expand their ranges to areas far outside of the former distribution areas. Finally, the Dalmatian pelican is presented as an indicator species reflecting special climate conditions. The present study demonstrates not only the possibility to recover avian DNA from at least 7 ka old bones, but the relevance of such genetic analysis in combination with archaeological data, particularly if bones could not be assigned to species level by morphological features. In such cases, aDNA is shown as a valuable tool for the reconstruction of the avifauna of the past. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
41. Abrupt cooling events during the Early Holocene and their potential impact on the environment and human behaviour along the southern North Sea basin (NW Europe).
- Author
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Crombé, Philippe
- Subjects
HOLOCENE Epoch ,ALLUVIUM ,CLIMATE change ,PALEOCLIMATOLOGY ,GEOLOGICAL basins - Abstract
ABSTRACT: In this paper the potential impact of the 9.3k cal a BP cooling event on the environment and human occupation in the Rhine–Meuse–Scheldt region of NW Europe is investigated. Although various environmental (decreased fluvial activity, increased wildfires and changing vegetation) and cultural changes (lithic technology, raw material circulation, decreasing site density) can be identified in the (late) Boreal, a serious problem of equifinality remains. Lacking a high‐resolution chronology for these events, it is still difficult to separate the impact of gradual from punctuated climatic changes. However, at present it seems that (some) environmental and cultural changes were already ongoing before the 9.3k cal a BP event but were accelerated by the latter. To gain a better understanding of these processes, it is necessary to take a holistic, multidisciplinary approach towards the Early Holocene in the southern North Sea basin. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
42. 10Be Exposure Ages Obtained From Quaternary Glacial Landforms on the Tibetan Plateau and in the Surrounding Area.
- Author
-
ZHANG, Mengyuan, MEI, Jing, WANG, Jian, ZHANG, Zhigang, and XU, Xiaobin
- Subjects
GLACIAL Epoch ,GLACIAL landforms ,HOLOCENE Epoch ,COSMOGENIC nuclides - Abstract
Abstract: In situ terrestrial cosmogenic nuclide (TCN) exposure dating using
10 Be is one of the most successful techniques used to determine the ages of Quaternary deposits and yields data that enable the reconstruction of the Quaternary glacial history of the Tibetan Plateau and the surrounding mountain ranges. Statistical analysis of TCN10 Be exposure ages, helps to reconstruct the history of glacial fluctuations and past climate changes on the Tibetan Plateau, differences in the timing of glacier advances among different regions. However, different versions of the Cosmic‐Ray‐prOduced NUclide Systematics on Earth (CRONUS‐Earth) online calculator, which calculates and corrects the TCN ages of Quaternary glacial landforms, yield different results. For convenience in establishing contrasts among regions, in this paper, we recalculate 184810 Be exposure ages from the Tibetan Plateau that were published from 1999 to 2017 using version 2.3 of the CRONUS‐Earth calculator. We also compare the results obtained for 159410 Be exposure ages using different versions (2.2, 2.3 and 3.0) of the CRONUS‐Earth calculator. The results are as follows. (1) Approximately 97% of the exposure ages are less than 200 ka. A probability density curve of the exposure ages suggests that greater numbers of oscillations emerge during the Holocene, and the peaks correspond to the Little Ice Age, the 8.2 ka and 9.3 ka cold events; the main peak covers the period between 12 and 18 ka. (2) In most areas, the newer versions of the calculator produce older10 Be exposure ages. When different versions of the CRONUS‐Earth calculator are used, approximately 29% of the10 Be exposure ages display maximum differences greater than 10 ka, and the maximum age difference for a single sample is 181.1 ka. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
43. Holocene permafrost history and cryostratigraphy in the High‐Arctic Adventdalen Valley, central Svalbard.
- Author
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Cable, Stefanie, Elberling, Bo, and Kroon, Aart
- Subjects
HOLOCENE Epoch ,PERMAFROST ,SOIL degradation ,MARINE sediments ,STRATIGRAPHIC geology ,PARTICLE size distribution - Abstract
This paper presents the history and cryostratigraphy of the upper permafrost in the High‐Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents, and grain‐size distribution, and were
14 C‐ and OSL‐dated. Spatial variability in ice and carbon contents is closely related to the sedimentary history and mode of permafrost aggradation. In the valley bottom, saline epigenetic permafrost with pore ice down to depths of 10.7 m depth formed in deltaic sediments since the mid‐Holocene; cryopegs were encountered below 6 m. In the top 1 to 5 m, syngenetic and quasi‐syngenetic permafrost with microlenticular, lenticular, suspended and organic‐matrix cryostructures developed due to loess and alluvial sedimentation since the colder late Holocene, which resulted in the burial of organic material. At the transition between deltaic sediments and loess, massive ice bodies occurred. A pingo developed where the deltaic sediments reached the surface. On hillslopes, suspended cryostructure on solifluction sheets indicates quasi‐syngenetic permafrost aggradation; lobes, in contrast, were ice‐poor. Suspended cryostructure in eluvial deposits reflects epigenetic or quasi‐syngenetic permafrost formation on a weathered bedrock plateau. Landform‐scale spatial variations in ground ice and carbon relate to variations in slope, sedimentation rate, moisture conditions and stratigraphy. Although the study reveals close links between Holocene landscape evolution and permafrost history, our results emphasize a large uncertainty in using terrain surface indicators to infer ground‐ice contents and upscale from core to landform scale in mountainous permafrost landscapes. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
44. An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea.
- Author
-
Petrie, Hannah E., Eide, Christian H., Haflidason, Haflidi, Brendryen, Jo, and Watton, Timothy
- Subjects
HOLOCENE Epoch ,GEOLOGY ,GAS migration ,DATA integration - Abstract
Subsurface deposits in recently glaciated marine areas are highly heterogeneous, representing a range of glacial and postglacial environments and processes including glacitectonism, overconsolidation, fluvial and lacustrine deposition, and transgression. These heterogeneities are often linked to variations in engineering properties, with important implications for the design and installation of offshore wind infrastructure. In this study we present an integrated geological characterization of the Sørlige Nordsjø II offshore wind site, located in waters of 50–70 m depth along the southern border of the Norwegian North Sea, focusing on the evolution of the area's depositional setting during the late Quaternary period and its implications for offshore wind development. We integrate interpretations from a marine geological data set acquired in 2022 with legacy 3D seismic data and a review of the current understanding of the southern North Sea's complex glacial history. A preliminary ground model and accompanying risk map for the site is presented with five main geological units: (i) homogeneous and layered marine sands covering most of the site, with patchy distribution and coarser‐grained deposits in the east; (ii) buried, layered channel deposits containing organic material and possible associated shallow gas; (iii) buried, stiff glacilacustrine clay deposits; (iv) a buried, layered, glacitectonized unit incised by tunnel valleys, with a sandy marine infill; and (v) mounded tills and glacitectonized deposits containing boulders, exposed to shallowly buried in the east. Salt diapirism and gas migration were also found to be important potential geohazards at the site. Three‐dimensional seismic attribute maps were found to be a powerful aid to understanding the distribution and genesis of seismic facies identified on 2D high‐resolution sub‐bottom profiles. This type of data integration is an under‐utilized methodology for generating detailed preliminary ground models, which can inform more cost‐effective site survey and early foundation concept planning at geologically complex offshore wind sites. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
45. Lagoa do Quari (São Raimundo Nonato, Piauí): Palaeoenvironment and wetland archaeology in Northeastern Brazil.
- Author
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Parenti, Fabio, Aimola, Giulia, Candelato, Federica, Chaves, Sérgio, Faure, Martine, Ferrari, Sonia, Guérin, Claude, Mengoli, Davide, Natali, Luca, Rioda, Vittorio, Scardia, Giancarlo, and Valli, Andrea M. F.
- Subjects
- *
BIOLOGICAL extinction , *WETLANDS , *PLEISTOCENE Epoch , *ARCHAEOLOGY , *HOLOCENE Epoch - Abstract
Northeastern Brazil has thousands of wetland fossiliferous deposits with megafauna and, in some cases, associated lithic artifacts. The timing of the arrival of humans in South America and the extinction of megafauna is still debated and these sites contribute both to this discussion and to the reconstruction of the Late Pleistocene and Holocene paleoenvironment. Lagoa do Quari, 40 km south of São Raimundo Nonato, Piauí state, is a marsh deposit in the present semiarid caatinga environment, excavated by an interdisciplinary team in 2002–2003. This paper presents the archaeological, palaeontological, geological, chronological, stratigraphical and palynological results and their implications for the Quaternary of northeastern Brazil. The site has a rich megafaunal bonebed at the bottom, dominated by Eremotherium giant sloth remains with poor biodiversity, and a sandy‐silty deposit at the top; two 14C dates constrain this latter layer to 9,944–9,557 and 6,308–6,177 cal. years BP and the associated rich lithic industry of quartz and chert shows a technical continuity throughout the Holocene in the region. Palynology describes an open landscape with periodic wet phases, which could explain the richness of the archaeological occurrences in Holocenic Brazilian prehistory. This study offers a model of interdisciplinary enquiry into the paleoenvironment and prehistory of lowland South America. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
46. Late Quaternary channel and floodplain formation in a partly confined subtropical river, eastern Australia.
- Author
-
Daley, James, Croke, Jacky, Thompson, Chris, Cohen, Tim, Macklin, Mark, and Sharma, Ashneel
- Subjects
FLOODPLAINS ,VALLEYS ,RIVERS ,HOLOCENE Epoch ,CLIMATOLOGY - Abstract
ABSTRACT Along the eastern margin of Australia, hydrological variability reaches a peak in the subtropics of south-east Queensland and many rivers have entrenched characteristics. To address the nature of entrenchment and the relationship with adjacent alluvium, this paper presents the results of detailed chrono-stratigraphic analysis of alluvial units in the partly confined mid-reaches of Lockyer Creek, Australia. Four sites were investigated using topographic, sedimentological and chronological data. Radiocarbon and single grain optically stimulated luminescence dating indicate a large proportion of the valley fill reflects a major phase of aggradation of fine-grained alluvium from ca. 35 ka throughout the Last Glacial Cold Period. Synchronous incision of Pleistocene alluvial fills between 11.5 and 9.3 ka suggests the current entrenched Lockyer Creek formed in response to changes in late Quaternary climate. Holocene floodplains set within the entrenched Pleistocene valley floor have basal ages of ca. 7.5 ka, but whose proximal margins are still actively accreting. This Holocene fill has accreted over the mid- to late Holocene but overlaps with the contemporary hydrological regime. The sedimentary nature of the Holocene fill appears to be related to persistent antecedent controls in the form of bedrock and terrace constriction. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
47. New dates for earth mounds at Weipa, North Queensland, Australia.
- Author
-
BROCKWELL, SALLY, Ó FOGHLÚ, BILLY, FENNER, JACK N., STEVENSON, JANELLE, PROSKE, ULRIKE, and SHINER, JUSTIN
- Subjects
CARBON isotopes ,HOLOCENE Epoch ,CLIMATE change ,ARCHAEOLOGICAL chronology - Abstract
Copyright of Archaeology in Oceania is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2017
- Full Text
- View/download PDF
48. From outwash to coastal systems in the Portneuf-Forestville deltaic complex (Québec North Shore): Anatomy of a forced regressive deglacial sequence.
- Author
-
Dietrich, Pierre, Ghienne, Jean‐François, Schuster, Mathieu, Lajeunesse, Patrick, Nutz, Alexis, Deschamps, Rémy, Roquin, Claude, Duringer, Philippe, and Fielding, Chris
- Subjects
GLACIAL isostasy ,INTRENCHMENTS ,GLACIAL melting ,HOLOCENE Epoch ,SEDIMENTARY basins - Abstract
Deglacial sequences typically include backstepping grounding zone wedges and prevailing glaciomarine depositional facies. However, in coastal domains, deglacial sequences are dominated by depositional systems ranging from turbiditic to fluvial facies. Such deglacial sequences are strongly impacted by glacio-isostatic rebound, the rate and amplitude of which commonly outpaces those of post-glacial eustatic sea-level rise. This results in a sustained relative sea-level fall covering the entire depositional time interval. This paper examines a Late Quaternary, forced regressive, deglacial sequence located on the North Shore of the St. Lawrence Estuary (Portneuf Peninsula, Québec, Canada) and aims to decipher the main controls that governed its stratigraphic architecture. The forced regressive deglacial sequence forms a thick (>100 m) and extensive (>100 km
2 ) multiphased deltaic complex emplaced after the retreat of the Laurentide Ice Sheet margin from the study area ca 12 500 years ago. The sedimentary succession is composed of ice-contact, glaciomarine, turbiditic, deltaic, fluvial and coastal depositional units. A four-stage development is recognized: (i) an early ice-contact stage (esker, glaciomarine mud and outwash fan); (ii) an in-valley progradational stage (fjord head or moraine-dammed lacustrine deltas) fed by glacigenics; (iii) an open-coast deltaic progradation, when proglacial depositional systems expanded beyond the valley outlets and merged together; and (iv) a final stage of river entrenchment and shallow marine reworking that affected the previously emplaced deltaic complex. Most of the sedimentary volume (10 to 15 km3 ) was emplaced during the three-first stages over a ca 2 kyr interval. In spite of sustained high rates of relative sea-level fall (50 to 30 mm·year−1 ), delta plain accretion occurred up to the end of the proglacial open-coast progradational stage. River entrenchment only occurred later, after a significant decrease in the relative sea-level fall rates (<30 mm·year−1 ), and was concurrent with the formation and preservation of extensive coastal deposits (raised beaches, spit platform and barrier sands). The turnaround from delta plain accretion to river entrenchment and coastal erosion is interpreted to be a consequence of the retreat of the ice margin from the river drainage basins that led to the drastic drop of sediment supply and the abrupt decrease in progradation rates. The main internal stratigraphic discontinuity within the forced regressive deglacial sequence does not reflect changes in relative sea-level variations. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
49. Controls on Holocene denudation rates in mountainous environments under Mediterranean climate.
- Author
-
Molliex, S., Jouet, G., Freslon, N., Bourlès, D. L., Authemayou, C., Moreau, J., and Rabineau, M.
- Subjects
HOLOCENE Epoch ,CHEMICAL denudation ,CRYSTALLINE rocks ,WEATHERING ,REGOLITH - Abstract
The Mediterranean domain is characterized by a specific climate resulting from the close interplay between atmospheric and marine processes and strongly differentiated regional topographies. Corsica Island, a mountainous area located in the western part of the Mediterranean Sea is particularly suitable to quantify regional denudation rates in the framework of a source-to-sink approach. Indeed, fluvial sedimentation in East-Corsica margin is almost exclusively limited to its alluvial plain and offshore domain and its basement is mainly constituted of quartz-rich crystalline rocks allowing cosmogenic nuclide
10 Be measurements. In this paper, Holocene denudation rates of catchments from the eastern part of the island of Corsica are quantified relying on in situ produced10 Be concentrations in stream sediments and interpreted in an approach including quantitative geomorphology, rock strength measurement (with a Schmidt Hammer) and vegetation cover distribution. Calculated denudation rates range from 15 to 95 mm ka-1 . When compared with rates from similar geomorphic domains experiencing a different climate setting, such as the foreland of the northern European Alps, they appear quite low and temporally stable. At the first order, they better correlate with rock strength and vegetation cover than with morphometric indexes. Spatial distribution of the vegetation is controlled by morpho-climatic parameters including sun exposure and the direction of the main wet wind, so-called 'Libecciu'. This distribution, as well as the basement rock strength seems to play a significant role in the denudation distribution. We thus suggest that the landscape reached a geomorphic steady-state due to the specific Mediterranean climate and that Holocene denudation rates are mainly sustained by weathering processes, through the amount of regolith formation, rather than being transport-limited. Al/K measurements used as a proxy to infer present-day catchment-wide chemical weathering patterns might support this assumption. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
50. Can people change the ecological rules that appear general across space?
- Author
-
Šizling, A. L., Pokorný, P., Juřičková, L., Horáčková, J., Abraham, V., Šizlingová, E., Ložek, V., Tjørve, E., Tjørve, K. M. C., Kunin, W., and Kerr, Jeremy
- Subjects
BIODIVERSITY ,HUMAN behavior ,SNAILS ,HOLOCENE Epoch ,PLANT remains (Archaeology) - Abstract
Aim Projections of human impact on the environment and biodiversity patterns are crucial if we are to prevent their destruction. Such projections usually involve the assumption that the same human activities always affect biodiversity in the same way, either in geographically distant areas within the same time-scale or in the same areas in different periods. In this paper, plant and snail fossils from central Europe that cover the last 12,000 years provide evidence against this assumption. Location Central Europe. Methods We examined fossil data on central European plants and snails and extracted time-series of (1) local species richness (alpha diversity) at a scale of approximately 300 m × 300 m and decays of (2) the Jaccard index and (3) Simpson's beta with increasing distance (up to approximately 400 km) through time. Results We show that two vital biodiversity patterns follow neither oxygen-isotope nor borehole temperature proxies, but instead vary between archaeologically known periods, with the most noticeable and irreversible breaks (1) when arable agriculture was introduced into central Europe, (2) when the Roman Empire collapsed, and (3) during the event known as the 12th-century colonization in central Europe. The patterns computed from data across time sometimes contradicted the patterns computed across space. Main conclusions We therefore infer that people can, and sometimes have, contributed to temporal changes in ecological rules that are seemingly general across space. Our findings indicate that the changes in ecological rules are so substantial that efforts to project future biodiversity based on space-for-time substitution might fail, unless we gain knowledge about how these general rules are altered. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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