Search results for "18"
showing 10 items of 12732 documents
Winter climate signal in boreal clastic-biogenic varves : a comprehensive analysis of three varved records from 1890 to 1990 AD with meteorological a…
2017
Clastic-biogenic varves are widely used for reconstructing past climate: in boreal environments, the accumulation of minerogenic clasts on the lake floor is generally considered a proxy for past variations in spring floods reflecting previous winter conditions. However, the physical mechanisms behind this winter climate sensitivity and the influence of catchment type on the varve formation are not fully investigated. Here, we present a winter climate record inferred from the clastic laminae of three lakes located on the region of fine-grained tills in Eastern Finland spanning from AD 1890 to 1990. The minerogenic varve data are compared with instrumental meteorological and hydrological time…
North Atlantic Oscillation recorded in carbonate δ18O signature from Lagunillo del Tejo (Spain)
2016
Abstract Oxygen (δ18O) and carbon (δ13C) isotope compositions of authigenic carbonates measured in Lagunillo del Tejo sediment document precipitation variability during the last millennium in the Iberian Range. Modern water samples show that Lagunillo δ18O and δD plot below the Global Meteoric Water Line (GMWL). Sediment samples show a covariant trend between carbonate δ18O and δ13C, indicating that the precipitation/evaporation ratio has largely controlled the isotopic composition of this lake. This covariant trend is used to extract information about past lake level changes. Humid periods occurred around AD 1300–1450, AD 1620–1775 and AD 1950–1980, while the driest periods were concentrat…
Shell sclerochronology and stable isotopes of the bivalve Anomalocardia flexuosa (Linnaeus, 1767) from southern Brazil: Implications for environmenta…
2017
Abstract This study presents the first stable isotopic and sclerochronological calibration of the bivalve Anomalocardia flexuosa (Linnaeus, 1767) in relation to environmental variables in a subtropical coastal area of southern Brazil. We investigate incremental shell growth patterns and δ18O and δ13C values of modern specimens collected alive from the Laguna Lagoonal System (LLS). Shells of Anomalocardia flexuosa are also one of the main biological components of pre-Columbian archaeological shell mounds and middens distributed along the Brazilian coastline. We therefore selected archaeological specimens from a local late Holocene shell mound (Cabecuda) to compare their stable carbon and oxy…
Digital and Handcrafting Processes Applied to Sound-Studies of Archaeological Bone Flutes
2016
Bone flutes make use of a naturally hollow raw-material. As nature does not produce duplicates, each bone has its own inner cavity, and thus its own sound-potential. This morphological variation implies acoustical specificities, thus making it impossible to handcraft a true and exact sound-replica in another bone. This phenomenon has been observed in a handcrafting context and has led us to conduct two series of experiments (the first-one using handcrafting process, the second-one using 3D process) in order to investigate its exact influence on acoustics as well as on sound-interpretation based on replicas. The comparison of the results has shed light upon epistemological and methodological…
A 2000-year record of lake ontogeny and climate variability from the north-eastern European Russian Arctic
2016
A lake sediment record from the north-eastern European Russian Arctic was examined using palaeolimnological methods, including subfossil chironomid and diatom analysis. The objective of this study is to disentangle environmental history of the lake and climate variability during the past 2000 years. The sediment profile was divided into two main sections following changes in the lithology, separating the limno-telmatic phase between ~2000 and 1200 cal. yr BP and the lacustrine phase between ~1200 cal. yr BP and the present. Owing to the large proportion of semi-terrestrial chironomids and poor modern analogues, a reliable chironomid-based temperature reconstruction for the limno-telmatic p…
Meteorological validation of chironomids as a paleotemperature proxy using varved lake sediments
2016
In order to improve the reliability of climate models in their projections for the future, spatially and temporally detailed paleoclimate proxy data are needed. In this study, we examined annually laminated sediments from Lake Nurmijärvi (Finland) for their fossil Chironomidae assemblages over a time period with available meteorological observational data (since 1830s). In doing so, we correlated chironomid-based inferences of summer air temperatures against instrumentally measured values using two different reconstruction approaches, namely, calibration-in-space (CiS, multilake training set) and calibration-in-time (CiT, calibration of time series data against meteorological data). The re…
Oxygen isotope analysis of Equus teeth evidences early Eemian and early Weichselian palaeotemperatures at the Middle Palaeolithic site of Neumark-Nor…
2019
Abstract Here we present phosphate oxygen isotope (δ 18OPO4) data from horse (Equus sp.) tooth enamel (bioapatite) from early Eemian and early Weichselian find levels at the archaeological site of Neumark-Nord 2, Germany. Based on the relationship between δ18OPO4 of bioapatite, body water, local precipitation and air temperature, these data are used to reconstruct palaeoclimatic conditions contemporary to the different phases of Neanderthal activity at the site. Bulk enamel samples representing one year of growth were taken from horse teeth from early Eemian (NN2/2b [∼121 ± 5 ka], and NN2/1c) and early Weichselian (NN2/0; ∼93 ± 7 ka) find levels, and δ18OPO4 values were then utilised to cal…
Hydroclimate variability of western Thailand during the last 1400 years
2020
Mainland Southeast Asia is located on the moisture transport route of the Indian summer monsoon (ISM) where hydroclimate records from speleothems have rarely been investigated. Here, we present a new multi-proxy (δ18O and δ13C values, trace element concentrations, and grayscale values) data set of stalagmite KPC1 from Khao Prae cave in western Thailand spanning the last 1400 years (500–1900 CE; the Common Era). These multi-proxy data reveal a high variability between the wet and dry periods during 500–850 CE and 1150–1300 CE, stable climate conditions during 850–1150 CE, and overall dry conditions since 1300 CE. The δ13C values, trace elements concentrations, and grayscale values show cente…
A tough travesía: Mobility constraints among late Holocene Patagonian hunter-gatherers through oxygen stable isotopes in enamel and water sources
2020
Central-eastern North Patagonia is characterized by a severe environmental fragmentation due to the scarce and heterogeneous distribution of fresh water. The main local wet zones, the Negro and Colorado river valleys in the North and the Somuncura Foothills in the South are separated by a large and harsh dry land, the travesia. In this paper, we assess the effects of this environmental fragmentation in the mobility of the Late Holocene hunter-gatherers through the analysis of the stable isotopes of oxygen in both enamel and water sources. We analyzed the δ18O of the enamel carbonate of 64 human teeth from 42 individuals from the Negro River valley (n = 30) and the Somuncura Foothills (n = 1…
REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH-RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND…
2012
Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high-resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high-resolution sclerochronology and a micro-milled sampling strategy for δ18O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ18O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen i…