Search results for "pit"
showing 10 items of 9314 documents
Rapid climate change during the early Holocene in western Europe and Greenland
2006
Based on microfacies analyses of seasonally laminated varved sediments from lake Holzmaar, Germany, we report evidence of decadal-to century-scale climate variability during the early Holocene. The shifts in climate are documented in the thickness variations and changes in the composition of the varves in response to subtle shifts in limnological conditions. The close similarity between the Holzmaar varve record and the GRIP oxygen isotope record during 7.4-9.0 calendar (cal.) ka suggests that the high frequency climatic variations in both regions were controlled by the same mechanism. Our more detailed studies covering the central 409-yr period (∼7.846-8.255 cal. ka, encompassing the 8.2 …
The stable isotope composition of organic and inorganic fossils in lake sediment records: current understanding, challenges, and future directions
2018
This paper provides an overview of stable isotope analysis (H, C, N, O, Si) of the macro- and microscopic remains from aquatic organisms found in lake sediment records and their application in (palaeo)environmental science. Aquatic organisms, including diatoms, macrophytes, invertebrates, and fish, can produce sufficiently robust remains that preserve well as fossils and can be identified in lake sediment records. Stable isotope analyses of these remains can then provide valuable insights into habitat-specific biogeochemistry, feeding ecology, but also on climatic and hydrological changes in and around lakes. Since these analyses focus on the remains of known and identified organisms, they …
Rhinocerotid tooth enamel 18O/16O variability between 23 and 12 Ma in southwestern France.
2006
Abstract The relationship between the oxygen isotope ratio of mammal tooth enamel and that of drinking water was used to reconstruct changes in the Miocene oxygen isotope ratio of rainfall (meteoric water δ 18 O MW ). These, in turn, are related to climatic parameters (temperature, precipitation and evaporation rate). δ 18 O values of rhinocerotid teeth from the Aquitaine Basin (southwestern France) suggest a significant climatic change between 17 and 12 Ma, characterized by cooling together with precipitation increase, in agreement with other terrestrial and oceanic records. To cite this article: I. Bentaleb et al., C. R. Geoscience 338 (2006).
Annually resolved δ<sup>2</sup>H tree-ring chronology of the lignin methoxyl groups from Germany reflects averaged Wester…
2019
Abstract. Stable hydrogen isotopes ratios of lignin methoxyl groups (expressed as δ2HLM) of wood have been shown to reflect the climate-sensitive δ2H values of precipitation (expressed as δ2Hprecip) modulated by a large uniform negative isotope fractionation. However, a detailed calibration study among temporal variabilities of δ2HLM in tree-ring series, site-specific δ2Hprecip and climate parameters has not been performed yet. Here, we present annually resolved δ2HLM values from nine tree-ring series (derived from four Fagus sylvatica L. trees) collected near stations of the Global Isotope Network of Isotopes in Precipitation (GNIP) and the Deutsche Wetterdienst (DWD) meteorological observ…
Le système palatial franc: genèse et fonctionnement dans le nord-ouest du regnum
1990
Barbier Josiane. Le système palatial franc : genèse et fonctionnement dans le nord-ouest du regnum.. In: Bibliothèque de l'école des chartes. 1990, tome 148, livraison 2. pp. 245-299.
Modern sedimentary analogues and integrated monitoring to understand varve formation in the Mediterranean Lake Montcortès (Central Pyrenees, Spain)
2018
Este artículo contiene 13 páginas, 6 figuras, 1 tabla.
A multiproxy study of Younger Dryas and Early Holocene climatic conditions from the Grabia River paleo-oxbow lake (central Poland)
2015
International audience; A multi-proxy reconstruction of water depth, temperature and precipitation inferred from Cladocera, Chironomidae and pollen assemblages has been obtained from Świerczyna paleo-oxbow (central Poland) during the Younger Dryas (YD) and Early Holocene. Results suggest that the YD was relatively cold and comprised two main phases. The first (ca. 12,500–12,000 cal. yrs BP) is characterized by a continental climatic regime and a decrease in winter temperatures and precipitation but an increase in spring/summer precipitation. The second phase (ca. 12,000–11,500 cal. yrs BP) was more mild with a variable continental climate, an increase in summer and winter temperature, a len…
Tree-ring δ2H values from lignin methoxyl groups indicate sensitivity to European-scale temperature changes
2020
Abstract Stable hydrogen isotope ratios of lignin methoxyl groups (δ2HLM) of wood have been shown to reflect climate-sensitive δ2H values of precipitation (δ2Hprecip). However, a detailed calibration study between high-resolution δ2HLM and δ2Hprecip data has not been performed yet. Here, we present annually resolved δ2HLM values from nine tree-ring series (derived from four Fagus sylvatica L. trees) collected near a station of the Global Isotope Network of Isotopes in Precipitation (GNIP) and the meteorological observatory at Hohenpeisenberg (Germany; ~48°N, 11°E). The nine δ2HLM tree-ring series show highly significant inter-series correlations (Rbar = 0.52) over the common period of overl…
Ion fractionation in young sea ice from Kongsfjorden, Svalbard
2011
AbstractThe fractionation of major sea-water ions, or deviation in their relative concentrations from Standard Mean Ocean Water ratios, has been frequently observed in sea ice. It is generally thought to be associated with precipitation of solid salts at certain eutectic temperatures. the variability found in bulk sea-ice samples indicates that the fractionation of ions depends on the often unknown thermal history of sea ice, which affects the structure of pore networks and fate of solid salts within them. Here we investigate the distribution of ions in Arctic sea ice that is a few weeks old with a reconstructible thermal history. We separate the centrifugable (interconnected) and entrapped…
Reconstruction of late Holocene autumn/winter precipitation variability in SW Romania from a high-resolution speleothem trace element record
2018
We present the first high-resolution trace element (Mg/Ca, Sr/Ca, Ba/Ca) record from a stalagmite in southwestern Romania covering the last 3.6 ka, which provides the potential for quantitative climate reconstruction. Precise age control is based on three independent dating methods, in particular for the last 250 yr, where chemical lamina counting is combined with the identification of the 20th century radiocarbon bomb peak and Th-230/U dating. Long-term cave monitoring and model simulations of drip water and speleothem elemental variability indicate that precipitation-related processes are the main drivers of speleothem Mg/Ca ratios. Calibration against instrumental climate data shows a si…