Search results for "RF"
showing 10 items of 23683 documents
The north-eastern aeolian ‘European Sand Belt’ as potential record of environmental changes: A case study from Eastern Latvia and Southern Estonia
2016
Abstract The Latvian and Estonian inland dunes belong to the north-eastern part of the ‘European Sand Belt’ (ESB). These dunes are widely distributed over broad glaciolacustrine plains and Late Glacial alluvial deltas, considered to be potential sources for the aeolian material. Little is known about these aeolian sediments and their substratum; here we present a detailed sedimentary structural and textural characterisation together with a luminescence-based chronology. Through a comparison between grain-size, rounding of quartz grains and surface characteristics in medium/coarse (0.5–0.8 mm) sand, and the light mineral content, we found an alternation of aeolian and periglacial components.…
Summer air temperature, reconstructions from the last glacial stage based on rodents from the site Taillis-des-Coteaux (Vienne), Western France.
2014
AbstractThe oxygen isotope composition of phosphate from tooth enamel of rodents (δ18Op) constitutes a valuable proxy to reconstruct past air temperatures in continental environments. This method has been applied to rodent dental remains from three genera, Arvicola sp., Microtus sp. and Dicrostonyx sp., coming from Taillis-des-Coteaux, Vienne, France. This archaeological site contains an exceptionally preserved sedimentary sequence spanning almost the whole Upper Palaeolithic, including seven stratigraphic layers dated from 35 to 17 cal ka BP. The abundant presence of rodent remains offers the opportunity to quantify the climatic fluctuations coeval of the various stages of human occupation…
High-frequency climate fluctuations over the last deglaciation in the Alboran Sea, Western Mediterranean: Evidence from calcareous plankton assemblag…
2018
Abstract A high resolution study, with a centennial scale resolution, has been performed on the calcareous plankton assemblage (coccolithophores and planktonic foraminifera) at Ocean Drilling Program Site 976, Alboran Sea (Western Mediterranean), focusing on the interval between 20 and 9 ka, in order to reconstruct changes in surface and subsurface water dynamics and productivity. The biotic surface water proxies integrate the extremely detailed (multi-decadal scale) geochemical data set and the pollen record already available at the core, thus providing a complete paleoenvironmental/paleoceanographic reconstruction. The results highlight the sensitivity of the calcareous plankton in record…
Palaeoecological implications of Neanderthal occupation at Unit Xb of El Salt (Alcoi, eastern Spain) during MIS 3 using small mammals proxy
2018
Nearly 250 small mammal remains from Unit Xb of El Salt Middle Palaeolithic site have been studied in order to reconstruct the palaeoecological conditions during a phase of Neanderthal occupation in this locality at 52.3 ± 4.6 ka. A total of 7rodents (Microtus arvalis, M. agrestis, M. (Terricola) duodecimcostatus, Microtus (Iberomys) cabrerae, Arvicola sapidus, Eliomys quercinus and Apodemus sylvaticus), 4 insectivores (Erinaceus cf. europaeus, Crocidura sp., Sorex sp. and Talpidae indet.) and 1 lagomorph (Oryctolagus cf. cuniculus) have been identified. Applying the Mutual Ecogeographic Range and Habitat Weighting methods, Unit Xb may correspond to a relatively cold (−3.3 °C in comparison …
New research in the methods and applications of sclerochronology
2017
Abstract Because the instrumental record is short and does not extend to periods before the initiation of significant human impacts, full understanding of the processes and dynamics involved in the modern phase of very rapid global change depends on the interpretation of high resolution and precisely dated proxy archives. The identification of very long-lived species of bivalve mollusc in the extratropical marine environment has been a crucial recent advance. These molluscs form patterns of periodic (usually annual) banding in their shells that are synchronous within populations, so that long (centennial and millennial) stacked chronologies can be built by crossdating from live collected to…
An intractable climate archive — Sclerochronological and shell oxygen isotope analyses of the Pacific geoduck, Panopea abrupta (bivalve mollusk) from…
2008
Abstract Annual growth increment patterns of cardinal teeth (CT) of Panopea abrupta (Conrad) can reportedly provide information about past climate variations. However, little is known about the intra-annual timing and rate of shell growth necessary to interpret such records. In addition, it remains unclear whether actual temperatures can be reliably inferred from δ18O values of geoduck {goo'e-duk} shells. This study compared high-resolution environmental records (hourly to monthly resolved temperature, bi-weekly to monthly δ18Owater and salinity data) with temperatures reconstructed from oxygen isotope values of the outer shell layer (Tδ18OOSL) and cardinal tooth portions (Tδ18OCT) of diffe…
The response of a shallow lake and its catchment to Late Glacial climate changes — A case study from eastern Poland
2015
In this study we investigate how climate fluctuation in the Late Glacial period influenced the development of a lake and its catchment located in the East European Plain. We analyzed the sediments of the lake for pollen, subfossil Cladocera, macrofossils and chemical composition. We aimed at disentangling: (1) the climate changes and their limno-ecological responses, (2) temperature dynamics with the use of Cladocera-based transfer function (MJT) and macrofossil-based reconstruction of mean minimum July temperature (MMJT), (3) timing of the response of different proxies to environmental changes. The results of multiproxy analyses explicitly suggest that the main driver for changes in aquati…
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…
Debitage by fracturing in the osseous industry of Cova del Parpalló (Gandía-Valencia, Spain): A preliminary study
2016
Abstract The excavations carried out by L. Pericot from 1929 to 1931 in the Cova del Parpallo documented the Gravettian in the base, a Solutrean layer, and a Magdalenian. This sequences comprise an exceptional assemblage of portable art because of the number of plaquets/objects and the great chronological amplitude. With all this information, Parpallo was included in the reduced list of reference sites to organize the European Upper Paleolithic sequence in the first half of the 20th century. The Magdalenian layers were organized in four phases, following H. Breuil's classical proposal. Changes in bases morphology and decorative topics on osseous points permitted this correlation, identifyin…