Search results for "EOT"
showing 10 items of 4111 documents
The SISAL database: a global resource to document oxygen and carbon isotope records from speleothems
2018
Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide “out-of-sample” evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxyg…
Late Quaternary palaeoenvironmental reconstruction of sediment drift accumulation in the Malta Graben (central Mediterranean Sea)
2018
The Malta Graben is a deep tectonic depression in the Sicily Channel, bounded by NW-SE normal faults and filled by thick Pliocene-Quaternary deposits. A previous analysis of a giant piston core (LC09) from the Malta Graben had revealed a wide range of sedimentary features (carbonate turbidites, bioturbated mud and scours), although the chronostratigraphic constraint of the stacking pattern has remained elusive. After establishing a reliable chronological framework based on seven radiocarbon dates for a shorter core from the Malta Graben (ANSIC03-735), a down-core analysis of planktonic foraminifer and coccolith abundance, stable isotopes and sediment grain size was carried out. Since the la…
Subaerial exposure and drowning processes in a carbonate platform during the Mesozoic Tethyan rifting: The case of the Jurassic succession of Western…
2016
Abstract The Liassic carbonate platform succession outcropping at Monte Maranfusa (central Western Sicily) consists of a shallowing-upward sequence of peritidal carbonates, with Jurassic to Paleogene pelagic limestone and siliciclastic Tertiary covers above. The cyclic sequences of subtidal wackestones/packstones, intertidal microcrystalline carbonates with bird's-eye pores, and supratidal bioclastic grainstones are interbedded with dark layers of the following composition: 1) dark-gray, compact, and well-cemented limestone with blackish clasts, interpreted as calcretes (a type of carbonate soil) and 2) reddish calcite laminae, deformed by elongated cavities, filled with vadose silt, interp…
A low seasonality scenario in the Mediterranean Sea during the Calabrian (Early Pleistocene) inferred from fossil Arctica islandica shells
2017
Understanding past seasonal temperature variability in the ocean is essential to evaluate the effects of future climate change on marine ecosystems. Here, we estimate seasonal water temperature amplitudes from stable oxygen isotope (δ18Oshell) values of fossil shells of Arctica islandica (assuming δ18Owater= + 0.9 ± 0.1â° V-SMOW). Specimens were collected from three Pleistocene successions (Emilian and Sicilian substages of the Calabrian) in Central and Southern Italy (i.e., Rome, Lecce and Sicily). Biostratigraphic analyses from Rome Quarry deposits indicate an age between 1.6 and 1.2 Ma, whereas Sicily and Lecce successions are slightly more recent (between 1.1 and 0.62 Ma). Prior to …
Diagenesis of clay minerals and K-bentonites in Late Permian/Early Triassic sediments of the Sichuan Basin (Chaotian section, Central China).
2014
10 pages; International audience; Detailed clay mineralogical analyses were carried out on Late Permian/Early Triassic carbonate sediments exposed on the Chaotian section (Sichuan Basin, Central China). The clay assemblages are dominantly composed of illite in platform carbonates and clay seams, and illite-smectite mixed-layers (I/S) in tuff layers (K-bentonites) intercalated in the carbonate succession. Detrital and authigenic volcanogenic clay minerals have been partially replaced through illitisation processes during burial, raising questions about diagenetic effects. The precise determination of I/S occurring in K-bentonites shows that the sediments reached a temperature of about 180 °C…
The Use of Medicinal Clay from Silesia “Terra sigillata Silesiaca”, Central Europe - A New Chance for Natural Medicine?
2019
Silesia is a region in Central Europe with beneficial conditions for the presence of clay, including those with potential therapeutic efficacies, due to its very diverse and mosaic geological landscape. The first use of clay deposits in medicine in Silesia, “terra sigillata Silesiaca”, has been dated to 1550 AD, and the oldest written information related to this use has been dated to 1586 AD. Medicinal clay is formed by the accumulation of a mixture of minerals such as smectite, bentonite, montmorillonite, kaolinite, illite, and metahaloisite, with impurities of other minerals and fractions, resulting from the chemical weathering of rocks and the sedimentation of detritus. The quantitative …
Climatic fluctuations and seasonality during the Late Jurassic (Oxfordian–Early Kimmeridgian) inferred from delta18O of Paris Basin oyster shells.
2008
10 pages; International audience; Oxygen isotope data from biostratigraphically well-dated oyster shells from the Late Jurassic of the eastern Paris Basin are used to reconstruct the thermal evolution of western Tethyan surface waters during the Early Oxfordian–Early Kimmeridgian interval. Seventy eight oyster shells were carefully screened for potential diagenetic alteration using cathodoluminescence microscopy. Isotope analyses were performed on nonluminescent parts of shells (n=264). Intra-shell δ18O variability was estimated by microsampling along a transect perpendicular to the growth lines of the largest oyster shell. The sinusoidal distribution of the δ18O values along this transect …
Pseudoshasticrioceras bersaci nov. sp. (Ammonoidea, Gassendiceratinae), and new ammonite biohorizon for the Upper Barremian of southeastern France
2009
International audience; Research in the Feraudianus Subzone of the Sartousiana Zone of the Barremian stage led to the discovery of a new species of Pseudoshasticrioceras: P. bersaci nov. sp. Its study provides evidence concerning the developments of the latest Gassendiceratinae BERT et alii, 2006, and the relationship between the genus Pseudoshasticrioceras DELANOY, 1998, and Gassendiceras BERT et alii, 2006. In particular, this new species is derived from Pseudoshasticrioceras magnini (DELANOY, 1992) by a minor revision in the processes of ontogenesis (retardation of ornamentation - neoteny). However, the evolution towards Pseudoshasticrioceras autrani DELANOY, 1998, implies a "failure" in…
Geology of Monte Gallo (Palermo Mts, NW Sicily)
2016
The promontory of Monte Gallo (Palermo, NW Sicily) is a spectacular site where Upper Triassic-Eocene carbonate platform rocks and Quaternary continental to marine deposits are well exposed. A Mesozoic-Paleogene rock succession allows the potential visitor to easily detect the features and the evolution of the Panormide carbonate platform, a shallow-water paleogeographic domain of the Southern Tethyan margin. Quaternary deposits, as well many landforms, enable the visitor to directly identify the interplay between climate changes, tectonics and fluctuations of marine level that occurred during the Quaternary Period. A detailed geological map (1:15,000 mapping scale) is presented, accompanied…
Carbon and Oxygen Isotope Signals from the Callovian–Oxfordian in French Sedimentary Basins
2013
3 pages; International audience; High-resolution carbon and oxygen isotope data from the Paris Basin and the Subalpine Basin (France) are available in a precise biostratigraphic framework for the Callovian-Oxfordian stages. A biostratigraphically well-constrained δ13C curve, derived from bulk carbonates in the Paris Basin and the Subalpine Basin, is provided in order to document carbon-cycle evolution and to serve as a chemostratigraphic reference for the Callovian-Oxfordian in the Tethyan domain. Sea-temperature reconstructions, using diagenetically screened belemnite and oyster data, reveal major climate perturbations at the Middle-Late Jurassic transition.