Search results for "PET"
showing 10 items of 12749 documents
Amphibians and reptiles as palaeonvironmental proxies during the Late Pleistocene (MIS3): The case of Stratigraphic Unit V of El Salt, Alcoi, Spain
2021
The locality of El Salt (Alcoi, Spain) is a key site for understanding the extirpation of Neanderthals in the eastern part of Iberia. In this paper, we analyse an assemblage of amphibians and reptiles from Stratigraphic Unit V (45.2 ± 3.4 ka to 44.7 ± 3.4 ka), which corresponds to one of the last regional records of Neanderthals, to improve knowledge of the palaeoecology and palaeoclimate of this event. The assemblage comprises three anurans (Pelodytes sp., Alytes obstetricans, and Epidalea calamita), two lizards (Lacertidae indet. and Chalcides bedriagai), and five snakes (Colubridae indet., Coronella sp., Coronella sp./Zamenis sp., Natrix maura, and Vipera latastei). Palaeoclimatic recons…
Tectonic evolution of the northern Austral-Magallanes basin in the Southern Patagonian Andes from provenance analysis
2019
We studied the northern tip of the Austral-Magallanes basin in the Southern Patagonian Andes, between the Buenos Aires Lake and the Mayer River at 46°35′ SL and 48°35′ SL, respectively. Proposed objectives were: i) to differentiate Mesozoic-Cenozoic tectonostratigraphic units and, ii) to characterize the different deformational events that took place in the area linked to a variable regional geodynamic context. Sandstones provenance analysis was performed on the Aptian - Albian compressive retroarc deposits and Cenozoic foreland deposits. Studied samples were classified using tectonic discrimination diagrams which show: i) for Cretaceous rocks a dominant sediment source from a recycled orog…
Electron Paramagnetic Resonance and petrographic analysis for dating Mesolithic and Neolithic pottery from Al Khiday (Sudan)
2016
Abstract Electron Paramagnetic Resonance (EPR) dating, like luminescence techniques, is based on the time-dependent accumulation of trapped charges at mineral defect centres. However, Fe(III) ions prevent the common Continuous Wave (CW-EPR) approach for dating pottery, which always contains iron. The Pulsed method (ED-EPR) allowed this limitation to be overcome, with recording of radiation-induced defect signals, as shown by increased signal intensity after artificial irradiation of samples. The method was applied to studying Mesolithic and Neolithic pottery from Al Khiday (Central Sudan), characterized by quartz-rich tempers and coming from dated contexts. As the occurrence of a natural ED…
Weathering evolution in lutites of the K/Pg transition red beds of the Tremp Group (Tremp-Isona Basin, south Pyrenees)
2017
AbstractThe Tremp–Isona basin (south-central Pyrenees, Lleida, Spain) shows maximum development of the Tremp Group (early Maastrichtian to late Paleocene) covering a wide geological record across the Cretaceous–Paleogene (K/Pg) boundary in continental facies. The mineralogy and geochemistry of lutites were used to assess the evolution of weathering from the Maastrichtian to the Eocene, and particularly for the red beds of the Lower Red and Upper Red Units (pre- and post-K/Pg, respectively). Chemical weathering decreased initially in the Maastrichtian (Gray Unit to Lower Red Unit), increasing subsequently from the Paleocene (Upper Red Unit) to Eocene units. ANOVA analysis of mineralogical co…
Intact seismic-scale platforms and ramps in the Lower to Middle Jurassic of Morocco: implications for stratal anatomy and lithofacies partitioning.
2017
9 pages; International audience; The Jurassic carbonate platforms of the central High Atlas in Morocco are well known for several high-quality outcrops. In the central High Atlas, there are two complementary locations that offer critical lessons for our understanding of Jurassic carbonate system evolution in extensional basins: a Lower Jurassic high-relief, carbonate platform with steep slopes that developed on the footwall of a rotating fault block in an active half-graben (Djebel Bou Dahar [DBD]) and an upper Lower to Middle Jurassic low-angle prograding carbonate ramp rich in ooids (Amellago ramp [AR]). The DBD and AR outcrops provide superbly exposed, structurally intact, and fully acce…
Spongy-like porosity in peritidal carbonates: An interaction of cyclic sea-level oscillations, fresh water supply and sediment texture
2016
Abstract This paper focuses upon the analysis of a complex paleokarstic system recorded within uppermost Triassic peritidal cycles in northwestern Sicily. Besides documenting spectacular karstification at the Triassic/Jurassic boundary, it provides an example of stratabound ‘spongy’ or ‘swiss-cheese’ dissolution. On the base of field observations, microfacies analysis, transmitted-light and cathodoluminescence petrography and stable-isotope analyses we put forward an original model for the formation of this peculiar stratabound dissolution. It implies a complex interaction of several controlling factors at the interface between the marine and meteoric diagenetic realms during the relative c…
Hydrothermalism in the Tyrrhenian Sea: Inorganic and microbial sulfur cycling as revealed by geochemical and multiple sulfur isotope data
2011
15 pages; International audience; The Palinuro volcanic complex and the Panarea hydrothermal field, both located in the Tyrrhenian Sea (Italy), are associated with island arc magmatism and characterized by polymetallic sulfide mineralization. Dissolved sulfide concentrations, pH, and Eh measured in porewaters at both sites reveal a variable hydrothermal influence on porewater chemistry. Multiple sulfur isotopic measurements for disseminated sulfides (CRS: chromium reducible sulfur) extracted from sediments at Palinuro yielded a broad range in δ34S range between −29.8 and +10.2‰ and Δ33S values between+0.015 and+0.134‰. In contrast, sediments at Panarea exhibit a much smaller range in δ34SCR…
Water mass exchange and variations in seawater temperature in the NW Tethys during the Early Jurassic: evidence from neodymium and oxygen isotopes of…
2009
10 pages; International audience; Oxygen and neodymium isotope analyses performed on biostratigraphically well-dated fish remains recovered from the Hettangian to Toarcian of the Paris Basin were used to reconstruct variations of Early Jurassic seawater temperature and to track oceanographic changes in the NW Tethys. Our results indicate a strong correlation between δ18O trends recorded by fish remains and belemnites, confirming the paleoenvironmental origin of oxygen isotope variations. Interestingly, temperatures recorded by pelagic fishes and nektobenthic belemnites and bottom dwelling fishes are comparable during the Late Pliensbachian sea-level lowstand but gradually differ during the …
Revised phosphate-water fractionation equation reassessing paleotemperatures derived from biogenic apatite.
2010
8 pages; International audience; Oxygen isotopes of biogenic apatite have been widely used to reassess anomalous temperatures inferred from oxygen isotope ratios of ancient biogenic calcite, more prone to diagenetic alteration. However, recent studies have highlighted that oxygen isotope ratios of biogenic apatite differ dependent on used analytical techniques. This questions the applicability of the phosphate–water fractionation equations established over 25 years ago using earlier analytical techniques to more recently acquired data. In this work we present a new phosphate–water oxygen isotope fractionation equation based on oxygen isotopes determined on fish raised in aquariums at contro…
Facies variations in response to Holocene sea-level and climate change on Bora Bora, French Polynesia: Unravelling the role of synsedimentary siderit…
2017
International audience; Five mixed carbonate-siliciclastic sedimentary facies were identified in the barrier-reef lagoon of Bora Bora using microfacies and statistical analyses of 70 sediment samples taken at high resolution from two vibrocores. Fades and fades successions were interpreted with respect to Holocene sea-level and climate changes. The windward lagoon core is characterized by sideritic marly wackestones and foraminifera-sideritic wackestones, deposited around 7700 years BP (years before present) during the early-mid Holocene transgression. At that time, extensive weathering and erosion of iron-bearing minerals from the volcanic island, due to a wetter climate, were expressed in…