Search results for "Ven"
showing 10 items of 31764 documents
Ammonite paleobiogeography during the Pliensbachian-Toarcian crisis (Early Jurassic) reflecting paleoclimate, eustasy, and extinctions.
2011
14 pages; International audience; The Pliensbachian-Toarcian crisis (Early Jurassic) is one of the major Mesozoic paleoecological disturbances when ca. 20% of marine and continental families went extinct. Contemporaneously, profound paleobiogeographical changes occurred in most oceanic domains including a disruption of ammonite provincialism during the Early Toarcian. Here, we quantitatively reappraise the structure and evolution of paleobiogeographical patterns displayed by ammonite faunas before, during, and after the biological crisis, over a time-interval including 13 biochronozones. The high-resolution study presented here involves the use of hierarchical Cluster Analyses, non-metric M…
The end-Triassic mass extinction: A new correlation between extinction events and δ13C fluctuations from a Triassic-Jurassic peritidal succession in …
2018
Abstract A new δ13Ccarb curve was obtained from an expanded peritidal succession in western Sicily and was used to investigate the relationships between isotopic signatures and biological events on carbonate platforms across the Triassic-Jurassic boundary (TJB). The resulting curve shows two main negative carbon isotopic excursions (CIEs) that fit well with the “Initial” and “Main” CIEs that are recognized worldwide and linked to the End-Triassic Extinction (ETE). In the studied section, the first negative CIE marks the disappearance of the large megalodontids, which were replaced by small and thin-shelled specimens, while the “Main” CIE corresponds to the last occurrence (LO) of the megalo…
Taphonomic processes inconsistent with indigenous Mesolithic acculturation during the transition to the Neolithic in the Western Mediterranean
2018
Abstract We applied taphonomic analysis combined with geostatistical approaches to investigate the hypothesis that Cocina cave (Eastern Iberia) represents an acculturation context for the appearance of Neolithic Cardial pottery. In the 1970s, Fortea suggested that this important site was a prime example of acculturation because of the presence of early Neolithic pottery in late Mesolithic contexts. Since that time Cocina cave has been heralded as an example of indigenous hunter-gatherers incorporating Neolithic cultural elements into their lifeways. We analyzed the area excavated by Fortea in the 1970s by digitizing archaeological records and testing the spatial distribution of artifacts us…
The Valanginian isotope event: a complex suite of palaeoenvironmental perturbations.
2011
17 pages; International audience; The Valanginian records a severe crisis of carbonate systems, both on platforms and in the pelagic realm. This crisis is roughly concomitant with the Weissert Event, characterized by a positive δ13C excursion of about 2‰in marine carbonates. However, it is unclear if the response of these two carbonate systems to the global perturbations is contemporaneous, or if they react differently. For this purpose, accumulation rates of pelagic carbonates produced by nannofossils and of platform-derived carbonates have been quantified in a hemipelagic environment (the Vocontian Basin, SE France) that has the potential to record the reaction of both shallow-water and p…
Cocina cave revisited: Bayesian radiocarbon chronology for the last hunter-gatherers and first farmers in Eastern Iberia
2018
Abstract Recent excavations and radiocarbon work conducted at Cocina Cave (Valencia region, Eastern Iberia) provide new insights into the transition from foraging to farming in the eastern Iberian Peninsula between 8000 and 7300 cal yrs. BP. Cocina cave was discovered in 1940 and excavated by L. Pericot from 1941 to 1945. J. Fortea continued excavations in the 70s. Despite early international recognition and great promise of significance, the materials recovered from these excavations have only been partially analyzed and published. A new project started in 2012 is focused on these cave deposits with the main goal of understanding the occupation sequence during the neolithization process in…
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…
The early Upper Palaeolithic of Cova de les Cendres (Alicante, Spain)
2019
Abstract This paper presents a synthesis of the Early Upper Palaeolithic of Cova de les Cendres. Points of special attention are the sedimentary and micromorphological characterisation of level XVI, the analysis of the vegetal and animal resources and their incidence on the economy of the Gravettian human groups, and the characterisation of the landscape during this period. Furthermore, the paper offers important information of the lithic and bone assemblages, economic behaviour and radiocarbon dates of sub-levels XVIA and XVIB, related to the Gravettian, and XVIC and XVID, corresponding to the Aurignacian. Finally, the Gravettian and Aurignacian regional contexts in the Mediterranean Basin…
Carbon-isotope records of the Early Jurassic (Toarcian) Oceanix Anixic Event from the Valdorbia (Umbria-Marche Apennines) and Monte Mangart (Julian A…
2009
The Toarcian oceanic anoxic event (ca 183 Ma) coincides with a global perturbation marked by enhanced organic carbon burial and a general decrease in calcium carbonate production, probably triggered by changes in the composition of marine plankton and elevated carbon dioxide levels in the atmosphere. This study is based on high-resolution sampling of two stratigraphic successions, located in Valdorbia (Umbria-Marche Apennines) and Monte Mangart (Julian Alps), Italy, which represent expressions of the Toarcian oceanic anoxic event in deep-water pelagic sediments. These successions are characterized by the occurrence of black shales showing relatively low total organic carbon concentrations (…
Late Holocene seasonal temperature variability of the western Scottish shelf (St Kilda) recorded in fossil shells of the bivalve Glycymeris glycymeris
2021
Abstract The North Atlantic Ocean and adjacent shelf seas play a crucial role in global climate. To better constrain long-term natural variability and marine-terrestrial linkages in this region, a network of highly resolved marine archives from the open ocean and continental shelves is needed. In recent decades, bivalve sclerochronology has emerged as a field providing such records from the mid- to high latitudes. In May 2014, dead valves and young live specimens of the bivalve Glycymeris glycymeris were collected at St Kilda, Scotland. A floating chronology spanning 187 years was constructed with fossil shells and radiocarbon dated to 3910–3340 cal yr before present (BP), with a probabilit…
Benefits for nurse and facilitated plants emerge when interactions are considered along the entire life-span
2019
The structure of plant communities is often influenced by facilitative interactions where ‘facilitated’ plants benefit from growing associated with ‘nurse’ plants. Facilitation has been mostly studied from the facilitated plant's perspective, and bidirectional effects between nurse and facilitated plants have received less attention. We hypothesized that reciprocal benefits in plant-plant interactions may emerge when interactions are considered along the life-span of the plants involved. Over one spring, we selected five species with similar life-form and growth strategy, and using a full factorial design, we compared different fitness components along the plants’ life-span (seedling establ…