1,721,243 research outputs found
A bio-chronostratigraphic study of the upper Miocene from the northern Caltanissetta Basin, Sicily (core 3AGN2S04). Implications for dating the Messinian Salinity Crisis onset
No full textThe late Miocene deposits from core 3AGN2S04, located in the northern Caltanissetta Basin (Sicily), display the pre-Messinian Salinity Crisis (MSC) and the MSC events. The present study describes the entire core in terms of lithology, biostratigraphy and magnetostratigraphy and aims to enlighten the relationship between MSC evaporite cyclicity and astronomical forcing. The lithological and micro-/macro-paleontological descriptions document the MSC record, with Stage 1 (onset and Calcare di Base member), Stage 2 (Messinian Erosional Surface) and part of Stage 3 (Upper Gypsum and Lago Mare). Detailed micro-fossil analyses of the pre-evaporites reveal several biostratigraphic events that permit correlations to the well-dated Mediterranean planktonic foraminiferal biostratigraphic zonation of the late Tortonian and Messinian. An integrated bio-cyclostratigraphic analysis allows bed-to-bed correlations of core 3AGN2S04 with the reference sections of Falconara/Gibliscemi (Sicily) and Sorbas (Spain), but also with various other sections from the Caltanissetta Basin. Our cyclostratigraphic correlations show a stratigraphical gap in the core between the late Tortonian Terravecchia Formation and the pre-evaporitic Messinian Tripoli Formation. This hiatus is probably related to the tectonically active geological setting of the northern Caltanissetta Basin. Finally, we show that the repercussions of the paleoenvironmental evolution towards evaporitic deposition and the MSC onset seem to have been diachronous throughout the various perched basins on Sicily characterized by different paleobathymetries. In particular, the onset of the Calcare di Base took place around 40-100 ka before the deposition of the first gypsum bed of the Primary Lower Gypsum units.(c) 2023 Elsevier B.V. All rights reserved
Astrochronology of the Burdigalian-Langhian in the Mediterranean: understanding climatic and environmental changes
No full textIntegrated stratigraphy and astronomical calibration of the Serravallian/Tortonian boundary section at Monte Gibliscemi, Sicily
No full textPaleoenvironmental evolution of the eastern Mediterranean during the Messinian: Constraints from integrated microfossil data of the Pissouri Basin (Cyprus)
No full textIntegrated data of calcareous nannofossils, as well as planktonic and benthic foraminifera from the Pissouri Motorway section on Cyprus allow the reconstruction of surface- and bottom-water paleoenvironments of the eastern Mediterranean during the interval preceding the Messinian salinity crisis (MSC). Contrary to deeper-water locations, where benthic foraminifera faunas are suppressed or absent just after the Tortonian-Messinian boundary, sediments deposited at intermediate water depths do contain benthic assemblages. From the earliest Messiman onwards, a development towards increasingly unfavourable paleoenvironments is reflected in the planktonic and benthic microfossil records of the Pissouri section and proceeds with rather discrete time steps that can be correlated to sequences throughout the Mediterranean. Shortly after the Tortonian-Messinian boundary a transition is recorded in the sedimentology and the open marine, deeper-water taxa disappear from the benthic foraminifera assemblages; subsequently, the diversity of all fauna groups diminishes. The changes recorded at species level in both surface-water and sea-floor dwelling taxa suggest decreasing circulation of the bottom waters, associated with changes in the surface waters, most likely due to increasing stratification. From similar to 6.73 Ma onwards, our data indicate a prominent change to more restricted conditions and increasing salinity at the sea floor together with intermittently rising surface water salinity. The dominance of oligotypic and monospecific assemblages and the frequent shifts in assemblage compositions of all microfossil groups indicate severely stressed environments after similar to 6.4 Ma, probably related to increased salinity. The major changes in palcoenvironmental conditions, including oxygen deprivation due to stagnation and hypersalinity, can be explained by hydrographical changes in the Mediterranean basin, which are probably caused by tectonic movements in the Rif Corridor acting in concert with astronomical cyclicity. Evaluation of the paleodepth proxies indicates that the depth of the Pissouri Basin remained rather constant at similar to 300-500 in, with a minimum of 200 in, until deposition of the "barre jaune", the transitional interval towards the evaporites and that early shallowing to neritic depths, as was proposed before, is highly unlikely
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
INTEGRATED STRATIGRAPHY AND ORBITAL TUNING OF THE RAS IL PELLEGRIN SECTION ON MALTA: EC-CENTRICITY AND OBLIQUITY CONTROL ON MIDDLE MIOCENE CLIMATE COOLING AND OXYGEN ISOTOPE EVENT MI-3
No full textIntegrated stratigraphy and astrochronology of the Serravallian and lower Tortonian at Monte dei Corvi (Middle- Upper Miocene, Northern Italy)
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