1,721,107 research outputs found
A Late Holocene pollen record from marine sediments in SE Sicily
No full textThe new pollen record from marine core SW104_ND2-ND2, collected in the Sicily Channel 20 km from
the coast, is presented. The central position of this marine record in the Mediterranean Basin is strategic to
investigate past climate variability and ecological changes in a transitional climatic zone, highly sensitive to
hydroclimatic variations. The intricate interplay of the climatic patterns acting over the Central Mediterranean,
North Africa, and continental Europe determines a complex bioclimatic configuration, which is also reflected
in the floristic richness and vegetational diversity of SE Sicily. Our analysis provides a detailed reconstruction
of palaeoecological changes in relation to climatic variability and human impact over the last 3000 years.
The pollen record depicts a permanent open vegetational landscape with several fluctuations of land cover,
corresponding to alternate forests expansions and reductions. This pattern is consistent with fluctuations in
solar activity and the cyclicity of independent stratigraphic evidence at a global scale. The palynostratigraphy
of the study record, based on changes in vegetation structure and floristic composition, reflects the main
climatic events in historical times. During the Roman Period, a forest development is observed that suggests a
centennial-scale humid climate, matching the so called Roman Humid Period. In contrast, a marked decrease
in arboreal pollen percentages and concentration is observed since the 14th century AD, suggesting dry climatic
conditions during the Little Ice Age. The comparison of our palaeovegetational reconstruction with independent
palaeoclimate proxies reveals the recurrence of arid phases concomitant with negative or declining positive
phases of the North Atlantic Oscillation (NAO), underlining the pivotal role of this forcing in determining
precipitation distribution at centennial to decadal scales. At the same time, the detection of African taxa in
the pollen record, testifying the southwestern provenance of air masses, suggests an interaction of northward
shifts of North African high pressures with NAO-determined synoptic conditions. Extra-regional pollen inputs
are especially frequent during the last millennium, indicating an increasing influence of the North African
anticyclone over the Central Mediterranean region.
The SW104_ND2-ND2 pollen record offers new detailed information on the extent of human impact on the
landscape in relation to historical management policies and land use, and provides insights into past vegetation
trends, atmospheric dynamics, and hydroclimatic conditions, which contribute to a better understanding of
Late Holocene climate variability in the Central Mediterranean
Middle Miocene high-resolution calcareous plankton biostratigraphy focussed on the Burdigalian/Langhian and Langhian/Serravallian boundaries
No full textClimate and human influence on the vegetation of Tyrrhenian Italy during the last 2000 years. New insights from microcharcoal and non-pollen palynomorphs
No full textLa storia della vegetazione degli ultimi 2000 anni nella penisola italiana è stata determinata da una complessa interazione di diversi fattori, tra i quali spiccano la storia delle società umane, i cambiamenti nell'uso del suolo e la successione di eventi climatici. Al fine di distinguere l’effetto di questi fattori, abbiamo svolto uno studio multidisciplinare di una carota di sedimenti marini campionata nel Golfo di Gaeta e interpretata alla luce di altre ricerche paleoambientali dell'Italia tirrenica. I dati pollinici, integrati da palinomorfi non pollinici e da concentrazioni di microcarbone, sono stati usati per ricostruire i cambiamenti nel paesaggio
vegetale, attività di allevamento, incendi e uso del suolo. I dati degli isotopi dell'ossigeno e dei foraminiferi forniscono informazioni indipendenti sui cambiamenti climatici. Le curve dell'indice NAO e delle macchie solari sostengono l'interpretazione dei cambiamenti nella circolazione atmosferica. In questo articolo, esaminando l'effetto del clima e dell'attività umana sul paesaggio in una serie di periodi storici degli ultimi 2000 anni, che rappresentano fasi culturali o climatiche (Periodo Romano, Medio Evo, Anomalia climatica medievale, Piccola Età Glaciale e Periodo moderno), abbiamo documentato un declino generale e progressivo della vegetazione forestale prodotto dall’attività antropica. Tuttavia, indipendentemente dalla fase storica, si sono registrate riduzioni
delle foreste anche quando oscillazioni NAO negative hanno indotto siccità del clima, specialmente durante i minimi dell’attività solare.The history of vegetation in the Italian peninsula during the last 2000 years was shaped by a complex interplay of several factors, including the history of human societies, changes in land use, and the succession of climate events. In order to disentangle these factors, we present a multidisciplinary record from a marine core collected in the Gulf of Gaeta, interpreted in the light of other palaeoenvironmental records from Tyrrhenian Italy. Pollen records, complemented by new data on Non-Pollen Palynomorphs (NPPs) and microcharcoal, are used to reconstruct changes in the vegetational landscape, stock-breeding activities, fire, and land use. Foraminiferal and oxygen isotope data provide independent information on climate changes. NAO-index and sunspot data support the interpretation of changes in atmospheric circulation. In this paper, by examining the effect of climate and human activity on the landscape during a series of periods of the last 2000 years, representing cultural or climate phases (Roman Period, Dark Ages, Medieval Climate Anomaly, Little Ice Age, and
Modern Period), we found that human impact produced a general and progressive decline of forest vegetation. However, irrespective of the societal
cultural phase, forest declines occurred when negative NAO oscillations induced dry climate, especially during sunspot minima
Middle Miocene stepwise climate evolution in the Mediterranean region through high-resolution stable isotopes and calcareous plankton records
No full textThe middle Miocene is marked by a changeover from a warm climatic period (Miocene Climatic Optimum, ~17-14.7 Ma), to a transitional phase (Middle Miocene Climatic Transition), culminating in a cold stage (Icehouse Mode, ~13.8 Ma). This period is associated with a positive excursion of δ13C (“Monterey Excursion”), showing a series of δ13C maxima (CM events) highlighted by cooling peaks in the δ18O values (Mi events). DSDP Site 372 obtained a high-resolution record of the middle Miocene of the western Mediterranean (Balearic Islands), and represents one of the best marine sedimentary records for the considered time interval. In this study, highresolution stable isotope and quantitative calcareous plankton records for the Langhian to the early Serravallian time interval are presented. The stable oxygen and carbon isotope records allowed us to recognize and chronologically frame the Mi and CM events falling between 15.82 and 13.04 Ma. Furthermore, by integrating the stable isotope data with those obtained by the quantitative analyses of the calcareous plankton content, the three-folded climatic and environmental evolution was outlined for the considered time interval in the Mediterranean region. During the first stage (Miocene Climatic Optimum = MCO; from 17 up to 14.55 Ma), an initial warm-surfacewater, oligotrophic, high salinity and restricted environment is followed by an open marine setting (starting from 15.18 Ma) within still warm-surface-water and oligotrophic conditions. The re-opening of the connections between the Mediterranean Sea and the Indian Ocean would have likely triggered this latter environmental change. From 14.55 to 13.75 Ma (second stage; Middle Miocene Climatic Transition; MMCT) an initial (up to 14.05 Ma) temperate-warm-surface-water and eutrophic environment occurred, followed by the onset of warm-surfacewater, oligotrophic and slightly restricted marine conditions. The third stage (Icehouse Mode = IHM; from 13.75 Ma onwards) points to the development of a cold-water, eutrophic, high salinity environment in an open-marine setting
Deep-water paleoenvironmental changes based on early-middle Miocene benthic foraminifera from Malta Island (Central Mediterranean)
No full textA detailed quantitative, statistical and isotopic study on benthic foraminiferal assemblages from the upper Burdigalian -lower Langhian of Malta Island (St. Peter's Pool section) was carried out in order to gain more insights on paleoenvironmental changes that affected the central part of the Mediterranean Basin during the early-middle Miocene. The most abundant and/or palaecologically significant taxa were grouped into Group A (oxic/oligotrophic and oxic/oligo-mesotrophic opportunistic behaving) and Group B (hypoxic/eutrophic) and, on the base of their microhabitat in superficial microhabitat taxa (epifaunal + epifaunal to shallow infaunal taxa), intermediate microhabitat taxa (shallow infaunal + shallow to intermediate infaunal taxa) and deep microhabitat taxa (deep infaunal species). The changes in the structure of the benthic foraminiferal assemblages, together with isotopic data and statistical analysis results, identify five main intervals SPP1-SPP5, testifying the evolution of bottom water conditions between 16.12 and 15.36 Ma, corresponding to warm climate conditions due to the onset of the Miocene Climatic Optimum (MCO). The main benthic foraminiferal turnover occurred between 16.01 and 15.91 Ma. It has been recorded in both the palaecological and geochemical data and can be related to the Miller's Mi2 cooling event. This turnover correlates to a sea level falling that we believe caused an increase of the primary productivity due to runoff intensification. We suggest that the fluctuations of superficial microhabitat oxic/oligo/oligo-mesotrophic Group A, opposite to those of intermediate and deep microhabitat hypoxic/eutrophic Group B, and the occurrence of the superficial microhabitat, oxic/oligo-mesothrophic opportunistic behaving species are indicative of increased seasonality, which in turn affect food flux and oxygenation at the sea-floor. Moreover, the calculation of %P and the well-defined depth distribution range of some significant species allowed us to estimate a middle bathyal paleodepth, ranging from 600 m to 1000 m for the entire composite section
Analisi polliniche di sedimenti marini tardo-olocenici della Sicilia sudorientale
No full textLa carota di sedimento ND2, prelevata a 89 m di profondità nel Canale di Sicilia a circa 20 km dalla costa,
occupa una posizione strategica nel centro del Mar Mediterraneo. In quest’area della Sicilia meridionale,
il clima tipicamente mediterraneo, influenzato anche dalla complessa interazione tra il regime climatico
subtropicale del continente africano e quello temperato del continente europeo, determina una variegata
biodiversità floristica e una notevole ricchezza di configurazioni vegetazionali.
L’analisi pollinica della successione sedimentaria ND2 ha permesso di ricostruire in maniera dettagliata le
dinamiche vegetazionali degli ultimi 3000 anni riconducibili alle oscillazioni climatiche del tardo Olocene,
nonché all’attività umana nel corso dei secoli. Le variazioni della copertura forestale rilevate presentano una
corrispondenza con oscillazioni note dell’attività solare e mostrano ciclicità riscontrate in ambito stratigrafico a
livello globale (Bond et al., 1997). La caratterizzazione ecologica di tali variazioni ha permesso di identificare
periodi di pronunciata aridità in grado di influenzare gli ecosistemi forestali del settore sudorientale della
Sicilia. La zonazione biostratigrafica del diagramma pollinico, basata sull’alternanza di fasi a vegetazione più
o meno aperta e sulla composizione floristica, riflette le principali fluttuazioni climatiche avvenute in epoca
storica. Un’espansione forestale durante il periodo romano indica una prolungata condizione di disponibilità
idrica. A partire dal XIV secolo, un marcato decremento nella concentrazione pollinica dei taxa arborei
suggerisce condizioni climatiche più aride per l’intera durata della Piccola Età Glaciale. Il rinvenimento di taxa
a distribuzione prettamente africana testimonia episodi di rivenute polliniche dal Nord Africa e permette di
tracciare la provenienza di venti da sud/sud-ovest, conuna maggiore frequenza negli ultimi 1000 anni (Sabatier
et al., 2020). I maggiori cambiamenti di paesaggio vegetale legati all’intervento antropico riflettono una
significativa intensificazione delle pratiche agricole in epoca recente, accompagnata da riforestazioni massive
durante il periodo fascista e dall’introduzione di specie alloctone nel secondo dopoguerra
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The Global Stratotype Section and Point (GSSP) of the Langhian stage and the Middle Miocene subseries
No full textThe Global Stratotype Section and Point (GSSP) of the base of Langhian Stage (base of the Middle Miocene Subseries) is defined at a level of 17.84 m in the “Lower La Vedova Beach” section in central Italy. This level marks the mid-point of the darker marly interval above “Megabed IV” which has been astronomically calibrated to the most prominent ~100-kyr eccentricity maximum, with an astronomical age of 15.981 Ma according to La2004 nominal solution, and of 15.978 Ma according to the La2011, in the 405-kyr maximum around 16.0 Ma. The GSSP level in the Lower La Vedova Beach section corresponds closely to the top of Chron C5Cn (at 15.795 m), which is considered the principal event for recognizing the boundary globally. This magnetic reversal with an astronomical age of 16.017 Ma (Turco et al., 2017) (15.97 Ma in Hilgen et al., 2012 ATNTS, 2012; 15.994 Ma in Raffi et al., 2020 in GTS2020) is preferred to the historical guiding criterion, the Praeorbulina datum, which has been complicated by taxonomic confusion and revision (Turco et al., 2011a), and hence is considered less suitable for recognizing the boundary. The Lower La Vedova Beach section is preferred to the St. Peter’s Pool section (in Malta) as it has an independent astronomical tuning and a better paleomagnetic signal. With the selected astrochronologic criterion close to an important magnetic reversal boundary we follow standard procedures developed by SNS to define Neogene GSSPs over the years. This procedure guarantees that the Langhian GSSP is directly incorporated in the integrated astronomically dated stratigraphic framework that nowadays underlies our standard GTS, while it is sufficiently close to the top of Chron C5Cn that the latter can be used for correlating the boundary time-stratigraphically on a global scale. In addition, a Standard Auxiliary Boundary Stratotype (SABS) is designated at Integrated Ocean Drilling Program (IODP) Site U1337, in the eastern equatorial Pacific, with the aim to directly link the open ocean benthic foraminiferal stable isotope record to the boundary definition. This level marks the mid-point of a darker interval that has been astronomically calibrated to the same prominent ~100-kyr eccentricity maximum. This level coincides with distinctive features in the stable isotope record, falls right in the middle of the Miocene Climatic Optimum (MCO) and is approximately one 405-kyr cycle older than the most dramatic oxygen isotope minimum dated astronomically at 15.6 Ma, marking the most extreme warming during the entire Miocene (Holbourn et al., 2013). It further corresponds closely to the top of Chron C5Cn, based on detailed cyclostratigraphic correlations to parallel Sites U1335 and U1336, which have an excellent magnetostratigraphy. Biostratigraphically, the Langhian GSSP falls in the lower part of the Mediterranean planktonic foraminiferal Subzone MMi4a (Di Stefano et al., 2008; Iaccarino et al., 2011; Lirer et al., 2019), delimited by the First Occurrence (FO) of Globigerinoides sicanus (3 apertures) at the base and the Beginning of the Paragloborotalia siakensis Acmea at the top, and calcareous nannofossil Subzone MNN4b (Di Stefano et al., 2008; 2023), defined by the Last Common Occurrence (LCO) of Helicosphaera ampliaperta and the Beginning of the Sphenolithus heteromorphus Paracme interval. With respect to (sub)tropical biozonations, the later can be used for correlating the boundary time-stratigraphically on a global scale. In addition, a Standard Auxiliary Boundary Stratotype (SABS) is designated at Integrated Ocean Drilling Program (IODP) Site U1337, in the eastern equatorial Pacific, with the aim to directly link the open ocean benthic foraminiferal stable isotope record to the boundary definition. This level marks the mid-point of a darker interval that has been astronomically calibrated to the same prominent ~100-kyr eccentricity maximum. This level coincides with distinctive features in the stable isotope record, falls right in the middle of the Miocene Climatic Optimum (MCO) and is approximately one 405-kyr cycle older than the most dramatic oxygen isotope minimum dated astronomically at 15.6 Ma, marking the most extreme warming during the entire Miocene (Holbourn et al., 2013). It further corresponds closely to the top of Chron C5Cn, based on detailed cyclostratigraphic correlations to parallel Sites U1335 and U1336, which have an excellent magnetostratigraphy. Biostratigraphically, the Langhian GSSP falls in the lower part of the Mediterranean planktonic foraminiferal Sub zone MMi4a (Di Stefano et al., 2008; Iaccarino et al., 2011; Lirer et al., 2019), delimited by the First Occurrence (FO) of Globigerinoides sicanus (3 apertures) at the base and the Beginning of the Paragloborotalia siakensis Acmea at the top, and calcareous nannofossil Subzone MNN4b (Di Stefano et al., 2008; 2023), defined by the Last Common Occurrence (LCO) of Helicosphaera ampliaperta and the Beginning of the Sphenolithus heteromorphus Paracme interval. With respect to (sub)tropical biozonations, the Langhian GSSP falls within the planktonic foraminiferal Zone M5 (Wade et al., 2011) and Zone N8 (Blow, 1969), defined by Base Praeorbulina sicana (B) and Base Orbulina suturalis, and at the top of the calcareous nannofossil Zone CNM6 (Backman et al., 2012), defined by Base S. heteromorphus and Base Discoaster signus (= D. petalosus), corresponding to the upper part of Zone NN4 (Martini, 1971
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