1,192 research outputs found
supplementary_material – Supplemental material for Climate variability of the last ~2700 years in the Southern Adriatic Sea: Coccolithophore evidences
No full textSupplemental material, supplementary_material for Climate variability of the last ~2700 years in the Southern Adriatic Sea: Coccolithophore evidences by Antonio Cascella, Sergio Bonomo, Bassem Jalali, Marie-Alexandrine Sicre, Nicola Pelosi, Sabine Schmidt and Fabrizio Lirer in The Holocene</p
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
La Piccola Era Glaciale e il suo clima tra mare, terra e arte
No full textLa Piccola Era Glaciale e il suo clima tra mare, terra e arte
GEOLOGICAL MAP OF THE GORGOGLIONE BASIN (EASTERN SECTOR)
No full textIn this paper we report new stratigraphic data related to a new geological map of the Miocene Gorgoglione Basin of southern Italy, traditionally considered as a piggy-back or wedge-top basin filled by a turbidite-like succession. Well exposed outcrops in the study area (eastern sector of the basin) show four unconformities in the Castelmezzano-Pietrapertosa area. Two of these unconformities pass to paraconformities southeastward, in the Cirigliano-Gorgoglione area. Based on new stratigraphic data the “succession of the Gorgoglione Flysch” can be divided into different informal units: Val Miletta formation and Gorgoglione supersynthem. The latter can be subdivided into the Cirigliano and Castelmezzano synthems. The previously established Cirigliano synthem is here divided into three subsynthems. The lowermost sediments of the Gorgoglione Flysch on the eastern sectors correspond to a complex unit (Val Miletta formation) including Numidian-like quartzarenites, Gorgoglionelike sandstones, and, at the top of the formation, an olistostrome of varicoloured clays, belonging to the Argille Variegate Group. The stratigraphic analyses and the biostratigraphic results based on calcareous plankton assemblage, improve the reconstruction of the geometries of the sedimentary bodies and the time-space facies evolution of the synthems. Sedimentologic and petrographic characters of the upper part of the Castelmezzano synthem show a clear fining and thinning upward trend. Medium- and fine-grained arenites, varying in composition from quartz sandstones to siltstones and shales, are locally marked by abundant planktonic foraminifera and are interpreted as contourites. Moreover, the relationships between tectonics and sedimentation are analyzed. The data are used to propose a scheme of the Burdigalian to Tortonian tectono-stratigrafiphic evolution of the eastern sector of the basin
Climate 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
CALCAREOUS PLANKTON BIOSTRATIGRAPHY AND AGE OF THE MIDDLE MIOCENE DEPOSITS OF LONGANO FORMATION (EASTERN MATESE MOUNTAINS, SOUTHERN APENNINES)
No full textThe integrated calcareous plankton biostratigraphy (planktonic foraminifera and calcareous nannofossils) and an accurate fieldwork, allowed us the reconstruction of the sedimentary evolution of the Longano Formation (Orbulina Marls). In particular the correlation between the bioevents recognised in the Orbulina Marls sequence and those recorded in astronomically calibrated Middle Miocene sections, offered the possibility to date the passage from the shallow-water Cusano Formation to the deep-water deposits of the Longano Formation at about 13.21 Ma and the successive onset of terrigenous deposits of the Pietraroia Formation at 10.54 Ma. In addition, an high resolution study of the terrigenous sequence, showed that this sedimentary event is not abrupt but it is characterised by a progressive increase, bed by bed, of the siliciclastic fraction up to the deposition of the sandstones. The recognition in all the studied sections of the base of the first Acme (AB1) of Paragloborotalia siakensis dated at 13.21 Ma, just above the phosphate-rich interval (this interval marks the transition between Cusano and Longano Formations), proved that the transgression which led to the deposition of the Orbulina Marls was synchronous in all the south-eastern Matese Mountains
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
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
Large-signal device simulation in time- and frequency-domain: a comparison
No full textThe aim of this paper is to compare the most common time- and frequency-domain numerical techniques for the determination of the steady-state solution in the physics-based simulation of a semiconductor device driven by a time-periodic generator. The shooting and harmonic balance (HB) techniques are applied to the solution of the discretized drift-diffusion device model coupled to the external circuit embedding the semiconductor device, thus providing a fully nonlinear mixed mode simulation. The comparison highlights the strong and weak points of the two approaches, basically showing that the time-domain solution is more robust with respect to the initial condition, while the HB solution provides a more rapid convergence once the initial datum is close enough to the solution itsel
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