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Agnini, Claudia
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Agnini, Claudia
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- PublicationOpen AccessAn astronomically dated record of Earth's climate and its predictability over the last 66 million years(2020-09-11)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ; ; ; ;Much of our understanding of Earth's past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states-Hothouse, Warmhouse, Coolhouse, Icehouse-are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.98 5 - PublicationRestrictedAn early Eocene carbon cycle perturbation at ~52.5 Ma in the Southern Alps: Chronology and biotic response(2009-05-14)
; ; ; ; ; ; ; ; ; ; ;Agnini, C.; Dipartimento di Geoscienze, Università di Padova, Padua, Italy ;Macrì, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Backman, J.; Department of Geology and Geochemistry, Stockholm University, Stockholm, Sweden ;Brinkhuis, H.; Palaeoecology, Laboratory of Palaeobotany and Palynology, Institute of Environmental Biology, Utrecht University, Utrecht, Netherlands ;Fornaciari, E.; Dipartimento di Geoscienze, Università di Padova, Padua, Italy ;Giusberti, L.; Dipartimento di Geoscienze, Università di Padova, Padua, Italy ;Luciani, V.; Dipartimento di Scienze della Terra, Polo Scientifico Tecnologico, Università di Ferrara, Ferrara, Italy ;Rio, D.; Dipartimento di Geoscienze, Università di Padova, Padua, Italy ;Sluijs, A.; Palaeoecology, Laboratory of Palaeobotany and Palynology, Institute of Environmental Biology, Utrecht University, Utrecht, Netherlands ;Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; ; ; ; ; ; ; ; ; At least two transient events of extreme global warming occurred superimposed on the long-term latest Paleocene and early Eocene warming trend in the Paleocene-Eocene thermal maximum (PETM) (or ETM1 ~55.5 Ma) and the Elmo (or ETM2 ~53.6 Ma). Other than warmth, the best known PETM is characterized by (1) significant injection of 13C-depleted carbon into the ocean-atmosphere system, (2) deep-sea carbonate dissolution, (3) strong biotic responses, and (4) perturbations of the hydrological cycle. Documentation of the other documented and suspected "hyperthermals" is, as yet, insufficient to assess whether they are similar in nature to the PETM. Here we present and discuss biomagnetostratigraphic data and geochemical records across two lower Eocene successions deposited on a continental margin of the western Tethys: the Farra and Possagno sections in the Venetian pre-Alps. We recognize four negative carbon isotope excursions within chron C24. Three of these shifts correlate to known or suspected hyperthermals: the PETM, the Eocene thermal maximum 2 (~53.6 Ma), and the informally named "X event" (~52.5 Ma). The fourth excursion lies within a reverse subchron and occurred between the latter two. In the Farra section, the X event is marked by a ~0.6% negative carbon isotope excursion and carbonate dissolution. Furthermore, the event exhibits responses among calcareous nannofossils, planktic foraminifera, and dinoflagellates that are similar to, though less intense than, those observed across the PETM. Sedimentological and quantitative micropaleontological data from the Farra section also suggest increased weathering and runoff as well as sea surface eutrophication during this event.365 36 - PublicationOpen AccessReworked Coccoliths as runoff proxy for the last 400 years: The case of Gaeta Gulf (central Tyrrhenian Sea, Central Italy)(2016)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We present the results of a high resolution study carried out on a shallow water sediment core, recovered in the central Tyrrhenian Sea to reconstruct the runoff story of the catchment basin of Volturno and Garigliano rivers (Gulf of Gaeta, Italy), over the past ~400years. We compared the abundance distribution pattern of Reworked Coccoliths to the surface runoff model simulation for the Volturno and Garigliano rivers hydrographic basins, the Global Historical Climatology Network index, the Palmer drought severity index, the Tevere river discharge anomaly, the summer average rainfall of the Southern Italy and the North Atlantic Oscillation reconstructed signal. This comparison suggested that the biotic signal of the Reworked Coccoliths may be used to detect climatic events from local to “global” scale. The calcareous nannofossil assemblages as well as their diversity index are modulated by oscillation in solar activity, where minima in solar activity correspond to minima calcareous nannofossil diversity and viceversa. In particular, the antiphase correlation between the abundance of Reworked Coccoliths and the North Atlantic Oscillation index, which modulates the winter precipitation, suggests that this biotic index could be used as a reliable proxy to reconstruct the variations in the hydrographic basin runoff of the Volturno and Garigliano rivers. In addition, power spectral and wavelet analysis carried out on both signals documented the occurrence of climatic cycles of the duration of about 95yr. From 1900 AD upwards, a turnover in the periodicity from 95yr climatic cycles to 22-26 yr cycles occurred in the Reworked Coccoliths signal, suggesting a strong control of solar forcing (Hale cycle) over the last century.292 113