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Università di Urbino
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- PublicationOpen AccessHolocene Critical Zone dynamics in an Alpine catchment inferred from a speleothem multiproxy record: disentangling climate and human influences(2019-11-28)
; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ;Disentangling the effects of climate and human impact on the long-term evolution of the Earth Critical Zone is crucial to understand the array of its potential responses to the ongoing Global Change. This task requires natural archives from which local information about soil and vegetation can be linked directly to climate parameters. Here we present a high-resolution, well-dated, speleothem multiproxy record from the SW Italian Alps, spanning the last ~10,000 years of the present interglacial (Holocene). We correlate magnetic properties and the carbon stable isotope ratio to soil stability and pedogenesis, whereas the oxygen isotope composition is interpreted as primarily related to precipitation amount, modulated at different timescales by changes in precipitation source and seasonality. During the 9.7-2.8 ka period, when anthropic pressure over the catchment was scarce, intervals of enhanced soil erosion are related to climate-driven vegetation contractions and occurred during drier periods. Immediately following the onset of the Iron Age (ca. 2.8 ka), by contrast, periods of enhanced soil erosion coincided with a wetter climate. We propose that the observed changes in the soil response to climate forcing were related to early anthropogenic manipulations of Earth's surface, which made the ECZ more sensitive to climate oscillations.221 19 - PublicationRestrictedCyclochronology of the Eocene–Oligocene transition from the Cape Roberts Project-3 core, Victoria Land basin, Antarctica(2012)
; ; ; ; ; ; ; ;Galeotti, S.; Dipartimento di Scienze della Terra, della Vita e dell'Ambiente, Università degli Studi di Urbino, Campus Scientifico ‘Enrico Mattei’, Località Crocicchia, 61029 Urbino, Italy ;Lanci, L.; Dipartimento di Scienze della Terra, della Vita e dell'Ambiente, Università degli Studi di Urbino, Campus Scientifico ‘Enrico Mattei’, Località Crocicchia, 61029 Urbino, Italy ;Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Naish, T. R.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand ;Sagnotti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Sandroni, S.; Museo Nazionale dell'Antartide, Università degli Studi di Siena, via del Laterino 8, 53100 Siena, Italy ;Talarico, F. M.; Dipartimento di Scienze della Terra, Università degli Studi di Siena, via del Laterino 8, 53100 Siena, Italy; ; ; ; ; ; About 34 million years ago, at the Eocene–Oligocene (E–O) transition, Earth's climate underwent a substantial change from relatively ice-free “green house” conditions to a glacial state marked by the establishment of a permanent ice sheet on Antarctica. Our understanding of the Antarctic cryospheric evolution across the E–O climate transition relies on indirect marine geochemical proxies and, hitherto, it has not been possible to reconcile the pattern of inferred ice-sheet growth from these “far-field” proxy records with direct physical evidence of ice sheet behaviour from the proximal Antarctic continental margin. Here we present a correlation of cyclical changes recorded in the CRP-3 drill hole sediment core from the western Ross Sea, that are related to oscillations in the volume of a growing East Antarctic Ice Sheet, with well dated lower latitude records of orbital forcing and climate change across the E–O transition. We evaluate the results in the light of the age model available for the CRP-3A succession. Our cyclostratigraphy developed on the basis of repetitive vertical facies changes and clast peak abundances within sequences matches the floating cyclochronology developed in deep-sea successions for major glacial events. The astrochronological calibration of the CRP-3 succession represents the first high-resolution correlation of direct physical evidence of orbitally controlled glaciation from the Antarctic margin to geochemical records of paleoclimate changes across the E–O climate transition.241 30 - PublicationOpen AccessA 10,000 yr record of high-resolution Paleosecular Variation from a flowstone of Rio Martino Cave, Northwestern Alps, Italy(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ;; ;Speleothems are potentially excellent archives of the Earth’s magnetic field, capable of recording its past variations. Their characteristics, such as the continuity of the record, the possibility to be easily dated, the almost instantaneous remanence acquisition and the high time-resolution make them potentially unique high-quality Paleosecular Variation (PSV) recorders. Nevertheless, speleothems are commonly characterized by low magnetic intensities, which often limits their resolution. Here we present a paleomagnetic study performed on two cores from a flowstone from the Rio Martino Cave (Western Alps, Italy). U/Th dating indicates that the flowstone’s deposition covers almost the entire Holocene, spanning the period ca. 0.5–9.0 ka, while an estimation of its mean growth rate is around 1 mm per 15 years. The flowstone is composed of columnar calcite, characterized by a highly magnetic detrital content from meta-ophiolites in the cave’s catchment. This favorablegeological context results in an intense magnetic signal that permits the preparation and measurement of thin (∼3 mm depth equivalent) samples, each representing around 45 yr. The Characteristic Remanent Magnetization (ChRM), isolated after systematic stepwise Alternating Field demagnetization, is well defined, with Maximum Angular Deviation (MAD) generally lower than 10◦. Paleomagnetic directional data allow the reconstruction of the PSV path during the Holocene for the area. Comparison of the new data with archeomagnetic data from Italian archeological and volcanic records and using the predictions of the SHA.DIF.14k and pfm9k.1a global geomagnetic field models shows that the Rio Martino flowstone represents an excellent recorder of the Earth’s magnetic field during the last 9,000 years. Our high resolution paleomagnetic record, anchored by a high-quality chronology, provides promising data both for the detection of short term geomagnetic field variations and for complementing existing regional PSV curves for the prehistoric period, for which well-dated data are still scarce198 70 - PublicationOpen AccessCyclochronology of the Global Stratotype Section and Point for the Eocene/Oligocene boundarySpectral analyses of high-resolution records from the upper Eocene-lower Oligocene from the Massignano section, GSSP for the Eocene/Oligocene (E/O) boundary, and the nearby Massicore reveal orbitally controlled fluctuations in the percent concentration of calcium carbonate (wt% CaCO3) and magnetic susceptibility. Extraction of orbital components provides a consistent cyclochronology for the two sites that straddles the E/O boundary. Detection of longer-term modulation in the short eccentricity enabled tuning to the astronomical solution and development of a robust astrochronology for the E/O boundary transition in the GSSP section. Correlation with astrochronologically dated records allowed us to identify the local sedimentary response to the global paleoclimatic and palaeoceanographic events that characterize the greenhouse-icehouse transition during the late Eocene-early Oligocene.
35 49 - PublicationRestrictedNoble-gas signature of magmas from a heterogeneous mantle wedge: the case of Stromboli volcano (Aeolian Islands, Italy)(2014-01)
; ; ; ; ; ; ;Martelli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Rizzo, A. l.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia ;Renzulli, A.; Università di Urbino ;Ridolfi, F.; Università di Urbino ;Arienzo, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Rosciglione, A.; Università di Palermo; ; ;; ; We report on the variation of the elemental (He, Ne, and Ar) and isotopic (He and Ar) compositions of olivine and clinopyroxene-hosted fluid inclusions hosted in lavas, pyroclastics, and cumulate xenoliths from the last 60 ka of the eruptive history of Stromboli volcano, Italy. Samples belong to (i) the present-day activity as represented by shoshonitic (SHO) basalts, i.e., pumices with low porphyritic (LP) content and high porphyritic (HP) scoriae; (ii) the subalkaline versus alkaline products erupted at Stromboli during its subaerial history among the extrememagmatic series, i.e., calc-alkaline (CA) and potassic (KS); and (iii) the only known ultramafic cumulates (San Bartolo wehrlite xenoliths, SBX) outcropping in the island, carried to the surface by recent (ca. 2 ka) basaltic lava. To interpret the results better, we also investigated trace elements in the clinopyroxenes of wehrlite xenoliths and the Sr and Nd isotopes of all of the products in which the 3He/4He ratio was measured. Wehrlite xenoliths are igneous cumulates crystallized at mantle depth that mostly consist of clinopyroxene and olivine crystals with limited compositional variation. The texture, mineral chemistry, pattern of trace elements and Sr–Nd-isotope ratios (in clinopyroxene) suggest that these cumulates were produced by the early crystallization of a primitive basaltic magma with CA or HKCA–SHO affinity. The gas contents measured in themafic crystals decrease fromthewehrlite xenoliths through LP pumice, CA and KS lavas and, finally, to the HP scoria. This observation is consistent with crystallization and fluid entrapment frommantle depths to progressively shallower crustal levels. The lowgas content extracted from the HP crystals did not allow measurement of their 3He/4He ratios. Most of the investigated crystals exhibit a 3He/4He ratio in the range of 4.0–4.9 Ra, with only the KS mafic minerals exhibiting lower 3He/4He values (≤3.5 Ra). The low values of He-isotope ratios relative to those of the most-uncontaminated mantle source of the Aeolian lavas (i.e., 3He/4He ~7 Ra at Alicudi) and in common volcanic arcs suggest that the Stromboli mantle wedge is more contaminated by sediments and aqueous fluids derived by the active subduction of the Ionian slab. We also hypothesize that a process of mantle He loss that occurred during the mantle metasomatism contributed to the decrease of 3He/4He. The low 3He/4He values of the KS minerals with respect to the other Stromboli magmatic series are consistent with the higher Sr- and lower Nd-isotope ratios measured in the same samples and are attributed to source heterogeneity. Finally, data for the 3He/4He ratios from mafic minerals were compared with those of currently emitted hydrothermal fluids, which are regularly sampled for volcano surveillance. The maximum 3He/4He ratio found in the hydrothermal fluids matched the maximum ratio measured in the LP fluid inclusions (i.e., 4.6 Ra) and thus corresponds to the upper limit that should be expected for surface gases during or before high-intensity eruptive events in which a deep gas component401 106