Alpine Laboratory of Paleomagnetism ALP

Peveragno, Italy

Alpine Laboratory of Paleomagnetism ALP

Peveragno, Italy
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Zanella E.,University of Turin | Zanella E.,Alpine Laboratory of Paleomagnetism ALP | Sulpizio R.,University of Bari | Sulpizio R.,CNR Institute for the Dynamics of Environmental Processes | And 3 more authors.
Geological Society Special Publication | Year: 2015

The temperature of the deposits (Tdep) emplaced by the pyroclastic density current (PDC) generated by the seven major explosive eruptions from Somma-Vesuvius during the last 22 kyr were investigated using the thermal remanent magnetization (TRM) of lithic clasts embedded within the deposits. New data are presented for the Pomici di Base, Greenish Pumice, Mercato and 1631 AD deposits and compared to the literature data from the Avellino, 79 AD-Pompeii and 472 AD-Pollena eruptions. The Tdep mainly fall in the range 270-370 °C and no significant correlation is evidenced between sedimentological features, eruptive and depositional processes and the final Tdep. The admixture of ambient air during the run-out appears the most effective process to cool the temperature of the ash and gases of the PDC, and is therefore the main factor affecting the deposit temperature. © 2015 The Geological Society of London.


Roveri M.,University of Parma | Roveri M.,Alpine Laboratory of Paleomagnetism ALP | Flecker R.,University of Bristol | Krijgsman W.,University Utrecht | And 13 more authors.
Marine Geology | Year: 2014

Forty years after the image of the Mediterranean transformed into a giant salty lake was first conceived, the fascinating history of the Messinian Salinity Crisis (MSC) still arouses great interest across a large and diverse scientific community. Early outcrop studies which identified severe palaeoenvironmental changes affecting the circum-Mediterranean at the end of the Miocene, were followed by investigations of the marine geology during the 1950s to 1970s. These were fundamental to understanding the true scale and importance of the Messinian event. Now, after a long period of debate over several entrenched but largely untested hypotheses, a unifying stratigraphic framework of MSC events has been constructed. This scenario is derived mainly from onshore data and observations, but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep Mediterranean basins. The MSC was an ecological crisis, induced by a powerful combination of geodynamic and climatic drivers, which had a great impact on the subsequent geological history of the Mediterranean area, and on the salinity of the global oceans. These changed the Mediterranean's connections with both the Atlantic Ocean and the freshwater Paratethyan basins, causing high-amplitude fluctuations in the hydrology of the Mediterranean. The MSC developed in three main stages, each of them characterized by different palaeoenvironmental conditions. During the first stage, evaporites precipitated in shallow sub-basins; the MSC peaked in the second stage, when evaporite precipitation shifted to the deepest depocentres; and the third stage was characterized by large-scale environmental fluctuations in a Mediterranean transformed into a brackish water lake. The very high-resolution timescale available for some Late Miocene intervals in the Mediterranean makes it possible to consider environmental variability on extremely short time scales including, in some places, annual changes. Despite this, fundamental questions remain, some of which could be answered through new cores from the deepest Mediterranean basins. Improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal Messinian succession for the first time. The resulting data would allow us to decipher the causes of this extreme environmental change and its global-scale consequences. © 2014 Elsevier B.V.


Gurioli L.,CNRS Magmas and Volcanoes Laboratory | Zanella E.,University of Turin | Zanella E.,Alpine Laboratory of Paleomagnetism ALP | Gioncada A.,University of Pisa | Sbrana A.,University of Pisa
Bulletin of Volcanology | Year: 2012

The historic Breccia di Commenda (BC) explosive eruption of Vulcano (Aeolian Islands, Italy) opened with a phase that generated a gray fine ash layer dispersed to the northwest (phase 1). The eruption continued with a dilute pyroclastic density current (PDC) that was dispersed to the east, followed by the emplacement of radially distributed, topographically controlled PDC deposits (phase 2). The last phase of the eruption produced a sequence of accretionary lapilli and gray fine ash dispersed toward the southeast (phase 3). The most impressive feature of the BC is its high lithic/juvenile clast ratio and the yellow color of the deposits of phase 2. Lithic fragments are mainly hydrothermally altered rocks, in the silicic and advanced argillic facies. Juvenile fragments, ranging from 20 % to 40 % by volume, are mainly confined to the ash component of the deposits and comprise rhyolitic to trachyandesite, poorly to non-vesicular fragments. The fine ash fraction of the deposits is richer in S, Cu, Zn, Pb, and As than the BC juvenile lapilli and bombs, and also the juvenile components of other La Fossa units, suggesting that the BC formed in the presence of an anomalously high amount of S and metals. Sulfur and metals may have been carried as aerosols by chloride- and sulfate-bearing micro-crystals, derived from the condensation of magmatic gas in the eruptive cloud. The high content of hydrothermally altered lithic clasts in the deposits suggests that explosions involved the fluid-saturated hydrothermally altered rocks residing in the conduit zone. However, the presence of a juvenile component in the deposits supports the idea that this explosion may have been triggered by the ascent of new magma. We categorize this eruption as magmatic-hydrothermal to emphasize that in this type of phreatomagmatic eruption the external water was an active hydrothermal system. Rock magnetic temperatures of non-altered lava lithic fragments indicate a uniform deposit temperature for the PDC deposits of between 200 and 260 °C, with a maximum at 280 °C. These homogeneous, relatively low temperatures are consistent with the idea that the phase 2 explosions involved the expansion of abundant steam from the flashing of the hydrothermal system. In addition, recent paleomagnetic dating of the BC provides an age of between 1000 and 1200 AD, younger than that reported in the previously published data, suggesting that previous interpretations and the recent history of La Fossa and Mt. Pilato require re-evaluation. © 2012 Springer-Verlag.


Dallanave E.,Ludwig Maximilians University of Munich | Agnini C.,University of Padua | Bachtadse V.,Ludwig Maximilians University of Munich | Muttoni G.,University of Milan | And 7 more authors.
Bulletin of the Geological Society of America | Year: 2015

The Mead Stream section (South Island, New Zealand) consists of a 650-m-thick series of continuous, well-exposed strata deposited on a South Pacific continental slope from the Late Cretaceous to the middle Eocene. We examined the uppermost Paleocene-middle Eocene part of the section, which consists of -360 m of limestone and marl, for detailed magnetic polarity stratigraphy and calcareous nannofossil and foraminifera biostratigraphy. Magneto-biostratigraphic data indicate that the section straddles magnetic polarity chrons from C24r to C18n, calcareous nannofossil zones from NP9a to NP17 (CNP11-CNE15, following a recently revised Paleogene zonation), and from the Waipawan to the Bortonian New Zealand stages (i.e., from the base of the Ypresian to the Bartonian international stages). The Mead Stream section thus encompasses 17 m.y. (56-39 Ma) of southwest Pacific Ocean history. The ages of calcareous nannofossil biohorizons are consistent with low-to midlatitude data from the literature, indicating that during the early-middle Eocene, the low-to midlatitude calcareous nannofossil domain extended at least to -50°S-55°S in the South Pacific. Correlation of the magnetic polarity stratigraphy from the Mead Stream section with the geomagnetic polarity time scale allows us to derive sediment accumulation rates (SAR), which range between 8 and 44 m/m.y. Comparing the SAR with paleotemperature proxy records, we found that two intervals of increased SAR occurred during the early Eocene climatic optimum (52-50 Ma) and during the transient warming event peaking with the middle Eocene climatic optimum (40.5 Ma). This correlation indicates that, at Mead Stream, the climate evolution of the early-middle Eocene is recorded in a sedimentation pattern whereby, on a millionyear time scale, warmer climate promoted continental weathering, transportation, and accumulation of terrigenous sediments. © 2014 Geological Society of America.


Manzi V.,University of Parma | Manzi V.,Alpine Laboratory of Paleomagnetism ALP | Lugli S.,University of Modena and Reggio Emilia | Roveri M.,University of Parma | And 4 more authors.
Bulletin of the Geological Society of America | Year: 2011

Three different types of carbonate deposits are included within the "Calcare di Base," commonly envisaged to record the Messinian salinity crisis onset: type 1 consists of sulfur-bearing limestones, representing the biogenic product of bacterial sulfate reduction after original gypsum; type 2 comprises dm-thick, laminated dolomitic limestones interbedded with diatomites, sapropels, and marls found at the top the Tripoli Formation; type 3, the most common variety, consists of m-thick, brecciated limestones interbedded with shales and clastic gypsum. Type 3 shows sedimentary features suggesting a clastic origin and deposition from high- to low-density gravity flows; thus, these deposits can be regarded as an end-member of a large variety of evaporite-bearing, gravity-flow deposits, with a dominant carbonate component. The genetic and stratigraphic characterization of these carbonates has strong implications for a better comprehension of Messinian events; the three types of Calcare di Base seem to have formed during different stages of the Messinian salinity crisis (MSC). Type 2 formed in the first stage (5.96-5.60 Ma), and is the only type that can be regarded as the Lower Gypsum time-equivalent. Type 3 was deposited in the second stage (5.60-5.55 Ma), and its base is associated with a regional-scale hiatus and erosion (Messinian erosional surface). Type 1 formed even later, likely in post-Messinian time, through diagenetic processes affecting resedimented gypsum deposited during the second stage of the MSC. It follows that not all the Calcare di Base deposits record the onset of the Messinian salinity crisis, as commonly thought. Thus, a detailed facies characterization of these carbonate deposits is fundamental for both stratigraphic reconstructions and a better comprehension of Messinian events. © 2011 Geological Society of America.


Agnini C.,University of Padua | Agnini C.,CNR Institute of Geosciences and Earth Resources | Fornaciari E.,University of Padua | Giusberti L.,University of Padua | And 10 more authors.
Bulletin of the Geological Society of America | Year: 2011

The Alano section has been presented at the International Subcommission on Paleogene Stratigraphy (ISPS) as a potential candidate for defining the global boundary stratotype section and point (GSSP) of the late Eocene Priabonian Stage. The section is located in the Venetian Southern Alps of the Veneto region (NE Italy), which is the type area of the Priabonian, being exposed along the banks of the Calcino torrent, near the village of Alano di Piave. It consists of ~120-130 m of bathyal gray marls interrupted in the lower part by an 8-m-thick package of laminated dark to black marlstones. Intercalated in the section, there are eight prominent marker beds, six of which are crystal tuff layers, whereas the other two are bioclastic rudites. These distinctive layers are useful for regional correlation and for an easy recognition of the various intervals of the section. The section is easily accessible, crops out continuously, is unaffected by any structural deformation, is rich in calcareous plankton, and contains an expanded record of the critical interval for defining the GSSP of the Priabonian. In order to further check the stratigraphic completeness of the section and constrain in time the critical interval for defining the Priabonian Stage, we performed a high-resolution study of integrated calcareous plankton biostratigraphy and a detailed magnetostratigraphic analysis. Here, we present the results of these studies to open a discussion on the criteria for driving the "golden spike" that should define the middle Eocene-late Eocene boundary. © 2011 Geological Society of America.


Roveri M.,University of Parma | Roveri M.,Alpine Laboratory of Paleomagnetism ALP | Lugli S.,University of Modena and Reggio Emilia | Manzi V.,University of Parma | And 4 more authors.
Marine Geology | Year: 2014

New 87Sr/86Sr data from DSDP-ODP Messinian cores from deep Mediterranean basins suggest that the usually envisaged correlation of offshore Upper Evaporites with onshore Upper Gypsum deposits of Sicily, Cyprus and Crete recording the stage 3 (5.53-5.33Ma) of the Messinian salinity crisis may be not entirely correct. High-resolution stratigraphic calibration of Sr isotope data indicates that only a very thin unit (commonly <50m) in the uppermost part of the "seismic" Upper Evaporites is characterized by the typically lower values for Sr isotopes with respect to the global Ocean which characterize stage 3 onshore successions ("Lago Mare event"). These deposits mainly consist of interbedded clastic or cumulate gypsum and marls; halite recovered from cores in the Upper Evaporites unit is actually characterized by Sr isotope values consistent with stage 2 deposits of onshore successions. According to these results, the Messinian trilogy of the western Mediterranean basin could be as a whole correlated with the halite unit of the eastern basin, suggesting that different hydrologic conditions characterized the two deep areas during the peak of the salinity crisis. © 2014 Elsevier B.V.


Dallanave E.,University of Padua | Dallanave E.,Alpine Laboratory of Paleomagnetism ALP | Dallanave E.,Ludwig Maximilians University of Munich | Muttoni G.,Alpine Laboratory of Paleomagnetism ALP | And 3 more authors.
Geophysical Journal International | Year: 2012

In the lowermost Eocene sedimentary record of Ocean Drilling Program Site 1262 (Leg 208, Walvis Ridge, South Atlantic Ocean), the presence of a ∼53-kyr-long normal polarity event has been recorded within the ∼2.55-Myr-long reverse polarity Chron C24r (∼53.3-55.9 Ma) and termed Palaeocene-Eocene magnetic reversal (PEMR). The origin of the PEMR has been speculatively related to a change in the Earth's rotation rate that was in turn influenced by an abrupt overturning of the ocean-atmosphere circulation that occurred during the Palaeocene-Eocene thermal maximum (PETM) at ∼55 Ma. Such provocative genesis for a magnetic-polarity reversal demands the PEMR to be confirmed (or refuted) in additional PETM sections. Here, we present detailed palaeomagnetic and rock-magnetic data from the Forada and Cicogna sections of the Belluno Basin in NE Italy, which contain an expanded and continuous record of the PETM termed clay marl unit (CMU). Our data indicate that these sediments were deposited during a continuous interval of reverse geomagnetic field polarity. We therefore conclude that no magnetic-polarity reversals occurred throughout the PETM. In addition, we studied the origin of the high degree of flattening affecting the characteristic magnetic component directions of the sediments, which we interpret as due to a combination of depositional inclination shallowing typical of detrital haematite, and post-depositional compaction of clays, particularly abundant in the carbonate-depleted CMU. © 2012 The Authors Geophysical Journal International © 2012 RAS.


Manzi V.,University of Parma | Manzi V.,Alpine Laboratory of Paleomagnetism ALP | Gennari R.,University of Parma | Gennari R.,Alpine Laboratory of Paleomagnetism ALP | And 6 more authors.
Terra Nova | Year: 2013

We propose a revised age calibration of the Messinian salinity crisis onset in the Mediterranean at 5.971 Ma based on the recognition of an extra gypsum cycle in the transitional interval of the Perales section (Sorbas basin, Spain) and the revision of the magnetostratigraphy of the Monticino section (Vena del Gesso basin, Italy). This age re-calibration allows to state more accurately that: (i) the interval encompassing the MSC-onset is continuous, thus ruling out any erosional feature or stratigraphic hiatus related to a major sea-level fall affecting the Mediterranean; (ii) the first gypsum was deposited during the summer insolation peak at 5.969 Ma associated with an eccentricity minimum and roughly coincident with glacial stage TG32; (iii) the MSC-onset was preconditioned by the tectonically-driven reduction of the hydrological exchanges with the Atlantic Ocean and finally triggered by glacial conditions in the northern hemisphere and by arid conditions in northern Africa. © 2013 John Wiley & Sons Ltd.

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