Osservatorio Geologico di Coldigioco
Osservatorio Geologico di Coldigioco
Boschi S.,Lund University |
Schmitz B.,Lund University |
Schmitz B.,Robert itzker Center For Meteoritics And Polar Studies |
Heck P.R.,Robert itzker Center For Meteoritics And Polar Studies |
And 9 more authors.
Geochimica et Cosmochimica Acta | Year: 2017
During the late Eocene there was an enigmatic enhancement in the flux of extraterrestrial material to Earth. Evidence comes from sedimentary 3He records indicating an increased flux of interplanetary dust during ca. 2 Myr, as well as two very large impact structures, Popigai (100 km diameter) and Chesapeake Bay (40–85 km), that formed within 10–20 kyr at the peak of the 3He delivery. The Massignano section in Italy has one of the best sedimentary records of these events, including a well-defined 3He record, an Ir-rich ejecta bed related to the Popigai impact event, and two smaller Ir anomalies. Recently we showed that the Popigai ejecta is associated with a significant enrichment of chromite grains (>63 μm) with an H-chondritic elemental composition (17 grains in 100 kg of rock). Most likely these grains are unmelted fragments from the impactor. Slightly higher up (ca. 20 cm) in the section, where a small Ir anomaly possibly related to the Chesapeake Bay impact has been measured, we found a weak enrichment in L-chondritic grains (8 grains in 208 kg of rock). Here we report an extended data set increasing the total amount of sediment dissolved in acid and searched for extraterrestrial chromite grains from 658 to 1168 kg. In altogether 760 kg of background sediment from 17 levels over 14 m of strata outside the interval corresponding to the Popigai and Chesapeake Bay impacts, we only found 2 extraterrestrial chromite grains. Both grains have L-chondritic compositions and were found in a 100 kg sample from the ca. 10.25 m level in the section where the second of the smaller Ir anomalies has been reported. A correlation appears to exist between Ir, 3He and chromite from ordinary chondrites. We also report oxygen three-isotope measurements of the extraterrestrial chromite grains associated with the Popigai ejecta and confirm an H-chondritic composition. The new results strengthen our scenario that the upper Eocene 3He and Ir enrichments originate from the asteroid belt rather than the Oort cloud as originally proposed when the 3He anomaly was discovered. The generally low background concentrations of extraterrestrial chromite through the section speak against any major single asteroid breakup event such as in the mid-Ordovician after the break-up of the L-chondrite parent body. Instead the data reconcile with a small, possibly a factor of 2–3, increase in the flux of extraterrestrial material to Earth, but of both H- and L-chondritic composition. We also report the composition of all the 2310 terrestrial chrome spinel grains recovered, and show that their chemical composition indicates a dominantly regional ophiolitic source. Four anomalous chrome spinel grains with high Ti and V concentrations were found in the Popigai ejecta. These grains originate from Siberian Traps basalts in the Popigai crater at the time of impact. © 2017 The Author(s)
Richards M.A.,University of California at Berkeley |
Alvarez W.,University of California at Berkeley |
Self S.,University of California at Berkeley |
Karlstrom L.,University of Oregon |
And 9 more authors.
Bulletin of the Geological Society of America | Year: 2015
New constraints on the timing of the Cretaceous- Paleogene mass extinction and the Chicxulub impact, together with a particularly voluminous and apparently brief eruptive pulse toward the end of the "main-stage" eruptions of the Deccan continental flood basalt province suggest that these three events may have occurred within less than about a hundred thousand years of each other. Partial melting induced by the Chicxulub event does not provide an energetically plausible explanation for this coincidence, and both geochronologic and magnetic-polarity data show that Deccan volcanism was under way well before Chicxulub/Cretaceous-Paleogene time. However, historical data document that eruptions from existing volcanic systems can be triggered by earthquakes. Seismic modeling of the ground motion due to the Chicxulub impact suggests that the impact could have generated seismic energy densities of order 0.1-1.0 J/m3 throughout the upper ~200 km of Earth's mantle, sufficient to trigger volcanic eruptions worldwide based upon comparison with historical examples. Triggering may have been caused by a transient increase in the effective permeability of the existing deep magmatic system beneath the Deccan province, or mantle plume "head." It is therefore reasonable to hypothesize that the Chicxulub impact might have triggered the enormous Poladpur, Ambenali, and Mahabaleshwar (Wai Subgroup) lava flows, which together may account for >70% of the Deccan Traps main-stage eruptions. This hypothesis is consistent with independent stratigraphic, geochronologic, geochemical, and tectonic constraints, which combine to indicate that at approximately Chicxulub/Cretaceous- Paleogene time, a huge pulse of mantle plume-derived magma passed through the crust with little interaction and erupted to form the most extensive and voluminous lava flows known on Earth. High-precision radioisotopic dating of the main-phase Deccan flood basalt formations may be able either to confirm or reject this hypothesis, which inturn might help to determine whether this singular outburst within the Deccan Traps (and possibly volcanic eruptions worldwide) contributed significantly to the Cretaceous-Paleogene extinction. © 2015 Geological Society of America.
Bice D.,Pennsylvania State University |
Montanari A.,Osservatorio Geologico di Coldigioco |
Vucetic V.,Meteorological and Hydrological Service |
Vucetic M.,Meteorological and Hydrological Service
International Journal of Climatology | Year: 2012
We apply spectral analysis and sliding window correlations to monthly, seasonal, and annual climatological data from station records throughout Croatia going back to 1859 in order to investigate the potential influences of a set of important climatic drivers, including solar variability, and ocean-atmosphere oscillations in both the Pacific realm (El Niño-Southern Oscillation, ENSO and Pacific Decadal Oscillation, PDO) and the Atlantic realm (Atlantic Multidecadal Oscillation, AMO and North Atlantic Oscillation, NAO). In addition to a general long-term warming and drying, there are significant interannual to decadal scale variations. Positive phases of AMO correspond to higher Croatian temperatures and also times of greater interannual temperature variability. Higher frequency variations in NAO are positively correlated with temperature such that a negative phase of NAO is associated with lower Croatian temperatures. The strength of NAO's influence is modulated by the long-term cycles of AMO; stronger during positive decadal-scale phases of AMO. ENSO exerts a weaker influence on temperatures, and is only significant during positive phases of the PDO. NAO has a strong influence on Croatian winter precipitation, with negative NAO phases corresponding to higher precipitation, modulated by the longer term phases of AMO. Although weaker and less consistent, ENSO also influences Croatian winter precipitation, modulated by longer term cycles of the PDO. Both NAO and ENSO show signs of frequency-dependent correlation; NAO is influential at cycles of 8-9 and 2.4 yr in the Adriatic-Dinaric part of Croatia, while ENSO is especially influential at a 3.6 yr cycle in the Pannonian region. The influence of solar variability is apparently much weaker than that of NAO and ENSO, yet there is a remarkably coherent correlation between amplitude modulation of winter precipitation in the Pannonian region and the sunspot record. © 2011 Royal Meteorological Society.
Peterson D.E.,University of California at Berkeley |
Finger K.L.,University of California at Berkeley |
Iepure S.,Speleological Institute Emil Racovitza |
Mariani S.,Gruppo Speleologico CAI Fabriano |
And 2 more authors.
Journal of Cave and Karst Studies | Year: 2013
Rich, diverse assemblages comprising a total (live + dead) of twenty-one ostracod species belonging to fifteen genera were recovered from phreatic waters of the hypogenic Frasassi Cave system and the adjacent Frasassi sulfidic spring and Sentino River in the Marche region of the northeastern Apennines of Italy. Specimens were recovered from ten sites, eight of which were in the phreatic waters of the cave system and sampled at different times of the year over a period of five years. Approximately 6900 specimens were recovered, the vast majority of which were disarticulated valves; live ostracods were also collected. The most abundant species in the sulfidic spring and Sentino River were Prionocypris zenkeri, Herpetocypris chevreuxi, and Cypridopsis vidua, while the phreatic waters of the cave system were dominated by two putatively new stygobitic species of Mixtacandona and Pseudolimnocythere and a species that was also abundant in the sulfidic spring, Fabaeformiscandona ex gr. F. fabaeformis. Pseudocandona ex gr. P. eremita, likely another new stygobitic species, is recorded for the first time in Italy. The relatively high diversity of the ostracod assemblages at Frasassi could be attributed to the heterogeneity of groundwater and associated habitats or to niche partitioning promoted by the creation of a chemoautotrophic ecosystem based on sulfur-oxidizing bacteria. Other possible factors are the geologic age and hydrologic conditions of the cave and karst aquifer system that possibly originated in the earlymiddle Pleistocene when topographic uplift and incision enabled deep sulfidic waters to reach the local carbonate aquifer. Flooding or active migration would have introduced the invertebrates that now inhabit the Frasassi Cave system.
Goderis S.,Vrije Universiteit Brussel |
Goderis S.,Ghent University |
Tagle R.,Bruker |
Belza J.,Vrije Universiteit Brussel |
And 5 more authors.
Geochimica et Cosmochimica Acta | Year: 2013
The discovery over 30years ago at Gubbio (Italy) and Caravaca (Spain) of an enrichment in the concentrations of iridium (Ir) and the other platinum group elements (PGE) by up to four orders of magnitude (Irmax=0.10-87ng/g) compared to average continental crustal background levels remains one of the most important discoveries in the Earth sciences. Since then, similar anomalies have been detected in more than 120 Cretaceous-Paleogene (K-Pg) boundary sites worldwide. Highly elevated Ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact-related lithologies (melt rocks, impact ejecta material, etc.), delivered when an extraterrestrial object strikes Earth. The presented work adds 113 unpublished PGE analyses of 38 K-Pg sections worldwide to the existing literature. The analytical protocol relied on for this purpose consisted of a combination of a nickel-sulfide fire assay pre-concentration technique and subsequent trace metal determination via inductively coupled plasma-mass spectrometry (ICP-MS). Through repeated determination of key siderophile elements (i.e., Cr, Co, Ni, and PGE), the importance of sampling, nugget effects, and analytical methodologies applied becomes more apparent. Even more critically, these analytical effects are superimposed by the local syn- and post-depositional conditions that have affected the pristine meteoritic signature of the K-Pg impactor, including potential fractionation during vaporization and condensation, dissimilar PGE carrier phases, terrestrial PGE input, sedimentation rate, reworking, diagenesis, bioturbation, and chemical diffusion. While chondrite-normalized PGE patterns of individual sites appear relatively flat (i.e., chondritic), strong variations in siderophile element content and inter-element ratios exist between K-Pg locations, inter-laboratory measurements, and replicate analyses, hampering a precise projectile identification using (highly) siderophile elements. Only when considering improved databases of siderophile element concentrations in meteorites, in combination with linear regression analysis to calculate inter-element ratios from a large suite of ejecta deposit sites, the nature of the K-Pg projectile can be resolved. Application of this methodology to an extensive data set of continental and marine sites, very proximal to distal to the Chicxulub impact structure, supports a carbonaceous chondritic impactor (type CM or CO). © 2013 Elsevier Ltd.
Bennett R.A.,University of Arizona |
Serpelloni E.,Italian National Institute of Geophysics and Volcanology |
Hreinsdottir S.,University of Arizona |
Brandon M.T.,Yale University |
And 11 more authors.
Journal of Geophysical Research: Solid Earth | Year: 2012
We present crustal deformation results from a geodetic experiment (Retreating-Trench, Extension, and Accretion Tectonics (RETREAT)) focused on the northern Apennines orogen in Italy. The experiment centers on 33 benchmarks measured with GPS annually or more frequently between 2003 and 2007, supplemented by data from an additional older set of 6 campaign observations from stations in northern Croatia, and 187 continuous GPS stations within and around northern Italy. In an attempt to achieve the best possible estimates for rates and their uncertainties, we estimate and filter common mode signals and noise components using the continuous stations and apply these corrections to the entire data set, including the more temporally limited campaign time series. The filtered coordinate time series data are used to estimate site velocity. We also estimate spatially variable seasonal site motions for stations with sufficient data. The RMS scatter of residual time series are generally near 1 mm and 4 mm, horizontal and vertical, respectively, for continuous and most of the new campaign stations, but scatter is slightly higher for some of the older campaign data. Velocity uncertainties are below 1 mm/yr for all but one of the stations. Maximum rates of site motion within the orogen exceed 3 mm/yr (directed NE) relative to stable Eurasia. This motion is accommodated by extension within the southwestern and central portions of the orogen, and shortening across the foreland thrust belt to the northeast of the range. The data set is consistent with contemporaneous extension and shortening at nearly equal rates. The northern Apennines block moves northeast faster than the Northern Adria microplate. Convergence between the Northern Apennines block and the Northern Adria microplate is accommodated across a narrow zone that coincides with the northeastern Apennines range front. Extension occurs directly above an intact vertically dipping slab inferred by previous authors from seismic tomography. The observed crustal deformation is consistent with a buried dislocation model for crustal faulting, but associations between crustal motion and seismically imaged mantle structure may also provide new insights on mantle dynamics.Copyright 2012 by the American Geophysical Union.
Farley K.A.,California Institute of Technology |
Montanari A.,Osservatorio Geologico di Coldigioco |
Coccioni R.,Urbino University
Geochimica et Cosmochimica Acta | Year: 2012
Late Cretaceous (100-73Ma) pelagic limestones were measured for helium concentration and isotopic composition to characterize the interplanetary dust flux using 3He as a tracer. In the Bottaccione section near Gubbio, Italy, three intervals of elevated 3He concentration were detected: K1 in the Campanian stage at ~79Ma, K2 in the Santonian stage at ~85Ma, and K3 in the Turonian stage at ~91Ma. All three of these episodes are associated with high 3He/ 4He and 3He/non-carbonate ratios, consistent with their derivation from an enhanced extraterrestrial 3He flux rather than decreased carbonate sedimentation or dissolution. While K2 is modest in magnitude and duration and thus is of limited significance, K1 and K3 are each identified by a few myr interval with an ~4-fold enhancement in mean 3He flux compared with pre-event levels. Samples from ODP Hole 762C in the Indian Ocean spanning both K2 and K3 (93-83Ma) confirm the presence of a peak in the Turonian stage, suggesting that K3 is a global event. The K1 and K3 3He events are similar in most respects to the two peaks previously detected in the Cenozoic, suggesting a similar origin. These have been attributed to a major asteroid collision in the Late Miocene and to a shower of either comets or asteroids in the Late Eocene. Based on the age and temporal evolution of K1, we suggest that it most likely records the collision which produced the Baptistina asteroid family independently dated at ~80Ma. The K3 event is less easily explained. It is characterized by an unusually spiky and erratic temporal progression, suggesting an unusual abundance of very 3He rich particles not previously seen in the sedimentary 3He record. We suggest this episode arises either from a comet shower or from an asteroid shower possibly associated with dust-producing lunar impacts. © 2012 Elsevier Ltd.
Houben A.J.P.,University Utrecht |
van Mourik C.A.,University of Stockholm |
Montanari A.,Osservatorio Geologico di Coldigioco |
Coccioni R.,Instituto Of Geologia ntro Of Geobiologia Delluniversita |
Brinkhuis H.,University Utrecht
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2012
The Eocene-Oligocene Transition (EOT ~. 34. Ma) reflects the onset of major Antarctic glaciation. The primary geochemical signature of the EOT is two ~. 300. kyr spaced shifts in increasing deep-sea oxygen isotope values, possibly reflecting both global cooling and/or increasing ice volume. A way to assess the respective contribution of continental ice is to quantify concomitant glacio-eustatic sea level change. This is usually expressed in relatively shallow marine depositional settings. One potentially suitable region is in the Vicentinian Alps, NE Italy, where marginal marine deposits document sea level changes during the EOT. By correlating stable isotope-, bio- and magnetostratigraphic information between three distant regions, we are able to relate the shallow marine sections to the Pacific oxygen isotope record from Ocean Drilling Program (ODP) Site 1218 of Coxall et al. (2005). Microfacies, sedimentological, and biotic analysis suggests that associated with the first isotope shift (EOT-1) sea level fell ~. 20. m, and with the ultimate shift, the Oligocene Isotope Event 1 (Oi-1) sea level fell some 50-60. m. Distribution patterns of temperature sensitive dinoflagellates from a coeval central Italian section reveal that the early stages of the EOT were accompanied by sea surface cooling, whereas no sustained cooling is noted in association with the Oi-1. This suggests that the initial EOT shift(s) reflect a mixed signal of ice volume and temperature whereas the Oi-1 primarily reflects expansion of the Antarctic cryosphere. © 2011 Elsevier B.V.
Coccioni R.,Urbino University |
Sideri M.,Urbino University |
Frontalini F.,Urbino University |
Montanari A.,Osservatorio Geologico di Coldigioco
Special Paper of the Geological Society of America | Year: 2016
The highest stages of the stratigraphic range of the planktonic foraminiferal Rotalipora cushmani were investigated in a 313-k.y.-long interval of the classical Tethyan Bottaccione section (Gubbio, Italy), the type locality of the Corg-rich Bonarelli Level, which is the sedimentary expression of the worldwide latest Cenomanian oceanic anoxic event 2 (OAE 2).The disappearance of R. cushmani is associated with the major turnover of marine microfauna and microflora that involves both planktonic and benthic foraminifera, and calcareous nannofossils, slightly before the onset of OAE 2, which, according to current available data, was triggered by a massive pulse of submarine mafic volcanism accompanying the initial emplacement of the Caribbean large igneous province (CLIP). This pulse of volcanic activity probably turned the climate in a strengthened greenhouse mode, accelerating continental weathering and increasing nutrient supply in oceanic surface waters via river runoff and triggering higher fertility in the global ocean. Our investigation shows that the marine biotic turnover started ∼55 k.y. before the onset of OAE 2 and is closely coeval with the first major episode, as recorded by the unradiogenic trend in 187Os/188Os, of the ongoing magmatic activity of the CLIP, which produced increasing pCO2, ocean dissolution and/or acidification with a severe carbonate crisis and fertilization through enormous quantities of biolimiting metals. The marine microfauna and microflora reacted rapidly to new conditions of higher pCO2 and fertility by undergoing marked changes following three main steps. We evaluate this pattern and postulate that the first pulse of volcanogenic CO2 from the CLIP emplacement (ca. 94.2 or 94.6 Ma) played a fundamental role in the marine biotic turnover recorded shortly before the onset of OAE 2 and notably in the local or regional disappearance of R. cushmani in the central-western Tethys. © 2016 The Geological Society of America. All rights reserved.
Smit J.,VU University Amsterdam |
Laffra C.,VU University Amsterdam |
Meulenaars K.,VU University Amsterdam |
Montanari A.,Osservatorio Geologico di Coldigioco
Natural Hazards | Year: 2012
Three distinct, 30- to 80-cm-thick, graded, multilayered, coarse-grained sandstone layers, intercalated in the late Messinian mudstones of the Colombacci formation in Lago Mare facies of the Trave section are interpreted as tsunamiites (Ts1-Ts3). Each of these layers is sheet-like and could be followed along strike over several tens of meters. The lower two layers (Ts1-Ts2) occur in the lower part of the Colombacci formation and the third (Ts3) just below a conspicuous white "colombacci" limestone near the top of the formation. The three sandstone layers represent unique sedimentary events within the 120-m-thick San Donato-Colombacci mudstones, which contain many thin, fine-grained, possibly storm-related turbidites. Each of the three clastic layers is overall graded and strongly cross-bedded. A single layer consists of a stack of several graded sublayers that are eroded into the underlying mudstones and into each other. Absence of hummocky cross-stratification (HCS) indicates that the layers are not produced during a large, catastrophic storm event. Current ripples such as dm-sized trough cross-beds suggest strong, prolonged, unidirectional currents, capable of carrying coarse conglomeratic sands. Climbing ripples in middle-fine sand units indicate a high suspension load settling under waning current strength. Each of the Ts1-Ts3 beds satisfies a combination of criteria, described in this paper, that allow interpretation as a tsunamiite in an offshore environment. Tsunamiite Ts2 is underlain by a 15-cm-thick meshwork of synsedimentary fissures, filled with coarse sand. Ground movements induced by strong earthquakes probably caused these crevasses. The uniqueness of each layer, the erosion of the base of each of the sublayers into underlying mudstones and previously deposited sublayer and the consistent stacking of graded sandstone beds within each of the three layers, underlain by earthquake-produced fissures, strongly point to deposition by traction currents produced by the surges of a large tsunami event, triggered by a large vertical fault movements. Vertical fault displacements most likely occurred along the thrust faults like the Sibilline thrust at the SW of the Laga foreland basin, which were active at late Messinian times. A series of cyclic graded turbidites, underlain by seismically induced sand-filled fissures in the Late Messinian Feos formation in SE Spain, are interpreted as tsunamiites produced by a tsunami or seiche. © 2011 The Author(s).