United States

This presentation set out with the aim of assessing the role of doubtful meteorites in the history of meteoritics. With respect to the research question, the presentation investigated the presumed witnessed fall that was recorded in Marsala (Sicily, Italy) on the night between 15 and 16 December 1834. Very little was found in the literature on this “extraordinary phenomenon,” and previous studies (e.g., Boguslawski, 1854; Grady, 2000) observed inconsistent results on whether the event was meteoritic in origin, because no meteorite fragments had ever been recovered. This explains why the Nomenclature Committee of the Meteoritical Society have classified this event as a doubtful meteorite, i.e., an object for which there was significant uncertainty over whether it was a real meteorite or, in some cases, whether it ever existed. The goal of this presentation is to contribute to the knowledge of the role of the doubtful meteorites in the history of meteoritics and to characterize the event that occurred in 1834 in Marsala. Thanks to the analysis of untapped sources, this presentation found that the event provoked a lively debate in the press and among the scholars of the time. Various Italian and foreign newspapers reported the news, while the pages of several Sicilian gazettes followed the scientific discussion about the real nature of the event. Even if doubtful meteorites have been discarded because they were not followed by the recovery of any meteorite samples and, in some cases, there is no certainty whether they really occurred, this research has found that their investigation may reveal unknown historical and scientific data. Although the current study is based on the analysis of a single doubtful meteorite, the findings revealed interesting aspects relative to the early stages of meteorite research, to the dissemination of science news, and to meteorite collecting over the centuries. Based on the results presented here, this presentation highlighted the role of doubtful meteorites as an important resource for the history of meteoritics and meteorite collecting as well as for studying the processes that have led to the scientific study of meteorites.

SGI 2021

Tell me who you are. The study of doubtful meteorites in meteoritics and its history. A case study

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L'Istituto Nazionale di Oceanografia e Geofisica Sperimentale - OGS e il Dipartimento di Matematica e Geoscienze dell'Università di Trieste sono orgogliosi di ospitare il 90° Congresso della Società Geologica Italiana a Trieste dal 14 al 16 settembre 2021. La modalità del congresso è interamente online.

Con il motto "Geologia senza frontiere" questo evento mira a promuovere le Scienze della Terra come disciplina scientifica proiettata nel futuro, oltre i confini geografici, politici e disciplinari, per comprendere meglio l'interno del Pianeta Terra e la struttura del sottosuolo, difendere la società da pericolosi eventi geologici, comprendere meglio la variabilità climatica, pianificare l'utilizzo delle georisorse in modo etico e nel rispetto dell'ambiente.


**Please note, times listed in the SCHEDULE tab (calendar icon) reflect YOUR LOCAL TIME ZONE. The main timezone for this conference will be Central European Summer Time.**

The National Institute of Oceanography and Experimental Geophysics - OGS and the Department of Mathematics and Geosciences of the University of Trieste are proud to host the 90th Congress of the Italian Geological Society in Trieste on 14-16 September 2021.  The Congress will be held entirely online.

With the motto "Geology Without Borders" this event aims to promote Earth Sciences as a scientific discipline projected into the future, beyond geographical, political and disciplinary boundaries, to better understand the interior of Planet Earth and the structure of the subsurface, defend society from dangerous geological events, better understand climatic variability, plan the use of geo-resources in an ethical way and respecting the environment.


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Earth Sciences should be understood not only as necessary for a better understanding of the interior of the planet Earth, but also as a defense of society from dangerous geological events, for the understanding of climatic variations, for the planning and use of georesources in a ethical and respecting and protecting the environment.

poster

Transgressive deposits accumulate during relative sea-level rises and accompanying the landward migration of the coastline can be recognised through gradual or abrupt landward shifts of facies, or  deepening-upward  facies trends that culminate in a surface of maximum flooding. The offshore area of Marzamemi (SR, Sicily), in the south-eastern portion of the Hyblaean foreland, represents an excellent site for the study of transgressive deposits and their connection with the sea-level changes. From a geomorphological point of view, the study area is part of the Pantani area, a coastal stretch characterized by a series of lagoons, elongated parallel to the actual coastline and separated by the open sea by elevated ridges of Tyrrhenian calcarenites and by coastal sand barriers.In this area, through the integrated interpretation of  new multibeam data (MBES) and high-resolution seismic profiles (SPARKER), we have reconstructed the development of deposits connected to the Transgressive System Tract and Highstand System Tract of the last eustatic cycle. Along the northern sector, three submerged lagoonal systems (L1, L2 and L3) mark important steps, of the Late Quaternary sea-level rise, possibly representing periods of lowered sea-level rise. The deepest lagoon L1 is bounded to the west by the 45 m isobath, which identifies a cuspate relief representing a paleo-coastline constituted by the outcropping Tyrrhenian substratum (Calcarenites of Marzamemi), only locally covered with highstand deposits. Southwards, the L1 is characterized by a smooth morphology interpreted to correspond with beach deposits, while in the central portion a system of tidal bars and channels is widespread as imaged in the seismic profiles. Westwards, the lagoon L2 marks a second step of the last sea-level rise, with the development of a paleo-coastline in correspondence of the 35 m isobath. The L2 shows morphological features similar to the L1, with the presence of extensive beach deposits to the south and two cliffs that bounded L2 to the west and to the east. Finally, 20 m isobath corresponds to the third significant step of the sea-level rise, and is associated with the paleo-coastline bounding to the west the lagoon L3. The latter hosted two islets and was confined to the east and west by high cliffs made up by the calcarenite substratum. Only to the south L3 displays a smooth morphology corresponding to beach deposits. Furthermore, a wide delta oriented west-east and characterized by an irregular trend due to the presence of numerous distributary channels is present within L3. In the southern sector, likely due a different inheritance of regressive morphologies the transgressive setting features was significantly different and submerged lagoons did not form. Here the outcropping calcarenite substratum is affected by the development of meandering paleo-rivers and karst structures, such as numerous depressions (poljes), commonly developed along the Mediterranean karst regions.

Morphological quaternary evolution of coastal plain in response to sea-level changes: example from South-East Sicily

The reconstruction of timing and modes of the last marine transgression is often hampered by the scarceness of available indicators due to bad preservation, lack of formation or difficult accessibility. This is particularly true for the first period of the Holocene, between 11.7 and 7.5 ka cal BP, when the rate of transgression was high and the relative sea level rose from -80 to -10 m MSL (Vacchi et al., 2016). Shoreline deposits and erosional landforms have long been recognized as the main geomorphological indicators of past sea levels. However, such features (e.g. beach ridges, tidal notches) can only form and be preserved over peculiar geometries of the shelf (Cattaneo & Steel, 2003). A major group of potential indicators which, up to date, is largely underrepresented, is constituted by paleo tidal inlets. Being excavated up to several meters below the surrounding lagoon and filled during the migration or deactivation of the inlet, such landforms may represent outstanding archives with a potentially high chance of preservation from erosion. Paleo tidal inlets can be recognized and cataloged through shallow sub-bottom profiling methods. Through the analysis of almost 7000 km of high resolution seismic profiles collected in the northern Adriatic Sea, more than 100 paleo tidal inlets were recognized. Such features date to the early Holocene and constitute one of the few widespread witnesses of the post-LGM marine transgression in the area. The paleo tidal inlets of the northern Adriatic represent essential features for the paleo-geographic and paleo-environmental reconstruction and provide new data to constrain the position of transgressive coastlines. Reference examples of paleo tidal inlets have been recognized near the Po Delta (Ronchi et al., 2019), offshore of Chioggia (Ronchi et al., 2018), but also in the Gulf of Trieste. The unexpected presence of widespread lagoons environments during a phase of strong RSL rise is the result of the interplay between sediment dispersal operated by the main fluvial actors of the area and phases of slowdown of the RSL rise.

Transgressive lagoons and paleo tidal inlets in the northern Adriatic Shelf: geomorphological indicators of the last RSL rise

The Luminescence dating method is based on the capability of quartz and k-feldspar to absorb and store energy from environmental ionising radiation and release it after sunlight exposition. The method date the last daylight exposure of these siliciclastic grains. Sun exposition also for very little time bleached (zeroed) the system that, eventually, could be recharged again. Recently, Sohbati et al. (2011) demonstrated that the zeroing effect of light on luminescence signal works also on rock surfaces, leaving an increasing residual signal with depth. On this principle is based a brand-new luminescence technique termed Rock Surface Dating (RSD), that analyses the luminescence signal-VS-depth profiles and can yield both burial and exposure ages of rock surfaces. The RSD is used to calculate the burial age of gravelly sediment (pebbles to boulders) and, it has been successfully applied on Holocene gravelly beaches deposits (Souza et al., 2021). The Late Pleistocene marine terrace of Cala Mosca (Sardinia, Italy) is composed of gravel beach deposits and considered one of the Mediterranean Sea reference-sites for the Last Interglacial (Eemian/Tyrrhenian; Marine Isotopic Stage 5e). The sedimentary sequence is characterised by a thick cobbly transgressive gravel lag resting unconformable on the wave cut platform carved on Miocene bedrock overlain by a well-developed, highly fossiliferous, prograding mixed sandy-gravelly pocket beach system. The attribution to Tyrrhenian of the marine terrace, has been based on presence of fossils of the so-called “Senegalese fauna” (Strombus bubonius and Patella ferruginea) considered typical of the Eemian/Tyrrhenian stage and U/Th ages performed on fragments of Cladocora caespitosa (138 ± 8 ka and 122 ± 5 ka) which confirmed the MIS 5e stage. Here we present the preliminary independent results performed with RSD technique on cobbles collected at the base of the Cala Mosca gravelly beach deposits. The RSD estimated burial age is of 117 ± 8 ka. This is in good agreement with previous data, confirming the enormous potential of RSD method to date gravel beach deposits and extending its application to Late Quaternary period. Furthermore, the cobbles exposure-time before burial has been estimated of about two months, giving some clues on the beach dynamics.

The Rock Surface luminescence Dating: a new technique to date Late Quaternary gravelly marine terraces

A new database made of 430 radiocarbon dated sea-level data, allowed evaluating the variability of Relative Sea Level along the Atlantic African coast (Morocco to South Africa) since the Last Glacial Maximum (LGM). Sea-level data were standardized following the International Geoscience Programme (IGCP) protocols to produce a suite of validated sea-level index and limiting points. The Atlantic African coast database was grouped in 21 regions according to geographical position and the distance from LGM ice-sheets. A Gaussian model was then applied to the new suite of sea-level data to estimate regional rates of RSL change. Our analysis indicates the RSL lowstand at the end of LGM did not exceed -105 ± 4 m as indicated by a suite of marine limiting points. This agrees with the recently produced global sea level curve (Gowan et al., 2021). Since the LGM, RSL rose rapidly with average rates of up to 15 mm a-1 between 16 and 9 ka. The rates of RSL rise decrease to < 3 mm a-1after ~7 ka BP. The mid-Holocene illustrates the emergence of a RSL high-stand which exceed the present mean sea-level. This high-stand, produced by the combined effect of ocean syphoning and continental levering (Milne and Mitrovica, 2002) shows temporal and spatial variability along the western African coast.  In those regions placed in the northern tropical region, the high-stand reached elevations up to 2.0  m between 6.5 and 5.0 ka BP and was followed by a gradual drop to the present datum. In the equatorial and southern tropical regions, we observed a delayed high-stand which occurred at about 4.0 ka BP followed by late Holocene fluctuations, which are not reproduced by current GIA models (Peltier et al., 2015). The origin of these fluctuations are presently difficult to explain but they can be related to an isostatic response to the Antarctic ice-sheet deglaciation. This new dataset allows providing new insights into the pre-industrial factors which controlled the sea-level evolution along the densely populated western African coast. These data are fundamental to provide constraints for more robust future sea-level projections of the west African coast in the framework of the on-going climatic change (Nicholls and Cazenave, 2010). 

On the variability of the postglacial sea-level changes along the western African coasts 

Based on highly focused laser beams, optical tweezers are novel tools enabling contactless, non-invasive trapping and manipulation of particulate matter in different media including liquids, air and vacuum. Coupled with Raman spectrometers, optical tweezers allow high-resolution (i.e., no background noise from substrate) spectroscopic analysis of physico-chemical properties of dust grains.  Although in recent years they have been widely and successfully used in a variety of research fields (Jones et al.,2015), their application in space science is in its infancy (Alali et al., 2020, Polimeno et al., 2021). In principle, optical tweezers have key prerequisites for maximizing the scientific return from the analyses of planetary dust samples collected by the current and future sample return missions (e.g. Hayabusa-2, OSIRIS-Rex, Mars 2020; Chang’e 5), particularly during the preliminary investigation procedures in receiving/curatorial facilities (e.g. Smith et al., 2021). High-resolution, contactless and non-invasive analyses of planetary dust are actually expected to provide unprecedented information on the astrophysical origin and geologic evolution of their parent bodies. They are also expected to be instrumental for biohazard assessment for constrained sample return missions – like those targeting Mars or the icy bodies in the outer solar system, and the detection of past or extant extraterrestrial life. Optical tweezers, developed in our laboratories (Gillibert et al., 2019), were used to collect individual dust grains from powdered analogues and extraterrestrial materials (e.g. carbonaceous chondrites and lunar regolith; (Collareta et al., 2016) of known composition and to determine their composition and response to optical forces without substrate effects. Results document the high potential of this novel technique and will be used to assess its effectiveness in the micromanipulation and analysis of extraterrestrial dust from space sample return missions in receiving/curatorial facilities and its potential role within coordinated multiscale analytical protocols.

Optical Tweezers: Evaluating their analytical potential for space sample-return missions

An improved understanding of the chronology of Antarctic ice sheet deglaciation since the Last Glacial Maximum-LGM represents a fundamental tool to better define the origin of past and future meltwater influx in the global oceans (Whitehouse et al., 2012). Relict shorelines and other evidence of past Relative Sea Level (RSL) evolution were widely used to understand past ice sheet history and to improve predictions of climate-sea level relationship evolution (Khan et al., 2015). In the last decades, RSL data in the Antarctic region have been mostly produced using raised marine features such as beach and marine deposits, marine terraces and isolation basins. The chronology of these paleo sea-level stands has been established through geomorphological and stratigraphic techniques (John & Sugden, 1971; Fretwell at al., 2010) and supported by radiometric dating from samples found in beach deposits and marine/freshwater sediments (Simms et al., 2011; Watcham et al., 2011). Here we present a new cartographic approach, currently carried out along the Antarctic Peninsula and South Shetland Islands, which has a twofold aim: (i) the creation of an open access dataset including information about paleo-shorelines by using a uniform collecting pattern, and (ii) the production of a coherent database which can be used for improved spatial analyses useful to define the Antarctic shoreline evolution as well as better constrain the chronology of the deglacial history. As demonstrated by other free data-repositories (https://www.bgs.ac.uk/geological-data/national-geological-repository/) and similar examples (https://warmcoasts.eu/world-atlas.html), the new cartographic instrument, built in web-GIS format, will represent a very important tool for Antarctic coast investigations and a tool for better focusing future researches.

Implementing a cartographic repository of the postglacial Antarctic paleo-shorelines

The marine sedimentary sequence of Cala Mosca bay (Sw Sardinia) is well-known and studied since the beginning of the past century and is considered a key stratigraphic section for the Marine Isotope Stage (MIS) 5e (~125 ka) or “Tyrrhenian/Eemian” highstand around the Mediterranean basin. In particular, this sedimentary wedge is interpreted as a beach system placed on a wave-cut platform forming a single marine terrace craved on the Miocene bedrock. A newly performed multidisciplinary (sedimentological, stratigraphical, chronological and tectonical) approach clearly reveals that the Cala Mosca single geomorphological marine terrace is in fact the result of two superimposed marine units (unconformity bounded unit U3a and U3b) separated by a composite unconformity surface associated with two different transgressive-regressive (T-R) cycles (T1 and T2). The lower T1 cycle is characterized by a cobbly transgressive gravel lag resting unconformable (wave-cut platform) on Miocene bedrock overlain by a well-developed prograding mixed sandy-gravelly pocket beach system (regressive phase). Obtained luminescence ages (pIRIR225 protocol), date T1 at 137±7, 134±7 ka confirming the MIS 5e stage attribution. The second marine cycle T2 lays unconformable on T1 and consists of a m-thick maximum gravelly body interpreted as a poorly-developed beach system formed on a rocky shore at the toe of retreating cliffs (transgressive phase). Obtained luminescence age dates T2 at 92 ± 6 ka supporting the MIS 5c stage attribution. T1 and T2 two cycles are separated by a composite unconformity surface developed during the post-MIS 5e sea-level fall and subsequent rise (early MIS5c). The T1 deposits were almost completely eroded during the second transgressive event and T2 sedimentary bodies reoccupied in part the same position of T1 forming an apparent single morphological unit. In this new light, the paradigm of Late Pleistocene tectonic stability of the Island seems to be abandoned and a more complex evolutionary history of Sardinia has to be build up. In particular, the interplays between global sea-level changes, region low-rate uplift, and localized rapid normal fault activity would explain the presence of a MIS5e and MIS5c composite marine terrace at the "locus typicus" of the Eemian in Sardinia.

The Late Quaternary composite marine terrace of Cala Mosca site, SW Sardinia (Italy): global sea-level change VS Tectonic activity

The nakhlite meteorites are igneous rocks from Mars (Treiman 2005). The nakhlites sample a single volcanic edifice that erupted several times between 1.4-1.3 Ga (Cohen et al., 2017). They have also been affected by hydrothermal activity on Mars ~630 Ma (Borg & Drake 2005) and were ejected from Mars in a single impact event at ~11 Ma (Treiman 2005). Therefore, the nakhlite meteorites are a key sample suite for understanding volcanic activity, habitability and impact processes on Mars. A key challenge in making inferences regarding the red planet from the study of Martian meteorites is that the samples that we have on Earth lack their geological context – we do not know from where on the Martian surface they originated. Advanced machine learning crater counting algorithms are being developed to identify candidate craters (Benedix et al., 2020) while the Mars Sample Return campaign has been initiated to bring samples to Earth from known localities on Mars. Additionally, by applying new quantitative petrographic techniques it is possible to reconstruct the formation and geological history of the meteorites we already have such as the Martian nakhlite igneous rocks. Here we applied correlative microscopy including electron backscatter diffraction, transmission electron microscopy and atom probe tomography alongside numerical simulations to Martian nakhlite meteorites to provide new insights into their geological history, including: 1) evidence of multiple igneous emplacement mechanisms (Daly et al., 2019a); 2) providing tight constraints on the geomorphology of the launch site on Mars (Daly et al., 2019b); 3) outline a analytical pipeline to maximize the science obtained by Mars Sample Return (Daly et al., 2020). 

The geological history of a Martian volcano

The Cavezzo meteorite, felt on January 1st 2020, is the first meteorite recovered by the Italian PRISMA fireball network. Two specimens, weighing 3.1 g (F1) and 52.2 g (F2), were collected three days after the bolide was observed. The two specimens have a completely different lithology, geochemistry, and oxygen isotopic composition. Specimen F1 is anomalous both for the textural-structural features, varying from chondritic to achondritic, and a very unusual modal mineralogy. Conversely, F2 characterization is closer to the one of an ordinary L chondrite, given its texture, crystal chemistry and modal mineralogy. The oxygen isotope composition of F1 plots at the boundary between the H and L groups, whereas F2 plots at the boundary of the L and LL fields. These results support the classification of Cavezzo as a L5 anomalous chondrite. Measurements of F2 gamma activity revealed the presence of many cosmogenic isotopes (47Ca, 52Mn, 48V, 51Cr, 7Be, 58Co, 56Co, 46Sc, 57Co, 54Mn, 22Na, 60Co, 44Ti, 26Al) with half-lives down to few days, thus confirming the recent fall of the sample. Short-lived cosmogenic radioisotopes are not often measured, since this is possible only for meteorites recovered just after the fall. Besides information about solar activity on different time scales, the measured concentrations of cosmogenic isotopes will provide constraints on the pre-atmospheric size of the meteoroid and shielding depth of the counted sample, to be compared with results from dynamical mass computed from PRISMA observations.

Characterization of Cavezzo, the anomalous L5 chondrite recovered by PRISMA

Phosphorus is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorus is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and non-reactive materials, and, accordingly, unavailable for being readily incorporated in living organisms [1]. A possible source of phosphorus is from the exogenous meteoritic bombardment and, in particular, in iron/nickel phosphides [3,4,5]. These materials, by simple interaction with water, produce oxygenated phosphorus compounds, which can easily react with organic molecules, thus forming C-O-P bonds [6,7]. It has been estimated that up to 10% of the early Earth crust was composed by phosphide minerals, after the heavy meteor bombardment, and that many tons per year of phosphorus oxygenated compounds have been produced [8]. In the present work, periodic ab-initio simulations at PBE level (inclusive of dispersive interactions) have been carried out on Fe2NiP-schreibersite, as a relative abundant component of metallic meteorites, in order to characterize structural, energetics and vibrational properties of both bulk and surfaces of this material [9]. Moreover, also the interaction with water was analyzed, modelling both high and low coverage regimes, in order to study the corrosion process which ultimately leads to the production of phosphorus oxygenated compounds, like phosphites (HPO32-/H2PO3-) and phosphates (HPO42-/H2PO4-).

Tell me who you are. The study of doubtful meteorites in meteoritics and its history. A case study

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