United States

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 &amp; 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). 

SGI 2021

The geological history of a Martian volcano

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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.

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). 

technical paper

The genus Xenophora comprises species of marine gastropods, known from the Cretaceous and still living today, which have the ability to form their shells agglutinating objects with different origins, from other shells to bio- or lithoclasts. Different agglutination potentials are shown by species of Xenophora, from species lacking attachments to others completely covered, as the case of the Mediterranean Xenophora crispa (König, 1825). Shell sections of fossil (Early Pleistocene, Arda and Stirone Rivers, Italy) and recent specimens (Mediterranean Sea, Spain) of X. crispa were here analyzed at the Scanning Electron Microscope (SEM) and powders, collected from different parts of the shell, at X-Ray Diffraction (XRD), in order to characterize in detail the microstructure and the mechanisms, function and behaviour of the agglutination in the same species through time, in this case over about 2 millions of years. Also, as the Arda and Stirone River sections were deposited during the Early Pleistocene, this research allows to examine if and how these parameters varied during a climate change. Indeed, the Early Pleistocene was a time interval characterized by several climatic oscillations linked to glacial/interglacial cycles and the Mediterranean area was strongly affected by these climatic changes showing in marine environment a progressive climatic cooling. This study shows that the functional purpose of the agglutination in X. crispa may be related to a snowshoe strategy to successfully colonize muddy substrates, coupled with tactile and olfactory camouflage. Indeed, this species secretes in the columella and peripheral edge of both fossil and recent specimens a less dense and a more organic rich calcitic fabric, possibly to lighten the shell thickest parts in order not to sink in soft sediments and to facilitate the shell raising from the substrate to create a protected feeding area. This behaviour and the shell microstructure seem to have been maintained by X. crispa over 2 My time span, thus allowing to suppose that this species did not suffer the climatic cooling of the Early Pleistocene.

From the Early Pleistocene to the Recent: how is Xenophora crispa biomineralization varied?

The Mediterranean is a semi-enclosed sea formed by two sub-basins, the eastern Mediterranean (E-Med) and the western Mediterranean (W-Med), connected through the Strait of Sicily. Four main deep-water convection cells fuel the Thermohaline circulation of the Mediterranean (Med-THC). In the E-Med, deep water is formed in the Adriatic Sea and the Aegean Sea, while an intermediate-water is formed in the Levantine Sea (Levantine Intermediate Water, LIW). The Western Mediterranean Deep Water is formed in the Gulf of Lions. Since all cells are interconnected, variations in one cell could be transferred to the others by modifying the Med-THC. The present study focuses on the analysis of the sediment core NDT-6-2016 at the west flank of Sicily channel, recovered at 1066 m of water depth, which is nowadays located bellow the interphase layer between the eastern and western originated water-masses. Therefore, this location is suitable for exploring changes in the inter-basin water exchange along the last 15 kyr cal. BP. Nd isotopes measured in planktic foraminifera coatings allow estimating changes in the export rates of the eastern Mediterranean source-water (ESW) masses underlying the occurrence of two anomalous events: The Younger Dryas characterized by an outflowing excess of ESW and the last sapropel (S1) with opposite circumstances. The export rates of EMS waters are estimated to have been up to three times higher during the YD than during the S1. These results are discussed in the context of other geochemical, sedimentological and micropaleontological proxies that allow us to have a more complete picture of the oceanographic changes associated to these events of Med-THC major reorganization.

Water-Masses exchange through the Straitof Sicily during the Last Deglacial and Early Holocene

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 

The study of the climate changes of the last centuries allows comparison of data from historical documents, instrumental and paleodata records with multi-decadal variability arising from external forcing and internal climate variability. In this framework, the marine fossil records represent a fantastic archive to document the climatic variability over the last 500 yrs. In this framework, Globorotalia truncatulinoides oscillations have been recorded from several marine sediment cores collected in the central and western Mediterranean Sea. G. truncatulinoides represents a deep dwelling winter species in the Mediterranean Sea and its life-cycle is characterized by a vertical migration in the water column. The abundances of this species over the last 500 yrs demonstrates its potential value as bio-indicator of particular oceanographic condition during the Maunder Minimum (MM) event of the Little Ice Age (LIA). The comparison between the G. truncatulinoides abundance patterns of the Balearic Basin, central and south Tyrrhenian Sea and central and eastern Sicily Channel allows to highlight a similar response of this species during the MM event in the central-western Mediterranean Sea. The ecological meanings of this species and its peculiar high abundance percentage values in the total assemblages suggest the development of enhanced vertical mixing conditions during MM winter season with a strong advection of nutrients from the nutrient-rich deeper layers and enhances the productivity levels in the mixed layer. The intensified vertical mixing could be linked to persistence of an atmospheric blocking event recorded by several authors during the MM. In fact, this time-interval is characterized by an atmospheric blocking event. These particular climatic conditions could be responsible of intense deep vertical mixing phenomenon during the winter season producing the ideal ecological conditions for G. truncatulinoides proliferation. In addition, we suggest that maximum abundance of G. truncatulinoides left coiled is a response to more active dense water formation within the Mediterranean Sea during a cold time-period such as the MM. This research has been financially supported by the ERC-Consolidator TIMED project (REP-683237).

The planktonic foraminifera Globorotalia truncatulinoides in Central - Western Mediterranean Sea during the Little Ice Age

During the late Quaternary, the Kurdistan Region of Iraq (north-eastern part of ancient Mesopotamia) was the scenario of several fundamental cultural events including the dispersal of Homo to Eurasia, the origin of agriculture and adoption of domesticates, the beginning of urbanization, and the formation of the first state entities. The role played by climate and environmental changes on these cultural processes was highly debated, but local, continuous, and well-dated paleoclimatic records are still missing. In this contribution, we present the preliminary results of a palaeoclimatological and paleoenvironmental investigation in this area, which aims to reconstruct a detailed framework of the relationship between global climatic changes, regional environmental and hydrological responses, and human adaptation during the Late Quaternary, with a special look to the Holocene. Speleothems were collected along the eastern slopes of northern Zagros from the Hassārok Cave, near Shaqlawa township, in the northern Kurdistan Region of Iraq. Preliminary geochemical and geochronological results provide information on Holocene climatic variability in the region. Environmental and paleoclimatic data have been compared with archaeological information to infer and quantify the effects of climatic changes (if any) on human exploitation of natural resources, settlement dynamic and major shift in subsistence strategies and land use.

A speleothem-based reconstruction of the Late Quaternary climate-environmental-human nexus in the Kurdistan Region of Iraq

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 geological history of a Martian volcano

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From the Early Pleistocene to the Recent: how is Xenophora crispa biomineralization varied?

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The geological history of a Martian volcano

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From the Early Pleistocene to the Recent: how is Xenophora crispa biomineralization varied?

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Small-scale instability processes affecting volcanic island shelves: the case study of the southern shelf of Porto Santo Island (Madeira Archipelago)

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