Florindo, Fabio

During the Jurassic and Early Cretaceous, Earth's magnetic field experienced a high frequency of polarity reversals. This hyperactivity period is followed by a ∼38 Myr prolonged period of stable normal polarity from the Aptian until the Santonian, known as the Cretaceous Normal Superchron (CNS; chron C34n, from 121.4 to 83.65 Ma). Ho wever , the CNS might have been characterized by more variability than previously thought, but the current database is uneven in its spatial and temporal distribution. In this study, we integrate paleomagnetic and biostratigraphic data from the SER-03 sedimentary core, drilled onshore in the Sergipe-Alagoas Basin, NE Brazilian margin, South Atlantic Ocean. The 183-m cored interval spans 5.2 Myr (114.7-109.5 Ma), including the Aptian-Albian transition. It records the evolution from restricted marine settings to the complete opening of the South Atlantic Ocean. Magnetic remanence and rock magnetic parameters, such as magnetic susceptibility, anhysteretic remanent magnetization and isothermal remanent magnetization, were measured. Rock magnetic analyses indicated that primary magnetizations were preserved throughout the interval, with detrital magnetite identified as the primary magnetic carrier, predominantly in the pseudo-single domain and low-coercivity states. Normalizations by χ , ARM 15mT and IRM 15mT were used to determine relative paleointensity curves and were compared to the curve resulting from the pseudo-Thellier method. The SER-03 relative paleointensity record shows marked changes in both intensity and inclination. Inclination instability results are comparable with those found in volcanic rocks from surrounding the region. The high-resolution SER-03 magnetic record revealed that the field variability was higher than expected during the CNS, but remaining substantially lower than during other periods, such as the late Jurassic. The new SER-03 can serve as a dating and correlation tool for coe v al records.

With this volume, Annals of Geophysics proudly presents a special issue dedicated to celebrating the anniversary of Istituto Nazionale di Geofisica e Vulcanologia (INGV) for its "25 years of geosciences for society". This collection of scientific articles is authored by dedicated researchers whose active participation and collaboration have brought prestige to both INGV and our journal. Although the list of authors is not exhaustive among the numerous past and present INGV collaborators, it offers an exciting and insightful journey through the fields of seismology, volcanology, and environmental science. This volume is divided into three parts: the first is dedicated to topics more closely related to seismology, the second to volcanology, and the last part is focused on environmental issues, including both review articles and articles addressing specific problems. There are contributions dedicated to the study of tsunamis and multi-hazard analyses, as well as articles on the history of globally significant infrastructure and sections focused on the most widely used seismological models.

The Capo di Bove (CDB) lava flow was emplaced at~277 ka during the Faete eruptive Phase of Colli Albani volcanic district near the city of Rome. The CDB lava has a historical significance as it provided the slabs used in the paving of the ancient Appian Way, built in the 4 th century BCE. Puzzlingly beyond the seventh milestone, the ancient Appian Way deviates briefly from an otherwise straight SE-NW direction, abandoning the top of the lava flow and resuming its elevation and the SE-NW trend within less than 1 km. This peculiarity raised a question as to whether the deviation could have been the result of a tectonic deformation caused by a (buried) fault. To test this hypothesis, we sampled the CDB lava flow at four locations over a~10 km transect near the ancient Appian Way around the bend and performed a detailed rock magnetic, paleomagnetic, and petrographic study. Rock magnetic data indicate that pseudo-single-domain magnetite and low-Ti titanomagnetite particles are the main magnetic carriers for three sampling locations, located in freshly cut quarries, which reliably recorded the paleomagnetic field at the time of emplacement. Conversely, the samples collected in the upper part of the lava flow, within the bent segment of the ancient Appian Way, show multi-domain low-and moderate-Ti titanomagnetites as main magnetic carriers which fail to record a paleomagnetic direction. Anisotropy of magnetic susceptibility data are consistent with an overall CDB lava flow direction from SE to NW and the paleomagnetic directional data from the three reliable sampling sites are statistically indistinguishable. Hence, data from this study show no evidence of post-emplacement tectonic rotations. We suggest that the origin of the bend could be identified in the pre-existing morphology (for the lava flow path) and in historical reasons (for the ancient Appian Way).

The purpose of this study was to prove the direct correlation of a successions of gravel-clay beds recovered in borehole with the melt-water pulses associated with the sea-level oscillations indicated in the δ 18 O record in the time-span preceding the 100-kyr glacial cycles. Aimed at this scope, we provide combined 40 Ar/ 39 Ar and paleomagnetic constraints to a set of seven aggradational successions recovered from a 120 m deep borehole drilled in the buried Paleo-Tiber delta in Rome (central Italy). The geochronologic constraints enable the correlation of each aggradational succession, characterized by a sudden transition from coarse gravel at the base to sandy clay sediments, with periods of sea-level rise indicated by the δ 18 O curve encompassing MIS 37 through MIS 19, from 1250 to 780 ka. This stratigraphy, provides a unique and unprecedented well-dated evidence of glacial/deglacial events, matching the global benthic δ 18 O stack during this time frame. Furthermore, this study validates the hypothesis that gravel deposition in the catchment basin and the delta of the main rivers in central Italy is triggered by the melting of glaciers in the Apennines Mountain range. It demonstrates the significant potential of these deglaciation proxies to be used worldwide to unravel the chronology of glacio-eustatic events. Plain Language Summary In this study, we used a combination of dating techniques and paleomagnetic data to examine a series of sediment layers found in a buried ancient river delta in Rome, Italy. These sediment layers were collected from a 120 m deep borehole. By analyzing the age of these sediment layers, we were able to link them to a period in the past when sea level was rising. This sea-level rise occurred between 1250 and 780 ka, covering a range of time from MIS 37 to MIS 19. These sediment layers show a distinct change from coarse gravel to sandy clay, which provides valuable information about glacial and deglacial events. These findings support the idea that the deposition of gravel in river catchment areas and deltas in central Italy is linked to the melting of glaciers in the Apennines Mountain range. This research not only validates this hypothesis but also highlights the potential for using similar techniques globally to better understand the timing of glacio-eustatic events.

Ongoing studies conducted in northern polar regions reveal that permafrost stability plays a key role in the modern carbon cycle as it potentially stores considerable quantities of greenhouse gases. Rapid and recent warming of the Arctic permafrost is resulting in significant greenhouse gas emissions, both from physical and microbial processes. The potential impact of greenhouse gas release from the Antarctic region has not, to date, been investigated. In Antarctica, the McMurdo Dry Valleys comprise 10 % of the ice-free soil surface areas in Antarctica and like the northern polar regions are also warming albeit at a slower rate. The work presented herein examines a comprehensive sample suite of soil gas (e.g., CO2, CH4 and He) concentrations and CO2 flux measurements conducted in Taylor Valley during austral summer 2019/2020. Analytical results reveal the presence of significant concentrations of CO2, CH4 and He (up to 3.44 vol%, 18,447 ppmv and 6.49 ppmv, respectively) at the base of the active layer. When compared with the few previously obtained measurements, we observe increased CO2 flux rates (estimated CO2 emissions in the study area of 21.6 km2 ≈ 15 tons day-1). We suggest that the gas source is connected with the deep brines migrating from inland (potentially from beneath the Antarctic Ice Sheet) towards the coast beneath the permafrost layer. These data provide a baseline for future investigations aimed at monitoring the changing rate of greenhouse gas emissions from Antarctic permafrost, and the potential origin of gases, as the southern polar region warms.

New constraints were set on the age of marine deposits in the Pontine Plain and of the related sea level indicators on the Tyrrhenian Sea coast of central Italy by twelve new 40Ar/39Ar dates on detrital sanidine from these deposits. By combining a new geomorphologic analysis and previous morpho-pedostratigraphic studies with these geochronological constraints we reconstructed the geometry of four marine terraces and correlated these with the highstands during the marine isotopic stages (MIS) 9.3, 7.5, 5.5 and 5.3. Results point to a progressive tilting of the terraces, the elevation increasing from the SE to the NW due to differential tectonic uplift that occurred over the last 300 ka. We identified a MIS 9 sea level at 30 - 25 m asl in the northwestern sector, whereas the MIS 7.5 sea level reached a maximum of 24 m asl in the NWand descended to 18 m asl in the central sector. Moderate tilting affected the MIS 5.5 sea level, with an elevation of 12 to 9.5 m asl in between the Anzio and Circeo headlands. Finally, an undeformed MIS 5.3 sea level at ca. 3 m asl is indicated throughout this coastal reach, confirming previous data suggesting a much higher absolute sea level during this highstand with respect to the d18O-derived predicted level.

The geomagnetic field shows aperiodic reversals and excursions separated by stable polarity periods. Although the exact mechanisms responsible of reversals are still debated, several models of different complexity have been proposed. Here we use, for the first time, a different and novel approach based on the theory of tipping points to detect and characterize geomagnetic reversals occurred during the period 25–36 millions years ago by using a high-resolution magnetostratigraphic study conducted on a sedimentary section located on Maud Rise in the Southern Ocean. We detect a critical threshold for an early warning indicator of the occurrence of a polarity reversal below which a polarity reversal starts. Through the proper use of this early warning indicator we build up a simple non-autonomous stochastic model to describe the main features of polarity reversals. This approach could be helpful for building up a novel framework for paleomagnetic studies.

40Ar/39Ar geochronology constraints to aggradational phases and grain size variations show that the two large gravel beds occurring in the sedimentary filling of the Liri fluvial-lacustrine basin (central Italy) recorded the occurrence of deglaciation events synchronous within uncertainties with global meltwater pulses at ca. 450 and 350 ka. In particular, we find a precise match between the ages of gravel deposition and the occurrence of moderate sea-level rise events which anticipate those more marked during the glacial termination V and IV in the Red Sea relative sea level curve, as already verified by data from the Tiber River catchment basin. Such correspondence suggests that gravel deposition is facilitated by melting of Apennine mountain range glaciers, which provide the water transport energy and a surplus of clastic input to the rivers draining the mountain regions and flowing into the Tyrrhenian Sea. Therefore, the thick gravel beds intercalated in the sedimentary filling of the catchment basins of the major rivers in central Italy may be regarded as an equivalent proxy of large deglaciation events, similar to the ice-rafted debris in northern Atlantic. Consistent with this hypothesis, we also show the close correspondence between the occurrence of particularly mild (warmer) minima of the mean summer insolation at 65° N and these early aggradational phases, as well as with other anomalous early sea-level rises occurring c. 750 ka and 540 ka at the onset of glacial termination VIII and VI, and 40 ka at the onset of the so-called Heinrich events.

Paleocene-Eocene sedimentary archives record a series of global warming events called hyperthermals. These events occurred across a long-term increasing temperature trend and were associated with light carbon injections that produced carbon isotope excursions (CIEs). Early Eocene hyperthermals occurred close to both long (∼405 kyr) and short (∼100 kyr) eccentricity maxima. It has been proposed that under long-term global warming, orbital forcing of climate crossed a thermodynamic threshold that destabilized carbon reservoirs and produced Early Eocene hyperthermals. However, orbital control on triggering of the largest hyperthermal, the Paleocene-Eocene Thermal Maximum (PETM), remains unclear. Identification of the precise orbital phasing of the PETM has been hindered by extensive calcium carbonate (CaCO3) dissolution, which introduces uncertainty into PETM age models. Here, we report orbital signatures in marine sediments from Contessa Road (Italy), a western Tethyan section with reduced PETM CaCO3dissolution compared to other deep ocean sites. Orbitally controlled lysocline depth adjustments and orbital phasing of the PETM CIE onset close to both long and short eccentricity maxima are documented here. Precession-based age models from the well-resolved PETM section of Ocean Drilling Program (ODP) Site 1262 (South Atlantic) confirm these results and reveal that the PETM CIE onset was partially triggered by an orbitally controlled mechanism. Climate processes associated with orbital forcing of both long and short eccentricity maxima played an important role in triggering the carbon cycle perturbations of all Paleocene-Eocene CIE events.

Spectral analyses of high-resolution records from the upper Eocene-lower Oligocene from the Massignano section, GSSP for the Eocene/Oligocene (E/O) boundary, and the nearby Massicore reveal orbitally controlled fluctuations in the percent concentration of calcium carbonate (wt% CaCO3) and magnetic susceptibility. Extraction of orbital components provides a consistent cyclochronology for the two sites that straddles the E/O boundary. Detection of longer-term modulation in the short eccentricity enabled tuning to the astronomical solution and development of a robust astrochronology for the E/O boundary transition in the GSSP section. Correlation with astrochronologically dated records allowed us to identify the local sedimentary response to the global paleoclimatic and palaeoceanographic events that characterize the greenhouse-icehouse transition during the late Eocene-early Oligocene.