The new Beyond EPICA Antarctic ice core plays a crucial role in deciphering the contribution and behaviour of atmospheric proxies before and during the Mid-Pleistocene transition. In order to fully understand and correctly interpret the connection between different proxies both from the ice and gas phase of the ice core, as well as from other climactic archives, an accurate chronology of the entire ice core is needed. This can be achieved with orbital dating, exploiting the unique relationship between insolation and some of the isotopic and elemental ratios of atmospheric constituents such as nitrogen, oxygen, and argon of the air bubbles trapped in the ice. Using new atmospheric δ18O of O2, δ(O2/N2), and δ(Ar/N2) data in the depth range between 2400-2507 m from the Beyond EPICA ice core, we propose new chronological tie points, which are independent of alignment to marine archives, for the construction of a gas and ice chronology of the Beyond EPICA ice core before 800,000 years before present.Additionally, δ15N of N2 measurements provide a way to quantify variations in the lock-in depth and the age difference between the ice and the gas phase (Δage) over the entire time period covered by the Beyond EPICA ice core. The new δ15N dataset provided here is key for the coherence between the ice and gas timescale. Moreover, we use the expected depth difference (Δdepth) between the same event recorded in the ice phase (through δD or δ18O of the ice) and in the gas phase (through δ15N of N2) as a test for the integrity of the stratigraphy: a concomitant change in δD or δ18O of the ice and δ15N of N2 may be the signature of an ice hiatus or folding event.

Italy's Holocene climate can be characterised by a latitudinal division with a climatic contrast between the northern and southern regions, notably characterised by a stronger winter-summer precipitation seasonality in southern regions. The latitudinal boundary is located between latitudes 40 degrees and 43 degrees N, creating a climatic transition zone. However, the mechanisms underpinning this hydro-climatic partition remain poorly understood, due in part to a scarcity of precisely dated, high-resolution records at key latitudes. Lago Grande di Monticchio similar to 41 degrees N) lies within this critical transitional band and presents a valuable opportunity to refine the latitudinal boundary location. Lago Grande di Monticchio is one of southern Italy's most comprehensively studied sediment archives, stretching back to the last interglacial. In this study, we employ a novel, high-resolution sediment core from Monticchio, applying a multi-proxy methodology that combines branched glycerol dialkyl glycerol tetraether (brGDGT) and pollen data to reconstruct seasonal temperature and precipitation changes during the Holocene. Results confirm that temperature reconstructions derived from brGDGT and pollen records are particularly consistent for most of the signal. Comparison with other palaeoclimate records and proxies in Italy allowed us to place Lago Grande di Monticchio's climate signal within southern climate regimes (i.e., summer cooling and aridity in contrast to wetter and warmer winters), corresponding to a stronger "Mediterraneanization" process throughout the Holocene. Multi-proxy comparison indicates that the most marked contrast during summer likely lies near the upper bound of 41 degrees-43 degrees N. Persistent inconsistencies in the transition zone suggest added climatic complexity around similar to 43 degrees N, involving ocean-atmospheric teleconnections and local topography. We advocate further high-resolution, multi-proxy palaeoenvironmental studies in this transitional latitude band to refine understanding of the north-south hydro-climatic boundary across Italy in the Holocene.

Here we present a 40,000-year long tephrostratigraphic record from a Southern Tyrrhenian Sea marine core DED87-07, establishing key linkages to the nearby previously studied KET80-04 core site, and thus facilitating strengthened tephra correlations across the central Mediterranean region. Major and trace element volcanic glass geochemistry obtained through electron microprobe and laser ablation have enabled the successful characterisation and identification of key tephra markers, such as the Neapolitan Yellow Tuff (C-2 marine tephra marker), Masseria del Monte Tuff (C-7/Y-3), and the Campanian Ignimbrite (C-13/Y-5) from Campi Flegrei, as well as the widespread Codola (C-10) and Schiava (C-9) tephra units from Somma-Vesuvius all enhancing robust core-to-core tephra correlations. Moreover, the DED87-07 marine succession is established as a central, integrative, node in the central Mediterranean tephrostratigraphic framework through the identification of tephra layers from numerous other volcanic sources, including the other Neapolitan volcanoes (Ischia, Procida), but also those derived from explosive volcanism on Mount Etna (Sicily), and the Aeolian Islands. Coupling this tephrostratigraphy with a newly acquired high-resolution oxygen isotope (δ¹⁸O) record and anage-depth model enhances the temporal framework, allowing for precise climato-stratigraphic positioning of volcanic events, along with new age estimates for those eruptions still lacking accurate age-determinations. Our results advance a more comprehensive and accessible record of explosive volcanism in the central Mediterranean, highlighting the key chronostratigraphic markers.

We present fourteen new Ar-40/Ar-39 ages, based on 287 single crystals analyzed from proximal and semi-proximal pyroclastic deposits, that significantly refine the chronology of Monte Vulture's initial volcanic activity (Foggianello synthem). The earliest identified eruption is the Fara d'Olivo A ignimbrite, dated at 784.7 +/- 4.7 ka (2 sigma), closely followed by the Fara d'Olivo B unit at 774.7 +/- 0.9 ka (2 sigma), which encompasses at least four distinct eruptions. We also recognize a new explosive phase at 740.0 +/- 1.6 ka (2 sigma) that we named Rapolla and that preceded the effusive Spinoritola phase (731.5 +/- 2.0 ka (2 sigma)). The youngest activity belonging to the Foggianello synthem, named "Campanile phase", is composed of pyroclastic deposits dated between 708.4 +/- 2.0 ka (2 sigma) and 700.2 +/- 1.2 ka (2 sigma). According to our results, the duration of the Foggianello system spans approximately similar to 85 ka, much longer than previously proposed. Geochemical analyses of fresh glass shards indicate a dominating phonolitic magma composition during this interval. However, a progressive change of the magmatic source, probably controlled by crustal contamination, has been observed. Furthermore, our results establish a precise correlation of Fara d'Olivo B Ignimbrite with distal tephra layers from Montalbano Jonico (V4) and Lake Ohrid (OH-DP-2869), showing that this eruption represents a robust regional stratigraphic marker of the Brunhes-Matuyama reversal. Finally, the recognition of inherited sanidines up to similar to 934 ka potentially pushes back the onset of magmatism at Monte Vulture into the Early Pleistocene, substantially earlier than previously inferred. Our results thus have implications also for the geodynamic evolution of the Apulian slab, suggesting an earlier onset of extensional tectonics and mantle upwelling.

We present volcanological, geochronological, and geochemical evidence suggesting that the Miocene Tar-Jato "middle tuffs" in the North Pannonian Basin all belong to the same volcanic system that produced multiple silicic explosive eruptions. These eruptions probably originated from a caldera (now buried under the Pannonian Basin) during a period around 15 Ma. Based on Bayesian age modelling of the dated ignimbrite horizons, the recorded eruptive activity lasted for 300-500 kyr between c. 15.3-14.9 Ma. Such prolonged, multi-episodic ignimbrite volcanism is considered unique in the region, as similar eruptive sequences of a single system have not been previously documented. The Tar-Jato eruptions deposited mostly successive ignimbrites with a total preserved thicknesses of up to 200 m. They were fuelled by geochemically nearly homogeneous magma, which nevertheless differs from any other ignimbrite in the Pannonian Basin and thus provides a distinguishable marker horizon. The vertically varying FeO content of the ignimbrites, together with locally interbedded epiclastic layers, is consistent with the extended duration of the volcanism, which probably occurred in three subsequent series, characterized by low, hybrid and high FeO content, respectively. This conclusion contrasts with a single eruption phase proposed earlier and dated at 14.9 Ma; we suggest that this age represents only the youngest eruption series. Trace-element geochemistry shows the southward distribution of this presumably youngest unit, as it correlates with the 14.9 Ma Plaz tuff (Mt. Medvednica, Croatia), located 300 km of the reconstructed source vent. On the other hand, the slightly younger (14.8 Ma) Bidrovec tuff also from Mt. Medvednica correlates with the Tibolddaroc tuff (14.7 Ma) in the North Pannonian Basin. Other definite distal counterparts of the Tar-Jato tuffs remain unknown. Comparative trace-element geochemistry also demonstrates that the Tar-Jato tuffs cannot be correlated with the 15.3-15.4 Ma tuffs widespread across the western-southwestern part of the Pannonian Basin System and the Dinarides (e.g., Kuchyna, Lucane-1, Gacko, and Pozeska gora tuffs).

Single-crystal sanidine 40Ar/39Ar dating revealed at least six new explosive eruption events during the 4.0-3.5 Ma and 3.0-2.5 Ma periods in the eruptive history of the Kozuf-Voras volcanic system located in the central parts of Southeastern Europe. The precise ages helped to redefine the timing and eruptive style of the volcanic system, as the 4.0-2.5 Ma period was previously considered as mainly quiescent, with dominantly lava dome building activity recognized so far. The pyroclastic layers (mainly massive tuff-lapilli tuff and massive lithic breccia) are deposited from phreatomagmatic and subplinian eruptions, and block-and-ash flows in the volcano-sedimentary Mariovo basin, west of the volcanic system. The newly recognized pyroclastic layers could serve as regional marker layers, as neither their ages nor their geochemical and isotopic (bulk and glass) compositions overlap with those previously studied tephra layers, either from the Kozuf-Voras volcanic system or from other volcanic sources (e.g., Aegean arc). Differences in the geochemical and isotopic data imply sequential evacuation of closely emplaced, discrete, melt-dominant bodies during the older period. In contrast, the younger sequence might represent a compositionally zoned single melt body. The latter also represents an explosive-to-effusive transition as the top layer is a block-and-ash flow unit resulting from a dome collapse.

Magmatism's role in continental rupture and ocean formation remains a critical question in Earth Sciences. The Red Sea, where Arabia is rifting from Nubia, offers an ideal setting to explore this process. This study analyses geochemical and isotopic data from gabbros and basaltic dikes in the Tihama Asir complex, formed during early Red Sea rifting (Late Oligocene). The results show that asthenospheric melts assimilated ancient lower crust before rising into shallow magma chambers with minimal upper crustal contamination. Rising asthenosphere driven by the Afar plume and by extensional stresses thermally weakened the lower crust, allowing it to decouple from the mantle, causing depth-dependent deformation. The generated asthenospheric melts underplated and intruded the thinning continental crust protracting continental rifting by re-thickening of the crust and accommodating extension. This study provides the evidence of tholeiitic underplating beneath thick continental crust during early rifting, substantially postponing the onset of seafloor spreading.

Super-eruptions disperse volcanic ash over vast areas, impacting the environment and human health. Fine ash, particularly its respirable fraction (< 4 µm), poses a significant health hazard by inhalation due to its high dispersal potential. Understanding the aerodynamic properties but also composition of ash particles is fundamental to constrain dispersal and deposition mechanisms in both proximal and distal environments. Current atmospheric dispersal models rely on empirical drag equations calibrated with geometric shape descriptors. However, these models often overlook the effects of the actual particle density, as a uniform componentry is typically assumed. In addition, particles have variable shapes but such data from super-eruptions remains limited and no standardized measurement methods exist. Here, we determine the terminal fall velocity ( v t ) of fine ash from the Campanian Ignimbrite super-eruption (~ 40 ka, Campi Flegrei), by evaluating the components and particle shapes from proximal to ultra-distal locations. To verify the attribution of the proximal sample to the CI eruption, a 40 Ar/ 39 Ar dating was performed, allowing its correlation with the ultra-distal deposits. Results show that, due to the influence of shape and density, glass particles exhibit lower v t compared to mineral phases ( v t , feldspar / v t , glass = 1.05 ± 0.03, v t , SiO2 / v t , glass = 1.09 ± 0.02), enabling greater travel distances. Drag equations accounting for measured particle shapes differ significantly from spherical approximations. The spherical model overestimation of v t highlights the necessity of shape-specific models to produce more accurate dispersal predictions. Extremely low v t (< 0.1 cm/s) for respirable ash fraction, which indicates prolonged atmospheric suspension and long-time resuspension potential, along with the presence of cristobalite, lead to important implications for health hazards. These findings further enhance our understanding of volcanic ash aerodynamic behaviour and the far-reaching impact of super-eruptions .

The southern Apennine chain ranks among Europe's regions with the highest historical seismicity, yet its seismogenic structures remain poorly defined or completely unknown, including those of highly destructive Mw similar to 7.0, 1456 and 1688 Sannio earthquakes, which are examined in this study. Using a multi-scale, interdisciplinary approach - combining detailed field investigations (stratigraphic, geomorphological, structural, and paleoseismological analyses), tephrochronological and OSL dating, and reassessment of macroseismic intensity distribution from archival sources - this study identifies a possible source for these earthquakes. It corresponds to a similar to 45 km normal fault system composed by two main branches (Eastern Calore Fault and Western Calore Fault) with primary segments trending E-W to ESE-WNW and dipping N- to NNE. Segments extend along the southern border of both eastern and western Calore River sub-basins and are partially connected by NNW-SSE to N-S trending, east-dipping, transfer zone fault splays. Although the morphostructural evidence of Quaternary tectonic activity is unevenly expressed in both sub-basins, they share a similar Middle Pleistocene-to-Holocene morpho-sedimentary evolution, suggesting a common driving factor, ascribable to the sub-coeval activity of the fault segments delimiting both sub-basins. On a short-time scale, this study provides the first evidence of a post-14 ka occurrence of a paleoearthquake with a surface displacement greater than or similar to 0.7 m, as well as of a decametric off-set affecting post-9 ka sediments. These coseismic surface ruptures have an estimated recurrence time of approximately 1400 years, with the two more recent events likely corresponding to the Mw similar to 7.0, 1456 and 1688 Sannio earthquakes. Further detailed paleoseismological investigations are recommended to uncover direct evidence of co-seismic displacement linked to the 1456, 1688, and earlier earthquakes.

The Earth surface, where life develops and stands, is strongly affected by denudation which is the sum of physical erosion and chemical weathering. Denudation impacts soil formation and agriculture, affects the relief stability and, at the geological time scale, controls the atmospheric CO2 via the weathering of silicates and the production of sediments that later bury organic matter in the oceans. In the context of global warming, it is particularly important to predict how denudation will change and hence impact the Earth Surface where we live. This requires to understand the links between past climate variability and denudation changes, especially during the Quaternary when Earth experienced rapid climate oscillations of amplitude similar to what is expected in the future due to anthropic impact. To reach this goal, quantitative estimate of past denudation rates during the Quaternary are needed especially in Volcanic island located in tropics because here silicate weathering and hence CO2 consumption is particularly efficient. In this study, we reconstruct Quaternary paleo-denudation rates in Santoa Antao, one of the largest islands of the Cabo Verde archipelago that is located in the Atlantic ocean 800 km off the coast of Senegal. To reconstruct the paleo-denudation rates we measured in situ cosmogenic 3He concentrations in ancient fluvial sediments stored in deep entrenched valleys across the island. The depositional ages of sediments were determined by dating using Ar/Ar adjacent volcanic layers (pumices or basalt lavas). For comparison between all data, paleo-denudation rates are normalized to modern 3He derived denudation rates across the same drainage basin obtained from the analysis of modern river sand in a previous study. This yields to a 0-550ka record of paleo-denudation rates that is compared to climate variations to discuss the potential links between the two.

Voluminous Miocene silicic volcanism sourced mainly from the extensional Pannonian Basin played a major role in the evolution of the Central Paratethys. Here, we identify a widely distributed (> 3150 km2) member of the Upper Rhyolite Tuff in Hungary, called the Dobi Ignimbrite, with a precise sanidine/plagioclase 40Ar/39Ar age of 13.064 ± 0.065 Ma (~ Badenian/Sarmatian boundary in Central Paratethys chronology). It has distinctive glass geochemistry with wide compositional variations, which conforms with large-scale silicic explosive eruptions. In line with this, the calculated minimum volume (~ 200 km3) of the Dobi Ignimbrite is consistent with a high-end VEI 7 eruption, with possible ultradistal transport distance of over 300 km. Most of the pyroclastic succession, which erupted in two phases, was emplaced on land, as it contains leaves and tree trunks in the basal layer that we correlate with the Badenian/Sarmatian 'volcanic floras' of northern Hungary. At the same time, the ignimbrite has a strongly phreatomagmatic character, and, together with the presence of free-floating foraminifera, this suggest that the source vent was located in coastal waters of the Central Paratethys. These findings indicate either a late Badenian marine incursion prior to the eruption, or the shift of the eruption center toward the sea.

Kinetic isotopes effect (KIEs) describes a very common phenomenon related to change in chemical reaction rate due isotopic substitution. If in biological sciences, KIEs has received a lot of interest with the aim at understanding reaction mechanisms, their control on the isotopic composition of biogenic carbonate has long been overlooked. However, the initial assumption that isotopic fractionation primarily reflects a thermodynamic equilibrium process in the H2O-DIC-CaCO3 system is challenged by a growing number of observations. Not accounting for these disequilibrium effects leads to inaccurate estimates of carbonate growing temperature. In this scientific context, Triple oxygen isotopes systematic can help constraining kinetics isotopes fractionation associated with metabolic reactions implicated in biocarbonates formation. We thus took advantage from recent development in spectroscopic technique (VCOF-CRDS) to measured O17 isotopic anomalies in CO2 produced by carbonate acid reaction [1]. These samples were also analyzed for their δ13C, δ18O and Δ47 composition using a more classical mass spectroscopy technic. In this contribution we investigated cold-water corals (CWC) known to display strong isotopic disequilibria. For this 1st application, we selected four modern CWC species for which calcification conditions (T, S, pH, δ18Owater, Δ17Owater and δ13CDIC) are independently constrained. The measured isotopic signatures were compared to their respective expected values based on environmental constrains, assuming “pseudo-equilibrium” carbonate precipitation. In particular, corals Δ17O signatures were compared to the newly established equilibrium for O17 fractionation between calcite-water based on slow growing carbonates from Laghetto Basso and Devils Hole, measured using the same VCOF-CRDS technic [2]. We finally compared our experimental data with theoretical predictions for KIEs on DIC isotopic composition [3]. Interestingly, the correlation slope among Δ47 - Δ17O disequilibrium differ from the previous one derived from dual clumped (Δ47 - Δ48) isotopic measurements of the same species [4]. This founding suggesting that other biological parameter(s) should be taken into account to resolve CWC isotopic disequilibria. [1] Chaillot. J., Daëron. M., Casado, M., Landais. A., Pesnin. M., Clauzel. T., Kassi. S. (in prep) Triple oxygen analyses of carbon dioxide, water and carbonates using VCOF-CRDS. [2] Clauzel, T., Chaillot, J., Pesnin, M., Jautzy, J., Kessy, S., Daëron, M. (in prep) Advancing triple oxygen isotope analysis of carbonate and water using V-shaped Cavity Optical Feedback Cavity Ring-Down Spectroscopy (VCOF-CRDS): Calibration and implications for paleoclimate reconstruction. [3] Guo. W. (2020). Kinetic clumped isotope fractionation in the DIC-H2O-CO2 system: Patterns, controls, and implications. Geochimica et Cosmochimica Acta, 268, 230-257. [4] Davies. A. J., Guo. W., Bernecker. M., Tagliavento. M., Raddatz. J., Gischler. E., Floter. S., Fiebig. J. (2022). Dual clumped isotope thermometry of coral carbonate. Geochimica et Cosmochimica Acta, 338, 66-78.

In the lacustrine succession F4‐F5 of the Fucino Basin, central Italy, 20 visible tephra layers were identified in the time interval 250–315 ka (Marine Isotope Stages 8–9). Fifteen of them contained suitable material to explore their volcanic sources. Among these tephra some well‐known eruptions and eruptive sequences of the Roman and Roccamonfina volcanoes were identified, such as the Tufo Giallo di Sacrofano and the Lower White Trachytic Tuff, respectively. Furthermore, the sediment succession documents a more complex eruptive history of the Sabatini, Vulsini, Colli Albani and Roccamonfina volcanic complexes during the investigated period, as inferred from previously undescribed tephra deposits. Single‐crystal‐fusion 40 Ar/ 39 Ar dating of two of the inspected tephra layers combined with two already published tephra ages provided the basis for a Bayesian age‐depth model. The modelled tephra ages allow chronological constraining of so‐far undefined eruptions of the Sabatini (272.5±4.7, 281.8±4.7, 308.5±2.8, 312.8±2.1 ka), the Vulsini (311.7±2.3, 311.9±2.3 ka) and the Colli Albani (301.0±3.6 ka) volcanic districts. Two tephra layers of an undefined volcanic source from the Roman volcanoes have modelled ages of 309.5±2.7 and 310.5±2.6 ka. The new 40 Ar/ 39 Ar and modelled ages were further used for a reassessment of the timing of already known and dated eruptive units, such as the Tufo Giallo di Sacrofano ( 40 Ar/ 39 Ar: 289.3±4.8 ka). Tephra tentatively correlated with the Valle Santa Maria, Case Pisello and the White Trachytic Tuff Unit E3 or Unit F offer modelled ages for these eruptions of 296.6±3.9, 301.8±3.5 and 303.6±3.4 ka, respectively. The results complete the tephrostratigraphical investigations of the c. 425 ka old F4‐F5 record, extend the Mediterranean tephrostratigraphical framework and provide a significant contribution for improving knowledge on Italian volcanic explosive activity.

The numerous volcanic centres in the Main Ethiopian Rift (MER) present significant but poorly understood hazards to local populations. The MER is also an important site to gain insights into tectonic processes as it captures the transition from continental rifting (to the south) to incipient seafloor spreading (to the north). Peralkaline magmas account for around 90% of the volcanic products found in the MER. Determining the conditions under which these magmas evolve is critical to understanding rift-related volcanism and its associated hazards. Corbetti Caldera has an extensive record of large-scale, predominantly aphyric, peralkaline rhyolite eruptions. However, little is known about the mafic magmas from which these highly differentiated melts have evolved. Here we present data from the only basaltic deposit found within the caldera, coupled with whole rock, glass and mineral analysis of the peralkaline products, to investigate magma storage conditions at Corbetti. We demonstrate that magma mixing played a role in the evolution of the basaltic magmas and use RhyoliteMELTS modelling to show Corbetti's peralkaline magmas likely evolved at pressures between 100 and 250 MPa, from a magma with an initial water content of 0.5-1 wt%, at or below the QFM buffer. Mineral hygrometry on the sparse crystal populations corroborates the RhyoliteMELTS modelling, suggesting that the basaltic magma had 0.1-1.2 +/- 0.32 wt% H2O, and the peralkaline magmas an average of similar to 5.5 +/- 1.25 wt% H2O. These results also match melt inclusion data for Corbetti and other peralkaline systems. We also provide new Ar-40/Ar-39 ages for two eruptions, a pre-caldera rhyolitic lava flow (206.7 +/- 0.9 ka) and a post-caldera peralkaline ignimbrite (160 +/- 0.8 ka). These results add to our understanding of the history of Corbetti and the storage conditions of peralkaline magmas within a continental rift setting and highlight the hydrous nature of Corbetti's magmas and the role that H2O plays during explosive eruptions.

In the Basilicata region, located in southern Italy and known for hosting among the first occurrences of the Acheulean culture in southwestern Europe, the Lower Paleolithic site of Loreto at Venosa is located less than a kilometer from the emblematic site of Notarchirico and less than 25 km from Cimitero di Atella. The Loreto site has not been studied as thoroughly as the two other sites and, although geological investigations have been carried out in the Venosa basin, no direct numerical dating has ever been published for the three archaeological levels brought to light during the excavation campaigns. We present a multi-method geochronological approach combining ESR/U-series, ESR, and 40Ar/39Ar permitting to refine the age of the most ancient archaeological level (A) of the Loreto site. These data allow us to propose an MIS 13 age for this level, in accordance with previous hypotheses based on geological and paleontological data. We also propose a technical review of the lithic tools preserved in the collection of the National Archaeological Museum of Venosa to integrate Loreto in the evolution scheme of the European Acheulean techno-complex emergence and diffusion.

Extensive bryozoan fossil records date back to the early Ordovician, forming an important part of sedimentary archives, yet the applicability of classical 18‑oxygen thermometry to bryozoan carbonate is still a matter of debate, with mineralogical and biological issues still hindering paleoclimate reconstructions. Complementing other methods (i.e., δ18O, Mg/Ca), clumped-isotope thermometry (Δ47) could provide more accurate paleotemperature estimates and help identify potential biotic factors influencing the isotopic composition of bryozoans. Here we report on the first investigation of clumped-isotope thermometry applied to bryozoan carbonate, spanning a broad range of modern species living in different environments from two localities (Atlantic Ocean and Mediterranean Sea). We confirm that bryozoan δ13C and δ18O records are affected by biotic and abiotic factors susceptible to bias in growth condition estimates. Our Atlantic bryozoans yield Δ47 derived temperatures (T47) consistent with spring/fall seawater temperature (but only after correcting for minor mineralogical effects), reflecting seasonal growth bias or, more likely, moderate isotopic disequilibrium. By contrast, Mediterranean samples display large positive offsets from Δ47 equilibrium values. We propose that this stronger disequilibrium is related to the higher salinity at this site, decreasing Carbonic Anhydrase activity, favoring CO2 hydroxylation over hydration, and slowing down DIC (dissolved inorganic carbon) equilibration reactions at the precipitation site. Our findings highlight how “vital effects” in bryozoans is not only species-specific as often assumed for other biocalcifiers, but could also depend on mineralogy and environmental factors.

The Ideale section (IS) at Montalbano Jonico, Italy, has been approved as a Standard Auxiliary Boundary Stratotype (SABS) for the Global boundary Stratotype Section and Point (GSSP) of the Middle Pleistocene Subseries/Subepoch and Chibanian Stage/Age at the Chiba section, Japan. The proposal was submitted to the voting members of the International Commission on Stratigraphy's Subcommission on Quaternary Stratigraphy (SQS) on May 4, 2023, and following discussions was approved on July 8, 2023. The 74 m thick IS continuously spans the Marine Isotope Stage (MIS) 20-18 interval, and is part of the longer Montalbano Jonico succession (Basilicata, southern Italy in the Mediterranean region) encompassing MIS 37 to early MIS 16. The IS provides a detailed record based on multiple chronologically well constrained marine and terrestrial proxies, which are particularly useful for outlining the paleoclimatic evolution through the Lower-Middle Pleistocene transition. The high-resolution carbon and oxygen isotope stratigraphy outlines glacial-interglacial and stadial-interstadial phases as well as the sub-millennial-scale features of Termination IX and the onset of MIS 19c. The sapropel layer equivalent to insolation cycle 74 (784 ka) occurs in early MIS 19c. A prominent peak in the Be-10/Be-9 record at the MIS 19c-19b transition identifies the low geomagnetic dipole moment associated with the Matuyama-Brunhes boundary interval. Two tephra layers (V3 and V4) relevant to boundary interval are Ar-40/Ar-39 dated. The V4 layer, occurring at the MIS 19c-b transition and in the middle of the Be-10/Be-9 peak, has an age of 774.1 +/- 0.9 ka, corresponding to the age of the Middle Pleistocene GSSP. A high-resolution alkenone sea-surface temperature and several paleobiological records complement the rich chronological and paleoenvironmental dataset from MIS 20 to the inception of MIS 18. The GSSP boundary interval in the IS is represented from 35.50 to 39.50 m, which corresponds to the interval of the highest values of the Be-10/Be-9 ratio (similar to 776.35-771.87 ka) and includes the V4 tephra layer and the MIS 19c-MIS 19b transition. This SABS extends the correlation potential of the Middle Pleistocene Subseries/Subepoch GSSP interval to the Mediterranean region.