Elisa Malinverno

The upper Zanclean Spungone Sandstone records the onset of a major transgression along the western margin of the Periadriatic Basin, eastern central Italy, and comprises a 130 m-thick succession of shallow-marine strata characterized by a highly regular cyclical stratigraphy. Integrated analysis of both physical and biogenic structures, together with the identification of major stratal surfaces and the reconstruction of the stratigraphic framework, proved essential for understanding the erosional and depositional processes that occurred during sediment deposition. Eight high-frequency depositional sequences, typically a few to tens of meters thick, have been identified based on the repetitive vertical stacking of facies associations. Sequences are bounded by low-relief erosional discontinuities recording abrupt shallowing and modest basinward shifts of facies, interpreted as amalgamated sequence boundaries formed by subaerial exposure during relative sea-level lowering and marine planation during the subsequent relative rise.Each sequence is characterized by remarkably similar facies successions organized in a deepening-upward pattern and interpreted as transgressive systems tracts, partially truncated by erosional beveling at the overlying sequence boundary. Deposits attributable to the highstand and falling-stage systems tracts are absent, an architectural style typical of depositional sequences formed in low-accommodation basin-margin settings. Patterns in facies composition are suggestive of deposition in shoreface settings under storm conditions of varying intensity, revealing two fundamental types of sedimentary motif: weakly storm-affected and strongly storm-dominated shorefaces. The overall sequence-stratigraphic organization of the Spungone Sandstone exhibits an aggradational stacking pattern of component sequences, suggesting that they were almost certainly generated by high-rate, small-amplitude glacio-eustatic sea-level fluctuations superimposed on lower rate, tectonically-induced subsidence.Petrographic analysis of these well-sorted mixed siliciclastic-carbonate sandstones indicates that the bioclastic component mainly consists of skeletal debris derived from a contemporaneous cool-water carbonate factory. The terrigenous fraction is instead dominated by limestone lithic fragments, chert, and metamorphic quartz that were sourced from the progressive unroofing of the Mesozoic-Cenozoic cherty limestones of the Umbria-Marche domain and the Messinian turbiditic sandstones of the Laga Formation exposed in the uplifted Apennine sectors west of the study area.

Ice cores are exceptional archives of past climate variability, preserving forcing factors and proxies of the climate system’s response. Volcanic eruptions, when recorded as englacial tephra layers, provide insights into explosive volcanism, volcano–climate interactions, and enable long-range synchronization of paleoclimate records, provided the eruptive source is identified. Source attribution of far-travelled tephras requires geochemical characterisation of volcanic glass and comparison with known reference compositions. This task is complicated by the broad range of potential sources and the geochemical similarity of eruptive products. In this context, volcanic minerals, though less commonly used than glass, offer a valuable complementary tool for fingerprinting their source rocks.More broadly, most analytical protocols rely on melting ice cores, compromising the preservation and future reuse of this important natural archive. As climate change poses increasing threat to global ice reserves, developing an innovative approach is critically needed.Here, we present a novel, non-destructive Raman spectroscopy–based approach to analyse the mineralogy of visible tephra layers in ice cores. A tephra from Campbell Glacier, Antarctica (74°16′59″ S 164°10′52″ E), has been used to demonstrate advantages and pitfalls of this approach. The observed mineral assemblage is consistent with a strongly alkaline source and with its geochemical signature. This mineralogical dataset enables tephrochronological reconstructions and improves the precision and reliability of established analytical approaches for volcanic source fingerprinting.

The pattern of atmospheric and climate changes recorded by coastal Antarctic ice core sites and the processes they illustrate highlight the importance of multiproxy studies on ice cores drilled from such peripheral areas, where regional- to local-scale processes can be documented. Here, we present a 2 kyr long record of aeolian mineral dust and diatoms windblown to Roosevelt Island, obtained from the Roosevelt Island Climate Evolution project (RICE) ice core. Mineral dust and diatoms are highly complementary at RICE, since they are related to the large-scale South Pacific atmospheric circulation regime, carrying dust-rich air masses that travelled above the marine boundary layer, and local oceanic aerosol transport by low-level marine air masses, respectively. The period from 550 to 1470 CE is marked by increased mineral dust transport from Southern Hemisphere continents, a reduction in sea ice cover in the Eastern Ross Sea (ERS) and Amundsen Sea (AS), and more frequent incursions of humid air masses, which contributed to a relative rise in snow accumulation. After 1470 CE, relatively lower dust and snow deposition at RICE suggests an increase in pack ice in the eastern Ross and Amundsen seas. This period is characterized by prominent peaks of sea-ice-related aeolian diatoms that are unprecedented over the last 2 kyr, indicating a rapid reorganization of atmospheric circulation. Data suggest an eastward enlargement of the Ross Sea polynya culminating with the opening of the proposed Roosevelt Island polynya and an increased influence of low-level marine air masses to the site during the Little Ice Age (LIA).

This study presents the living coccolithophore communities and the morphological variability of Emiliania huxleyi in the South Aegean Sea from three sampling regions during winter-early spring (March 2017, March 2019) and summer (August 2019). Emphasis is given to March 2017 to monitor the variations in coccolithophore assemblages after an exceptionally cold event in December 2016, which resulted in newly produced dense waters that ventilated the Aegean deep basins. The assemblages displayed distinct seasonality with the predominance of E. huxleyi and Syracosphaera molischii during winter-early spring, associated with the water column mixing. By contrast, summer assemblages were featured by holococcolithophores and typical taxa of warm, oligotrophic upper waters. It seems that the phytoplanktonic succession as well as the nutrient supply to the upper euphotic layers were affected by the water column perturbation during the extreme winter of 2016–2017, which led to strong convective mixing and dense water formation. The decreased coccosphere densities during March 2017, accompanied by the notable presence of diatoms, were most probably associated with a prolonged diatom bloom, causing delay in the development of the coccolithophore community and resulting in a nitrogen-limited setting. Emiliania huxleyi morphometry showed the characteristic seasonal calcification trend of the Aegean, with the dominance of smaller coccoliths in the summer and increased coccolith length and width during the cold season. The intense cold conditions and wind-induced mixing during the winter of 2016–2017 possibly increased the absorption of atmospheric CO₂ in surface waters, causing increased acidity and the subsequent presence of etched/undercalcified E. huxleyi coccoliths and other taxa, most probably implying in situ calcite dissolution.

Coccolithophores are the main type of calcifying phytoplankton in the Southern Ocean (SO) and are key organisms in the production of particulate inorganic carbon (PIC). However, in situ studies of coccolithophores and in particular of their importance for the input of PIC in the SO are sparse in space and time due to the harsh weather conditions in the subantarctic realm. An alternative tool for monitoring PIC is the use of optical remote sensing, as coccolithophores account for most of the optical PIC backscattering in the sea. The aim of the present study is to provide coccolithophore-based estimates of PIC derived from Scanning Electron Microscope coccolith morphometric analyses and MODIS Aqua Level-2 and Level-3 PIC concentration values along two latitudinal transects from New Zealand to Antarctica and across the Drake Passage. In general, the coccolith-estimated PIC and satellite-derived PIC datasets show comparable trends in the Subantarctic and Polar Frontal zones of both transects, with coccolith-derived PIC values being generally lower than satellite PIC values. According to the coccolithophorid data, Emiliania huxleyi type A, over-calcified type A, and other taxa (e.g., Calcidiscus leptoporus) only contribute to coccolithophore PIC in the northernmost sampling locations, whereas E. huxleyi morphogroup B contributes substantially to the PIC content south of the Subantarctic Front in both transects. High satellite-derived PIC concentrations south of the Polar Front are not apparent in the coccolith-based PIC data. We suggest that the high reflectance signal in the Antarctic Zone may instead relate to the presence of small biogenic opal particles (e.g., diatoms, silicoflagellates, and/or small siliceous plankton) or other unknown highly reflective particles (such as Phaeocystis aggregations). Our results highlight the challenges presented by the lack of reliable satellite data in some parts of the SO as well as the importance of in situ measurements and methodological accuracy when estimating PIC values.

Aeolian mineral dust and diatom influxes at the summit of Roosevelt Island (79.364°S, 161.706°W, 550 m a.s.l.) were investigated over the last 2 kyrs from the RICE ice core (Bertler et al., 2018). Mineral dust at the site is mainly related to large-scale atmospheric circulation patterns within the Eastern Ross and Amundsen Seas, while aeolian diatoms, mainly consisting of Fragilariopsis spp. (F. nana , F. cylindrus, , F. curta), depend on the local oceanic influence of air masses from the marine boundary layer. Thus, the complementarity of these proxies allows appreciating climatic and atmospheric changes experienced at Roosevelt Island over the last 2000 years, in response to some major forcing factors such as ENSO. During the 550-1470 CE period, when higher/less depleted stable water isotope values are observed, the increased importance of blocking ridges in the Amundsen Sea and a weakened Amundsen Sea Low promoted dust-rich air mass advection to RICE. This pattern was accompanied by an increasing trend in snow accumulation and reduced sea ice in the Eastern Ross and Amundsen Seas. At about 1300 CE, the maximum expression of the Ross Sea dipole is reached, with enhanced katabatic outflow in the Western Ross Sea and reactivation of the Ross Sea polynya. At the same time, the Eastern part of the Ross Sea was still under the influence of blocking ridges promoting maritime air mass advection to RICE and southward shift of the South Westerly Winds. After 1470 CE, unprecedented peaks of aeolian diatom concentration suggest a rapid reorganization of local atmospheric circulation, that probably occurred in relation to the eastward enlargement of the Ross Sea polynya culminating with the opening of the Roosevelt Island polynya.For the RICE site, we suggest that several drivers contribute to the long-term dust, sea-ice and polynya variability, but ENSO-driven teleconnections are particularly prominent. On a longer (multidecadal) timescale it seems that El Niño-dominating conditions promoted the establishment of the Ross Sea dipole, while La Niña conditions favored a deeper Amundsen Sea Low and an eastward expansion of the polynya.

The evolution of baleen whales (Mysticeti) comprises two main phases, namely, (i) a Paleogene phase, which saw the diversification of stem lineages, and (ii) a Neogene phase, dominated by modern-looking, toothless, baleen-bearing forms in the monophyletic group Chaeomysticeti. These two phases are separated by a global turnover event coinciding with a gap—or “dark age”—in the mysticete fossil record. This dark age occurred between 23 and ~18 Ma and is apparently detected worldwide, except in Zealandia. Here, we report on a new mysticete fossil from the Lower Miocene (Burdigalian: ~19.2 Ma) strata of the Chilcatay Formation cropping out at the newly discovered locality of Cerro Tiza (East Pisco Basin, Peru), which represents a limited but precious testament from the last phase of the baleen whale dark age. Two previously mentioned, slightly geologically younger fossils from the same formation are also reappraised herein, revealing the occurrence of at least another baleen whale taxon in the upper Chilcatay strata—one that belongs in the mysticete crown group. Although the Early Miocene remains a problematic time interval for the fossil record of baleen whales, our new results encourage the search for mysticete fossils in the Lower Miocene strata of the East Pisco Basin, whose basin fill preserves a cornucopia of extraordinarily informative marine vertebrate fossils of the Cenozoic age, as well as in coeval deposits worldwide.

The East Pisco Basin is a world known Fossil-Lagerstätte that provided an abundant and exceptionally well-preserved record of marine vertebrate fauna (Bosio et al., 2021) within a middle Eocene to late Miocene sediment succession. In particular, the Miocene Pisco Formation is the most studied: its stratigraphic architecture has been recently redefined in the Ica River Valley (Di Celma et al., 2017, 2022) with the identification of three depositional sequences, namely P0, P1, P2 in ascending order, separated by extended unconformities which testify subaerial exposure and correlate with major climatic cycles (Di Celma et al., 2018). While P2 (8.4-6.7 Ma) and P1 (9.5-8.6 Ma) provided abundant diatom markers and common volcanic ash layers that were dated through the 40Ar/39Ar method (Bosio et al., 2020a), P0 (14.7-12.6 Ma), lacking microfossils and ash layers, was chronologically constrained by Strontium Isotope Stratigraphy (Bosio et al., 2020b).A new section sampled at Cerro Tiza in the Ica River Valley provided a fossiliferous P0 and the basal P1, allowing to constrain the age and paleoenvironment of these early deposits of the Pisco Formation. The age of P0 is now constrained by the occurrence of Denticulopsis hyalina (14.9-13.1 Ma), D. simonsenii (14.5-8.7 Ma), D. vulgaris (~13.5-8.5 Ma), Koizumia adaroi (14.2-9.0 Ma) and Crucidenticula nicobarica (15.1-12.3 Ma) - similar to the assemblage observed further south in the Laberinto area (DeVries et al., 2021) and well in agreement with isotopic dating - in a high productivity (abundant Thalassionema) coastal setting (common phytoliths, Paralia, Melosira, Actinoptychus and Grammatophora). The early deposits of P1 are constrained by the occurrence of Lithodesmium reynoldsii (10.0-9.0 Ma), D. vulgaris (~12.0-8.6 Ma) and D. praekatayamae (9.6-8.6 Ma) still in a high productivity (common Thalassionema, Chaetoceros) coastal setting (common Delphineis, Actinoptychus, Grammatophora). Few to abundant calcareous nannofossils (Reticulofenestra pseudoumbilicus, R. perplexa, Discoaster variabilis, Coccolithus pelagicus) are also here reported for the first time, testifying to a more open coastal environment, as compared to the previously-analyzed settings located more on-shore.ReferencesBosio et al., 2020a. Tephrochronology and chronostratigraphy of the Miocene Chilcatay and Pisco formations (East Pisco Basin, Peru). NOS, 53 (2), 213-247.Bosio et al., 2020b. Strontium Isotope Stratigraphy and the thermophilic fossil fauna from the middle Miocene of the East Pisco Basin (Peru). JSAES, 97, 102399.Bosio et al, 2021. Taphonomy of marine vertebrates of the Pisco Formation (Miocene, Peru): Insights into the origin of an outstanding Fossil-Lagerstätte. PLoS ONE, 16, e0254395.Di Celma et al., 2017. Sequence stratigraphy and paleontology of the upper Miocene Pisco Formation along the western side of the lower Ica Valley (Ica desert, Peru). RIPS, 123 (2): 255-273.Di Celma et al., 2018. Intraformational unconformities as a record of late Miocene eustatic falls of sea level in the Pisco Formation (southern Peru). JOM, 14 (2), 607-619.Di Celma et al., 2022. Towards deciphering the Cenozoic evolution of the East Pisco Basin (southern Peru), JOM, 18 (2), 397-412.DeVries et al., 2021. The Miocene stratigraphy of the Laberinto area (Río Ica Valley) and its bearing on the geological history of the East Pisco Basin (south-central Peru). JSAES, 111, 103458