Maria Cristina Salvatore

Fluvial origin of the valley system in northern Victoria Land (Antarctica) from quantitative geomorphic analysis

A network of sinuous valleys with typical dendritic pattern characterizes northern Victoria Land (NVL) in Antarctica. Subparallel to parallel and angular to rectangular patterns are also present. Quantitative geomorphic analysis of the valley network has been carried out utilizing GIS spatial analysis. While drainage densities and drainage frequencies show low values, segments of the NVL valley network are substantially well organized, as indicated by bifurcation ratio (R b ) and direct bifurcation ratio (R bd ) parameters. All basins faithfully adhere to Horton’s laws of drainage network composition. Quantitative geomorphic analysis suggests that the valley system can be ascribed to fl uvial origin and that consequently, a morphoclimatic system completely different from that of present day must have driven its carving. The resulting data provide indications about the origin of the valley network and this invaluable information can be used for the reconstruction of earlier phases of glacial history and climatic and tectonic evolution of this signifi cant Antarctic region. Fluvial erosion enhanced the denudation of the Transantarctic Mountains from at least 55 Ma to at least the Eocene-Oligocene boundary (ca 34 Ma). Fluvial basins adapted to the tectonic structure, following the main regional fault systems. A well-developed alpine topography postdates the fl uvial morphology. Temperate glaciers were responsible for denudation until the Late Miocene. Parasitic glaciers presently mantle the previously sculpted topography. Present-day glacial erosion is negligible and denudation has been exceedingly slow since 7.5 Ma.

Surface exposure ages imply multiple low-amplitude Pleistocene variations in East Antarctic Ice Sheet, Ricker Hills, Victoria Land

Abstract One of the major issues in (palaeo-) climatology is the response of Antarctic ice sheets to global climate changes. Antarctic ice volume has varied in the past but the extent and timing of these fluctuations are not well known. In this study, we address the question of amplitude and timing of past Antarctic ice level changes by surface exposure dating using in situ produced cosmogenic nuclides (10Be and 21Ne). The study area lies in the Ricker Hills, a nunatak at the boundary of the East Antarctic Ice Sheet in southern Victoria Land. By determining exposure ages of erratic boulders from glacial drifts we directly date East Antarctic Ice Sheet variations. Erosion-corrected neon and beryllium exposure ages indicate that a major ice advance reaching elevations of about 500 m above present ice levels occurred between 1.125 and 1.375 million years before present. Subsequent ice fluctuations were of lesser extent but timing is difficult as all erratic boulders from related deposits show complex exposure histories. Sample-specific erosion rates were on the order of 20–45 cm Ma-1 for a quartzite and 10–65 cm Ma-1 for a sandstone boulder and imply that the modern cold, arid climate has persisted since at least the early Pleistocene.

Dating late Cenozoic erosional surfaces in Victoria Land, Antarctica, with cosmogenic neon in pyroxenes

Abstract We present 21Ne exposure ages of erosional glaciogenic rock surfaces on nunataks in northern Victoria Land, Antarctica: i) in the Prince Albert Mountains and ii) near Mesa Range. These nunataks are located directly at the margin of the polar plateau and therefore provide an immediate record of ice volume changes of the East Antarctic Ice Sheet, not biased by ice shelf grounding or narrow valley sections downstream the outlet glaciers. The sampling locations overlook the present ice surface by less than 200 m, but were last covered by ice 3.5 Ma bp (minimum age, not corrected for erosion). This strongly indicates that the ice sheet has not been substantially thicker than today since at least the early Pliocene, which supports the hypothesis of a stable East Antarctic Ice Sheet. First absolute ages are reported for the alpine topography above the erosive trimline that typically marks the upper limit of glacial activity in northern Victoria Land. Unexpectedly low nuclide concentrations suggest that erosion rates on the alpine topography are considerably higher due to the steep slopes than those affecting flat erosional surfaces carrying Antarctic tors.

From cold to warm-stage refugia for boreo-alpine plants in southern European and Mediterranean mountains: the last chance to survive or an opportunity for speciation?

During glacial phases of the Quaternary, Southern European and Mediterranean mountains (SEMms: Pyrenees, Apennines, Balkan Mountains, Maritime Alps, etc.) provided suitable habitats for numerous cold-adapted (boreo-alpine) plant species migrating from northern regions, which have been described as cold-stage refugia. Speciation events occurred in these refugia through adaptation and evolution by genetic differentiation; other species still survive as peripheral populations. In the current phase of climate change, SEMms are (macro-)refugia of great interest because they still host important populations of glacial relicts and alpine flora, often in isolated occurrences. Such species can be found in topographic niches generally linked to peculiar landforms such as fossil glacial cirques, scree slopes and gorges that may perform as warm-stage (micro-)refugia. We present a review on the boreo-alpine species living across SEMms with the aim to describe their genetic patterns evolved during Quaternary climatic oscillations as well to highlight the role of microtopographic/microgeomorphologic niches as microrefugium areas under the current scenario of climate change.

Reconstructing Fluctuations of La Mare Glacier (Eastern Italian Alps) in the Late Holocene: New Evidence for a Little Ice Age Maximum Around 1600 AD

Abstract Field observations, old terrestrial photographs and maps, aerial orthophotos and detailed geomorphological mapping were used for compiling and validating a 119‐year cumulative record of terminus changes for a are lacier, astern talian lps. ate olocene glacier maxima preceding direct observations were reconstructed by applying age dating techniques (radiocarbon and lichenometry) to glacial deposits in the proglacial area of the glacier. Results show that the glacier reached its maximal position around 1600 ad, followed by smaller advances in the eighteenth century, while in the nineteenth century it did not reach or overrun these positions. A similar behaviour for neighbouring glaciers was reported by previous works, documenting absolute ate olocene maxima in the seventeenth or eighteenth centuries. By contrast, multi‐century reconstructions available for the north‐western lps show that in the nineteenth century, glaciers were at their maximum or very close to previous maxima achieved in the first half of the seventeenth century. Climatic causes for these discrepancies have been examined, analyzing multi‐proxy climatic reconstructions starting in 1500 ad, but also morphodynamic processes linked to the bedrock characteristics of a are lacier could have played a role in modulating its response to climatic changes.

Ancient population genomics and the study of evolution

Recently, the study of ancient DNA (aDNA) has been greatly enhanced by the development of second-generation DNA sequencing technologies and targeted enrichment strategies. These developments have allowed the recovery of several complete ancient genomes, a result that would have been considered virtually impossible only a decade ago. Prior to these developments, aDNA research was largely focused on the recovery of short DNA sequences and their use in the study of phylogenetic relationships, molecular rates, species identification and population structure. However, it is now possible to sequence a large number of modern and ancient complete genomes from a single species and thereby study the genomic patterns of evolutionary change over time. Such a study would herald the beginnings of ancient population genomics and its use in the study of evolution. Species that are amenable to such large-scale studies warrant increased research effort. We report here progress on a population genomic study of the Adélie penguin (Pygoscelis adeliae). This species is ideally suited to ancient population genomic research because both modern and ancient samples are abundant in the permafrost conditions of Antarctica. This species will enable us to directly address many of the fundamental questions in ecology and evolution.

Neutron activation analysis on sediments from Victoria Land, Antarctica: multi-elemental characterization of potential atmospheric dust sources

The elemental composition of 40 samples of mineral sediments collected in Victoria Land, Antarctica, in correspondence of ice-free sites, is presented. Concentration of 36 elements was determined by instrumental neutron activation analysis, INAA. The selection of 6 standard reference materials and the development of a specific analytical procedure allowed to reduce measurements uncertainties and to verify the reproducibility of the results. The decision to analyze sediment samples from Victoria Land ice-free areas is related to recent investigations regarding mineral dust content in the TALos Dome ICE core (159°11′E; 72°49′S, East Antarctica, Victoria Land), in which a coarse local fraction of dust was recognized. The characterization of Antarctic potential source areas of atmospheric mineral dust is the first step to identify the active sources of dust for the Talos Dome area and to reconstruct the atmospheric pathways followed by air masses in this region during different climatic periods. Principal components analysis was used to identify elements and samples correlations; attention was paid specially to rare earth elements (REE) and incompatible/compatible elements (ICE) in respect to iron, which proved to be the most discriminating elemental groups. The analysis of REE and ICE concentration profiles supported evidences of chemical weathering in ice-free areas of Victoria Land, whereas cold and dry climate conditions of the Talos Dome area and in general of East Antarctica.

Insights into the Holocene environmental setting of Terra Nova Bay region (Ross Sea, Antarctica) from oxygen isotope geochemistry of Adélie penguin eggshells

An oxygen isotope record of Adélie penguin (Pygoscelis adeliae) eggshells from Terra Nova Bay (Victoria Land, Antarctica) has been reconstructed in order to provide insights into the palaeoenviroment of this region during the last ~8000 years. The δ18O values measured in eggshell carbonate show a great variability over the course of the studied period, with maximum values consistently around +27.5‰. Adopting a metabolic enrichment relative to water source of ~+28.5‰, eggshell δ18O values can be interpreted in terms of marine water uptake by the penguins. The spread in δ18O of eggshell carbonate at any given time toward more negative values reflects the existence of a low δ18O water end member, most plausibly snow or snowmelt. Samples younger than 2000 years are characterized by a general lack of very negative δ18O values. As also attested by other proxies, this shift toward more positive isotopic values is likely to be related both to a decreasing contribution of snow or meltwater in the seawaters and consequently to an absence or paucity on the boundary of the nesting sites of snow or snowfall and freshwater that could be directly eaten or drunk by penguins.

Mid-Holocene relative sea-level changes along Atlantic Patagonia: New data from Camarones, Chubut, Argentina

This paper concerns the relative sea-level changes associated with the Atlantic Patagonian coast derived from sea-level index points whose elevation was determined by a differential global position system (DGPS). Bioencrustations from outcrops located near Camarones, Chubut, Argentina, consist of autochthonous deposits characterized by Austromegabalanus psittacus (Molina, 1782), encrusting acervulinid foraminifera, coralline red algae and bryozoans. The association of the different organisms is interpreted as being associated with an intertidal environment, and they have been used as index points to establish the relative sea-level position. The main conclusion is that the relative sea-level between c. 7000 and 5300 cal. yr BP was in the range of c. 2–4 m a.s.l., with a mean value of c. 3.5 m a.s.l. Our data seem to support the existence of different rates of relative sea-level fall in different sectors of Atlantic Patagonia during the Holocene and highlight the importance of a more precise and accurate relative sea-level estimation by producing new data and revisiting the indicative meaning of most of the indicators so far used in the area.

Geophysical Imaging of the WWI Archeological Site of Linke Peak (Forni Glacier, Italian Central Alps)

The centenary of World War I triggered several and relevant studies in the fields of Conflict Archeology. The research scenario becomes even more challenging when the study site is located at high altitude in the Alps were past battles and also the modern research should face extreme conditions. A major research project was recently undertaken in the saddle between Mount Vioz and the Linke peak, in the Cevedale massif, where the progressive retreat of the Forni and of the Vedretta Rossa glaciers exposed barracks, tunnels, barbed wire, sledges, ammunitions and several other war remains. Geophysical imaging was the core of the project that was focused on a double objective: mapping possible WWI remains embedded in the ice and a obtaining some information on the glacier. Results from two different geophysical campaigns were encouraging as radar and seismic profiling provided detailed data about geometry and properties of the glacier as well as unexpected evidences of buried structures.