Variazioni Pleistoceniche della calotta Est- Antartica: nuove età di esposizione (3He) di depositi e superfici di erosione glaciale in Terra Vittoria Settentrionale (Prince Albert Mountains e Southern Cross Mountains)
Bibliographic record
Abstract
RIASSUNTO L’evidente influenza esercitata dal climate change sulle dinamiche criosferiche antartiche, testimoniata dalla sensibilità delle calotte polari, oscillazioni glacio-eustatiche ed evidenti variazioni delle trimlines, è oggetto di rinnovato interesse della comunità scientifica e argomento centrale dei recenti reports IPCC (2007, 2013). In particolare, significative testimonianze delle modificazioni indotte dalle fluttuazioni climatiche cenozoiche sarebbero state registrate ai margini dell’ East Antarctic Ice-sheet e portate alla luce da ricerche multidisciplinari. Tra queste, nell’ambito del presente progetto di tesi, è stata adottata la tecnica del Surface Exposure Dating per l’acquisizione di nuove età di esposizione di depositi glaciali e superfici relitte nel territorio di Baia Terra Nova, in particolare nel settore delle Prince Albert Mountains (a Sud) e delle Southern Cross Mountains (a Nord). Il processo di selezione dei campioni prelevati durante le spedizioni del PNRA 1996-1997 e 1997-1998, è stato eseguito tenendo conto del contesto geomorfologico nel quale si trovavano i campioni e, successivamente, tenendo conto delle caratteristiche litologiche. Inoltre, rilevanti sono state le caratteristiche petrografiche dei diversi campioni in quanto queste ultime vincolano la scelta dei minerali target. Alla fase di selezione ha fatto seguito la preparazione dei campioni da sottoporre successivamente alla determinazione delle età di esposizione, è stata in parte eseguita presso il Dipartimento di Scienze della Terra dell’Università di Pisa ed in parte presso i laboratori specializzati del CNR (IGG, Pisa). L’estrazione dei minerali target (pirosseni e olivine) è stata eseguita presso il SUERC, Università di Glasgow (UK), dove sono state anche eseguite le analisi allo spettrometro di massa (HELIX SFT). I target mafici (olivine e pirosseni), ottenuti dalle operazioni preparatorie di macinatura, separazione magnetica, hand-picking e leaching process, hanno consentito l’estrazione di 3He cosmogenico, dalla cui concentrazione sono state ricavate età minime di esposizione alla radiazione cosmica dei campioni elaborati. I vincoli cronologici forniti dai campioni di erratici analizzati consentono di identificare una fase glaciale del Pleistocene medio (Mt Matz), mentre i campioni provenienti dal substrato levigato e striato sono presumibilmente legati a una storia glaciale complessa. ABSTRACT A clear influence of climate change on the Antarctic cryosphere dynamics, witnessed by polar ice-sheets sensitivity, glacial eustatic oscillations, and evident variations in trimlines, is one of the main interests of the scientific community and a central topic of recent IPCC reports (2007, 2013) . In particular, cenozoic climatic fluctuations are recorded at the margins of the East Antarctic Ice-Sheet and pointed out by multidisciplinary research. Among these, for this project it has been used Surface Exposure Dating technique for the acquisition of new ages on glacial deposits and relieves surfaces in Baia Terra Nova, in particular in Prince Albert Mountains (South field) and Southern Cross Mountains (North field). The sampling process was taken during 1996-1997 and 1997-1998 and founded by PNRA. The shipments was carried out taking into account the geomorphological context in which the samples were located and their lithological characteristics. In addition, the petrographic characteristics of different samples were significant to choice target minerals. The first selection step was followed by the preparation of samples which were submitted for the determination of exposure ages, partly by the Department of Earth Sciences of the University of Pisa and partly by the specialized laboratories of the CNR (IGG, Pisa). Extraction of target minerals (pyroxenes and olivine) was performed at the SUERC, Glasgow University (UK), where it was used a specific mass spectrometric analysis (HELIX SFT) . Mineral target (olivine and pyroxene) obtained from preparatory operations, such as crushing, magnetic separation, hand-picking and leaching processes, allowed the extraction of cosmogenic 3He from which there were obtained the minimum age of exposure to the cosmic radiation of the processed samples. The chronological constraints provided by the analyzed sample allow to identify a glacial phase of the Pleistocene Medium (Mt Matz), while bedrock samples are presumably linked to a complex glacial history.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".