Palaeomagnetism of Palaeogene strata from southern Zealandia: Implications for ice in the greenhouse

When did the first ice form on Antarctica? Large, stable ice sheets started to appear in the Oligocene, but there may have been earlier, transient Palaeocene glaciations which left only brief traces in the sedimentary record. Correlation of such traces across the New Zealand region requires the accuracy provided by magnetostratigraphic dating. However, the sediments that may contain these traces have extremely weak magnetizations, high glaucony concentrations, and other characteristics which complicate magnetic measurement. To address these problems, I developed measurement techniques for weakly magnetized samples and wrote a software package called PuffinPlot to process the measurements efficiently. (PuffinPlot is a fully-featured palaeomagnetic data plotting and analysis program also intended for use outside the scope of the thesis.) I also conducted an in-depth rock magnetic study to identify the remanence-bearing minerals and determine the effects of glaucony on magnetic behaviour. The rock magnetic results indicated that the remanence in the glauconitic sediments was carried by single-domain magnetite at extremely low concentrations, and the model I developed for remanence acquisition showed that this magnetite was capable of carrying a stable primary remanence. Using PuffinPlot and the results from the rock magnetic experiments, I conducted palaeomagnetic studies of early Palaeogene sections at the mid-Waipara River in Canterbury, Fairfield Quarry in eastern Otago, and Campbell Island, 700 km south of New Zealand. At each site I also measured the anisotropy of magnetic susceptibility (AMS) to determine variations in palaeocurrent. The wide spacing of the sites allows regional effects to be distinguished from local ones. The sections had several features in common: very weak magnetization, necessitating special measurement and analysis protocols; poor response to alternating-field demagnetization, necessitating thermal demagnetization; and thermal alteration at relatively low temperatures, necessitating great-circle remagnetization analysis to infer primary remanences. At Fairfield Quarry, I sampled a 25-metre composite section; 31 of the 58 sites sampled yielded usable data, all of them with reversed polarity. In conjunction with the known location of the K-Pg boundary within the section, this constrained the entire section to the C29r chron. At the mid-Waipara River, 9 sites (of 21 originally sampled) gave reliable directions, all reversed, constraining a 16-metre continuous section to the C26r chron. At Campbell Island, I sampled two sections in different parts of the island and constructed an integrated stratigraphy from a total of 38 site directions, which expanded the known duration of a major unconformity from around 9.5 Ma to 13.4 Ma. The improved age constraints on the Campbell Island section allowed the unconformity there to be correlated with a change in palaeocurrent at the mid-Waipara River, with a previously reported Palaeocene horizon of ice-rafted debris from eastern New Zealand, and with known fluctuations in oxygen isotopes during the Palaeocene, implying an extensive glaciation. Some of the glauconitic horizons at Fairfield Quarry may also be linked to earlier transient glaciations. Since Antarctica was still attached to Australia and South America during the Palaeocene, these results imply that circum-Antarctic ocean gateways are unnecessary for Antarctic glaciation

Techniques for utterance disambiguation in a human-computer dialogue system

Disambiguating an utterance occurring in a dialogue context is a complex task, which requires input from many different sources of information -- some syntactic, some semantic, and some pragmatic. The central question addressed by this thesis is how to integrate data sources for utterance disambiguation within a bilingual human-computer dialogue system. First, a simple scheme is proposed for classifying disambiguation data sources; then this scheme is used to develop a method for combining data sources in a principled manner. Next, several actual sources of disambiguation data are explored; each is fitted into the previously described implementation framework. In particular, a probabilistic grammar is developed and augmented using novel techniques to increase its performance with respect to the local dialogue context. In a dialogue system, ambiguities which cannot be resolved automatically can be clarified by asking the user what was meant. This thesis also presents a model of clarification subdialogues which is integrated within the utterance disambiguation framework. This is followed by a brief treatment of how user errors may be accommodated, and how this process can also be fitted -- conceptually and in implementation -- into the previously described disambiguation framework. Finally, I describe the details of implementing these techniques within an existing dialogue system, and give examples demonstrating their effectiveness

Techniques for utterance disambiguation in a human-computer dialogue system

Disambiguating an utterance occurring in a dialogue context is a complex task, which requires input from many different sources of information -- some syntactic, some semantic, and some pragmatic. The central question addressed by this thesis is how to integrate data sources for utterance disambiguation within a bilingual human-computer dialogue system. First, a simple scheme is proposed for classifying disambiguation data sources; then this scheme is used to develop a method for combining data sources in a principled manner. Next, several actual sources of disambiguation data are explored; each is fitted into the previously described implementation framework. In particular, a probabilistic grammar is developed and augmented using novel techniques to increase its performance with respect to the local dialogue context. In a dialogue system, ambiguities which cannot be resolved automatically can be clarified by asking the user what was meant. This thesis also presents a model of clarification subdialogues which is integrated within the utterance disambiguation framework. This is followed by a brief treatment of how user errors may be accommodated, and how this process can also be fitted -- conceptually and in implementation -- into the previously described disambiguation framework. Finally, I describe the details of implementing these techniques within an existing dialogue system, and give examples demonstrating their effectiveness

Palaeomagnetism of Palaeogene strata from southern Zealandia: Implications for ice in the greenhouse

When did the first ice form on Antarctica? Large, stable ice sheets started to appear in the Oligocene, but there may have been earlier, transient Palaeocene glaciations which left only brief traces in the sedimentary record. Correlation of such traces across the New Zealand region requires the accuracy provided by magnetostratigraphic dating. However, the sediments that may contain these traces have extremely weak magnetizations, high glaucony concentrations, and other characteristics which complicate magnetic measurement. To address these problems, I developed measurement techniques for weakly magnetized samples and wrote a software package called PuffinPlot to process the measurements efficiently. (PuffinPlot is a fully-featured palaeomagnetic data plotting and analysis program also intended for use outside the scope of the thesis.) I also conducted an in-depth rock magnetic study to identify the remanence-bearing minerals and determine the effects of glaucony on magnetic behaviour. The rock magnetic results indicated that the remanence in the glauconitic sediments was carried by single-domain magnetite at extremely low concentrations, and the model I developed for remanence acquisition showed that this magnetite was capable of carrying a stable primary remanence. Using PuffinPlot and the results from the rock magnetic experiments, I conducted palaeomagnetic studies of early Palaeogene sections at the mid-Waipara River in Canterbury, Fairfield Quarry in eastern Otago, and Campbell Island, 700 km south of New Zealand. At each site I also measured the anisotropy of magnetic susceptibility (AMS) to determine variations in palaeocurrent. The wide spacing of the sites allows regional effects to be distinguished from local ones. The sections had several features in common: very weak magnetization, necessitating special measurement and analysis protocols; poor response to alternating-field demagnetization, necessitating thermal demagnetization; and thermal alteration at relatively low temperatures, necessitating great-circle remagnetization analysis to infer primary remanences. At Fairfield Quarry, I sampled a 25-metre composite section; 31 of the 58 sites sampled yielded usable data, all of them with reversed polarity. In conjunction with the known location of the K-Pg boundary within the section, this constrained the entire section to the C29r chron. At the mid-Waipara River, 9 sites (of 21 originally sampled) gave reliable directions, all reversed, constraining a 16-metre continuous section to the C26r chron. At Campbell Island, I sampled two sections in different parts of the island and constructed an integrated stratigraphy from a total of 38 site directions, which expanded the known duration of a major unconformity from around 9.5 Ma to 13.4 Ma. The improved age constraints on the Campbell Island section allowed the unconformity there to be correlated with a change in palaeocurrent at the mid-Waipara River, with a previously reported Palaeocene horizon of ice-rafted debris from eastern New Zealand, and with known fluctuations in oxygen isotopes during the Palaeocene, implying an extensive glaciation. Some of the glauconitic horizons at Fairfield Quarry may also be linked to earlier transient glaciations. Since Antarctica was still attached to Australia and South America during the Palaeocene, these results imply that circum-Antarctic ocean gateways are unnecessary for Antarctic glaciation

New Developments in the PuffinPlot Paleomagnetic Data Analysis Program

PuffinPlot is a program for paleomagnetic data analysis and plotting, first released in 2012 and under continuous development since then. It is free, cross‐platform software and provides both a graphical desktop interface for interactive use and an application‐programmer interface for scripting. We present a major new release of the program, describe significant new features added since the first release, and demonstrate their application to real‐world data. New features include automatic magnetic declination realignment, relative paleointensity calculation, virtual geomagnetic pole determination, calculation of inclination‐only statistics, support for reproducible research via the export of self‐contained data bundles, and support for reading a number of popular paleomagnetic file formats. We also discuss the application of unit tests in ensuring PuffinPlot's long‐term reliability and outline directions for future development of the software.Published5578-55871A. Geomagnetismo e PaleomagnetismoJCR Journa

PuffinPlot: A versatile, user-friendly program for paleomagnetic analysis

PuffinPlot is a user-friendly desktop application for analysis of paleomagnetic data, offering a unique combination of features. It runs on several operating systems, including Windows,Mac OS X, and Linux; supports both discrete and long core data; and facilitates analysis of very weakly magnetic samples. As well as interactive graphical operation, PuffinPlot offers batch analysis for large volumes of data, and a Python scripting interface for programmatic control of its features. Available data displays include demagnetization/intensity, Zijderveld, equal-area (for sample, site, and suite level demagnetization data, and for magnetic susceptibility anisotropy data), a demagnetization data table, and a natural remanent magnetization intensity histogram. Analysis types include principal component analysis, Fisherian statistics, and great-circle path intersections. The results of calculations can be exported as CSV (comma-separated value) files; graphs can be printed, and can also be saved as publication-quality vector files in SVG or PDF format. PuffinPlot is free, and the program, user manual, and fully documented source code may be downloaded from http://code.google.com/p/puffinplot/.Peer Reviewe

Late Holocene forest dynamics in the Gulf of Gaeta (central Mediterranean) in relation to NAO variability and human impact

A new high-resolution pollen record, spanning the last five millennia, is presented from the Gulf of Gaeta (Tyrrhenian Sea, central Italy), with the aim of verifying if any vegetation change occurred in the central Mediterranean region in relation to specific well-known global and/or regional climate events, including the 4.2 ka event, the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA), and to detect possible vegetation changes related to still under-investigated climate signals, for example the so-called “Bond 2” cold event around 2.8 ka BP. The vegetation dynamics of the Gaeta record shows a recurrent pattern of forest increase and decline punctuating the mid- and late Holocene. When the timing of these patterns is compared with the climate proxy data available from the same core (planktonic foraminifera assemblages and oxygen stable isotope record) and with the NAO (North Atlantic Oscillation) index, it clearly appears that the main driver for the forest fluctuations is climate, which may even overshadow the effects of human activity. We have found a clear correspondence between phases with negative NAO index and forest declines. In particular, around 4200 cal BP, a drop in AP (Arboreal Pollen) confirms the clearance recorded in many sites in Italy south of 43°N. Around 2800 cal BP, a vegetation change towards open conditions is found at a time when the NAO index clearly shows negative values. Between 800 and 1000 AD, a remarkable forest decline, coeval with a decrease in the frequencies of both Castanea and Olea, matches a shift in the oxygen isotope record towards positive values, indicating cooler temperatures, and a negative NAO. Between 1400–1850 AD, in the time period chronologically corresponding to the LIA (Little Ice Age), the Gaeta record shows a clear decline of the forest cover, particularly evident after 1550 AD, once again in correspondence with negative NAO index. © 2017 Elsevier Lt

Rapporto di fine campagna oceanografica I-AMICA_2013_01 : foce del fiume Volturno - Golfo di Gaeta, Mar Tirreno

La campagna oceanografica I-AMICA_2013_01, svoltasi dal 29 gennaio al 11 febbraio 2013, costituisce una parte integrante delle attività di ricerca previste dall’Obiettivo Realizzativo OR4 - Attività 4.4 (Processi interfaccia biosfera idrosfera e funzionalità degli ecosistemi costieri) del Progetto PON03 di potenziamento strutturale I-AMICA (Infrastruttura di Alta tecnologia per il Monitoraggio Integrato Climatico-Ambientale; http://www.i-amica.it). L’attività di ricerca di monitoraggio ambientale integrato della foce del Fiume Volturno, attraverso studi del fondo mare e della colonna d’acqua, vuole chiarire quali interazioni incorrono a scala stagionale tra il suddetto fiume, che interessa un bacino idrografico di circa 6000 km2, ed un tratto della zona costiera del Golfo di Gaeta fortemente antropizzato. In particolare, alcune delle attività svolte nel corso della campagna oceanografica, rientrano nel monitoraggio stagionale delle variazioni dell’ecosistema marino‐costiero alla Foce del Fiume Volturno (Golfo di Gaeta - Tirreno centrale). Le operazioni sono state effettuate utilizzando la nave oceanografica Urania del CNR, ed hanno avuto una durata di 14 giorni (29 gennaio al 11 febbraio 2013) con imbarco e sbarco al porto di Napoli. Il personale presente a bordo comprende ufficiali e personale di bordo, tecnici di laboratorio e personale scientifico afferente a IAMC-CNR di Napoli, ISMAR di Bologna, ISAC di Lamezia Terme, INGV di Roma, Università di Palermo e Università Roma3