Dissertations / Theses on the topic 'Deccan Traps'

New major, minor, and trace element data for the Chakhla- Delakari sill and three nearby lava flows in the proximal area of Tamia are presented. Based on abundances of trace elements, it is inferred that the sill was the feeder of the two uppermost lava flows which tapped magmas from a LREE-, Rb-enriched source. The oldest (lowermost) flow shows greater affinity with the western Deccan lavas. The association of the feeder sill with a large network of parallel trending sills and dikes, and the elongate Satpura Dome, is taken to infer that a major locus of eruption of the Deccan Trap lavas existed in the eastern part of the province. A model is presented for the evolution of the magma source of the sill and the two uppermost flows in a chamber beneath the Satpura Dome in the easternmost Deccan Traps. Results of equilibrium crystallization experiments at 6.35 kbars conducted on two compositions which represent probable near primary liquids are presented. One of these starting compositions has 9.5% MgO and the other 13% MgO. The sequence of crystallization in both starting liquids at 6.35 kbars is as follows: olivine; olivine + Ca- clinopyroxene; ol + Ca-clinopyroxene + Ca-poor clinopyroxene; olivine + Ca-clinopyroxene + Ca-poor clinopyroxene + plagioclase. Based on the present experimental data, it is inferred that typical Deccan magmas (MgO 5-9%) are produced by early fractionation of olivine, pyroxene (Ca-augite and pigeonite), and late fractionation of plagioclase. Deccan basalts with MgO 9-10% appear to have crystallized from melts lower in Ti02 than the starting materials of this study which fractionated olivine and plagioclase. Basalts with MgO2source which has fractionated olivine and plagioclase will produce of the bulk of Deccan basalts.

Dans cette thèse, nous tentons de contraindre la date, la séquence et la durée du volcanisme des traps du Deccan en Inde, et de commencer à en modéliser les conséquences climatiques. Pour cela, nous avons échantillonné 12 nouvelles coupes sur 300km (du Nord au Sud) le long de l’escarpement des Western Ghats. Les résultats paléomagnétiques ont permis de reconnaître des groupes de directions statistiquement identiques dans de nombreuses coulées, soit situées en séquence dans une même coupe, soit séparées latéralement de plus de 130km. Nous proposons, sur la base des caractéristiques de la variation séculaire récente du champ géomagnétique et de la taille des intervalles de confiance à 95% des directions rémanentes, que ces groupes directionnels correspondent à des méga-coulées ou “unités de refroidissement” qui se sont refroidies en quelques décennies à moins d’un siècle. Ces méga-coulées sont alors capables d’émettre de fortes quantités de dioxyde de soufre dans l’atmosphère. Nous estimons la durée totale de mise en place du volcanisme (le temps réel d’éruption) à moins de 10. 000 ans, la plupart du temps (de 400 à 500. 000 ans) étant représentée par une dizaine de “red boles” épais. Les données géochronologiques ont permis d’obtenir pour les Western Ghats un âge absolu (64. 7±0. 6Ma; 1s) qui est statistiquement identique à celui de la limite Crétacé-Tertiaire (qui ne peut cependant pas encore être localisée avec précision dans la coupe). Pour tenter de commencer à modéliser l’impact climatique d’un grand trap, nous avons choisi comme “brique élémentaire” l’éruption fissurale de 1783 au Laki en Islande (l’une des plus grandes éruptions historiques basaltiques). Avec le modèle LMDZ-INCA, nous avons pu reproduire l’extension (semi-globale) du nuage de brouillards exceptionnels qui fut observé cette année-là, et nous avons pu nous faire une idée des raisons de la crise de mortalité qui l’a accompagné. Un seul “pulse” du Deccan pouvant atteindre dix fois le flux injecté par le Laki et ce pendant près de 100 fois plus longtemps, les traps du Deccan sont alors fortement susceptibles d’induire une extinction en masse
In this thesis, we attempt to constrain the date, timing and duration of flood basalt volcanism in the particular case of the Deccan traps of India, and to model the climatic impact of such massive volcanism. With this goal in mind, we have sampled 12 new sections of the traps along 300km (from North to South) of the Western Ghat escarpment. Sections were selected based on previously available petrologic, geochemical and volcanological data. Using the paleomagnetic analysis we have been able to recognize groups of statistically identical directions in a number of flows, either superimposed in the same section, or laterally separated by up to 130km. We hypothesize, based on the characteristics of recent secular variation and the typical sizes of the 95% confidence intervals of the remanence directions, that these directional groups represent mega-flows or cooling units that cooled within a period of decades to at most a century. We estimate that the total amount of time represented by the flows could be less than 10,000 years, and that most of the time (400 to 500. 000 years) is represented by less than 10 thick bole levels. Therefore we have established an absolute age undistinguishable from that of the Cretaceous-Tertiary boundary (although this boundary cannot yet be precisely located within the section) at 64. 7±0. 6Ma. In order to start modeling the climatic impact of such flood basalt sequences, we have first used as a “building block” the 1783 fissure eruption at Laki in Iceland (one of the largest historical basaltic eruptions). Using the LMDZ-INCA model, we replicate the observed (semi-global) dispersal over much of northern hemisphere of the unusual haze that was observed at the time and are able to understand the spread and intensity of the mortality crisis which ensued. A single Deccan pulse could have reached 10 times the flux of Laki, and for up to 100 times longer. And there were tens of pulses suggesting the causal consequences of the climatic impact of flood basalts regarding mass extinctions

Crystallization experiments were performed at one-atmosphere pressure and Quartz- Fayalite-Magnetite (QFM) buffer conditions on tholeiitic basalts from Ambenali and Bushe formations of the Deccan Traps. The sequence and chemistry of the experimentally produced phase assernblages are in general agreement with the observed petrographic and geochemical variation of the natural Ambenali samples. When Bushe and Ambenali basalts are plotted on a cpx-ol-qz diagram, Ambenali plots close to the ol+aug+pl+l pseudo-cotectic whereas Bushe basalts define the pigeonite liquidus field which is somewhat different from that inferred by Grove and Bryan (1983) for midoceanic ridge basalts (MORBs). The difference can be ascribed to the different bulk composition of the starting materials used in the present experiments. Although ol → ol+ aug are near liquidus assemblages in the experiments on Neral at QFM, natural samples from this formation are rnostly aphyric. This may indicate that (1) the within-chamber crystal sorting processes were extremely efficient so that the crystals were totally removed from the melt prior to their eruption, or (2) the lavas erupted at super-liquidus temperatures (i.e., carried superheat).

La datation #4#0ar/#3#9ar et le paleomagnetisme sont deux methodes puissantes pour contraindre la duree d'emission des principaux traps. Nos resultats sur trois d'entre eux plaident en faveur d'une mise en place rapide, et une association possible (au moins temporelle) a des evenements biologiques ou climatiques majeurs. Les traps du deccan ont deja fait l'objet de nombreux travaux, mais les interpretations continuent a differer. Ainsi, courtillot et al. (1988) proposent une duree d'epanchement courte (moins d'1ma), principalement durant le chron 29r et un lien probable avec les extinctions de la limite cretace-tertiaire. Venkatesan et al. (1993) plaident en faveur d'une duree d'epanchement superieure a 3ma, associent les traps au chron 31r niant tout lien possible avec la limite kt. La decouverte par bhandari et al. (1994) d'un niveau d'iridium entre deux coulees de traps dans la province du kutch a offert l'opportunite de confirmer la simultaneite des deux evenements, impact et volcanisme. Nos resultats confirment que le volcanisme a commence avant la kt, chevauche la limite et continue apres. L'impact n'a donc pas cause l'epanchement des traps. Les deux catastrophes ont pu jouer un role dans les extinctions de la kt, dont le taux respectif reste a preciser. Nos resultats sur les traps de siberie concernent une aire plus vaste que celle des intrusions de noril'sk-1 abondamment etudiee, et nos ages semblent confirmer une mise en place rapide contemporaine de la limite permo-trias. L'age des traps d'ethiopie etait encore mal contraint au debut de ce travail. Nous pouvons aujourd'hui proposer un age de 30ma. Les ages obtenus dans une coupe de 2200m d'epaisseur sont indiscernables les uns des autres autour de cette valeur. Les magnetostratigraphies obtenues ne peuvent etre correlees de maniere unique mais confirment la brievete de l'epanchement. La regression majeure des niveaux marins vers 28. 5ma (haq et al. , 1987) pourrait lui etre attribue.

Detailed volcanostratigraphic logs of seven traverses up the lava sequence in the Western Ghats, Deccan Traps, India, are presented. The main study area, the Mahabaleshwar Plateau, was chosen because the lavas were emplaced around the time of the Cretaceous-Tertiary Boundary and because there is access to exposed lavas on three of its four sides, permitting investigation of the volcanic architecture in 3-D. Besides characteristics of the lava units, the logs include integrated geochemical and palaeomagnetic samples. The lava pile is dominated by pthoehoe sheet lobes and smaller lobes and toes. It can be divided into flow-fields, the products of one eruption, by the occurrence of weathering horizons. Palaeomagnetic results demonstrate that the chron 29R/29N reversal boundary horizon occurs in all four of the traverses around the Plateau and nearby Khumbarli Ghat. The elevation of the reversal horizon on each traverse varies between 897-945 m and 982 m, a value greater than that predicted by the small regional dip. Statistical analysis of geochemical data from samples taken between the reversal horizon and the base of the Mahabaleshwar Formation do not show any apparent correlation around the Mahabaleshwar Plateau, indicating that individual sheet lobes are less than 20 km wide. Determining the lateral extent of flow-fields is not possible using this method but from the occurrence of a similar number of flow-fields in three traverses of similar length round the Plateau, it is probable that most flow fields are at least as wide as the Mahabaleshwar Plateau (more than 20 km). Comparing the thickness of the lava pile between the base of the Mahabaleshwar Formation, the palaeomagnetic reversal horizon and the laterite cap, shows that as much as 95m of topography occurred on the surface of the active Deccan lavas over a distance of approximately 20 km. The volcanic architecture is controlled by the morphology of small sheet lobes, large sheet lobes, and, on a larger scale, flow-fields. These observations, and the varying number of individual sheet lobes making up flow-fields, demonstrates that the structure of the Deccan lava province at the level of eruptive units is extremely complex.

The Deccan Trap basalts are the remnants of a massive series of lava flows that erupted at the K/T boundary and covered 1-2 million km2 of west-central India. This eruptive event is of global interest because of its possible link to the major mass extinction event, and there is much debate about the duration of this massive volcanic event. In contrast to isotopic or paleomagnetic dating methods, I explore an alternative approach to determine the lifecycle of the magma chambers that supplied the lavas, and extend the concept to obtain a tighter constraint on Deccan’s duration. My method relies on extracting time information from elemental and isotopic diffusion across zone boundary in an individual crystal. I determined elemental and Sr-isotopic variations across abnormally large (2-5 cm) plagioclase crystals from the Thalghat and Kashele “Giant Plagioclase Basalts” from the lowermost Jawhar and Igatpuri Formations respectively in the thickest Western Ghats section near Mumbai. I also obtained bulk rock major, trace and rare earth element chemistry of each lava flow from the two formations. Thalghat flows contain only 12% zoned crystals, with 87Sr/86Sr ratios of 0.7096 in the core and 0.7106 in the rim, separated by a sharp boundary. In contrast, all Kashele crystals have a wider range of 87Sr/86Sr values, with multiple zones. Geochemical modeling of the data suggests that the two types of crystals grew in distinct magmatic environments. Modeling intracrystalline diffusive equilibration between the core and rim of Thalghat crystals led me to obtain a crystal growth rate of 2.03x10-10 cm/s and a residence time of 780 years for the crystals in the magma chamber(s). Employing some assumptions based on field and geochronologic evidence, I extrapolated this residence time to the entire Western Ghats and obtained an estimate of 25,000 – 35,000 years for the duration of Western Ghats volcanism. This gave an eruptive rate of 30 – 40 km3/yr, which is much higher than any presently erupting volcano. This result will remain speculative until a similarly detailed analytical-modeling study is performed for the rest of the Western Ghats formations.

The Deccan Traps are one of the most important Large Igneous Provinces (LIP) in the world, they are mainly constituted by tholeiitic lava flows, now covering almost one sixth of the Indian continent, and reaching the maximum exposed thickness of 1300 m. The emplacement of such quantities of magma and its timing (ca. 66Ma) close to the Cretaceous-Paleogene (K-Pg) boundary, have led several authors to propose a causal link between the formation of the province and the K-Pg boundary mass extinction . Moreover, a distinctive feature of the province is the presence, beside the tholeiites, of several alkaline bodies, associated with the main fault zones of India. These two important aspects of the Deccan Traps have been investigated in the northern portion of the province by sampling both alkaline and tholeiitic rocks, in order to provide precise timing of emplacement and to constrain the relationship between them through the definition of their mantle source. 40Ar/39Ar step-heating analyses provided two different age peaks that straddle the K-Pg boundary, one with an age comparable with the main phase of Deccan volcanism (ca 66.5 Ma), the other slightly younger (ca. 65.2 Ma), thus confirming the synchrony between the emplacement of the province and the end-Cretaceous mass extinction. Therefore, the input in the atmosphere of huge quantities of gas, produced by the emplacement of the Deccan Traps, could have contributed to the extinction. In particular a crucial role may be provided in this sense by the alkaline magmas, which are likely enriched in volatile elements. Whole rock analyses showed that the samples span a wide compositional range varying from little-evolved compositions such as picro-basalts to fairly evolved ones such as rhyolite; the large variation is observed in the total alkali content (Na2O+K2O) as well, ranging from the subalakaline basalt field, up to strongly alkaline samples like phonolites. Alkaline rocks appear enriched in the most incompatible elements and present higher La/Yb ratios (19.5-68.8). They are also characterized by negative K anomaly (possibly suggesting the presence of a K-rich residual mantle mineral), and Pb spikes; on average they present patterns similar to those displayed by other alkaline rocks of the Deccan Traps, thus suggesting analogous origin and source. Sr-Nd isotopes define a large spectrum of compositions, departing from a similar depleted end-member (εNdt ca. +3 and 87Sr/86Srt ca. 0.705) and trending towards low εNdt and relatively low 87Sr/86Srt (-12.96 and 0.71061, respectively), and toward very high 87Sr/86Srt (0.72788) and low εNdt (-12.50). The trend with higher 87Sr/86Srt has been interpreted as the result of Assimilation- Fractional Crystallization (AFC) process, starting from a magma similar to Réunion OIBs or Central Indian Ridge basalts progressively contaminated by rocks from the Indian cratons (Dharwar and Aravalli cratons). The trend towards low εNdt and relatively low 87Sr/86Srt is defined mainly by mafic sulbalkaline rocks from the Phenai Mata intrusion. These rocks are characterized also by very high 207Pb/204Pbt and 208Pb/204Pbt ratios. Given the preliminary 187Os/188Ost compositions (0.1584 to 0.2457), mafic subalkaline rocks assimilated only negligible amounts of crust. Their enriched Sr-Nd-Pb isotopic composition is thus best interpreted as resulting from recycling of ancient sediments in their mantle source. On the contrary, alkaline samples present quite homogeneous isotopic compositions, slightly more enriched than that of nearby carbonatite complexes (e.g. Amba Dongar) and substantially more enriched than Reunion basalts. Therefore, the alkaline rocks are unlikey a product of the Reunion mantle plume, but more probably of the subcontinental lithospheric mantle, as is consistent also with their incompatible trace element contents and patterns.
I Deccan Traps sono una delle più importanti grandi province magmatiche del mondo, sono principalmente costituiti da colate di lava tholeiitica, attualmente ricoprono circa un sesto del continente Indiano e raggiungono uno spessore massimo di 1300m. La messa in posto di queste grandi quantità di magma avvenuta al limite Cretaceo-Paleogene (K-Pg), ha portato diversi autori a proporre un rapporto di causalità tra la formazione di questa provincia e l’estinzione di massa al limite K-Pg. Inoltre, una caratteristica dei Deccan Traps è la presenza, oltre alle tholeiiti, di diversi corpi alcalini associati con le principali zone di faglia indiane. Questi due importanti aspetti dei Deccan traps sono stati studiati nella porzione nordoccidentale della provincia, campionando rocce alcaline e tholeiitiche, al fine di definire un preciso tempo di messa in posto e caratterizzare la relazione tra le diverse litologie, attraverso la determinazione della loro sorgente di mantello. Le analisi 40Ar/39Ar step-heating hanno restituito due diversi picchi di età a cavallo del limite K-Pg, il primo con un’età comparabile a quella della fase principale del magmatismo Deccan (ca. 66.5Ma), il secondo più giovane (ca. 65.2 Ma), confermando quindi l’effettiva sincronia tra la formazione della provincia e l’estinzione di massa alla fine del Cretaceo. Quindi, l’immissione in atmosfera di grandi quantità di gas, prodotta dalla messa in posto dei Deccan Traps, può aver contribuito all’estinzione. In particolare un ruolo molto importante potrebbe essere stato quello dei magmi alcalini, che verosimilmente sono arricchiti in elementi volatili. I campioni coprono un ampio range composizionale in termini di elementi maggiori, variando da composizioni poco evolute come i picro-basalti, a evolute come le rioliti; la variabilità è osservata anche nel contenuto di alcali (Na2O+K2O), variando dal campo subalcalino dei basalti a quello di campioni fortemente alcalini come le fonoliti. Le rocce alcaline sono arricchite negli elementi più incompatibili e presentano un rapporto La/Yb più alto (19.5-68.8). sono inoltre caratterizzate da una anomalia negativa in K, (probabilmente dovuta alla presenza di una fase residuale ricca in K nel mantello) e ad una positiva in Pb; in genere presentano pattern simili a quelli di altre rocce alcaline dei Deccan Traps, suggerendo quindi un’origine simile. Anche i rapporti isotopici di Sr e Nd definiscono un ampio range composizionale, partendo da un end-member impoverito (εNdt ca. +3 and 87Sr/86Srt ca. 0.705), verso composizioni a basso εNdt e relativamente basso 87Sr/86Srt (-12.96 and 0.71061, rispettivamente), e verso composizioni a 87Sr/86Srt (0.72788) molto alto e basso εNdt (-12.50). Il trend a più alto 87Sr/86Srt è stato interpretato come il risultato di un processo di assimilazione e cristallizzazione frazionata (AFC), a partire da un magma simile alle composizioni tipiche di Réunion o del Central Indian Ridge, progressivamente contaminato da rocce dei Cratoni indiani (Dharwar e Aravalli). Il trend verso composizioni a basso εNdt e relativamente basso 87Sr/86Srt è definito principalmente da rocce mafiche subalcaline dell’intrusione di Phenai Mata, queste rocce sono anche caratterizzate da rapporti 207Pb/204Pbt and 208Pb/204Pbt molto alti. Date le prime composizioni isotopiche 187Os/188Ost (da 0.1584 a 0.2457), queste rocce hanno assimilato porzioni trascurabili di crosta. Le loro composizioni Sr-Nd-Pb arricchite sono quindi meglio interpretate come il risultato del contributo nella sorgente di mantello di antichi sedimenti riciclati. Al contrario i campioni alcalini presentano composizioni isotopiche piuttosto omogene, leggermente più arricchite rispetto a quelle dei vicini complessi carbonatitici (p. es. Amba Dongar) e decisamente più arricchiti dei basalti di Réunion. Perciò le rocce alcaline sembrano non essere il prodotto del plume di Réunion, ma più probabilmente del mantello litosferico subcontinentale, come suggerito anche dai contenuti e dai pattern degli elementi in traccia.

Cette thèse s'appuie sur les travaux d'Alexander V. Sobolev sur le recyclage de matériel crustal dans le manteau terrestre en lien avec les processus de mise en place des provinces magmatiques et des iles océaniques. Il s'agit d'utiliser des outils pétrologiques et géochimiques couplés à des données de paléomagnétisme haute résolution, et à de la modélisation thermomécanique dans le but de contraindre les processus profonds à l'origine des Trapps du Deccan et leurs conséquences au niveau planétaire (extinction de masse). Dans un premier temps, cette thèse propose une réinterprétation des diverses contraintes temporelles sur la durée de l'éruption des Trapps du Deccan (datations radiochronologiques, paleomagnétisme, profiles d'altérations, et données paléo-environnementales) et suggère un scénario temporel pour la mise en place de cette province magmatique, le tout principalement basé sur des données paléomagnétiques de hautes résolution de Chenet et al (2008, 2009). Ce scénario implique que la phase principale de l'éruption des Trapps du Deccan s'est produite peu de temps avant la limite Crétacé-Paléogène et qu'elle correspond à la mise en place d'environ 1.106km3 de laves en 50ka. Ces chiffres sont équivalents à 150-200 fois le taux d'éruption actuel de l'ile volcanique d'Hawaii. Ce scénario temporel a ensuite été couplé à des données géochimiques élémentaires qui ont permis de mettre en évidence 1) une origine profonde pour la grande majorité des liquides primaires et 2) d'importantes variations de l'assimilation crustale au cours du temps, notamment juste avant la limite Crétacé-Paléogène. Ces phénomènes sont compatibles avec un unique épisode d'érosion lithosphérique de la plaque indienne par les processus magmatiques dans le manteau sous-jacent. Les données relatives aux Trapps du Deccan peuvent être comparées à celles des Trapps de Sibérie et révèlent notamment que l'importante érosion lithosphérique identifiée dans celles-ci n'ait pas eu lieu dans le cas des Trapps du Deccan malgré des caractéristiques mantelliques similaires. Cette différence peut être attribuée à la plus grande épaisseur de la plaque indienne, ainsi qu'à l'existence de zones de faiblesses, liées à l'héritage tectonique du bouclier indien. Ces zones de faiblesses auraient facilité le passage des magmas à travers la plaque de manière à ce qu'une faible proportion d'entre eux seulement ait été impliquée dans les processus de délamination lithospherique. Un ensemble de données géochimiques sur olivine ainsi que de modélisation des liquides magmatiques primaires et de leur source pour les Trapps du Deccan nous ont permis de montrer 1) l'importante contribution d'une source pyroxenitique à la composition des liquide magmatiques primaires (65%), 2) que la gamme de températures potentielles de ces mêmes sources avait due être de l'ordre de 1600°C et 3) que ces dernières contenaient environ 15% de matériel crustal recyclé. Des mesures et calculs similaires appliquées aux laves de la Réunion ont, par ailleurs, montrés des résultats très différents : 50% de liquides pyroxenitiques dans les liquides magmatiques primaires, une température potentielle mantellique de l'ordre de 1500°C et une teneur des sources magmatiques en matériel crustal recyclé de l'ordre de 7%. Ces résultats sont compatibles avec le modèle de panache matellique pour la mise en place des provinces magmatiques et des iles océaniques ainsi qu'avec l'hypothèse du refroidissement séculaire de ces mêmes panaches. Nous en concluons que l'éruption des Trapps du Deccan fut un événement d'une rapidité exceptionnelle et que son implication dans la crise biologique de la fin du Crétacé fut sans doute particulièrement importante
This PhD aims to build on the previous work by Alexander V. Sobolev and colleagues on crustal recycling within the Earth mantle and LIPs/ocean island magmatism. The PhD focus will be to apply petrology and geochemistry coupled with high-resolution paleomagnetism, and thermo-mechanical modelling in order to constrain the deep processes behind the Deccan Traps (mantle melting and crustal recycling) as well as the consequences at the surface of the Earth (eruption rates and related degassing). Upon revisiting published time constraints on the Deccan eruptions (radiometric dating, paleomagnetism, inter-flow weathering profiles and paleoenvironmental data), we propose a new, paleomagnetism-based (Chenet et al., 2008, 2009), eruption scenario for the Main Deccan Province (Western Ghats). We suggest that the main phase of volcanic activity occurred just before and ended at the Cretaceous-Palaeogene boundary and was responsible for the emplacement of about 1.106km3 of lavas in ~50kyr. This is equivalent to 150 to 200 times present-day eruption rates in Hawaii. Coupling of the paleomagnetism-based timeframe with bulk-rock trace element concentrations revealed that Western Ghats lavas feature 1) a strong garnet signature (Heavy Rare Earth Element depletion), indicative of a deep origin and 2) significant temporal variations in the intensity of crustal assimilation undergone by the rising melts, especially just before the Cretaceous-Palaeogene boundary. We suggest that these excursions are part of a single and localized plume-induced lithospheric erosion event of the Indian lithosphere by the Deccan plume. A comparison of the Deccan Traps with the Siberian Traps exposes significant geodynamical differences. Most notably, the widespread and extensive lithospheric erosion observed in the Siberian Traps did not take place in the Deccan Traps, despite similar mantle characteristics. This difference is attributed to 1) a thicker Indian lithosphere and 2) to the existence of weaknesses in the form of pre-existing structural lineaments. These pre-existing structures facilitated the passage of deep mantle-derived magmas and thus precluded or limited their involvement in a freezing-delamination process. Olivine geochemistry and olivine-based primary melt and source modelling in Deccan Traps lavas showed 1) large contributions of pyroxenite-derived melts (65%) to the primary melts, 2) high potential temperatures of the mantle sources (~1590-1600°C) and 3) that the mantle sources of Deccan Traps magmas contained ~15% of recycled crustal material. These observations contrast with those obtained from Réunion Island lavas (50% of pyroxenite-derived melts, mantle potential temperatures of 1490-1500°C and 7% of recycled crustal material in the sources of Réunion Island magmas. Our results are compatible with the plume model for LIPs and ocean island magmatism as well as with a secular cooling of mantle plumes. We conclude, along with many authors, that the emplacement of the Deccan Traps was a remarkably swift and catastrophic event at the end of the Cretaceous and that it likely played a significant role in the end-Cretaceous mass extinction

Les mesures paleomagnetiques de plus de 400 echantillons et la compilation des resultats anterieurs obtenus dans les series basaltiques du plateau du deccan (inde) sont presentees. Cette etude paleomagnetique associee a l'analyse des datations radiochronologiques et des contraintes paleontologiques a permis de localiser le volcanisme des traps du deccan dans la sequence d'anomalies magnetiques 30n-29r-29n et de contraindre sa duree d'activite a moins d'un million d'annees. L'etude topographique de l'inversion magnetique la plus frequemment observee dans le deccan (29r-29n) permet de proposer une structure de grande longueur d'onde parallele au rift narmada-son et a la cote ouest-indienne. La campagne de forage en mer menee par ocean drilling program dans l'ocean indien confirme que le point chaud de la reunion, apres sa premiere manifestation catastrophique sous le plateau du deccan, a construit la ride composite mascareignes-chagos-maldives-laccadives depuis 65 ma. Enfin, l'age du volcanisme des traps du deccan recouvrant la limite cretace-tertiaire (lct), les forts taux d'extrusion que l'on peut deduire de sa duree et son origine mantellique profonde (point chaud) en font le meilleur candidat pour l'hypothese interne de l'origine des extinctions biologiques de la lct (sans la demontrer pour autant)

Une eetude magnetostratigraphique de la limite jurassique/cretace au maroc permet de discuter les possibilites de correlation stratigraphique en l'absence d'une biostratigraphie bien etablie. Avec des donnees du forage de cony, on met en evidence des series triasiques et permiennes. Les resultats paleomagnetiques permettent de preciser la derive des poles magnetiques de l'eurasie. On modelise aussi le champ magnetique a l'interieur d'un forage

Ce travail a eu pour objet de rechercher des indices petrologiques permettant de mettre en evidence la presence de reservoirs magmatiques, de quantifier leur duree d'activite, de definir leur fonctionnement dynamique et d'etudier leur influence sur la geochimie des laves. Cette etude a porte sur les basaltes des trois dorsales oceaniques de l'ocean indien, de la dorsale medio-atlantique, de la mer rouge a 18n et, en domaine continental, des trapps du deccan entre nagpur et bombay. L'etude petrologique des basaltes permet de dire s'il y a melange ou non. C'est une condition necessaire mais non suffisante pour prouver l'existence d'un reservoir magmatique. La veritable question que l'on doit se poser est de connaitre la frequence d'arrivee des magmas dans le reservoir, et de quantifier la duree des periodes volcaniques afin de determiner la duree de vie du reservoir. Les contraintes temporelles deduites de l'etude petro-geochimique des basaltes et du traitement d'image d'une portion de dorsale ont permis de mettre en evidence des processus magmatiques operant a differentes echelles (temps et espace). L'ensemble des resultats a ete integre dans un modele geochimique simulant le fonctionnement d'un reservoir magmatique qui prend en compte la variabilite chimique du magma qui alimente le reservoir et le temps de residence des liquides dans la chambre magmatique. L'avantage du modele propose (par rapport a ceux qui existent dans la litterature) est qu'il n'exclut pas la possibilite d'absence de reservoir (temps de residence nul). Ce modele permettrait d'expliquer la variabilite geochimique rencontree a l'axe de la dorsale est-pacifique (temps de residence faible mais non nul), donnee inexpliquable jusqu'a ce jour

With only two ingredients, atomic nuclei exhibit a rich structure depending on the ordering of the different proton- and neutron-occupied states. This ordering can give rise to excited states with exceptionally long half-lives, also known as isomers, especially near shell closures. On-line mass spectrometry can often be compromised by the existence of such states that may even be produced in higher proportion than the ground state. This thesis presents the first results obtained from a nuclear spectroscopy setup coupled with the high-resolution Penning-trap mass spectrometer ISOLTRAP, at CERN’s radioactive ion beam facility ISOLDE. The isomerism in the neutron-deficient thallium isotopes was investigated. The data on 184,190,193−195 Tl allow an improvement of existing mass values as well as a mass-spin-state assignment in 190,193,194 Tl. Due to the presence of the ground and isomeric state for 194 Tl the excitation energy of the latter was determined for the first time experimentally. Systematic trends in the vicinity of the Z = 82 shell closure have been discussed.

Many intricate and highly conserved mechanisms have evolved to safeguard organisms against errors in gene expression. The nonsense-mediated mRNA decay pathway (NMD) exemplifies one such mechanism, specifically by eliminating mRNAs containing premature translation termination codons within their protein coding regions, thereby limiting the synthesis of potentially deleterious truncated polypeptides. Studies in Saccharomyces Cerevisiae have found that the activity of at least three trans-acting factors, known as UPF1, UPF2/NMD2, and UPF3is necessary for the proper function of the NMD pathway. Further research conducted in yeast indicates that the degradation of substrates of the NMD pathway is dependent on their translation, and that the sub-cellular site of their degradation in the cytoplasm. Although most evidence in yeast suggests that substrates of the NMD pathway are degraded in the cytoplasm while in association with the translation apparatus, some mammalian studies have found several mRNAs whose decay appears to occur within the nucleus or before their transport to the cytoplasm has been completed. In addition, study of the mammalian TPI mRNA found that this transcript was unavailable as a substrate for the NMD pathway once it had been successfully exported to the cytoplasm, further supporting the notion that the degradation of mammalian substrates of the NMD pathway occurs in association with the nucleus, or during export from the nucleus to the cytoplasm. To determine if yeast cytoplasmic nonsense-containing mRNA can become immune to the NMD pathway we examined the decay kinetics of two NMDS substrate mRNAs in response to repressing or activating the NMD pathway. Both the ade2-1 and pgk1-UAG-2nonsense-containing mRNAs were stabilized by repressing this pathway, while activation of NMD resulted in the rapid and immediate degradation of each transcripts. These findings demonstrate that nonsense-containing mRNAs residing in the nucleus are potentially susceptible to NMD at each round of translation. The remainder of this thesis utilizes protein overexpression studies to gain understanding into the function of factors related to the processes of nonsense-mediated mRNA decay and translation in Saccharomyces cerevisiae. Overexpression of a C-terminal truncated form of Nmd3p was found to be dominant-negative for cell viability, translation and the normal course of rRNA biogenesis. Overexpression studies conducted with mutant forms of the nonsense-mediated mRNA decay protein Upf1p, found that overexpression of mutants in the ATP binding and ATP hydrolysis region ofUpflp were dominant-negative for growth in an otherwise wild-type yeast strain. Furthermore, overexpression of the ATP hydrolysis mutant of Upf1p (DE572AA), resulted in the partial inhibition of NMD and a general perturbation of the translation apparatus. These results support previous studies suggesting a general role for Upf1p function in translation.

Nonsense-mediated mRNA decay (NMD) specifically targets mRNAs with premature translation termination codons for rapid degradation. NMD is a highly conserved translation-dependent mRNA decay pathway, and its core Upf factors are thought to be recruited to prematurely terminating mRNP complexes, possibly through the release factors that orchestrate translation termination. Upf1 is the central regulator of NMD and recent studies have challenged the notion that this protein is specifically targeted to aberrant, nonsense-containing mRNAs. Rather, it has been proposed that Upf1 binds to most mRNAs in a translation-independent manner. In this thesis, I investigated the nature of Upf1 association with its substrates in the yeast Saccharomyces cerevisiae. Using biochemical and genetic approaches, the basis for Upf1 interaction with ribosomes was evaluated to determine the specificity of Upf1 association with ribosomes, and the extent to which such binding is dependent on prior association of Upf1’s interacting partners. I discovered that Upf1 is specifically associated with Rps26 of the 40S ribosomal subunit, and that this association requires the N-terminal Upf1 CH domain. In addition, using selective ribosome profiling, I investigated when during translation Upf1 associates with ribosomes and showed that Upf1 binding was not limited to polyribosomes that were engaged in translating NMD substrate mRNAs. Rather, Upf1 associated with translating ribosomes on most mRNAs, binding preferentially as ribosomes approached the 3’ ends of open reading frames. Collectively, these studies provide new mechanistic insights into NMD and the dynamics of Upf1 during translation.

Nonsense-mediated mRNA decay (NMD) specifically targets mRNAs with premature translation termination codons for rapid degradation. NMD is a highly conserved translation-dependent mRNA decay pathway, and its core Upf factors are thought to be recruited to prematurely terminating mRNP complexes, possibly through the release factors that orchestrate translation termination. Upf1 is the central regulator of NMD and recent studies have challenged the notion that this protein is specifically targeted to aberrant, nonsense-containing mRNAs. Rather, it has been proposed that Upf1 binds to most mRNAs in a translation-independent manner. In this thesis, I investigated the nature of Upf1 association with its substrates in the yeast Saccharomyces cerevisiae. Using biochemical and genetic approaches, the basis for Upf1 interaction with ribosomes was evaluated to determine the specificity of Upf1 association with ribosomes, and the extent to which such binding is dependent on prior association of Upf1’s interacting partners. I discovered that Upf1 is specifically associated with Rps26 of the 40S ribosomal subunit, and that this association requires the N-terminal Upf1 CH domain. In addition, using selective ribosome profiling, I investigated when during translation Upf1 associates with ribosomes and showed that Upf1 binding was not limited to polyribosomes that were engaged in translating NMD substrate mRNAs. Rather, Upf1 associated with translating ribosomes on most mRNAs, binding preferentially as ribosomes approached the 3’ ends of open reading frames. Collectively, these studies provide new mechanistic insights into NMD and the dynamics of Upf1 during translation.

La future installation SPIRAL2 du GANIL, à Caen, permettra de produire une gamme étendue de noyaux exotiques avec des intensités très importantes. Cependant, ces faisceaux ne pourront pas être directement utilisés pour réaliser certaines études de haute précision et devront d'abord être purifiés. C'est pour réaliser ce travail que des équipes du CENBG, du MPIK (Heidelberg), du CSNSM, du LPC Caen, du GANIL et de l'IPNO développent un double-piège de Penning dans le cadre du projet PIPERADE. Ce double-piège nécessitant un travail de mise en forme préalable du faisceau (diminution de l'émittance transverse et mise en paquet), le CENBG est en charge de la réalisation d'un refroidisseur-regroupeur quadripolaire radiofréquence : le GPIB. C'est ce développement qui a constitué la majeure partie de mon travail de thèse, notamment en ce qui concerne les simulations de ce refroidisseur-regroupeur dont les résultats ont permis de trouver une méthode innovante pour la mise en paquet et de valider sa conception mécanique. Nous disposons également d'une source d'ions afin de pouvoir tester le GPIB et le double-piège et il m'a fallu la remonter, la comprendre et la caractériser pour que ces tests soient ensuite possibles. Dans un second temps j'ai aussi participer à l'analyse de l'expérience E622S menée au GANIL et qui avait pour but de déterminer précisément la demi-vie de 17F. Ce travail n'a pas permis d'améliorer la précision sur la demi-vie de 17F mais nous avons cependant quelques doutes sur les 2 précédentes mesures et sur leur détermination du taux de contamination de leurs échantillons
The future SPIRAL2 installation of GANIL, at Caen, will produce large range of exotic nuclei with very high intensities. Nevertheless, these beams could not be used directly for some high precision studies and will have to be purified first. To achieve this work, teams of CENBG, MPIK (Heidelberg), CSNSM, LPC Caen, GANIL and IPNO develop a double Penning trap in the framework of the PIPERADE project. Because this double Penning-trap needs some shaping work (reduction of transverse emittance and bunching), the CENBG team is in charge of the realisation of a radio-frequency quadrupole cooler and buncher : the GPIB. This developpement work was the main part of my PhD work, especially for the simulations of this cooler buncher whose results lead us to find a new bunching method and allowed us to approve its mechanical design. We also have an ion source to be able to test both GPIB and Penning trap and I had to reassemble it, to understand it and to characterise it before these tests could be achieved. In a second time I also took part to the analysis of the E622S experiment which aimed to determined precisely the 17F half-life. This work did not lead to a more precise determination of this half-life but we now have some doubts concerning the 2 last measurements and their way to determine the contamination rate of their radioactive samples

The several million years preceding the Cretaceous/Paleogene (K/Pg) boundary has been the focus of many studies. Changes in ocean circulation and sea level, extinctions, and major volcanic events have all been documented for this interval. Important research questions these changes raise include the climate dynamics during the warm, but not hot, time after the decay of the Late Cretaceous greenhouse interval and the stability of ecosystems prior to the mass extinctions at the end-Cretaceous. I document several biotic perturbations as well as changes in ocean circulation during the Maastrichtian stage of the latest Cretaceous that question whether the biosphere was being preconditioned for the end-Cretaceous extinction. The first event at Shatsky Rise in the tropical North Pacific was the brief acme of inoceramid clams at ~71 Ma, followed by their abrupt extinction during the “mid-Maastrichtian event” at 70.1 Ma. The second is an intriguing dissolution event that began ~67.8 Ma at Ocean Drilling Program Site 1209 (2387 m). The dissolution event is marked by very poor planktic foraminiferal preservation and sharply reduced calcareous plankton diversity. The shift into the dissolution interval was initially gradual, then rapid. Within the late Maastrichtian dissolution interval, the planktic/benthic (P/B) ratio is low, planktic foraminifera are highly fragmented, larger taxa are mostly absent, small taxa are relatively abundant, and planktic foraminifera and nannofossil species richness are low. The event is followed by an abrupt recovery in carbonate preservation ~300 kyr prior to the K/Pg boundary. Was the dissolution event caused by a change in deep water circulation, migration of the site out of the high productivity tropical belt, or ocean acidification associated with Deccan Traps volcanism? Our data show that changing deep water masses, coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the dissolution interval, while Deccan Traps volcanism may have caused surface ocean acidification ~200-kyr prior to the K/Pg mass extinction event.

Tese de mestrado em Ciências Geofísicas, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2010
A crise do Cretácico-Paleogénico foi uma das maiores crises biológicas que afectaram a Terra durante o Fanerozóico. Actualmente, ainda existe um forte debate sobre a natureza e origem desta extinção em massa: a ideia de que um grande impacto de meteorito poderia causar uma extinção em massa opõe-se à de uma origem terrestre ligada às erupções vulcânicas de basaltos continentais de uma vasta região na Índia (Deccan traps). Apesar de já existir uma considerável quantidade de dados geológicos desta altura, o sincronismo entre extinções de massa e o impacto de meteorito e/ou as erupções vulcânicas ainda não está comprovado. Estas limitações surgem devido à escassez de secções geológicas marítimas completas e à dificuldade em correlacionar sequências separadas, onde os marcadores de impactos apenas existem em níveis estratigráficos extremamente finos. Neste trabalho testou-se uma abordagem original, combinando a susceptibilidade magnética de alta resolução (uma amostra por cada cm de sedimentos), a mineralogia magnética, a análise espectral e a quimioestratigrafia, nos sedimentos do Cretácico-Paleogénico da Bacia Cantábrica, na Espanha e França, para estudar as alterações ambientais, antes e depois da fronteira Cretácico-Paleogénico. A variação da susceptibilidade magnética ao longo de um perfil estratigráfico geralmente reflecte os ciclos climáticos (i.e. ciclos de Milankovitch), enquanto os eventos brutais como o impacto de um meteorito, ou grandes erupções vulcânicas são registados por um sinal “anómalo” (acíclico), facilmente detectável através de análises espectrais ao sinal magnético. Por outro lado, atendendo ao facto de que os sedimentos marinhos registam as condições da água do mar durante a fase de deposição, os dados de quimiostratigrafia podem fornecer pistas importantes sobre o impacto catastrófico desses eventos na biosfera. Os nossos resultados revelaram que a fronteira do K/Pg é caracterizada por uma abruta anomalia positiva da susceptibilidade magnética interpretada como sendo o resultado de um aumento súbito do fluxo de detritos terrígenos para o ambiente marítimo, essencialmente, devido ao aumento de erosão continental induzida pelo impacto em Chicxulub. As várias anomalias de susceptibilidade magnética verificadas antes e depois da fronteira estão correlacionadas com alterações significativas nos índices de diversidade biológica, sugerindo que esses eventos geradores destas anomalias na susceptibilidade magnética tiveram um impacto considerável na biosfera. Particularmente, verificámos uma mudança abruta nos valores de susceptibilidade e de χARM, abaixo da fronteira Cretácico-Paleogénico, a cerca de 14 ka, que também foi observada noutras secções distantes da nossa, por exemplo em Gubbio (Itália) e em Abat (Oman), corroborando com a hipótese de um impacto global pré-Chixculub. Adicionalmente, um aumento registado neste nível dos elementos sensíveis às condições redox, leva a supor que o oceano já se encontrava anóxico antes de o impacto acontecer. Mesmo que a natureza exacta do evento responsável por esta anomalia pré-K/Pg ainda esteja por desvendar (impacto/traps), estes resultados preliminares são a favor de um cenário de múltiplas causas para a extinção em massa do Cretácico-Paleogénico.
The Cretaceous-Paleogene crisis is one of the major biological crises that affected the Earth at Phanerozoic times. There is still an acrimonious debate about the nature and origin of this mass extinction: proponents of the idea that large bolide impact caused the mass extinctions are opposed to those who are in favour of a terrestrial origin linked to continental flood basalt eruptions of the Deccan Traps. Despite the availability of considerable geological databases, the synchronism between mass extinctions and meteorite impact and/or volcanic eruptions is not yet proven. Limitations arise in part from the paucity of continuous marine sections and to the difficulty in correlating separated sequences where ejecta markers only exist within very thin stratigraphic levels. Here we have tested a new and original approach combining high-resolution (1sample/cm) magnetostratigraphy susceptibility, magnetic mineralogy, spectral analysis and chemostratigraphy on the Cretaceous-Paleogene sediments of the Basque Cantabric Basin, Spain and France to study the environmental changes before and after the Cretaceous-Paleogene boundary. The variation of magnetic susceptibility along a stratigraphic profile is usually reflects climate cycles (i.e., Milankovitch cycles), while catastrophic events as meteorite impact or large volcanic eruptions are recorded by an "anomalous" (acyclic) signal that can be easily detected by spectral analysis of the magnetic signal. On the other hand, because marine sediments are known to record paleonvironnmental conditions of the seawater at deposition time, chemostratigraphic data can provide better constrains of the impact of these catastrophic event on the biosphere. Our results show that the K-Pg boundary is characterized by an abrupt positive shift in magnetic susceptibility values interpreted to result from a rapid and sudden flux into the marine environment of a detrital component due to terrestrial erosion driven by the Chicxulub impact. Several magnetic susceptibility anomalies below and after the boundary are correlated to significant shifts in the biodiversity indexes suggesting that the events that generated these magnetic anomalies had a notable impact on the biosphere. Particularly, an abrupt shift of magnetic susceptibility values and χARM values is located just below the Cretaceous-Paleogene boundary, at around 14 kyr, and is also present in other distant sections, such as the Gubbio (Italy) and Abat (Oman) sections suggesting the existence of a global pre-KT event. In addition, increase of redox sensitive elements at this level indicates that the anoxia of the ocean already took place. Even if the exact nature of the global event (impact/traps) responsible for the pre-KT anomaly remains to be determined, these preliminary results are in favour of a multiple cause scenario forthe Cretaceous-Paleogene mass extinction.

碩士
國立中山大學
材料與光電科學學系研究所
99
Nanocrystal has non-negligible ratio of the surface atoms. The photophysics of the nanocrystal is strongly influenced by the surface states.There are two surface-related phenomena: the on-off blinking and the red-emission. On-off blinking is a phenomenon commonly observed in thesingle emitters, such as dye molecules and semiconductor quantum dots (QD).In the QD, the charged state caused by the charge transferring from the core to the surface states explains the off-state. Another surface-related phenomenon is the red-emission, which is the emission from the low-lying surface trapped states. This thesis investigates the correlation between the on-off blinking and the red-emissions of the semiconductor nanocrystals. CdSe/ZnS core/shell colloidal nanocrystals with 2.1nm in diameter and emission peak at 515nm were examined. PL spectrum in the solution indicates that besides the band-edge emission, there is a broadband emission spanning the wavelength range of 590 – 800 nm, which is called the red-emission. The lifetime of the band-edge emission is about 20ns, and that of the red-emission is about 200ns. Since they are with different fluorescence lifetime, the band-edge emission and the red-emission are from distinct emission species. Emission intensity from individual QDs of the band-edge emission and the red-emission are recorded by an imaging CCD. Most QDs exhibit band-edge emission. Only few QDs show the red-emission. Both emissions exhibit clear on-off blinking, indicating the two phenomena are with different mechanism.Moreover, the band-edge emission and the red-emission are mutual exclusive.None QDs exhibit both emissions. This indicates the tiny structure difference from one QD particle to another QD particle resulting in a dramatic different of the excitation energy relaxation pathway.

The objective of this diploma thesis is search processing of tourism, his problematics and protection of the nature. In the other part this thesis deal with analysis of hiking trail in Labske piskovce PLA in focus of potentional atractive with proposal of new hiking trails in this location. Analysis containe all hiking trails in this location according to colored tourism distinction of trails. Proposal of new hiking trails was formed with regard on protection of nature thus at the same time was surrounding area approached for visitors as much as possible. Proposal comprise new and turisty often attended attractiviness. This proposal can produce increase of attractiviness in this district and the influx of new turists.

With only two ingredients, atomic nuclei exhibit a rich structure depending on the ordering of the different proton- and neutron-occupied states. This ordering can give rise to excited states with exceptionally long half-lives, also known as isomers, especially near shell closures. On-line mass spectrometry can often be compromised by the existence of such states that may even be produced in higher proportion than the ground state. This thesis presents the first results obtained from a nuclear spectroscopy setup coupled with the high-resolution Penning-trap mass spectrometer ISOLTRAP, at CERN’s radioactive ion beam facility ISOLDE. The isomerism in the neutron-deficient thallium isotopes was investigated. The data on 184,190,193−195 Tl allow an improvement of existing mass values as well as a mass-spin-state assignment in 190,193,194 Tl. Due to the presence of the ground and isomeric state for 194 Tl the excitation energy of the latter was determined for the first time experimentally. Systematic trends in the vicinity of the Z = 82 shell closure have been discussed.