Дисертації з теми "Th dating"
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Loehn, Clayton William. "Investigation of the monazite chemical dating technique." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/27688.
Повний текст джерелаPh. D.
Simons, Suzanne Lee. "U-Th-Pb systematics of opaline silica: Implications for the dating of surface processes." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/36.
Повний текст джерелаPlaczek, Christa. "Stratigraphy, Geochronology and Geochemistry of Paleolakes on the Southern Bolivian Altiplano." Diss., The University of Arizona, 2005. http://hdl.handle.net/10150/194352.
Повний текст джерелаGuenthner, William Rexford. "Zircon (U-Th)/He Dates from Radiation Damaged Crystals: A New Damage-He Diffusivity Model for the Zircon (U-Th)/He Thermochronometer." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/306783.
Повний текст джерелаBurnside, Neil Murray. "U-Th dating of travertines on the Colorado Plateau : implications for the leakage of geologically stored CO2." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/1988/.
Повний текст джерелаDean, J. R. "Stable isotope analysis and U-Th dating of late glacial and Holocene lacustrine sediments from central Turkey." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14090/.
Повний текст джерелаYamada, Kunimi. "Thermochronology using (U-Th)/He dating method : investigation for effects of secular disequilibrium on (U-Th)/He ages and uplift history of the Tanzawa mountains in the south Fossa Magna region." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144205.
Повний текст джерела0048
新制・課程博士
博士(理学)
甲第12122号
理博第3016号
新制||理||1450(附属図書館)
23958
UT51-2006-J117
京都大学大学院理学研究科地球惑星科学専攻
(主査)助教授 田上 高広, 教授 嶋本 利彦, 教授 小畑 正明
学位規則第4条第1項該当
Xia, Qikai. "High precision TIMS U-Th disequilibrium dating and C, O, Sr isotope-based multi-proxy palaeoclimatic study of Speleothems in Australia /." [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18421.pdf.
Повний текст джерелаAdams, Byron A. "Exhumation and incision history of the Lahul Himalaya, northern India, based on (U-Th)/He thermochronometry and terrestrial cosmogenic nuclide dating techniques." Cincinnati, Ohio : University of Cincinnati, 2007. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1180546920.
Повний текст джерелаTitle from electronic thesis title page (viewed Oct. 8, 2007). Includes abstract. Keywords: Lahul, Himalaya, exhumation, incision, thermochronometry, terrestrial cosmogenic nuclides, strath terraces. Includes bibliographical references.
Brown, Summer Jasmine. "Integrating apatite (U-Th)/He and fission track dating for a comprehensive thermochronological analysis: refining the uplift history of the Teton Range." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32718.
Повний текст джерелаMaster of Science
Adams, Byron A. "Exhumation and incision histories of the Lahul Himalaya, northern India, based on (U-Th)/He thermochronology and terrestrial cosmogenic nuclide dating techniques." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1180546920.
Повний текст джерелаBuscher, Jamie Todd. "Long-term exhumation of landscapes along the Pacific-North American plate boundary as inferred from apatite (U-Th)/He and ArcGIS analyses." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27760.
Повний текст джерелаPh. D.
Sakata, Shuhei. "Development of analytical technique for precise age determination of Quaternary zircons with the correction of the initial disequilibrium on U-Th-Pb decay series using a laser ablation-ICP-mass spectrometry." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199112.
Повний текст джерелаKawata, Marcelo Takei. "Evolução tectono-metamórfica da formação São Tomé, Grupo Rio Doce, faixa Araçuaí." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-17072018-144805/.
Повний текст джерелаThe present dissertation presents an investigation on the tectono-metamorphic evolution of the São Tomé Formation, one of the metasedimentary units belonging to the Rio Doce Group, in the Araçuaí Orogen. This unit, of pelitic origin, occurs in a band with general direction approximately N-S, with vergence for NE, contrary to the São Francisco craton in this sector of the orogen. It has quartz-mica schist as main lithotype, with varying proportions of grarnet, staurolite, sillimanite and plagioclase. Two deformational phases are recorded through a continuous foliation S1 of the fracture cleavage type and a foliation S2 of crenulation cleavage. The textural relations indicate that part of the mineral phases crystallized both during the deformational event and in conditions absent of deviatore voltage, and record of metamorphic peak conditions of 6 kbar and 650 ° C. The geochronological data were obtained in monazite by means of Th-U-Pb dating in electron microprobe. Three distinct populations were identified: (i) The oldest population of 641 ± 32 Ma, 614 ± 39 Ma and 607 ± 47 Ma, which may represent detrital grains of igneous bodies, no longer outcrops, related to a possible pre- collisional or, being metamorphic monazites formed in a first thermal event; (ii) Populations with intermediate ages between 560 ± 32 Ma and 559 ± 29 Ma, compatible with regional metamorphic apex ages; (iii) Younger population between 501 ± 28 Ma and 491 ± 34 Ma, consistent with the formation concomitant with the generation of late igneous bodies. Although it is unclear whether these ages are related to distinct metamorphic events or are reflective of the low orogenic cooling rate, the three monazite groups of different ages are well established.
Marsden, Ruby Connemara. "Further Development and Testing of the Combined U-Thdisequilibrium/ U-Pb and (U-Th)/He Zircon Dating Method and its Application to Quaternary Volcanic Rocks." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/88743.
Повний текст джерелаSavignano, Elisa. "Apatite (U-Th)/He and Fission Track thermochronometry in the Northern Patagonian Andes: New insights into the exhumation history of the thrust belt foreland sector." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421962.
Повний текст джерелаLo studio dell’evoluzione Cretacico–Cenozoica delle Ande Nord Patagoniche offre l’opportunità di comprendere le relazioni intercorrenti tra processi profondi riguardanti la dinamica della litosfera e la deformazione più superficiale che coinvolge la crosta. Benché la catena andina sia caratterizzata da un generale andamento lineare nord-sud, nel dettaglio essa è fortemente segmentata da un punto di vista tettonico, come si evince dalla posizione variabile dell’arco magmatico e del fronte di deformazione verso le zone di avampaese. Pertanto, questo margine di placca risulta avere una complessa configurazione, che va oltre la comune nozione di sistema di subduzione di “tipo andino”. Localizzato nella zona di retrocatena, il settore Nord Patagonico della Cordigliera ha subito una complessa evoluzione, caratterizzata dall’alternanza di fasi di subduzione a basso e alto angolo, che ha controllato le fasi rispettivamente di raccorciamento e di estensione in corrispondenza della placca superiore. La variabilità deformativa in questa zona di retroarco è stata sia temporale—dunque legata a fasi di orogenesi e collasso della catena—sia spaziale, data la variabile trasmissione dello stress compressivo verso le zone esterne dell’orogene. La termocronologia di bassa temperatura è in grado di registrare i pattern irregolari di denudamento risultanti, essendo molto sensibile alle variazioni entro i primi chilometri della crosta. Tali sistemi termocronometrici sono ideali per identificare eventi tettonici a livello crostale, poiché sono in grado di registrare il momento e la velocità del raffreddamento legato all’esumazione. In particolare, i metodi (U-Th)/He (AHe) e tracce di fissione (AFT), entrambi su apatite, sono stati integrati in questa tesi con i metodi strutturali. L’area investigata è la regione ubicata tra 40° and 44°S, nel nord della Patagonia argentina. Durante le due campagne, condotte nelle Province di Neuquén, di Rio Negro e del Chubut, sono state campionate le rocce sulle quali compiere le analisi termocronologiche di bassa temperatura e sono stati analizzati dal punto di vista strutturale i lineamenti tettonici più importanti. Questi metodi hanno permesso sia di comparare i pattern di esumazione nella parte frontale della catena e nell’adiacente avampaese sia, al contempo, di comparare le differenze, a diverse latitudini, all’interno di uno stesso dominio morfo-strutturale. Complessivamente, sono stati raccolti, processati e analizzati quarantotto campioni. Le analisi (U-Th)/He sono state eseguite presso l’Università di Parigi Sud mentre quelle di tracce di fissione presso l’Università di Padova. Dal punto di vista geologico-strutturale, le maggiori strutture dell’area di studio sono state rilevate sul terreno e analizzate nel dettaglio, con particolare attenzione nelle zone meno studiate dell’avampaese. Infine, per un’analisi più approfondita di questo complesso scenario i due metodi sono stati integrati. Infatti, sono state costruite tre sezioni bilanciate e retrodeformate integrate con le informazioni termocronologiche al fine di produrre un modello termo-cinematico lungo due diversi transetti posti a 40° e 44°S, mediante l’utilizzo di un software dedicato in grado di modellare le età termocronometriche e fare previsione di queste lungo il profilo topografico odierno, che, a sua volta, è stato usato per validare lo scenario tettonico proposto. I nuovi dati AFT e AHe ottenuti nell’area di studio evidenziano due eventi tettonici principali interessanti l’area settentrionale della Patagonia: una fase d’inversione ed esumazione tra il tardo Cretacico e il Paleogene, che ha coinvolto l’intero sistema dalla catena all’avampaese, e una successiva, Mio-Pliocenica, in cui l’esumazione si è concentrata nella zona di catena. Questo scenario tettonico proposto è stato con successo testato lungo i due transetti analizzati attraverso FetKin, permettendo di chiarire il ruolo e l’entità di ogni fase tettonica avvenuta dal Mesozoico. Il pattern di esumazione così ottenuto è stato interpretato come il risultato del variabile grado di propagazione della deformazione dalla catena andina verso l’avampaese. Quest’ultimo sembra essere controllato principalmente da due parametri: (i) la configurazione della placca in subduzione, in altre parole la sua geometria più o meno orizzontale che gioca un ruolo fondamentale nella deformazione dell’avampaese, e (ii) la velocità di convergenza tra le placche pacifica e sud americana, che governa i processi di raccorciamento ed esumazione nella catena a pieghe e sovrascorrimenti.
Airaghi, Laura. "Etude pétro-chronologique de la chaîne des Longmen Shan (Tibet oriental) : héritage géologique et implications pour la géodynamique actuelle." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU029/document.
Повний текст джерелаOne of the major challenges in Earth Sciences is understanding how the continental lithosphere deforms in convergent settings, according to which timescales. For its elevation and extension the Tibetan plateau is an ideal natural laboratory for the study of deep crustal processes in active convergent settings. The rise and thickening of the Tibetan plateau has generally been related to the only collision between the Eurasian and Indian plates during the Cenozoic. However, this interpretation has been recently put into question by apparently contrasting geophysical and geological features observed at different locations on the plateau.The aim of this PhD is to quantify the importance of the geological inheritance in the long-term and short-term deformation of an active thrust belt, focusing on the Longmen Shan orogen, the most enigmatic border of the Tibetan plateau. In the Longmen Shan (eastern Tibet) the Tibetan crust is over thickened (>60 km), the tectonic activity is localized along lithospheric faults -as demonstrated by the occurrence of the Mw 7.9 Wenchuan (2008) and Mw 6.6 Lushan (2013) earthquakes- and a high topography survives despite low convergence rates measured by GPS (<3 mm/yr). These observations are hardly reconcilable in a unique model of crustal deformation, suggesting a contribution of the geological inheritance from the geological history preceding the India-Asia collision.A petro-chronological approach that combines microstructural observations, compositional mapping of major and accessory mineral phases, thermodynamic modelling, in-situ 40Ar/39Ar dating, Ar diffusion modelling and in-situ U/Pb-Th allanite dating was applied to metamorphic rocks on each side of the major faults that strike parallel to the belt. This high-resolution study shows that in garnet-bearing rocks of the internal units of the belt matrix minerals record different stages of the metamorphic path in their composition. This is due to an incomplete chemical re-equilibration explained by a variable fluid availability during metamorphism. Different stages of metamorphism and fluid-assisted reactions sequences are also recorded in the 40Ar/39Ar signal of micas and in the composition and textures of the accessory phases.The understanding of petrological processes at the small scale was combined with field observations to quantify the Mesozoic thickness of the Tibetan crust at > 30 km and to unravel a metamorphic jump of greater than 150°C across the major faults, inherited from the Mesozoic tectonics. While internal units of the belt were strongly deformed, decoupled from the basement and metamorphosed at T ~ 580-600°C (P ~11 kbar), external units were less deformed and experienced lower temperatures conditions (T < 400°C, P < 5 kbar). The partial exhumation of the crystalline basement from c. 20 km depth along the major fault (in both internal and external units) occurred at c. 120-140 Ma during a previously poorly documented tectonic event.The multi-method approach applied on a wide geographical area and on a large time interval enabled to quantify the rates and conditions of the different stages of the maturation of the belt; internal units reached the thermal relaxation at ~600°C 40 Ma after the beginning of the propagation of the orogenic load. The basement was re-activated 40 Ma later, at similar thermal conditions than its sedimentary cover. The Mesozoic geological inheritance is therefore a key element in the present structure of the belt and strongly controlled the rheological and structural state of the upper crust at the moment of the Cenozoic re-activation.The petro-chronological study of different segments of the belt showed an along-strike metamorphic segmentation of the Longmen Shan inherited from the Mesozoic. This segmentation corresponds to the present fault segmentation, underlying the potential role of inherited structure in controlling the geographic distribution of the recent earthquakes
Finné, Martin. "Climate in the eastern Mediterranean during the Holocene and beyond – A Peloponnesian perspective." Doctoral thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-108046.
Повний текст джерелаAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Accepted.
Cros, Alexandre. "Influence des propriétés cristallochimiques de la calcite sur la diffusion de l'hélium et essai de datation (U-Th-Sm)/He de calcite filonienne et de remplissage de brèche." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00719709.
Повний текст джерелаCRUZ, ROSANA PETINATTI DA. "DEVELOPMENT OF A METHODOLOGY FOR CORALS AND SPELEOTHEMS DATING USING THE 230-TH/234-U METHOD, THROUGH CHROMATOGRAPHIC SEPARATION AND QUANTIFICATION BY ALPHA SPECTROMETRY AND FIA-ICP-MS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8544@1.
Повний текст джерелаO presente trabalho aborda as determinações de idades de espeleotemas e corais, usando o método de desequilíbrio da série urânio, mais especificamente, o método de deficiência de filhos daughter deficient DD, em particular o método 230Th/234U. Foram testadas diferentes metodologias empregando separação por extração cromatográfica e quantificação por espectrometria alfa e ICP-MS. Foram testados três procedimentos diferentes: separação em batelada empregando-se colunas com Tri-octil óxido de fosfina (TOPO) em silica- gel e a coluna TRU comercializada pela Eichrom(R), composta de octil-N,N,- isobutil carbamoil óxido de fosfina dissolvido em fosfato de tributila (TBP) e quantificação por espectrometria alfa; separação em batelada com os mesmos sistemas mas quantificação por ICP-MS e separação em linha (flow injection) com cartuchos de TRU e quantificação por ICP-MS. As metodologias desenvolvidas foram validadas empregando-se amostras de referência certificada, IAEA-327 (solo) tendo sido obtidas incertezas de 2% para o método empregando a separação em linha (flow injection) com cartuchos de TRU e quantificação por ICP-MS. As amostras de espeleotema analisadas foram coletadas no Carste de Lagoa Santa, MG, pelo grupo do Prof. Luis Piló (USP) e suas idades variaram de 15,2±2,2 kanos a >350 kanos. Estes valores estão na faixa dos valores encontrados na literatura para amostras de espeleotema coletadas pelo mesmo grupo na mesma região. A amostra de coral, coletada na Bacia de Campos (RJ) era da espécie Lophelia pertusa, foi subdividida segundo suas ramificações (primária, secundária e terciária) e o ramo principal foi datado em 9,4 ± 0,3 kanos.
This paper discusses the age determination of speleothems and corals using Uranium-series- imbalance method, more specifically the daughter deficient method - DD, particularly the 230Th/234U method. Different methodologies were tested using chromatographic extraction separation and quantification by alpha spectrometry and ICP-MS. Three different procedures were tested: batch separation using columns with Tri-N-Octylphosphine Oxide (TOPO) in silica gel and TRU column commercialized by Eichrom(R) composed of octyl-N,N,-isobutyl carbamoylphosphine oxide dissolved in tri-n-butyl phosphate (TBP) and with quantification by alpha spectrometry; batch separation with the same systems, but with quantification by ICP-MS; and flow injection with TRU cartridges and qualification by ICP-MS. The methodologies developed were verified using certified reference samples, IAEA-327 (soil) with 2% imprecision rate for the method using flow injection with TRU cartridges and qualification by ICP-MS. The speleothem samples analyzed were collected at Carste de Lagoa Santa, in the state of Minas Gerais, by Prof. Luis Piló`s (USP) group, and their ages varied from 15,2±2,2 kyears to >350 kyears. These numbers are within the range found in the literature for speleothem samples collected by the same group in the same region. The coral sample, collected at Bacia de Campos (RJ), and from the Lophelia pertusa species, was subdivided according to its ramifications (primary, secondary and tertiary), and the main ramification dated 9,4 ± 0,3 kyears.
Didier, Amélie. "Comportement géochimique du chronomètre U-Th-Pb dans la monazite : approche par analyses in-situ au LA-ICP-MS." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-00966588.
Повний текст джерелаOostingh, Kornelia Fieneke. "Ultra-Precise 40Ar/39Ar Geochronology: Development of 38Ar cosmogenic exposure and olivine (U-Th)/He dating techniques; and deciphering the geochemical evolution of the Newer Volcanic Province, SE Australia." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/53004.
Повний текст джерелаBerger, Aaron Louis. "A Thermochronological Investigation of Orogenic Architecture, Kinematics, and Tectonic-Climatic Interactions within the St. Elias Orogen, Alaska." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26628.
Повний текст джерелаPh. D.
Boyd, Meighan. "Speleothems from Warm Climates : Holocene Records from the Caribbean and Mediterranean Regions." Doctoral thesis, Stockholms universitet, Institutionen för naturgeografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-121750.
Повний текст джерелаDenna avhandling bidrar till ökad kunskap om klimatets variationer och miljön i två geografiskt skilda områden på låga breddgrader och under tidsperioder inom den Holocena epoken. Genom att använda en droppsten (stalagmit) från Gasparee-grottan, Trinidad, som ett paleoklimatarkiv, har det bland annat varit möjligt att visa att Trinidad upplevde torrare förhållanden under den snabba klimatförändring som observerats ske för 8200 år sedan på många platser i världen. Denna torrare klimatsituation i Trinidad föreslås vara ett resultat av en sydlig förflyttning av den intertropiska konvergenszonen. Övriga stalagmiter som studerats för denna avhandling kommer från Kapsia-grottan och Alepotrypa-grottan som finns på Peloponnesos-halvön i Grekland. Resultaten därifrån speglar dels klimat- och vegetationsvariatoner och dels graden av mänsklig aktivitet, under tiden för ca 8000 år sedan till för 1000 år sedan. Alepotrypa-grottan är känd för att vara en av de större Neolitiska boplatserna i Grekland. Isotop- och spårämnesanalyser av stalagmiterna har bidragit med ny kunskap om tidpunkten för mänsklig aktivitet, hur människorna påverkade grott-miljön samt hur klimatet varierat efter det att grottan, genom en tektonisk händelse, stängdes för människans inverkan. Snabba klimatförändringar, för 4200 och 3200 år sedan, observerade i andra regioner, rekonstrueras här för första gången på Peloponnesos. En snabb förändring mot torrare förhållanden observeras även för 1600 år sedan. De klimatstyrande processerna föreslås vara en kombination av storskaliga processer som den nordatlantiska oscillationen och mer regionala processer som det så kallade North Sea Caspian Pattern Index. Variationer i spårämnen i stalagmiterna efter att Alepotrypa-grottan stängdes kan kopplas till två vulkaniska utbrott, nämligen det Minoiska utbrottet av Thera på ön Santorini kring 3600 år sedan och utbrottet av Somma (Vesuvius) kring 2700 år sedan. Spårämnesvariationer under bo-perioden ger tydliga indikationer på människans påverkan på grottmiljön och som delvis kan länkas till specifika aktiviteter, som eldning av dynga i grottan. Avhandlingen är ett resultat av en framgångsrik kombination av klimatstudier och arkeologisk kunskap och utgör ett viktigt underlag för fördjupat interdisciplinärt forskningssamarbete i Alepotrypa-grottan.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript. Paper 6: Manuscript.
Oliveira, Raphael Logato de. "Esclerocronologia, geoquímica e registro climático em coral Siderastrea stellata do Atol das Rocas, RN, Brasil." Niterói, 2017. https://appdesenv.uff.br/riuff/handle/1/4454.
Повний текст джерелаMade available in DSpace on 2017-09-11T18:18:13Z (GMT). No. of bitstreams: 1 diss-Raphael-Logato-de-Oliveira-PPGA.pdf: 25249109 bytes, checksum: bebdeef5c344d7c319f3fd7481af2cce (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geoquímica, Niterói, RJ
A taxa de crescimento de uma colônia do coral endêmico brasileiro Siderastrea stellata, proveniente da Reserva Biológica do Atol das Rocas (3° 45’ S / 33° 40’ O – 3° 55’ S / 33° 50’ O), baseada em conta gem de bandas de crescimento e datação absoluta pelo método U-Th, seguidas de analises geoquímicas e isotópicas, revelaram uma variablidade das Temperaturas de Superfície do Mar (TSM) durante os últimos 39 anos. Os resultados demonstram uma forte correlação entre o crescimento do coral e a razão Sr/Ca, como também entre o Sr/Ca e U/Ca. O crescimento, Sr/Ca e U/Ca indicaram um forte sinal com frequência decadal, que é correspondente a um dos principais regimes de variabilidade do Atlântico Tropical Sul. Além disto, pode ser dito que o sinal do δ18O apresentou uma boa coerência com a ZCIT, indicando um potencial para futuros estudos sobre flutuações de salinidade. Porém, a falta de correlação entre os parametros geoquimicos com a TSM pode ser atribuída à limitação dos registros instrumentais de TSM disponíveis para a área de estudo (PIRATA), que são provenientes de bóias oceanográficas espaçadamente distribuídas. Assim, este estudo destaca alguns importantes fatores: a necessidade de se obter os registros de TSM in situ, para que seja possível estabelecer boas correlações entre esta e os traçadores; a clara relação entre o crescimento e Sr/Ca, sugerindo que este traçador pode não ser regulado somente pela TSM no caso de S. stellata; e a predominância de influências de variabilidades decadais e semi-decadais para esta região
One colony growth rate of an endemic Brazilian coral Sideratrea stellata from Atol das Rocas Biological reserve (3° 45’ S / 33° 4 0’ O – 3° 55’ S / 33° 50’ O), based on growth band counting and U-Th dating method, followed by geochemical analysis, revealed Sea Surface Temperature (SST) variability for the last 39 years. Results show a strong correlation between coral growth and Sr/Ca ratio, and also strong correlation between Sr/Ca and U/Ca. Growth, Sr/Ca and U/Ca indicate strong signal at decadal frequencies, corresponding to one of major South Tropical Atlantic variability. Moreover, it can be said that δ18O signal has showed good coherence with respect to ITCZ, pointing out to potential future studies about salinity fluctuations. However, the lack of correlation between SST and geochemical tracers can be attributed to instrumental SST data restriction for the study site, which comes from sparsely distributed oceanographic buyos (PIRATA). Insofar, this study highlights some important factors: the need for in situ SST registry in order to establish good correlations for SST and geochemical data; the clear relationship between coral growth and Sr/Ca, suggesting that this ratio may not be regulated by SST only for S. stellata; and the predominance decadal and semi-decadal variabilities at this region.
Feneyrol, Julien. "Pétrologie, géochimie et genèse des gisements de tsavorite associés aux gneiss et roches calco-silicatées graphiteux de Lemshuku et Namalulu, Tanzanie." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0348/document.
Повний текст джерелаTsavorite, a (V, Cr, Mn)-bearing green grossular, is hosted by graphitic gneisses or calc-silicates, often asssociated with dolomitic marbles, and belonging to the Metamorphic Neoproterozoic Mozambique Belt. Tsavorite is found either as nodules or in quartz veins (primary deposits), or in placers (secondary deposits). The mineralogical study of tsavorites suggests a new protocol to certificate their geographical origin, based on the V/Cr ratio, Mn content and delta18O. The study of the Lemshuku and Namalulu deposits in Tanzania has shown that the metamorphism of organic matter-rich and evaporites-rich sedimentary protoliths occurred at P = 7.0 ± 0.4 kbar and T = 677 ± 14°C, at 634 ± 22 Ma (U-Th-Pb dating on monazite). The metamorphic series cooled down at around 500 Ma (40Ar-39Ar dating on muscovite). Two metasomatic stages are linked to the formation of tsavorite : (i) diffusion metasomatism forming nodules at P = 5.0-7.4 kbar and T = 580-691°C; (ii) calcitic infiltration metasomatism forming quartz veins at P = 3.6-4.9 kbar and T = 505-587°C. These last have been dated in situ with Sm-Nd dating at 606 ± 36 Ma. Continental evaporites, deposited in a coastal marine sabkha with (Si, Ca)-bearing sediments, transformed into tsavorite in the case of the nodules, while the molten salts are associated with the formation of the quartz veins. The mineralisations are controlled by lithostratigraphy and structure
El, Bakili Asmae. "Evolution tectono-metamorphique et chronologique des unités métamorphiques du Rif interne (Beni Bousera, Nord du Maroc)." Thesis, Université Côte d'Azur, 2021. http://www.theses.fr/2021COAZ4034.
Повний текст джерелаLocated at the extreme tip of the western Mediterranean, the Betic-Rif orogenic system is built through a complex alpine orogenic history involving processes of subduction related to convergence between Africa and Eurasia since the Cretaceous. A remarkable discovery during the last four decades of geological investigations, has been the remains of a variscan event in the internal zones of the belt. These results underline the presence of two superimposed orogenic systems, the internal zones of the belt thus remain a privileged area to study the importance of the structural and the metamorphic heritage in the partial or total reactivation by the most recent events. This work is located in the Beni Bousera sector, where crustal and mantle rocks that form the innermost units of the chain are exposed. Based on structural and petrological analyses, U-Th-Pb dating on monazite and 40Ar-39Ar dating on micas and amphiboles. The history of the Betic-Rif belt can be summarized as it follows: 1) a HP-HT event affects the base of the internal domain at around 281 ± 3 Ma. These new petrological and geochronological data obtained in the internal Rif, are correlated with the Betics, the Kabyle, the Edough massif of Algeria, the Mauritanian, and the Appalachian belts, attesting a convergent domain during the late Carboniferous – early Permian. All of these orogenic segments are part of the North African Variscides built at the north-western margin of Gondwana in response to convergence between the later and Laurentia. 2) at around 29-26 Ma, a Barrovian to Abukuma metamorphic event affects the Sebtides (the innermost units of the chain) and interpreted as the evolution of the upper plate of a subduction zone. This alpine event is typically characterized by a prograde metamorphic path marked by heating affecting the base of the Sebtides between 26 to 22 Ma, such conditions reflect thinning and heating of the crust related to the asthenosphere upwelling due to slab roll-back. This event marks the beginning of a major extensive event. 3) In the Miocene around 22-20 Ma, the internal zones are affected by an E-W extension contemporary to the opening of the Alboran Basin in a back-arc context, and the intrusion of granitic dykes into the peridotites and crustal metamorphic units, the exhumation of the Sebtides was complete at this time. 4) From early to middle Miocène, the Betic-Rif belt acquired its arcuate geometry (the Gibraltar Arc) during the collision between the Internal and the external zones, attested by de NE-SW to E-W shortening phases across the arc. 5) more lately prior to Pliocene, the Gibraltar arc was subjected to contractional possess related to a N-S shortening phase, which drastically altered its geometry
Ternois, Sébastien. "Reconstruction de la Dynamique Précoce d'un Orogène : Mise en évidence de la Transition Rifting-Collision dans le système est-pyrénéen (France) par la Géo-thermochronologie." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0086/document.
Повний текст джерелаCollisional orogens are classically described as the result of continental accretion of proximal margins. This accretion leads to the creation of relief and to the important export of erosion products in the directly adjacent foreland basins. In this geodynamic scheme, only the least deformed pre-orogenic domains are considered. However, a growing number of geological field evidences indicate the preservation or even the reuse of structures inherited from the rifting phase preceding convergence and collision within orogens. By conducting a geo-thermochronometric study of the easternmost, inverted hyperextended Aptian-Cenomanian rift system (Agly massif, North Pyrenean Zone) and the adjacent early retroforeland (Rennes-les-Bains syncline, Aquitaine Basin), this thesis aims to describe the evolution of a distal rifted margin during the first stages of convergence, to quantify the associated source-to-sink processes and to provide temporal and paleogeographic constraints regarding the creation of the very first Pyrenean reliefs resulting from inversion of the margin. Using the zircon and apatite (U-Th)/He multi-thermochronometers, I show that the Pyrenean retro-wedge records two clear phases of orogenic cooling, Late Campanian-Maastrichtian and Ypresian-Bartonian, which I relate to early inversion of the distal rifted margin and main collision, respectively. I have thus been able to propose a crustal-scale sequentially restored model for the tectonic and thermal transition from extension to peak orogenesis in the eastern Pyrenees, which suggests that both thrusting and underplating processes contributed to early inversion of the Aptian-Cenomanian rift system. The absence of Paleocene cooling record indicates little to no erosion of the Pyrenean retro-wedge, suggesting the existence of a more easterly source area supplying early retroforeland sediments at this time. To characterize this eastern edifice, which has since been destroyed by the Oligocene-Miocene opening of the Gulf of Lion, I used in situ (U-Th)/He - U/Pb double dating on detrital zircons and show rapid denudation rates during early convergence, characteristic of early topographic growth. This work shows for the first time clearly the progressive migration of deformation from east to west by inversion of inherited structures at the beginning of Pyrenean convergence. This suggests the existence of an open domain in the east at the end of the rifting phase preceding convergence. This study highlights the role of the architecture of hyper-thinned systems in the formation of collisional orogens and confirms the close links between an orogen and its foreland basins
Gregory, Courtney Jayne. "Allanite chemistry and the U-Th-Pb geochronology." Phd thesis, 2009. http://hdl.handle.net/1885/151732.
Повний текст джерела"(U-Th)/He, U/Pb, and Radiation Damage Dating of the Rochechouart-Chassenon Impact Structure, France." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.40296.
Повний текст джерелаDissertation/Thesis
Masters Thesis Geological Sciences 2016
Bo-RenWang and 王伯仁. "Behavior of U and Th isotopes in diagenetically-altered fossil corals: its implication for U-series dating." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/57774961542072695743.
Повний текст джерела國立成功大學
地球科學系碩博士班
98
To understand the behavior of uranium-series isotopes in diagenetically-altered fossil corals, this study collected fossil corals from Kenting, Heng Chun Peninsula, Taiwan. After separating each coral sample into 3-5 sub-coral samples, we measured the distributions of uranium (238U, 234U) and thorium (230Th, 232Th) isotopes in each of these subsamples. Results show that the modern and unaltered corals collected from Eruanbi (鵝鑾鼻) at modern sea-level have 238U activities 2.28 ± 0.08 dpm/g in consistence with those of unaltered corals reported previously for other locations of Kenting. Corals from Lung-Pan (龍磐) at ~80 m a.s.l. (above sea-level) and She-Ding (社頂) at ~150 m a.s.l. have 238U activities mostly smaller or equal to 1 dpm/g, which are much smaller than those of modern corals at Kenting as well as the unaltered corals from various parts of world oceans. The observed decrease of 238U activities in altered corals suggests that the diagenesis of coral results in significant loss of uranium to groundwater. Consistent with the observations on diagenesis-driven leads to loss of uranium from corals, 230Th/238U ratios are found in some corals to be significantly greater than 1, suggesting that significant diagenesis occurs during the last 350 kyrs. It is interesting that 234U/238U ratios from various parts of the same coral shows variable values of ~0.98 to 1.13, a result of exchange of uranium between coral and groundwater during the diagenesis. 230Th/238U ratios in various parts of the same coral were also found to vary significantly, suggesting various degree of diagenesis in various parts of the same corals. Based on these findings, we conclude that no reliable U-series dates can be obtained from those fossil corals by assuming a closed system for corals. To evaluate the impact of diagenesis on U-series dating of corals, we proposed three possible about timing of uranium loss from the corals : (1) The uranium loss by diagenesis occurs in the early short period of coral formation, (2) the uranium loss occurs recently, or (3) U loss occurs at any time after coral formation. Case (1) is datable but requires that the measured 230Th/238U and 234U/238U ratios in all subsamples are the same with the uncertainty. Case (2) is datable only if the recent loss of U can be corrected. Case (3) is undatable.
Chapman, Shay Michael. "Thermal and Structural Constraints on the Tectonic Evolution of the Idaho-Wyoming-Utah Thrust Belt." Thesis, 2013. http://hdl.handle.net/1969.1/151236.
Повний текст джерелаBense, Frithjof A. "Multi-Method Chronometric Constraints on the Thermal, Structural and Morphotectonic Evolution of the Eastern and Western Sierras Pampeanas with Special Emphasis on K-Ar Dating of Fault Gouges." Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0001-BB21-8.
Повний текст джерела"Tools, Techniques, and Applications For Detrital Thermochronology: From the Lab to the Eastern Sierra Nevada, California." Doctoral diss., 2019. http://hdl.handle.net/2286/R.I.54811.
Повний текст джерелаDissertation/Thesis
Doctoral Dissertation Geological Sciences 2019
Fanta, Martin. "Datování vývěrů radioaktivních minerálních vod v krkonošsko-jizerském krystaliniku metodou 230Th/234U." Master's thesis, 2016. http://www.nusl.cz/ntk/nusl-349028.
Повний текст джерелаMakhubela, Tebogo Vincent. "⁴⁰ Ar/³⁹Ar and (U-Th)/He dating attempts on the fossil-bearing cave deposits of the Malapa and Sterkfontein hominin sites of the Cradle of Humankind, South Africa." Thesis, 2015. http://hdl.handle.net/10210/13697.
Повний текст джерелаThe Cradle of Humankind is a 47 000 hectare demarcated area with over three dozen fossil-bearing cave sites well known for the preservation of fossil evidence of early hominin taxa such as Australopithecus Africanus, Australopithecus Sediba, Paranthropus Robustus and Early Homo. As a result, a database of precise and accurate chronological data for fossil-bearing cave deposits of the Cradle of Humankind (similar to that for East African fossil sites) is very important, but developing one has proven extremely challenging. The main challenge is that the fossil-bearing deposits at the cradle are mainly complex breccias with a chaotic, localized stratigraphy and no association to any volcanic ash beds, unlike the East African deposits which are lacustrine and fluviatile deposits interbedded with volcanic ash layers. However, substantial success has been obtained recently through the combination of U-Pb dating of CaCO₃ speleothems and palaeomagnetic dating (magnetostratigraphy) after many attempts and unconvincing results from techniques such as biostratigraphic correlations, electron spin resonance on teeth and cosmogenic burial dating of the sediments. The problem with U-Pb dating of CaCO₃ speleothems is that this requires samples that are extremely clean (i.e. detrital-free) and have an appreciable U content (close to 1 ppm), and such material is at many sites not available...
Haider, Viktoria L. "Evolution and decay of peneplains in the northern Lhasa terrane, Tibetan Plateau." Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-990C-4.
Повний текст джерела