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Dissertations / Theses on the topic 'Geochronological'

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Published: 10 December 2022
Last updated: 28 January 2023

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1

Milne, Alastair John. "The pre-Mesozoic geological evolution of Graham Land, Antarctica." Thesis, Open University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253302.

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2

Boygle, Jane E. "Tephra in lake sediments : an unambiguous geochronological marker?" Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/20193.

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This thesis has three aims: (1) to construct tephrochronologies on large and small scales at sites in Sweden and Iceland; (2) to assess the effects of erosional and depositional processes on the nature and distribution of tephra in the sedimentological record; (3) to use these case studies to propose a model of the deposition of tephra in lakes. The Swedish Timescale based on the annually laminated sediments (varves) has recently been linked to the present. To test the chronology, traces of volcanic glass (tephra) from five historical eruptions of Icelandic volcanoes were sought within relevant sections of the varve deposits. Difficulties in isolating and identifying tephra to define isochrones in distal deposits led to the adoption of an integrated catchment and lake basin sampling strategy to assess the processes which affect the temporal and spatial distribution of tephra in lakes. A detailed tephrochronology of Svínavatn, a lake in northern Iceland, was constructed by identifying and correlating 95 tephra deposits from five lake cores and twelve profiles situated in the lowland peats, hillslopes and delta areas of the catchment. The tephra record from each site was highly variable due to both uneven fallout of the tephra following the eruption, and later reworking of the deposits in the lake and the catchment. The environmental changes of Svínavatn and its catchment were reconstructed using tephra as a geomorphological tracer. The peats and soils of the catchment were stable throughout most of the Holocene until the deposition of Hekla 3 (2800 yBP). Repeating layers of reworked Hekla and Katla tephra after this period at several terrestrial and lacustrine sites reflect increasing episodic instability of the catchment and the effects of this disturbance on the lake record. Until the arrival of Norse settlers in the 9th century, much of this disturbance was linked to climate and vegetation changes around the catchment. Significant, but temporally discrete, secondary inputs of H3 and H4 (3800 yBP) into the lake occur several thousand years after the original airfall.
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3

Coombs, Henry. "Geochemical and geochronological constraints on terrane definition in Mexico." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/94626/.

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Mexico has played host to a variety of igneous events since the Paleozoic, relating to the formation and subsequent breakup of the supercontinent Pangaea, as well as to intermittent subduction along its western coast. Through analysis of the crystalline basement of the Western Gulf of Mexico this project has introduced the first detailed tectonomagmatic model relating to the pre- and post- amalgamation of Pangaea in Mexico. Additionally, post-Pangaea rifting has been investigated in the extensional basin of the northern Cuicateco terrane. This study has identified three igneous events in the crystalline basement of the Western Gulf of Mexico: 1) An Early Permian (294 Ma) continental arc that formed on Gondwana during the final amalgamation of Pangaea. These rocks appear to be related to Late Carboniferous-Early Permian plutons found in the Oaxaca area of Southern Mexico (Ortega-Obregon et al., 2014). 2) Late Permian-Early Triassic (274- 243 Ma) anatectic magmatism that formed in a post-collisional environment after the final amalgamation of Pangaea. These rocks appear to be related to plutons of comparable age found in the Oaxaca area and Chiapas Massif of Southern Mexico (Weber et al., 2005; Ortega-Obregon et al., 2014). 3) Early Jurassic (189-164 Ma) continental arc rocks that likely relate to the Nazas arc system that existed across Mexico at the time (Dickinson & Lawton, 2001). Major element and trace element geochemistry, used in conjunction with Hf and Nd isotopic analysis have revealed that the Early Cretaceous units of the northern Cuicateco terrane formed in a subduction related environment, likely associated with the closure of the Arperos oceanic basin. Extrusive and intrusive arc rocks have been dated between 140-133 Ma (Xonamanca Formation and Teotitlán Migmatitic Complex); with subduction of the Arperos ridge later causing extension (Chivillas Formation). Spreading in the Chivillas Formation stopped in the Earliest Aptian, likely due to the collision of the Guerrero terrane with Mexico.
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4

Bendall, Betina R. "Metamorphic and geochronological constraints on the Kimban Orogeny, Southern Eyre Peninsula /." Title page, abstract and contents only, 1994. http://web4.library.adelaide.edu.au/theses/09SB/09sbb458.pdf.

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5

Whattam, Scott A. "Evolution of the Northland ophiolite, New Zealand: geochemical, geochronological and palaeomagneticconstraints." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244890.

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6

Bowtell, Sophie Ann. "Geochronological and geochemical studies of Zermatt-Saas Fee Ophiolite, Western Alps." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305487.

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7

Bailey, Simon David. "A geophysical and geochronological assessment of coastal dune evolution at Aberffraw." Thesis, Birkbeck (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.483553.

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8

Pu, Judy (Judy P. ). "Geochronological constraints on the Trinity diamictite in Newfoundland : Implications for Ediacaran glaciation." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/114096.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 21-26).
The Avalon terrane in Newfoundland includes the Ediacaran Gaskiers Formation, which has been associated with a Snowball glaciation event. The complicated regional stratigraphy and lack of precise geochronological constraints has made it difficult to determine the spatial and temporal extent of the Gaskiers glaciation. Recent recognition of a diamictite facies on the nearby Bonavista Peninsula correlative with the Gaskiers diamictite has allowed for new, high-precision geochronological constraints on the Gaskiers glaciation and constrains the duration of the event to less than 390 ±320 kyr. The Snowball Earth hypothesis requires that glaciation continued for several millions of years so that CO2 could build up to high enough levels in the atmosphere for catastrophic deglaciation; the short duration of the Gaskiers event makes it unlikely to have been a Snowball event. Further geochronological studies are needed to determine whether the Gaskiers glaciation was a discrete event or if it was a glacial maximum in a longer Ediacaran ice age.
by Judy Pu.
S.B.
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9

Weller, Owen M. "An integrated metamorphic and geochronological study of the south-eastern Tibetan plateau." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:f4104b43-389a-4d54-bd7b-ba3fc0e8ab95.

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The Tibetan plateau is a vast, elevated region located in central Asia, which is underlain by the thickest crust known on Earth (up to 90 km). An outstanding question of importance to many fields within geology is how and why did the Tibetan plateau form? Models attribute the growth of the plateau to a consequence of the ongoing India-Asia continental collision, but differ in the details of how the crustal thickening was accommodated: was it by underplating of Indian lower crust or by homogeneous shortening? High-grade metamorphic rocks sampled from the region potentially hold the key to answering this question, as they contain a record of past tectonic events that can discriminate between the various proposed models. This record can be decoded by integrating field, thermobarometric and geochronological techniques, to elucidate a detailed thermotectonic understanding of a region. This methodology was applied to three case studies, each of which targeted rare tectonic windows into the mid-crust of the plateau. These regions comprise Danba in eastern Tibet, Basong Tso in south-eastern Tibet and the Western Nyainqentanglha in southern Tibet. Each case study documents previously unreported metamorphic events that have allowed original interpretations to be made regarding tectonic evolution: in Danba, all metamorphism is shown to be early Jurassic; in Basong Tso, two metamorphic belts are documented that reveal a late Triassic--early Jurassic orogenic event; and in the Western Nyainqengtanglha, Cretaceous--Neogene magmatism is shown to overprint late Triassic metamorphism. Integration of the results has enabled commentary on the large scale evolution of the Tibetan plateau from the Permian until the present day, and even hinted at its future. The results indicate that the closure of the Paleotethys played an important role in the construction of the Tibetan plateau, and suggest that homogeneous crustal thickening is not a viable model for the documented exposure levels.
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10

Helbing, Heiko. "No suture in the Sardinian Variscides a structural, petrological and geochronological analysis /." Tübingen : Univ, 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10733113.

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11

Grodzicki, Kathryn R. "Structural, geochemical and geochronological analysis of the Coatlacco area, Acatlán Complex, southern Mexico." Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1154628676.

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12

Muir, D. D. "Petrological and geochronological constraints on magma storage conditions beneath Uturuncu volcano, SW Bolivia." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619259.

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Uturuncu is an effusive, dacitic volcano in the Bolivian altiplano of the Central Andes. A 70 km diameter InSAR anomaly associated with the volcano is thought to be caused by ongoing magma intrusion in the mid-crust. Detailed petrological study of Uturuncu lavas and domes has been conducted to better understand the sub-volcanic magma system. Phenocryst proportions, phase assemblage and bulk chemistry are relatively constant but wide ranging mineral compositions and the presence of mafic andesite enclaves suggest magma mixing plays a major role in the genesis of Uturuncu magmas. Norite cumulates testify to the role of fractional crystallisation. Dacite magmatic temperatures vary from 760 to 900 degree C with hottest temperatures most likely occurring due to recharge of andesitic magmas. Volatile compositions of plagioclase- hosted melt inclusions provide minimum trapping pressures of 50 to 120 MPa. Phase equilibria experiments using dacite bulk-rock and rhyolitic groundmass glass compositions constrain dacite pre-emptive storage conditions to <100±50 MPa «5.7 km deep). Existing geodetic inversions of deformation data require a deformation source> 17 km deep, therefore such shallow storage of dacites precludes intrusion of magmas in pre-eruptive storage regions as the cause of ongoing deformation at Uturuncu. Uturuncu dacites ultimately arc sourced from the Altiplano-Puna Magma Body (APMB), the largest known active magma body in the Earth's continental crust. Phase equilibria experiments using a mafic andesitic enclave composition at mid-crustal conditions have been performed. These experiments test whether dacites erupted at Uturuncu call be sourced from residual melts of mafic andesite’s at APMB levels. Results indicate that dacite melts form at mid-crustal pressures (0.5-1.1 GPa) from equilibrium crystallisation of mafic andesite. Melts in volatile-undersaturated experiments are most similar to erupted dacite compositions, mainly as a result of plagioclase crystallisation. In detail however, major and trace element concentrations do not match those of natural dacites. Melt fractions are too high suggesting drier or cooler conditions are required. Biotite and groundmass separates from 27 Uturuncu lavas and domes were dated using 4oAr/39Ar. Results show that eruptions between 1.05 and 0.25 Ma formed the 72 to 80 km3 edifice. Four eruptive hiatuses >50 kyrs one possibly as long as 240 kyrs, occurred in the past. Extrusive centres have migrated several kilometres throughout Uturuncu's history and are commonly marked by large domes. There are no systematic variations in textural and chemical data of erupted products through time and unpredictable temporal changes in trace element compositions preclude magma evolution from a single parental source. Instead multiple ephemeral , shallow crustal reservoirs with distinct trace element compositions are envisaged.
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13

Borel, Megan E. "A Microstructural and Geochronological Investigation of the Coyote Mountain Metamorphic Core Complex (AZ)." Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10814678.

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The Coyote Mountains is a metamorphic core complex that makes up the northern end of the 80-km long Baboquivari Mountain complex. The Baboquivari Mountain complex is composed of Mesozoic rocks, Cenozoic granites, pegmatites, and metasediments (Wright and Haxel, 1982; Haxel et al., 1980, 1984). In the Coyote Mountains, there is an intrusion of the Pan Tak granite, a muscovite-biotite-garnet peraluminous granite dated at 58 Ma based on U-Pb analysis of zircon. The Pan Tak and other intrusions within the Baboquivari Mountains have been interpreted as anatectics melts representing the culmination of a Laramide crustal shortening orogenic event that started in the Late Cretaceous, about ~70 mya (Goodwin and Haxel, 1990). However, field evidence, as well as petrographic and microstructural analyses of metamorphic and deformational fabrics/structures show that the ~58 mya intrusive/magmatic fabric is overprinted by a secondary tectonic event. This event is particularly well recorded in the northern part of the Coyote Mountains, where a northdipping mylonitic shear zone is exposed. This study focuses on the Pan Tak granite with twenty samples from the northern portion of the Coyote Mountains, directly north of Coyote Peak, from the mapped areas of granites and mylonites.

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14

Bailey, Simon David. "A geophysical and geochronological assessment of coastal dune evolution at Aberffraw, North Wales." Thesis, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533191.

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Aberffraw is a lkm wide and 3km long transgressive dune field on the Isle of Anglesey, North Wales, that extends inland along a northeast-southwest trending valley from a southwest facing beach, Traeth Mawr. The prevailing wind is from the southwest and both the parabolic dunes and the vaUey within which they lie are subparallel to the prevailing wind. The dune field at Aberffraw includes two foredunes ridges and three rows of active parabolic dunes. At the landward end is a lake, Llyn Coron, which has been formed by the dunes migrating up the valley and damming the river, Mon Ffraw. Rates of parabolic dune migration, calculated from aerial photographic analysis using a new linear fit method for compound dune forms, range from a minimum of 0 m1yr to 3.6 mJyr, with an average migration rate of 1 m1yr. Ground Penetrating Radar (GPR) was used to identify sedimentary structures in the subsurface of the two foredune ridges, four parabolic dune ridges and the associated interdune areas. Surveys at 100 MHz and 200 MHz allowed the resolution of both the gross dune field stratigraphy (bounding surfaces, erosion surfaces) and the smaller sedimentary structures (e.g. cross-stratification, foresets, cut and fill troughs), together with the water-table and basement. Interpretation of the GPR profiles used a combination of the radar facies technique and a radar sequence boundary stratigraphic approach to construct relative chronologies for sections of the stratigraphy. Detailed intersecting GPR surveys by Llyn Coron revealed a relative chronology of six sand packages younging successively towards the NE, bounded by erosion surfaces representative of relic lake beds. Large landward dipping erosion surfaces are interpreted as incursions by the lake, with a raised water-table resulting from highstand phases initiated by dune damming. Smaller troughs and planar based scours are interpreted as periods of deflation to a lowered water-table associated with lowstand phases of the lake. Prograding stacks of landward dipping foresets are interpreted as continued dune migration throughout these events. Hand augering was used to sample specific packages identified from the GPR profiles for Optically Stimulated Luminescence (OSL) dating to provide absolute ages for sand deposition. Samples were also acquired from the neighbouring site of Newborough Warren for comparison, and for radiocarbon dating. Quartz grains were dated using a single aliquot regenerative dose (SAR) protocol that allowed for sensitivity changes and monitoring of thermal charge transfer. Thirty-four dates ranged from AD 1281 for a 5 m deep sample to AD 1981 for a modern bleached sample, demonstrating good precision in contrast with the radiocarbon technique over this time scale. and confirming the relative chronology constructed from the GPR data. The OSL dates for sand movement at Aberffraw show good correlation with both local and regional temporal trends in sand movement for coastal dune areas in NW Europe, with a positive correlation between periods of sand movement and periods of increased storm frequency and severity associated with the North Atlantic Oscillation (NAO) and climatic deterioration during the Little Ice Age cooling event.
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15

Grodzicki, Kathryn. "Structural, Geochemical and Geochronological Analysis of the Coatlacco Area, Acatlan Complex, Southern Mexico." Ohio University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1154628676.

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16

Perlman, Zachary S. "STRATIGRAPHIC, GEOCHEMICAL, AND GEOCHRONOLOGICAL ANALYSIS OF THE WOLFCAMP-D INTERVAL, MIDLAND BASIN, TEXAS." UKnowledge, 2017. http://uknowledge.uky.edu/ees_etds/48.

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Subsurface data derived from ~388 ft of drill core from Martin County (TX) were used to understand the depositional setting of the Wolfcamp-D, a petroleum producing interval in the Midland Basin. Elemental geochemistry collected via x-ray fluorescence revealed a highly variable depositional history marked by the deposition of diverse siliciclastic and carbonate lithofacies. Integration of multiple datasets resulted in the interpretation of nine lithofacies, whose deposition appears cyclical. Correlations between molybdenum and total organic carbon indicate slow recharge of bottom waters and anoxic/euxinicconditions within the basin. The presence of phosphatic nodules coinciding with siliceous black mudrocks suggested high levels of primary productivity driven by upwelling. High-frequency sea level variability, driven by far-field glaciation and regional paleoclimate, were key controls on both the chemostratigraphy and lithofacies. Along-strike variability is seen throughout the basin due to paleobathymetry, proximity and connections to paleochannels, and localized structures. Rhenium-osmium (Re/Os) geochronology was conducted on siliceous mudrocks with high total organic carbon. A depositional age of 300 ± 18 Ma was obtained, partially confirming previous correlations to shelf biostratigraphic data. Scatter in the Re/Os data is likely due to mixing in the basin or non-hydrogenous Os incorporated into the analysis due to the method of preparation.
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17

Erickson, Timmons Manning. "Deformation microstructures in zircon and monazite: implications for shock, tectonic and geochronological studies." Thesis, Curtin University, 2016. http://hdl.handle.net/20.500.11937/51620.

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Zircon and monazite have been studied by quantitative microstructural analysis to constrain deformation processes in both tectonic and shock environments. Results provide new constraints on twinning, shock transformation to high pressure polymorphs and the conditions of formation of impact microstructures. Trace element mobility and modification of U – Pb ages, linked to crystal-plastic deformation in these environments, provides new strategies for dating the timing of deformation events by in situ analyses of microstructurally characterized accessory phases.
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18

Kröner, Stephan Ulrich Georg. "Geochronological and structural evolution of the western and central Kaoko Belt in NW Namibia." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976127385.

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19

Rieuwers, Mark Thomas. "Thermobarometric and geochronological constraints on reworking of the Palaeoproterozoic Strangways Metamorphic Complex, central Australia /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09SB/09sbr564.pdf.

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20

Peters, D. "A geochemical and geochronological assessment of the Great Glen Fault as a terrane boundary." Thesis, Keele University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.344063.

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The Great Glen Fault (GGF) is a major northeast to southwest trending structure and has been interpreted as a terrane boundary separating the Precambrian Moine terrane to the northwest from the Precambrian Dalradian terrane to the southeast (e. g. Bluck & Dempster 1991). If the GGF is a terrane boundary no `Moine' rocks could be found southeast of the GGF and no `Dalradian' rocks could be found to the northwest of the GGF and each crustal block would have distinct tectonometamorphic, provenance and igneous intrusive characteristics. To assess this, carefully selected orthoamphibolite and metasediment samples were collected from both the Northern and Central Highlands, and were analysed by a combination of petrography, geochemistry and geochronology. Geochemical analysis suggests that a Neoproterozoic metagabbro and metadolerite suite was emplaced during crustal extension across the Northern and Central Highlands at approximately the same time, and that this suite represents an earlier intrusive event to that represented by amphibolites in the Dalradian Appin Group. Geochemistry also suggests that the Upper Morar Psammite Formation of the Moine Supergroup in the Northern Highlands is unlikely to correlate with the pebbly psammite formations in the Central Highlands and shows that the Upper Shiaba Psammite Formation metasediments on the Isle of Mull are geochemically distinct from the Upper Morar Psammite Formation metasediments on the mainland. The Glen Urquhart Complex in the Northern Highlands cannot be correlated with the Ord Ban Subgroup or Grantown Formation in the Central Highlands. However, despite these differences U-Pb detrital geochronology shows that the Upper Morar Psammite and Central Highland pebbly psammite formations are dominantly derived from similar Mesoproterozoic and Palaeoproterozoic sources, with a small amount of material of Archaean derivation. This, together with the matching amphibolite suites, means that the Great Glen Fault is very unlikely to be a terrane boundary.
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21

Wong, Ping-mei Jean, and 王冰媚. "Geochemical and geochronological constraints on the Jiangshan-ShaoxingFault Zone in Zhejiang Province, Eastern South China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B45983860.

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22

Geng, Hongyan, and 耿红燕. "Geochemical and geochronological studies of carboniferous magmatism inthe West Junggar: ridge subduction in thelate paleozoic?" Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45983999.

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23

MAUAD, CRISTIANE RIBEIRO. "GEOCHRONOLOGICAL VARIATIONS OF CARBON BLACK AND PAHS IN GUANABARA BAY AS INDICATORS OF COMBUSTION SOURCES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16588@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
As pesquisas sobre carbono negro (BC) vêm ganhando grande importância nos últimos anos, não somente devido a sua capacidade de atuar como traçador histórico de processos de combustão em uma determinada região, mas também devido a sua capacidade de sorver contaminantes hidrofóbicos de ambientes aquosos. Buscou-se estudar a geocronologia de dois subprodutos provenientes de processos de combustão (BC e HPAs - hidrocarbonetos policíclicos aromáticos), que podem ter origem tanto de queima de biomassa quanto de combustíveis fósseis em um testemunho sedimentar coletado da região noroeste da Baía de Guanabara. Foram avaliadas suas possíveis relações, entre si e com o teor de carbono orgânico presente no sedimento. Avaliaram-se também as possíveis fontes dos HPAs presentes nas amostras, traçando um histórico de queima da região, caracterizada por um acentuado trafego veicular e poluição crônica por diversos compostos. O testemunho foi seccionados em intervalos de 2 cm, onde foram utilizados os segmentos entre 0-72 cm somando totalizando 30 amostras. A metodologia analítica utilizada para a determinação do BC foi a CTO-375, baseada na retirada da matéria orgânica (não-BC) por combustão na presença de oxigênio em excesso, restando somente a fração mais refratária composta pelo BC. Embora a variação percentual de BC tenha apresentado uma média de 0,36 (+-) 0,08 % p.s. ao longo do testemunho, foi observado que o mesmo compõe uma fração significativa do carbono orgânico total (TOC) desta região chegando a representar até 18% p.s. do TOC. A razão C/N possibilitou mostrar que grande parte de matéria orgânica presente neste local é proveniente de origem marinha. O método utilizado para a determinação da concentração dos HPAs foi o EPA 3540C, baseado na extração dos analitos da matriz, a purificação dos extratos através da remoção de interferentes. Através das razões diagnósticas e da análise de componentes principais (PCA) foi possível traçar uma transição das principais fontes de HPAs neste ambiente, mostrando a predominância de HPAs pirogênicos nas amostras mais antigas, para uma maior contaminação petrogênica nas amostras mais recentes. Ainda foi possível comprovar a afinidade de HPAs pirogênicos à presença de BC. Análises de microscopia eletrônica de varredura (SEM) contribuíram para uma maior compreensão das características morfológicas do sedimento, mostrando este ser rico em material amorfo e diatomáceas cêntricas. Esta análise também possibilitou a identificação visual da partícula de BC, porém, a falta de um pré-tratamento nas amostras dificultou o seu reconhecimento. Foram realizadas análises de ressonância magnética nuclear (CP/MAS (13)C NMR) visando possibilidades futuras de determinação de BC por esta técnica. As análises de NMR mostraram que o elevado teor de carbono aromático presente na amostra ambiental, relacionado principalmente a presença de lignina, interfere no sinal de NMR para a determinação de BC, sendo necessária a sua oxidação. Análises de CP/MAS-NQS (13)C NMR possibilitaram a separação das frações de BC, mostrando um teor acentuado de carbonos não-substituídos, sugerindo maior aporte de BC proveniente de queima ao longo do testemunho. Na amostra mais superficial, percebeu-se maior presença de carbonos quaternários, indicando o aumento no aporte de BC oriundo de combustão de combustíveis fósseis.
Researches about black carbon (BC) have been gaining importance in recent years, not only because of its ability to act as a tracer of historical combustion processes in a given region, but also for its ability to adsorb hydrophobic contaminants in aqueous environments. In a sediment core collected from the northwestern region of Guanabara Bay, was attempted to study the geochronology of two combustion sub-products processes (BC and PAHs - polycyclic aromatic hydrocarbons), which may originate both biomass burning and fossil fuels. Was evaluated their possible relationships between themselves and with the content of organic carbon in the sediment. Also was evaluated the possible PAHs sources in the samples, tracing a burning history in the region, characterized by a marked vehicular traffic pollution and chronic individual compounds. The core was sectioned at intervals of 2 cm, which were used from 0 to 72 cm segments, in a total of 30 samples. The BC analytical determination methodology was the CTO-375, based on organic matter (non-BC) removal by combustion in presence of excess oxygen, leaving only a fraction composed by most refractory BC. Although the BC percentage had an average of 0.36 (+-) 0.08% dry weight over the core, was observed that is a significant fraction of total organic carbon (TOC) in this place representing up to 18% d.w. of TOC. The C/N ratio permitted evaluate that much of organic matter on this site comes from sea sources. The method used for determining the concentration of PAHs was the EPA 3540C, based on the analytes extraction from the matrix, and the extracts purification through the interferences removal. Through diagnostic reasons and principal component analysis (PCA), were possible to evaluate a PAHs transition of the main sources in this environment, showing the PAHs predominance in older pirogenics samples to an increase of petrogenic contamination in the most recent samples. It was also possible to relate an affinity of PAHs pyrogens in the BC presence. Analysis of scanning electron microscopy (SEM) contributed to a better understanding about the sediment morphological characteristics, showing to be rich in amorphous material and centric diatoms. This analysis also allowed the visual identification of the BC particles, however, the lack of a pre-treatment in the samples made it difficult to recognize. Nuclear magnetic resonance (CP/MAS (13)C NMR) analysis were performed in order to future possibilities of BC determination by this technique. The NMR analysis showed that the high aromatic carbon content in the environment sample, is mainly related to the presence of lignin interferes with the signal of NMR for the determination of BC, which requires its oxidation. Analysis of CP/MAS-NQS (13)C NMR allowed the separation of fractions of BC, showing a strong level of carbon non-replaced, suggesting a greater contribution of BC from burning during the core. In the most superficial sample, it was observed the large presence of quaternary carbons, indicating an increase in the input of BC come from combustion of fossil fuels.
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24

Dymoke, Peter Lindsay. "Geochronological and petrological studies of the thermal evolution of the Dalradian, South West Scottish Highlands." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/13754.

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25

Hagemann, Lukas Falk [Verfasser], Jan [Akademischer Betreuer] Schwarzbauer, and Frank [Akademischer Betreuer] Lehmkuhl. "Geochronological investigations of anthropogenic contaminants in alluvial sediments / Lukas Falk Hagemann ; Jan Schwarzbauer, Frank Lehmkuhl." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1225401615/34.

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Hagemann, Lukas Falk Verfasser], Jan [Akademischer Betreuer] [Schwarzbauer, and Frank [Akademischer Betreuer] Lehmkuhl. "Geochronological investigations of anthropogenic contaminants in alluvial sediments / Lukas Falk Hagemann ; Jan Schwarzbauer, Frank Lehmkuhl." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1225401615/34.

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27

Ghassemi, Mohammad Reza. "Tectonic evolution of the Late Archean Pontiac Subprovince, Superior Province, Canada: Structural, metamorphic, and geochronological studies." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9932.

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The Pontiac Subprovince is a Late Archean (ca. 2.7 Ga) metasedimentary-metavolanic-granitoid-gneiss terrane situated along the southeastern margin of the Superior Province in Quebec. Detailed structural study of the northwestern part of this amphibolite facies metasedimentary belt has revealed a protracted history of deformation in Late Archean and Early Proterozoic time. An early contractional event (D$\sb1$) resulted in development of steep foliations now preserved as folded or straight relics within microlithons of S$\sb2$ foliation. During this stage, the Cadillac-Larder Lake fault zone acted as a major fault zone along which greenstones for the Abitibi Subprovince were thrust over the Pontiac Subprovince. Regional metamorphism resulted from both thickening of the crust, and intrusion of voluminous I-type graintes. D$\sb2$ structures record peak metamorphic high-temperature deformation of the crustal rocks during which large-scale D$\sb2$ nappes moved towards the south-southeast. The basal thrust faults of these nappes are preserved as high-strain shear zones within the study area. Second order east-trending recumbent F$\sb2$ folds, a penetrative S$\sb2$ crenulation foliation, and a north-northwest-trending L$\sb2$ elongation lineation are other important structures of this deformational event. A later D$\sb3$ contractional event superimposed east-trending upright folds on all earlier structures. Extensional D$\sb4$ structures are associated with reactivation of the Cadillac-Larder Lake fault zone as a normal fault zone, and are only recorded in or close to normal faults within this fault zone. Finally, brittle D$\sb5$ thrust faults and kink structures are superimposed on all older structures in the northwestern Pontiac Subprovince. Gneisses of the Lac Opasatica area record pre-D$\sb1$ penetrative structures that are not present within the other rock types of the study area. Increasing metamorphic grade from biotite zone to sillimanite zone is evident from north (the Cadillac-Larder Lake fault zone) to south in the study area, close to outcrops of the S-type granites. Thermobarometry of samples from the study area indicates that regional metamorphism of the rocks in the northwestern Pontiac Subprovince occurred at about 590$\sp\circ$C and 6.2 kbar. Investigation of the metamorphic and structural history of these Late Archean rocks suggests a clockwise PT path similar to that of Phanerozoic collisional belts. $\sp{40}$Ar/$\sp{39}$Ar age constraints from this study combined with other geochronologic indicate a slow cooling rate of about 2$\sp\circ$ to 6$\sp\circ$C/Ma, and reveal that temperatures as high as 350$\sp\circ$C and 280$\sp\circ$C were persistent in crustal rocks of the area until ca. 150 Ma after attainment of peak metamorphic conditions. (Abstract shortened by UMI.)
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Viskupic, Karen M. (Karen Marie) 1975. "Crustal melting in the Himalayan orogen : field, geochemical and geochronological studies in the Everest region, Nepal." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/59101.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.
Includes bibliographical references.
A combination of field studies and geochemical techniques were used to investigate the timing and processes involved in leucogranite generation in the Everest region of the Himalayan orogen. Geochemical investigations focused on samples from three outcrops at different structural levels in the Himalayan metamorphic core where in situ crustal melting and multiple generations of leucogranite intrusions were observed. Accessory phase thermochronological and U-Pb geochronological studies were combined to determine the timing of anatexis in a migmatite at the structurally lowest outcrop. Quantitative measurement of REE and Y in monazites and xenotimes, that were later dissolved and dated by U-Pb IDTIMS, revealed monazite growth at temperatures appropriate for crustal melting (>650⁰C) between 25.4 and 24.8 Ma, suggesting that anatexis was ongoing at that time. Further constraints were placed on the timing of crustal melting, granite crystallization and cooling with a detailed U-Pb IDTIMS and 40Ar/39Ar study of leucogranite dikes, sills, and the metamorphic rocks they intrude. Backscattered electron imaging of accessory minerals provided important insights into the petrogenesis of monazite, xenotime and zircon, and guided efforts to isolate accessory phase growth domains. In two granitic sills, extensive accessory phase crystallization between ca. 26 and ca. 23 Ma was interpreted to be the result of episodic to semi-continuous melt generation and crystallization at least between those times. These melt products were later entrained in melts that crystallized as syntectonic sills at 21-22 Ma. Younger crosscutting dikes crystallized between 17.5 and 18.3 Ma.
(cont.) The range in accessory phase dates from these dikes and sills that represent magmatic crystallization ages spans from 26.2 to 17.5 Ma, providing evidence for melt generation in one region over roughly 9 million years. Neodymium isotopic signatures of the same monazite and xenotime grains dated by U-Pb IDTIMS were used to investigate melting processes and granite source-rock characteristics. The dominant control of monazite on the Nd isotopic composition of its host rock was clearly demonstrated. Some Nd isotopic heterogeneities recorded in monazite and in xenotime support a model for melt generation where accessory phases grow from locally derived sources in an isotopically heterogeneous melt.
by Karen M. Viskupic.
Ph.D.
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Seydoux-Guillaume, Anne-Magali. "Experimental determination of the incorporation of Th into orthophosphates and the resetting of geochronological systems of monazite." Phd thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963521349.

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30

Brown, Hazel A. "A palaeomagnetic, geochronological and palaeoenvironmental investigation of late and post glacial maar lake sediments from NW-Europe." Thesis, University of Edinburgh, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489316.

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31

Harris, Nancy Ruth 1970. "Isotopic, geochemical, and geochronological constraints on the origin and evolution of Cenozoic volcanism, Baikal Rift Zone, Siberia." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/54432.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998.
Includes bibliographical references.
The Cenozoic Baikal Rift Zone, one of the world's major continental rifts, is expressed as an approximately 1800 km-long southwest-northeast oriented system situated along a suture between the Archean Siberian craton and younger Paleozoic fold belts. Oligocene to Recent age volcanic rocks and associated mantle xenoliths are distributed in three major regions of the rift zone: the Udokan volcanic field in the northeast, the Vitim volcanic field -200 km southeast of Lake Baikal, and a broad zone of volcanism to the southwest of Lake Baikal. This large-scale study investigates the geochemical evolution of the Baikal Rift Zone volcanism using major element, trace element, and isotopic (Sr, Nd, and Pb) geochemistry, as well as 40Ar/39Ar geochronology. In addition, a detailed isotopic study of megacrysts provides insight into the relationship between megacrysts and host lavas and the nature of the lithospheric mantle. Results of this study suggest that the source region for Baikal Rift Zone volcanic rocks is remarkably homogeneous considering the large region and time span over which these rocks erupted, and that crustal contamination has not been a significant controlling factor. The Tunka Basin, Oka Plateau, and Tuva volcanic fields in the western Baikal Rift Zone, and the Vitim volcanic field southeast of Lake Baikal, have a fairly restricted compositional range from basaltic andesite, alkaline basalt and hawaiite, to basanite and mugearite. In the Udokan volcanic field in the northeast, a more evolved series of rocks ranging to trachytic compositions erupted across the suture between the Archean craton and Paleozoic fold belts. Major and trace elements indicate that fractional crystallization of pyroxene, olivine, and plagioclase produced the observed range in compositions. The trace element and isotopic compositions of Baikal Rift Zone volcanic rocks are comparable to those observed in ocean island basalts. The Sr, Nd, and Pb isotope systematics can best be explained by mixing between the end-member mantle components DMM ( typical of the depleted source of MORB mantle) and EMI (enriched mantle type 1). Megacrysts of clinopyroxene, amphibole, garnet, biotite, and anorthoclase mirror the isotope systematics of the host volcanic rocks, and suggest that the megacrysts were derived from a melt closely related to their host rocks. Furthermore, megacrysts of clinopyroxene, as well as Cr-diopside from spinel lherzolites, have an unradiogenic Pb isotopic composition that may be representative of the EMI-like composition of the subcontinental lithospheric mantle.
by Nancy Ruth Harris.
Ph.D.
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32

Sarlus, Zimer. "Geochemical and geochronological constraints on 1.88 and 1.80 Ga magmatic events in the Gällivare area, northern Sweden." Licentiate thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25689.

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The Gällivare area is situated in northern Norrbotten, Sweden, and hosts the Aitik Cu-Au deposit and the Malmberget Fe deposit. In addition, more than 17 mineral prospects and mineralizations are present, among these the currently developed Nautanen Cu-Au deposit. All deposits are hosted within Paleoproterozoic volcanic and volcano-sedimentary successions intruded and surrounded by multiple generations of intrusive suites, including large bodies of ultramafic to mafic layered complexes. Detailed field mapping combined with geochemical and petrological investigations and geochronology have revealed suites of igneous rocks ranging in composition from ultramafic-mafic, intermediate to felsic. Main key igneous rocks include 1) tholeiitic, ultramafic-mafic layered intrusive complexes; 2) calc-alkaline mafic to intermediate plutonic and volcanic units; 3) calc-alkaline, mafic-intermediate dykes and sills; 4) calc-alkaline and shoshonitic granitoids. U-Pb multigrain zircon SIMS analysis combined with lithogeochemical investigations suggest two magmatic episodes at 1.88 and 1.80 Ga, respectively, with coeval mafic-felsic magmatism including the generation of voluminous layered complexes. Based on their MORB-type, tholeiitic character, these layered complexes are suggested to have formed in an extensional setting, preferentially in a back-arc environment. U-Pb multigrain zircon SIMS analysis and field mapping also reveal that granitoids in the area range from 1886 to 1779 Ma with the oldest granitoids containing mafic enclaves. This suggests magma interaction between basic and felsic magma sources. Geochemical data suggest generation of granitoids in a volcanic arc environment in a mainly post-collisional setting. Results suggest the formation of layered complexes and a volcanic arc system in an extensional setting followed by a subsequent compressional phase of arc accretion producing post-collisional granitoids. The 1.88 Ga event that generated the ultramafic-mafic layered complexes is associated with a back-arc setting generated in response to 1.90 Ga NNE trending subduction. The later event at ~1.80 Ga generating voluminous mafic-felsic units is associated with the TIB event which is also coupled to the regional IOCG overprint.
The Gällivare area is situated in northern Norrbotten, Sweden, and hosts the Aitik Cu-Au deposit and the Malmberget Fe deposit. In addition, more than 17 mineral prospects and mineralizations are present, among these the currently developed Nautanen Cu-Au deposit. All deposits are hosted within Paleoproterozoic volcanic and volcano-sedimentary successions intruded and surrounded by multiple generations of intrusive suites, including large bodies of ultramafic to mafic layered complexes. Detailed field mapping combined with geochemical and petrological investigations and geochronology have revealed the role of intrusive igneous events and their control on ore formation. Main key igneous rocks include 1) tholeiitic, ultramafic-mafic layered intrusive complexes; 2) calc-alkaline mafic to intermediate plutonic and volcanic units; 3) calc-alkaline, mafic-intermediate dykes and sills; 4) calc-alkaline and shoshonitic granitoids. U-Pb multigrain zircon SIMS analysis combined with litho-geochemical investigations suggest two magmatic episodes at 1.88 and 1.80 Ga, respectively, with coeval mafic-felsic magmatism including the generation of voluminous layered complexes. Based on their MORB-type, tholeiitic character, these layered complexes are suggested to have formed in an extensional setting, preferentially in a back-arc environment. U-Pb multigrain zircon SIMS analysis and field mapping also reveal that granitoids in the area range from 1886 to 1779 Ma with the oldest granitoids containing mafic enclaves. This suggests magma interaction between basic and felsic magma sources. Geochemical data suggest generation of granitoids in a volcanic arc environment in a mainly post-collisional setting. Results suggest the formation of layered complexes and a volcanic arc system in an extensional setting followed by a subsequent compressional phase of arc accretion producing post-collisional granitoids. The 1.88 Ga event that generated the ultramafic-mafic layered complexes is is associated with a back-arc setting generated in response to 1.90 Ga NNE trending subduction. The later event at ~1.80 Ga generating voluminous mafic-felsic units is associated with the TIB event also coupled to the regional IOCG overprint.
Godkänd; 2016; 20160518 (zimsar); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Zmar Sarlus Ämne: Malmgeologi /Ore Geology Uppsats: Geochemical and Geochronological Constraints on 1.88 and 1.80 Ga Magmatic Events in the Gällivare Area, Northern Sweden Examinator: Biträdande professor Christina Wanhainen, Institutionen för samhällsbyggnad och naturresurser, Avdelning: Geovetenskap och miljöteknik, Luleå tekniska universitet. Diskutant: PhD Paul Evins, WSP Sverige AB, Stockholm. Tid: Fredag 17 juni, 2016 kl 10.00 Plats: F341, Luleå tekniska universitet
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33

Hawkins, David Paul. "U-Pb geochronological constraints on the tectonic and thermal evolution of paleoproterozoic crust in the Grand Canyon, Arizona." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10588.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.
Includes bibliographical references (p. 214-217).
by David Paul Hawkins.
Ph.D.
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34

Makin, Sean W. "A Geochronological and Thermobarometric Investigation of Eclogites and overlying Hyllestad Schists from the Southern Western Gneiss Complex, Norway." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/83006.

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This thesis produced new pressure–temperature–time constraints on the 4D evolution of the southern Western Gneiss Complex (WGC) and overlying rocks, confirming that the Nordfjord–Sogn detachment (NSD) played a key role in developing their present-day positions. This coupled with data from further north lending weight to the WGC exhuming from flat-slab conditions. Recognition of large amounts of mechanical heating surrounding the NSD was key, with potential implications to large-scale crustal structures.
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35

Bertrand, Audrey [Verfasser]. "Exhuming the core of collisional orogens, the Tauern Window, (Eastern-Alps) : A geochronological, modelling and structural study / Audrey Bertrand." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1047579405/34.

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36

Bartz, Melanie [Verfasser], Helmut [Gutachter] Brückner, and Olaf [Gutachter] Bubenzer. "Quaternary fluvial environments in NE Morocco inferred from geochronological and sedimentological investigations / Melanie Bartz ; Gutachter: Helmut Brückner, Olaf Bubenzer." Köln : Universitäts- und Stadtbibliothek Köln, 2017. http://d-nb.info/1151298247/34.

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37

Friedrich, Anke Maria. "⁴⁰Ar/³⁹Ar and U-Pb geochronological constraints on the thermal and tectonic evolution of the Connemara Caledonides, Western Ireland." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/58264.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998.
Includes bibliographical references.
The Connemara region of the Irish Caledonides is a classical example of a regional-scale high-temperature metamorphic terrain. Its formation was related to intrusion of a compressional continental magmatic arc, for which a protracted thermal evolution was inferred based on a >75 Ma spread in U-Pb, Rb-Sr, and K-Ar mineral dates. Such a history is inconsistent with field observations which suggest a simple relationship between metamorphism and syntectonic magmatism. This study was designed to explore the significance of the large spread in apparent ages using higher resolution U-Pb and 40Ar/ 39Ar geochronometers. The results indicate that arc magmatism, sillimanite-grade metamorphism, anatexis, and late fluid infiltration spanned only about 12 million years. Cooling following the metamorphic peak was actually relatively rapid at 35*C/Ma until about 460 Ma, then 214*C/Ma until 450 Ma. Regional differences in 40Ar/ 39Ar cooling ages of >15 Ma are related to spatial and temporal variations in magmatism, metamorphism, and deformation, rather than differential unroofing of the orogen. 40Ar/ 39Ar dates older than the onset of magmatism or younger than a regional Silurian unconformity represent the combined effects of excess 40Ar contamination, metasomatism, thermal resetting or alteration related to post-orogenic pluton emplacement. This study shows that geochronologic data must be evaluated in the context of careful field mapping, structural and petrologic analysis. Geochronological data from Connemara suggest that arc magmatism related to the Grampian orogeny in this region spanned a brief interval between 475 and 462 Ma and was followed by rapid cooling. The oldest recognized Grampian processes included high P/T metamorphism, followed by intrusion of the Connemara Gabbros into Dalradian metasedimentary rocks, regional-scale ductile deformation, and sillimanite-grade metamorphism between 474.5 and 470.1 Ma. Voluminous -467 Ma quartz diorites only intruded in southern Connemara associated with more localized deformation, anatexis and metasomatism between 468 and 462 Ma. Intrusion of the 462.5 Ma Oughterard Granite marks the end of arc magmatism and contractional deformation at Connemara. The compressional continental magmatic arc at Connemara (the Grampian orogeny) was coeval with continental arc magmatism in Scotland and Newfoundland, and postdates ophiolite formation and obduction along strike in the Appalachian- Caledonian orogen.
by Anke Maria Friedrich.
Ph.D.
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38

Restrepo, Pedro Alonso. "Late Precambrian to Early Mesozoic tectonic evolution of the Colombian Andes, based on new geochronological geochemical and isotopic data." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187450.

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⁴⁰Ar/³⁹Ar and U/Pb geochronology of the basement rocks in the Colombian Andes confirm the presence of the Grenvillian age high metamorphic grade belt . The Grenvillian, or locally known as Nickerie-Orinoquiense orogenic belt, is exposed within basements uplifts along the Eastern Cordillera of Colombia and the Sierra Nevada of Santa Marta in the Caribbean coast. Rare Earth element geochemistry and petrology indicate that the Nickerie-Orinoquiense basement rock's protoliths are dominantly of continental affinity, now consisting mainly of metapsammites, metavolcanics and metaplutonic rocks metamorphosed to granulite facies PT conditions. Nd crustal residence ages and U/Pb zircon data indicate variable involvement of 'older' Late Archean - Early Proterozoic components and 'younger' ~ 1.1 Ga additions, which were tectonically mixed during the Nickerie-Orinoquian collisional metamorphic episode. Low metamorphic grade rocks that overlie the Nickerie-Orinoquian basement are exposed along the Eastern Cordillera of Colombia at the Quetame-Floresta-Santander massifs, Périja Range and Merida Andes. A U/Pb zircon age obtained from a synkinematic pluton structurally concordant with the low metamorphic grade belt from the Santander Massif, yielded a 477 ± 16 Ma, indicating a Mid-Ordovician regional greenschist to amphibolite facies metamorphic event for these rocks. The latter is referred-to as the 'Caparonensis Orogeny' in the Venezuelan Andes. Rare Earth Element geochemistry and petrologic data indicate that the low metamorphic grade belt consists of a thick supracrustal sequence i.e. metapelitic-metapsammitic sequence with minor crosscutting mafic dikes. Additional trace element discrimination plots indicate that the Caparonensis synkinematic plutons are of continental arc affinity. ⁴⁰Ar/ ³⁹Ar geochronology, petrology and field observations in Santander Massif, indicate a widespread regional metamorphic overprint took place in Late Triassic-Early Jurassic time. This event was the result of a thermal welt associated with back-arc extension and concomitant intrusion of a high volume of calk-alkalic plutons. Deposition of a thick molassic sequence (2000-4000 m) followed, flanking the uplifted region. The lower Paleozoic metamorphic rocks were elevated from greenschist to sillimanite (locally kyanite) PT metamorphic conditions and the Mid-Upper Paleozoic sedimentary cover was locally metamorphosed from greenschist to lower PT metamorphic conditions, as a function of relative distance to the plutonic centers at time of metamorphism.
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Maguire, Henry C. "Application Of Geophysical And Geochronological Methods To Sedimentologic And Stratigraphic Problems In The Lower Cambrian Monkton Formation: Northwestern Vermont." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/938.

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The Monkton Formation of the western shelf stratigraphic sequence in Vermont (VT) is identified as a Lower Cambrian regressive sandstone unit containing parasequences recording tidal flat progradation. Previous workers identified cycles believed to represent parasequences in a portion of a 1034' deep geothermal well drilled at Champlain College in Burlington, Vermont. For this study, both outcrop and well geophysical surveys were completed to better identify gamma emission curves and relative values for parasequences and select lithologies that are indicators of bathymetry and sea level. After using physical stratigraphic techniques to assemble a composite stratigraphic section for the Monkton Formation, analysis of the gamma emission curve and relative gamma values resulted in the identification and characterization of parasequences and select lithologies within the Monkton. Interpretation of bathymetry-sensitive lithologies along with parasequence architecture and thickness trends reveals three distinctive intervals over the thickness of the Monkton. It is recognized that the succession of these intervals represents an overall decreasing rate in accommodation space generation through Monkton deposition. Previous workers have suggested that biostratigraphic relationships of the Monkton Formation to the Potsdam Group in New York (NY) suggest that that they would be at least partially correlative. To further refine age relationships and constrain and compare the provenance of the Vermont stratigraphy locally and regionally, zircon samples were collected from the Monkton and the overlying Danby Formations and radiometric age determinations were completed by laser ablation–inductively coupled plasma mass spectrometry (LA-ICPMS) at University of Arizona Laserchron Center. Zircon age probability distribution curves show two dominate age peaks between 1.05-1.09 Ga and 1.15-1.18 Ga for the Monkton and Danby suggesting either a continuity of provenance through the Cambrian or the cycling of the Monkton's sand. The 1.05-1.09 Ga age range corresponds to rocks generated during the Ottawan Orogeny while the 1.15-1.18 Ga range is associated with the Shawinigan Orogeny and anorthosite-mangerite-charnockite-granite (AMCG) plutonism. Dominant age peaks in the Vermont samples between 1.15-1.18 Ga are similar to the 1.16 Ga age peak reported by other workers from the Altona and Ausable Formations of the Potsdam Group of New York. The shared dominant age peak and close proximity of the Vermont and New York stratigraphy may suggest a primarily shared provenance.
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40

Tam, Evan. "Geochronological Constraints On The Timing Of Deformation: An Examination Of The Prospect Rock Fault Footwall In North-Central Vermont." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/940.

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The Prospect Rock Fault (PRF) is key to our understanding of the regional tectonic evolution of Vermont during the Taconic, Salinic, and Acadian Orogenies, and may have played an important role in the exhumation of blueschist and eclogite-facies rocks in the Tillotson Peak Complex (TPC) during the Taconic Orogeny. The TPC is in the footwall of the PRF in the eastern limb of the Green Mountain Anticlinorium. In the TPC, the dominant foliation is S2 and E-W trending F2 folds parallel L2 stretching lineations, which trend orthogonal to regional N-S trending folds associated with the Taconic Orogeny. The PRF itself is folded by F2 folds. Presently, there is a lack of consensus about the role of the PRF in the exhumation of the TPC, and studies have not reconciled the formation of the E-W folds and lineations to a regional model. Oriented samples and structural data were collected from the footwall of the PRF over several transects. Samples were processed into orthogonal thin sections for microstructural analyses and for 40Ar/39Ar step heating of white mica. The dominant foliations in the PRF samples were identified through microstructural analysis and correlating the age of deformation as S2 and S3. These were defined in thin section by mica and quartz microlithons, and oriented mica grains. S1, and in some samples S2, are locally preserved in some mica domains and albite/garnet inclusion trails. S4 appears as crenulations of S3, with no significant new mineral crystallization. In the field, L2 and L3 lineations are defined by mineral and quartz rods, and L4 lineations are defined as intersection lineations on S2 surfaces. 40Ar/39Ar analyses yielded plateau ages ranging from 458.6 ± 2.0 Ma to 419.0 ± 2.4 Ma (1σ). The oldest plateau ages are just slightly younger, yet concordant, with published and new 40Ar/39Ar ages from the TPC and come from the structurally highest portions of the footwall in the northern part of the study area. Virtually all apparent age spectra show age gradients. Results from this study suggest the PRF played a role in exhumation of the TPC and ages obtained are closely aligned with deformation ages constrained from 40Ar/39Ar dating in southern Quebec for the Taconic D2 and Salinian D3 deformation. These dates may aid correlatation of ages and structures regionally and further refining of tectonostratigraphic models describing southern Quebec and New England.
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41

Atkins, M. "A geochemical and geochronological study of U and Th radioisotopes in paleosols, loess and tephra : A Middle-Rhine case study." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370805.

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42

Akciz, Sinan Osman 1974. "Structure and geochronological constraints on the ductile deformation observed along the Gaoligong Shan and Chong Shan Shear Zones, Yunnan (China)." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30289.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, September 2004.
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Includes bibliographical references.
The mechanism by which the Cenozoic post-collisional northward motion of India relative to Eurasia and South China was accommodated along its eastern boundary is still a poorly understood aspect of the tectonic evolution of SE Asia. This thesis focuses on a critically important area within the India-Eurasia collision zone, a region known as the Three Rivers area, and presents the first structural and geochronological data from several transects across two poorly documented linear metamorphic belts located in between the Sagaing fault and the Ailao Shan Shear Zone: the Gaoligong Shan Shear Zone (GSSZ) and the Chong Shan Shear Zone (CSSZ) in Yunnan, China. The presently inactive GSSZ is an important dextral Cenozoic (and possibly latest Mesozoic) ductile shear zone and appears to be the only right-lateral shear zone with the appropriate orientation to accommodate major pre- ca. 11 Ma northward movement of India relative to Eurasia. The previously unknown CSSZ is a long (>300 km) and wide (10- 20 km) metamorphic belt containing an assemblage low- to high-grade rocks from possibly several tectonic units which contain a prominent sub-vertical foliation and a sub-horizontal stretching lineation. Preliminary U/Pb results indicate that the ductile dextral shearing terminated by -18 Ma. Our regional map compilations indicate that the GSSZ and its proposed conjugate, the ASSZ, likely terminate within the Bangong Co-Nujiang suture zone.
(cont.) This thesis documents the dextral GSSZ as the conjugate pair to the sinistral ASSZ, and thus constrains the limits of the crustal fragments that extruded to the southeast. Based on our reinterpretations of the geological maps of Tibet and the Three Rivers area, however, we propose that the extruded crustal material originated east of the easternmost corner of the Indian indentor, and did not create space for the penetration of India;. while at least limited extrusion did occur, there is no compelling geological evidence to indicate large-scale eastward movement of crustal material from directly north of the India indentor. Data presented in this thesis also indicate that extruded region was dismembered into at least two major crustal fragments, separated by the CSSZ.
by Sinan Osman Akciz.
Ph.D.
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43

Baldwin, Julia A. (Julia Ann) 1974. "Petrological and geochronological constraints on the metamorphic evolution of high-pressure granulites and eclogites of the Snowbird tectonic zone, Canada." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30126.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2003.
Includes bibliographical references.
This thesis examines the petrology and geochronology of high-pressure granulites and eclogites within the Snowbird tectonic zone of the western Canadian Shield. The focus of this study is the East Athabasca mylonite triangle (EAmt), a well-exposed terrane of granulite facies mylonitic rocks along the trace of the Snowbird tectonic zone in northern Saskatchewan. This study focuses on the 400 km² Southern Domain of the EAmt, which contains a spectacular suite of high- pressure granulites and eclogites that have been metamorphosed at conditions exceeding 1.5 GPa and 1000⁰C. Each chapter of this thesis focuses on a different lithology within the Southern Domain - mafic granulite, eclogite, sapphirine granulite, and felsic granulite. The approach that is taken in understanding each of these rock types is an integrated study of the petrological and geochronological constraints that yield important information about the metamorphic evolution of these unique rocks. The main discovery through these integrated studies is that the Snowbird tectonic zone records a significant Paleoproterozoic high-pressure metamorphism that was previously unrecognized. Petrological and geochronological studies of each of these rock types constrains the pressure-temperature-time path of these rocks from their initial formation to their ultimate exhumation. The granulites and eclogites of the Southern Domain are derived from Archean igneous and sedimentary protoliths.
(cont.) The dominant rock type of the Southern Domain, the felsic gneiss, is interpreted to be derived from a pelitic protolith that underwent an early metamorphism at 2.62- 2.60 Ga. Protoliths of the mafic lithologies intruded at mid-crustal levels by 2.55-2.52 Ga. The eclogite protolith was derived from a plagioclase-bearing cumulate source at pressures <1.0 GPa. The eclogite and mafic granulite, and, to a lesser extent, the felsic gneiss record high-pressure metamorphism at 1.9 Ga. Near-isothermal decompression P-T paths in the mafic granulite and eclogite record rapid exhumation to medium-pressure granulite facies conditions of [approx.]1.0 GPa, 800⁰C. Sapphirine-bearing veins within the eclogite record further decompression, cooling, and re-equilibration in the middle crust at [approx.]0.6 GPa, 600-700⁰C. Final exhumation of these rocks occurred by more protracted erosional processes from 1.9 to 1.8 Ga.
by Julia A. Baldwin.
Ph.D.
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44

Grant, Steven Lloyd. "Geochemical, radiogenic tracer isotopic, and U-Pb geochronological studies of Yukon Tanana terrane rocks from the Money klippe, southeastern Yukon, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq22600.pdf.

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45

Swain, Greg Martin. "Provenance and tectonics of the late Archaean mulgathing complex, central Gawler Craton : geochronological, geochemical and isotopic evidence for plume-arc interaction /." Title page, table of contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SB/09sbs9715.pdf.

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46

Freeman, Hamish Stewart Rees. "A geochemical and isotopic study of mafic and intermediate rocks in the Oleary province, South Australia-Magma series discrimination and geochronological framework /." Title page, abstract and contents only, 1995. http://web4.library.adelaide.edu.au/theses/09SB/09sbf8553.pdf.

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47

Sindern, Sven [Verfasser]. "Mineralogical, geochemical and geochronological studies in the Uralides and Variscides : contributions to the understanding of dynamic processes in collisional orogens / Sven Sindern." Aachen : Universitätsbibliothek der RWTH Aachen, 2014. http://d-nb.info/1133201571/34.

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48

Ordóñez, Casado Berta. "Geochronological studies of the pre-Mesozoic basement of the Iberian Massif : the Ossa Morena zone and the Allochthonous Complexes within the Central Iberian zone /." Zürich, 1998. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12940.

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49

Tseng, Chia-Han [Verfasser]. "The tablelands in the Puli Basin (central Taiwan) : a geochronological and geomorphological approach to Late Quaternary fluvial sedimentary and erosional processes / Chia-Han Tseng." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1052530834/34.

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50

Evuk, David [Verfasser], and Gerhard [Akademischer Betreuer] Franz. "Geodynamic evolution of the central-eastern Bayuda Desert Basement, Sudan : structural, petrological, geochemical and geochronological investigations / David Evuk. Gutachter: Gerhard Franz. Betreuer: Gerhard Franz." Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1065665210/34.

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