Dissertations / Theses on the topic 'Stratigraphie – Iran'
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Hemmati, Soheil. "Stratigraphy and bio-event studies of the Guadalupian - Lopingian boundary in the northern margin of Sanandaj-Sirjan Zone, Central Iran and North-West of Iran." Electronic Thesis or Diss., Sorbonne université, 2024. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2024SORUS011.pdf.
Full textThe position of the Guadalupian-Lopingian Boundary (GLB) has long been a subject of contention among researchers. Among the numerous sections investigated, three specific regions Julfa (Ali-Bashi section), Tabas (Bagh-e-Vang section), and Abadeh (Baghuk section) have been chosen for focused study in this project. The Ali-Bashi section where sampling and an extensive collection of over 240 rock samples from a measured thickness of 189 meters and in the Bagh-e-Vang section a meticulous effort resulted in the collection of more than 160 rock samples from an outcrop measuring 200 meters in thickness in the Jamal Formation. Sampling the Baghuk section, encountered specific obstacles that impeded our progress including: climatic conditions, economic crisis in Iran and covid-19 pandemic. High-detailed lithostratigraphical investigation of the Khachik Formation in the Ali-Bashi section, led to identified 14 distinct rock units within the three main members. This discovery has the potential to stimulate the creation of a new lithostratigraphic inventory for these sequences, which can be aligned with the existing background research on the Khachik Formation in this particular section. Furthermore, in the Bagh-e-Vang section, 10 rock units from Jamal Formation strata's belonging to the three members have also been identified. Moreover, Various extraction methods, including CH₂O₂, CH₃COOH, hot acetolysis, and HF protocols, were evaluated for the isolation of microfossils. After extensive preparation efforts and carefully crafted protocol intended for conodont element identification, applying both the CH₂O₂ and CH₃COOH techniques, in the Ali-Bashi and the Bagh-e-Vang sections were not achieved any conodonts. Three other methods were tested for ostracod extraction from Ali-Bashi section samples. The samples were prepared with cold 10% formic acid (CH₂O₂) and 15% acetic acid (CH₃COOH). The CH₂O₂ protocol was productive with well-preserved ostracods, allowed us to determine ten taxa were obtained exclusively through the diluted CH₂O₂ protocol from the hard dolomitized limestones, while the other cold CH₃COOH procedures were unsuccessful. The application of the hot acetolysis protocol proved successful in extracting a significant quantity of excellently preserved ostracods, leading to the identification of a total of 56 species. Despite our unwavering commitment to the recommended protocol applied the HF technique in the processing of 12 cherty samples obtained from the Ali-Bashi and Bagh-e-Vang sections yielded a disheartening outcome for the radiolarian microfossils. Microfacies analysis in the Ali-Bashi section led to identified 28 sub-microfacies which, derived with 15 distinct microfacies. The assemblage of microfacies groups are, ranging from MKL1 to MKL2 (lagoonal environment), MKR2 to MKR3 (restricted), MKO1 to MKO4 (open-marine) of the inner ramp zone. The MKO1 to MKO4, suggests a confined setting, occurring in the final part of the inner ramp under an open marine environment. Microfacies groups MKM1 to MKM3 are inferred to have been deposited in open marine environment, within the mid-ramp zones, whereas MKT1 to MKT3 were identified in the basal parts of the outer ramp, corresponding to the lower part of the slope within the carbonate shelf setting. Additionally, adhering to the standard microfacies designated by Flugel (2010), the study proposes 10 microfacies of the RMF type, along with their corresponding 4 SMFs for the studied strata. Besides, based on the standard facies zones (FZ) introduced by Wilson (1975), three FZs exhibiting a shallowing-upward trend, namely FZ8, FZ7, and FZ3, have been successfully delineated
Taati, Qorayem Farid. "Stratigraphie séquentielle de systèmes carbonates dans un contexte tectonique actif : le groupe de Bangestan (Albien - Turonien) dans le Zagros (Iran)." Bordeaux 3, 2005. http://www.theses.fr/2005BOR30001.
Full textShahidi, Alireza. "Evolution tectonique du nord de l'Iran (Alborz et Kopet-Dagh) depuis le Mésozoïque." Paris 6, 2008. http://www.theses.fr/2008PA066249.
Full textAsghari, Afshin. "Environnement sédimentaire, stratigraphie séquentielle et paléogéographie du Paléozoique de succession pré-Khuff dans le sud de l'Iran (Zagros et le Golfe Persique)." Thesis, Dijon, 2014. http://www.theses.fr/2014DIJOS058/document.
Full textDuring the Precambrian and trough the Palaeozoic, the Zagros area was part of the Arabian platform (Beydon, 1993). The Palaeozoic succession of the Zagros extends from Cambrian to well-developed Permian deposits. The study area ranges from the Lurestan to Southern Fars onshore and to the Persian Gulf offshore wells. From Ordovician to Early Permian Palaeozoic succession of the Zagros area comprises four second-order tectonostratigraphic depositional cycles separated by major unconformities. Eustatic sea-level variation is the main controlling factor for accommodation space changes, whereas in West High Zagros and Kuh e Gahkum, the role of regional and salt tectonic activities may be also important. The first cycle (Ordovician) is composed of the Seyahou (Floian-Katian) and Dargaz (Hirnantian) Formations. They are characterized by deep- to shallow-water (offshore to shoreface) siliciclastic deposits. The Seyahou Formation contains seven 3rd-order depositional sequences. The glaciogenic Dargaz Formation consists of one 3rd- order sequence. The second cycle (Early Silurian) corresponds to the Sarchahan Formation is composed of two 3rd-order depositional sequences. They are characterized by deep-marine offshore to upper offshore environments. Locally in Kuh e Gahkum the base of the Formation presented continental fan delta deposits due to the salt tectonic activity.The third cycle (Devonian) corresponds to the Zakeen Formation and divided in three 3rd-order depositional sequences. It started with the deposition of continental to near-shore marine clastic deposits. In Late Devonian, it evolved to carbonate marine deposits in the south of Fars area and the Persian Gulf. The lack of Zakeen Formation in Kuh e Surmeh and Kuh e Siah, and is presence in neighboring areas (Naura, Aghar, etc…), suggests structural salt plug activities (Jahani, 2008). This megasequence is capped by a major unconformity related to the Hercynian orogeny.The last deepening-upward cycle of the Pre-khuff succession in the study area is the Early Permian Faraghan Formation. It capped the Hercynian orogeny and deposited throughout the Zagros area from Lurestan (west) to Bandar Abbas (East) areas as well as in Persian Gulf. The Faraghan Formation divided into three 3rd-order depositional sequences and deposited in coastal plain to shallow-marin near-shore environment. Basinward, in the deeper part (e.g. Kuh e Faraghan), they are replaced by marine upper offshore deposits. The Palaeozoic succession is marked by several major unconformities associated with hiatus. They resulted from: (i) major sea level drops at the end of the Ordovician related to the Hirnantian glaciation (Ghavidel Syooki et al., 2011) and of during the Carboniferous related to the southern Hemisphere glaciation (Golonka, 2000); (ii) An uplift of the Middle East area at the end of the Silurian associated with epeirogenic movements (Ala et al., 1980; Berberian and King, 1981; Al-Sharhan and Nairn, 1997) and a major sea level drop at the end of Silurian (Al-Husseini, 1991,1992; Sharland et al., 2001; Konert et al., 2001; Haq and Al-Qahtani, 2005); and (iii) impact of the Hercynian orogeny spanning from the Late Devonian up to the Carboniferous (Al-Hosseini, 1992; Sharland et al., 2001; Konert et al., 2001, Faqira et al., 2009)
Bessenay-Prolonge, Julie. "Au carrefour du plateau iranien et des steppes d'Asie Centrale : Tureng Tépé dans la plaine de Gorgan, des sociétés proto-urbaines aux forteresses de l'âge du Fer : étude strarigraphiques et architecturales menées d'après les archives inédites de la Mission Française à Tureng Tépé." Thesis, Paris 1, 2018. http://www.theses.fr/2018PA01H004.
Full textLocated in the northeast of Iran, at the crossroads of the Iranian plateau and the steppes of Central Asia, the Gorgân plain is, by the nature of its landscapes and climate, a particularly suitable region for human settlements. The site of Tureng Tépé, excavated in the years 1960-1970 by a team of French archaeologists, revealed an occupational sequence of several millennia since Chalcolithic until the modem time. The stratigraphic and architectural study conducted from unpublished documents from the excavation archives, permit us to reconstruct and characterize the oldest occupations of the site, from Chalcolithic to the Iron Age. The archaeological layers discovered in the areas of the Petit Tépé and the Tépé Sud demonstrate continuous occupation from the end of the 4th millennium to the beginning of the 2nd millennium BC. The Middle Bronze Age is marked by the construction of a large monumental brick terrace of which an in-depth architectural analysis has been carried out. In addition, the study of several categories of artifacts clearly shows the existence of long-distance contacts and exchanges between on the one band the plains of Gorgan and Damghan, and on the other hand South Central Asia and Khorasan and to a lesser extent the southeastem regions of the Iranian plateau and Baluchistan. After several centuries of abandonment, Tureng Tépé is reoccupied at the end of the Iron Age II. These occupations, which are clearly distinguishable from those of the Bronze Age, are represented by a succession of fortifications rebuilt several times
Dastanpour, Mohammad. "The Devonian stratigraphy of Kerman, southeast central Iran." Thesis, University of Bristol, 1990. http://hdl.handle.net/1983/5af05e94-ca3e-4e6e-ab46-e6dad2dde86d.
Full textPufahl, Peir Kenneth. "Stratigraphic architecture of a paleoproterozoic iron formation depositional system, the Gunflint, Mesabi and Cuyuna iron ranges." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ33432.pdf.
Full textGapara, Cornwell Sine. "A review of the deposition of iron-formation and genesis of the related iron ore deposits as a guide to exploration for Precambrian iron ore deposits in southern Africa." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005610.
Full textMuller, Katherine Charlotte. "Formation of iron-rimmed sandstone nodules on earth; terrestrial analogue for the formation of Martian blueberries?" Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Muller_2009_09007dcc8071b44c.pdf.
Full textVita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 11, 2009) Includes bibliographical references (p. 85-87).
Wightman, Gregory John. "Studies in the stratigraphy and chronology of iron age II-III in Palestine." Thesis, The University of Sydney, 1985. https://hdl.handle.net/2123/26034.
Full textMüller, Stefan G. "The tectonic evolution and volcanism of the Lower Wyloo Group, Ashburton Province, with timing implications for giant iron-ore deposits of the Hamersley Province, Western Australia /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0043.
Full textBaldwin, Geoffrey James. "THE STRATIGRAPHY AND GEOCHEMISTRY OF THE RAPITAN IRON FORMATION, NORTHWEST TERRITORIES AND YUKON, CANADA." Thesis, Laurentian University of Sudbury, 2014. https://zone.biblio.laurentian.ca/dspace/handle/10219/2194.
Full textZebari, Bahroz Gh A. "Controls on the spatial and temporal evolution and distribution of depositional components in the Paleocene-Lower Eocene Succession, Kurdistan Region-Iraq." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=239281.
Full textPang, Kwan-Nang. "Origin of the permian panzhihua layered gabbroic intrusion and the hosted Fe-Ti-V oxide deposit, Sichuan Province, SW China." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39634000.
Full textDelvigne, Camille. "The Archaean silicon cycle insights from silicon isotopes and Ge/Si ratios in banded iron formations, palaeosols and shales." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209652.
Full textFirst, this study focuses on Si inputs and outputs to ocean over a limited time period (~2.95 Ga Pongola Supergroup, South Africa) through the study of a palaeosol sequence and a contemporaneous banded iron formation. The palaeosol study offers precious clues in the comprehension of Archaean weathering processes and Si transfer from continent to ocean. Desilication and iron leaching were shown to be the major Archaean weathering processes. The occurrence of weathering residues issued of these processes as major component in fine-grained detrital sedimentary mass (shales) attests that identified weathering processes are widely developed and suggest an important dissolved Si flux from continent to the ocean. In parallel, banded iron formations (BIFs), typically characterised by alternation of iron-rich and silica-rich layers, represent an extraordinary record of the ocean-derived silica precipitation throughout the Precambrian. A detailed study of a 2.95 Ga BIF with excellent stratigraphic constraints identifies a seawater reservoir mixed with significant freshwater and very limited amount of high temperature hydrothermal fluids as the parental water mass from which BIFs precipitated. In addition, the export of silicon promoted by the silicon adsorption onto Fe-oxyhydroxides is evidenced. Then, both Si- and Fe-rich layers of BIFs have a common source water mass and a common siliceous ferric oxyhydroxides precursor. Thus, both palaeosols and BIFs highlight the significance of continental inputs to ocean, generally under- estimated or neglected, as well as the close link between Fe and Si cycles.
In a second time, this study explores secular changes in the Si cycle along the Precambrian. During this timespan, the world ocean underwent a progressive decrease in hydrothermal inputs and a long-term cooling. Effects of declining temperature over the oceanic Si cycle are highlighted by increasing δ30Si signatures of both chemically precipitated chert and BIF through time within the 3.8-2.5 Ga time interval. Interestingly, Si isotope compositions of BIF are shown to be kept systematically lighter of about 1.5‰ than contemporaneous cherts suggesting that both depositions occurred through different mechanisms. Along with the progressive increase of δ30Si signature, a decrease in Ge/Si ratios is attributed to a decrease in hydrothermal inputs along with the development of large and widespread desilication during continental weathering.
Le cycle externe du silicium au précambrien (4.5-0.5 Ga) reste mal compris malgré sa position clé dans la compréhension des processus opérant à la surface de la Terre primitive. En l’absence d’organismes sécrétant un squelette externe en silice, le cycle précambrien du silicium était vraisemblablement très différent de celui que nous connaissons à l’heure actuelle. Notre conception de l’océan archéen est limitée à l’hypothèse d’une concentration en silicium proche de la saturation en silice amorphe. Cette thèse vise à une meilleure compréhension des processus qui contrôlaient le cycle géochimique externe du silicium à l’archéen (3.8-2.5 Ga). Dans cette optique, le rapport germanium/silicium (Ge/Si) et les isotopes stables du silicium (δ30Si) représentent des traceurs idéaux pour démêler les différents processus contrôlant le cycle du Si.
Dans un premier temps, cette étude se focalise sur les apports et les exports de silicium à l’océan sur une période de temps restreinte (~2.95 Ga Pongola Supergroup, Afrique du Sud) via l’étude d’un paléosol et d’un dépôt sédimentaire de précipitation chimique quasi-contemporain. L’étude du paléosol apporte de précieux indices quant aux processus d’altération archéens et aux transferts de silicium des continents vers l’océan. Ainsi, la désilicification et le lessivage du fer apparaissent comme des processus majeurs de l’altération archéenne. La présence de résidus issus de ces processus d’altération en tant que composants majeurs de dépôts détritiques (shales) atteste de la globalité de ces processus et suggère des flux significatifs en silicium dissout des continents vers l’océan. En parallèle, les « banded iron formations » (BIFs), caractérisés par une alternance de niveaux riches en fer et en silice, représentent un enregistrement extraordinaire et caractéristique du précambrien de précipitation de silice à partir de l’océan. Une étude détaillée d’un dépôt de BIFs permet d’identifier une contribution importante des eaux douces dans la masse d’eau à partir de laquelle ces roches sont précipitées. Par ailleurs, un mécanisme d’export de silicium via absorption sur des oxyhydroxydes de fer est mis en évidence. Ainsi, les niveaux riches en fer et riche en silice constituant les BIFs auraient une même origine, un réservoir d’eau de mer mélangée avec des eaux douces et une contribution minime de fluides hydrothermaux de haute température, et un même précurseur commun. Dès lors, tant les paléosols que les BIFs mettent en évidence l’importance des apports continentaux à l’océan, souvent négligés ou sous estimés, ainsi que le lien étroit entre les cycles du fer et du silicium.
Dans un second temps, cette étude explore l’évolution du cycle du silicium au cours du précambrien. Durant cette période, l’océan voit les apports hydrothermaux ainsi que sa température diminuer. Dans l’intervalle de temps 3.8-2.5 Ga, les effets de tels changements sur le cycle du silicium sont marqués par un alourdissement progressif des signatures isotopiques des cherts et des BIFs. Le fort parallélisme entre l’évolution temporelle des compositions isotopiques des deux précipités met en évidence leur origine commune, l’océan. Cependant, les compositions isotopiques des BIFs sont systématiquement plus légères d’environ 1.5‰ que les signatures enregistrées pas les cherts. Cette différence est interprétée comme le reflet de mécanismes de dépôts différents. L’alourdissement progressif des compositions isotopiques concomitant à une diminution des rapports Ge/Si reflètent une diminution des apports hydrothermaux ainsi que la mise en place d’une désilicification de plus en plus importante et/ou généralisée lors de l’altération des continents.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Hayes, Dawn Schmidli. "Stratigraphic, Microfossil, and Geochemical Analysis of the Neoproterozoic Uinta Mountain Group, Utah: Evidence fo a Eutrophication Event?" DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/874.
Full textMuller, Stefan G. "The tectonic evolution and volcanism of the Lower Wyloo Group, Ashburton Province, with timing implications for giant iron-ore deposits of the Hamersley Province, Western Australia." University of Western Australia. School of Earth and Geographical Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0043.
Full textZhao, Xinfu. "Paleoproterozoic crustal evolution and Fe-Cu metallogeny of the western Yangtze Block, SW China." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43572261.
Full textSedlacek, Alexa R. C. "Strontium isotope stratigraphy and carbonate sedimentology of the latest Permian to Early Triassic in the western United States, northern Iran and southern China." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372971425.
Full textMacQueen, John Kenneth Carleton University Dissertation Geology. "Stratigraphy, structure and gold mineralization of the No. 5 vein/iron formation zone, Pickle Crow Gold Mines, Pickle Lake, Ontario." Ottawa, 1987.
Find full textAlonazi, Majed Turki F. "A re-evaluation of stratigraphic and ceramic evidence from the Bronze and Iron Age site of al-Ṣināʿiyyah at Tayma in Saudi Arabia." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12809/.
Full textPolteau, Stéphane. "The early proterozoic Makganyene glacial event in South Africa : its implication in sequence stratigraphy interpretations, paleoenvironmental conditions and iron and manganese ore deposition." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1007612.
Full textStone, Michelle Susanne. "Depositional history and mineralisation of tertiary channel iron deposits at Yandi, Eastern Pilbara, Australia." University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0082.
Full textVerdel, Charles Steven Eiler John Eiler John. "I. Cenozoic geology of Iran : an integrated study of extensional tectonics and related volcanism. II. Ediacaran stratigraphy of the North American cordillera : new observations from eastern California and northern Utah /." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-09182008-092505.
Full textGreentree, Matthew Richard. "Tectonostratigraphic analysis of the Proterozoic Kangdian iron oxide - copper province, South-West China." University of Western Australia. Tectonics Special Research Centre, 2007. http://theses.library.uwa.edu.au/adt-WU2009.0054.
Full text彭君能 and Kwan-Nang Pang. "Origin of the permian panzhihua layered gabbroic intrusion and the hosted Fe-Ti-V oxide deposit, Sichuan Province, SW China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39634000.
Full textLand, Jarred. "Genesis of BIF-hosted hematite iron ore deposits in the central part of the Maremane anticline, Northern Cape Province, South Africa." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1020905.
Full textRafuza, Sipesihle. "Carbonate petrography and geochemistry of BIF of the Transvaal supergroup : evaluating the potential of iron carbonates as proxies for palaeoproterozoic ocean chemistry." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018611.
Full textZaina, Federico. "Stratigraphy, chronology and architecture of the earliest phases at kish in Central Mesopotamia : from the Jemdet Nasr to the Ur III period (3100-2000 BC)." Thesis, Paris 1, 2015. http://www.theses.fr/2015PA010706.
Full textThe city of Kiš was one of the most important centersof Mesopotamia between the 4 th and 1st millenium BC The excavations carried out between 1923 and 1933 by the expedition from the University and the Field Museum of Chicago have largely explored the site, but despite significant results, the inadequate methods of excavation have negatively affected the archaeological interpretation produced in publications. The goal of this project is that of contributing to fill these gaps in knowledge, reconstructing archaelogical and historical phases searched to Kiš dating from the period Jemdet Nasr and the Ur III. The first aim was to understand the planning of Kiš between the 4th and the end of the first half of the 2nd millenium BC. To this aim I reconstructed the stratigraphic and architectural contexts discovered in some areas of the site. New sections and plans of each area and a general map of Kiš was produced. These were used as tools to interpret the development of urban and architectural development of Kiš. Beside the analysis of strcutural remains, there has been the study of layered materials. Careful selection of objects keps in deposits and university museums, will be made. In addition, radiocarbon analysis of selected samples was undertaken to provide more information on the site chronology. Finally, the materials were associated with their original context
Zhao, Xinfu, and 赵新福. "Paleoproterozoic crustal evolution and Fe-Cu metallogeny of the western Yangtze Block, SW China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43572261.
Full textFurlong, Pierce James. "Aspects of ancient Near Eastern chronology (c. 1600-700 BC)." Melbourne, 2007. http://repository.unimelb.edu.au/10187/2096.
Full textTaheri, Jafar. "Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian-Late Bathonian Kashafrud Formation, Northeastern Iran." Doctoral thesis, 2009. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-39966.
Full textTaheri, Jafar [Verfasser]. "Stratigraphy, ichnology, and sedimentary environments of the Late Bajocian, Late Bathonian Kashafrud Formation, Northeastern Iran / vorgelegt von Jafar Taheri." 2009. http://d-nb.info/998400831/34.
Full textPecoits, Ernesto. "Ediacaran iron formations and carbonates from Uruguay: palaeoceanographic, palaeoclimatic and palaeobiologic implications." Phd thesis, 2010. http://hdl.handle.net/10048/1296.
Full textQuarles, van Ufford Andrew I. (Andrew Ian) 1967. "Stratigraphy, structural geology, and tectonics of a young forearc-continent collision, western Central Range, Irian Jaya (western New Guinea), Indonesia." Thesis, 1996. http://hdl.handle.net/2152/30179.
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Nel, Brian Philip. "Petrography and geochemistry of iron formations of the Paleoproterozoic Koegas Subgroup, Transvaal Supergroup, Griqualand West, South Africa." Thesis, 2013. http://hdl.handle.net/10210/8762.
Full textNel, B.P. (2013). Petrography and geochemistry of iron formations of the Paleoproterozoic Koegas Subgroup, Transvaal Supergroup, Griqualand West, South Africa. MSc thesis (unpublished), University of Johannesburg, Aucklandpark, pp. 133. The Early Paleoproterozoic Koegas Subgroup comprises a succession of siltstone, mudstone, iron-‐formation, chert and carbonate rocks that overlies the iron-‐formations of the Asbestos Hills Subgroup with sharp contact. It is overlain with erosional unconformable contact by glaciogenic diamictites of the Makaganyene Formation. This study focused on the lithostratigraphy, mineralogy and geochemistry of the iron-‐ formations of the Koegas Subgroup based on fresh diamond drill core samples obtained during the Agouron scientific drilling project in South Africa in 2004. The iron formations the Koegas Subgroup are represented by a few important lithotypes, occurring in distinct sedimentary facies, which formed in unique depositional and diagenetic environments. The iron formations consist essentially of four facies, namely silicate lutite, mixed silicate-‐siderite lutite, siderite lutite and siderite peloidstone A repetitive sedimentary cycle consisting of fine-‐grained chemical lithotypes grading upward into reworked chemical lithotypes is evident throughout the Koegas Subgroup iron formations. Silicate lutite formed in deep water settings well below the wave base along a chemocline. Siderite lutite formed in shallower parts of the basin through transformation of primary ferric iron precipitate by iron respiration in presence of organic carbon. Peloidstone formed above normal wave base in shallow water by reworking of earlier siderite lutite deposits. The REE geochemistry provides important clues as to the depositional environment of the iron formation as follows. Depletion in LREE and enrichment in HREE combined with positive Y are typical of ocean water indicate that the iron formations were deposited in a marine environment. Positive Eu anomaly suggest the presence of a hydrothermal component in the ocean water from which the iron formations were deposited. Negative Ce anomalies indicate that somewhere in the marine system Ce3+ was oxidized to Ce4+ oxide, probably in the presence of free oxygen in the ocean water column (Bau and Dulski, 1996). The negative Ce anomalies seen in the Koegas iron formations are the oldest currently known from iron formations. As such the Ce anomalies most probably signify an increase in the oxygenation state of the ocean immediately prior to the rise of atmospheric oxygen as defined by Guo et al. (2009).
Verdel, Charles Steven. "I. Cenozoic Geology of Iran: An Integrated Study of Extensional Tectonics and Related Vulcanism. II. Ediacaran Stratigraphy of the North American Cordillera: New Observations from Eastern California and Northern Utah." Thesis, 2009. https://thesis.library.caltech.edu/3631/7/Verdel_thesis.pdf.
Full textI. The late Oligocene to Miocene collision of Arabia and Eurasia was preceded by ~175 My of subduction of Neotethyan oceanic crust. Associated magmatic activity includes late Triassic(?) to Jurassic plutons in the Sanandaj-Sirjan zone of southern Iran, limited Cretaceous magmatism in the Alborz Mountains of northern Iran, and widespread Eocene volcanism across central Iran. Metamorphic core complexes of Eocene age have recently been recognized in widely separated parts of Iran, suggesting that Tertiary volcanism was related to extension. Geochemical data indicate that Eocene volcanism was typical of continental arcs and was followed by less voluminous Oligocene basaltic volcanism of the type often associated with back-arc basins. This set of observations suggests that mid-Mesozoic plutons in southern Iran are the remnants of an original volcanic arc that was only weakly developed because of slow subduction rate. Magmatic activity largely ceased in southern and central Iran during the Cretaceous and shifted to the north, suggesting a period of flat slab subduction. Subsequent slab-rollback during the Eocene extended the overriding plate, forming metamorphic core complexes and inducing pressure-release melting of partially hydrated lithospheric mantle and upwelling of asthenosphere.
II. The Ediacaran Period spans from the base of cap carbonates overlying glacial deposits of the Marinoan “Snowball Earth” event to the Precambrian-Cambrian boundary, ~635 to 542 Ma. Sediments deposited during the rifting of southwest Laurentia, which are now exposed in a relatively narrow belt in the western US, are one of the best records on earth of the geological, geochemical, and geobiological events that occurred during this period. Evidence for one of the most significant of these, the final oxygenation of the oceans, is found within the upper Johnnie Formation in the southern Great Basin. C isotope data from thick, basinal facies of the Johnnie Fm. in the Panamint Range provide a more complete record of ocean chemistry associated with this event than previously determined from thinner, platformal facies. Strata in northern Utah of roughly the same age include a rift-related basalt, providing some of the youngest geologic evidence for the rifting of western Laurentia.
"Stratigraphy, petrology, and geochemistry of the North Touak-Cape Dyer volcanic belt, and implications for the tectonic setting of the Paleoproterozoic Hoare Bay group, eastern Baffin Island." Thesis, 2012. http://hdl.handle.net/10388/ETD-2012-09-787.
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