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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Geochemical Provenance of Clastic Sedimentary Rocks in the Western Cordillera: Utah, Colorado, Wyoming, and Oregon.

Peterson, John Aaron 01 May 2009 (has links)
Sedimentary rocks are an important source of information about previous orogenic conditions and the composition of which may describe the evolution of provenance and tectonic setting. Many factors influence sediment composition, namely, source rock composition, chemical weathering, climate, transport burial, and diagenesis. As the sediment composition changes through time, the geochemical characteristics of the sediment can be used to understand its geologic history. The geochemical characteristics of clastic sedimentary rocks are useful in determining the depositional setting and its associated provenance. Although many different studies have used geochemical discriminants to evaluate provenance and tectonic settings, none have used a defined geochemical method. This study evaluates the present-day geochemical approaches to see which, if any, are the most useful.
32

The Dynamics of the Late Neogene Antarctic Ice Sheets in the Central Ross Sea using a Multianalytical Approach

Mallery, Christopher Wallace 06 1900 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / With the goal of determining ice sheet history in the central Ross Sea since the late Miocene, the provenance of glacial till from IODP expedition 374 site U1522 was assessed using a suite of three analyses. A total of 3,869 zircons, between 250-63 microns in size, from sixteen different cores were measured for U-Pb isotopes via LA-ICP-MS. Zircon data was compared to neodymium isotope and clast lithology datasets from collaborators. Site U1522 shows three distinct provenance shifts from the late Miocene to the Pleistocene, two of which are coincident with Ross Sea Unconformities three and two. Late Miocene samples have abundant Cretaceous zircon populations, radiogenic neodymium values, and clasts interpreted as having a West Antarctic provenance. In latest Miocene samples, zircons are mostly Ross Orogeny age (c. 470 615 Ma) and Cretaceous zircon grains are almost absent, neodymium values are relatively un radiogenic, and dolerite clasts are present signaling a shift to East Antarctic derived ice. Above Ross Sea Unconformity 3, early to mid Pliocene samples show a shift back to West Antarctic provenance with abundant Cretaceous zircons and more radiogenic neodymium values. Late Pliocene to Pleistocene samples, deposited above Ross Sea Unconformity 2, reflect dominant East Antarctic provenance with few Cretaceous zircon dates, relatively un radiogenic neodymium values, and the presence of dolerite clasts. These data are broadly in agreement with ice sheet interpretations suggested by clast analysis from ANDRILL site AND-1B. Permo-Triassic zircon dates suggest the presence of unexposed bedrock of this age beneath the West Antarctic Ice Sheet based on their association with Cretaceous dates that have not been reported from East Antarctica. The zircon dataset also reveals two late Miocene intervals with a previously undocumented Eocene Oligocene magmatic event ~30 40 Ma. The coexistence of Cretaceous dates in these intervals suggests a likely West Antarctic source. The absence of Eocene Oligocene zircons in subsequent Plio Pleistocene sediments may be explained by substantial erosion and offshore deposition of the West Antarctic interior, including volcanic edifices following the Middle Miocene Climatic Transition.
33

Early prehistoric petrology: A case study from Leicestershire.

Parker, Matthew J. January 2013 (has links)
This research focused on the petrographic analysis of prehistoric ceramics within the East Midlands. Prior assessments have been intermittent and not drawn together by a research-based agenda, with a few notable exceptions. This research uses petrographic analysis to shed light on early prehistoric society within Leicestershire, a county overlooked in comparison to other regions. The aim of this research was to investigate the procurement of raw materials and the subsequent production of Neolithic and early Bronze Age ceramics in Leicestershire, placing the county in its regional context. Petrographic slides from several early prehistoric sites were produced and analysed to determine the presence of any non-local material within the fabric of the ceramics. Existing petrographic data from other sites in the East Midlands were used as a comparative data set to test whether the ceramics from Leicestershire were typical or atypical of the wider production and procurement pattern. The results of the petrographic analysis on the Leicestershire sites indicated that the clay and inclusions were most likely of local origin, with no definitive evidence for non-local inclusions. However, the results from the comparative petrographic data obtained from sites within the wider East Midlands does support the movement of raw materials and/or finished ceramic products within the region. Preferential sources appear to have been continually exploited, both chronologically and geographically. The prime target of the exploitation was the Charnwood Forest area of Leicestershire, with groups from Derbyshire and Nottinghamshire utilising this resource in addition to more local groups within Leicestershire.
34

Semantic construction with provenance for model configurations in scientific workflows

Thakur, Amritanshu 13 December 2008 (has links)
In the computationally intensive and diverse scientific environment of geosciences, substantial volumes of data are generated by specialized complex processing systems called ‘models’. These datasets contain little knowledge of their processing. Therefore a high degree of domain expertise is required to interpret, regenerate and tweak their production. Provenance is described as a general ability to record and evolve information related to the creation of data. We extend this idea further by proposing a mechanism by which a model’s setup and its domain semantics are integrated with the data it produces. This creates a scope for controlling model executions using their respective setups or ‘configurations’. In this work we created an application neutral framework which can be applied to models of a similar class in geosciences. Our objective is to allow scientists to share their experiments with anyone having an interest in it while allowing for formally controlled and extensible customizations.
35

Central Arctic Lithostratigraphy: Implication for Sediment Transport and Paleoceanography

Council, Edward Augustus, III 08 October 2012 (has links)
No description available.
36

Utilisation des isotopes stables (HOCN) et radiogéniques (SR) comme indicateurs pour déterminer la provenance des fromages fins du Québec, Canada

L. Desrochers, Stéphanie 11 1900 (has links) (PDF)
La mondialisation des marchés alimentaires ainsi que la facilité avec laquelle les produits sont transportés à travers et entre les pays, a pour impact que les consommateurs sont de plus en plus préoccupés par l'origine des aliments qu'ils consomment. Ainsi, un nombre croissant d'articles scientifiques ont été publiés au cours de cinq dernières années concernant l'utilisation de l'abondance naturellement variable des isotopes comme traceurs pour déterminer la provenance géographique des aliments. Le fromage fait partie des aliments qu'il est possible de retracer grâce à ces méthodes. Le concept de terroir est la combinaison des influences climatiques (isotopes stables), géologique (isotope Sr) et anthropogéniques (producteur de fromage) qui donnent un caractère (goût) particulier à un produit tel que le fromage. L'objectif premier de cette recherche est de vérifier la faisabilité d'une méthode permettant de déterminer la provenance géographique des fromages fins du Québec en utilisant les isotopes stables (H, O, C, N) et le strontium comme indicateur du climat et de provenance géologique afin de renforcer l'utilisation du concept de terroir pour les producteurs locaux. Six fromageries artisanales provenant de différentes régions du Québec ont été échantillonnées pour des fromages de vache et de chèvre. Grâce aux résultats obtenus, nous sommes en mesure de démontrer qu'il est possible de retracer les fromages québécois à l'aide d'isotopes stables et radiogéniques. L'oxygène et l'hydrogène nous permettent de différencier les différents milieux climatiques, mais dû aux variabilités saisonnières, il nous est impossible de distinguer les fromageries sur une plus petite échelle. Par contre, lorsque nous utilisons les compositions isotopiques du strontium combiné avec celles de l'oxygène, nous sommes en mesure de distinguer les fromageries appartenant au même milieu climatique jusqu'à l'échelle locale. D'autre part, le carbone et l'azote nous permettent de différencier si une fromagerie utilise des techniques de fertilisation différentes des autres ou si une fromagerie donne une alimentation particulière à ses animaux. Nous nous sommes finalement servis de ces conclusions afin de faire la distinction entre les fromages commerciaux et internationaux fournissant ainsi aux producteurs locaux du Québec des outils leur permettant de certifier la provenance de leurs fromages et de renforcer l'appellation du terroir québécois. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Fromage, Fromagerie, Isotopes stables, Isotopes radiogéniques, Hydrogène, Oxygène, Carbone, Azote, Strontium, Retraçage géographique, Terroir québécois.
37

Provenance et Qualité dans les Workflows Orientés Données : application à la plateforme WebLab / Provenance and Quality in Data Oriented Workflows : application to the WebLab Platform

Caron, Clément 03 November 2015 (has links)
La plateforme Weblab est un environnement de définition et d’exécution de chaines de traitements média-mining développé par le service IPCC1 d’Airbus Defence and Space. Il s’agit d’une plateforme ouverte d’intégration de composants externes dont la richesse permet aux concepteurs de construire des chaines média-mining très complexes, mais pose également des problèmes liés à la sensibilité de la qualité des résultats par rapport aux composants utilisés. Avant le début de cette thèse, aucun outil n’existait pour l’analyse et l’amélioration de la qualité de workflows WebLab. La problématique principale de la thèse repose sur le fonctionnement dit boite noire des services WebLab. L’approche choisie est non-intrusive : nous complétons la définition du workflow WebLab par des règles de provenance et de propagation de qualité. Les règles de provenance génèrent des liens de dépendance dit grains-fins entre les données et les services après l’exécution d’une chaine de traitements WebLab. Les règles de propagation de qualité profitent des liens inférés précédemment pour raisonner sur l’influence de la qualité d’une donnée utilisée par un service sur la qualité d’une donnée produite... / The WebLab platform is an application used to define and execute media-mining workflows. It is an open source platform, developed by the IPCC1 section of Airbus Defence and Space, for the integration of external components. A designer can create complex media-mining workflows using components, whose operation is not always known (black-boxes services). These complex workflows can lead to a problem of data quality, however, and before this work, no tool existed to analyse and improve the quality of WebLab workflows. To deal with black-box services, we choose to tackle this quality problem with a non-intrusive approach: we enhance the definition of the WebLab workflow with provenance and quality propagation rules. Provenance rules generate fine-grained data dependency links between data and services after the execution of a WebLab workflow. Then the quality propagation rules use these links to reason on the influence that the quality of the data used by a component has on the quality of the output data…
38

Designing scientific workflow following a structure and provenance-aware strategy / Conception de workflows scientifiques fondée sur la structure et la provenance

Chen, Jiuqiang 11 October 2013 (has links)
Les expériences bioinformatiques sont généralement effectuées à l'aide de workflows scientifiques dans lesquels les tâches sont enchaînées les unes aux autres pour former des structures de graphes très complexes et imbriquées. Les systèmes de workflows scientifiques ont ensuite été développés pour guider les utilisateurs dans la conception et l'exécution de workflows. Un avantage de ces systèmes par rapport aux approches traditionnelles est leur capacité à mémoriser automatiquement la provenance (ou lignage) des produits de données intermédiaires et finaux générés au cours de l'exécution du workflow. La provenance d'un produit de données contient des informations sur la façon dont le produit est dérivé, et est cruciale pour permettre aux scientifiques de comprendre, reproduire, et vérifier les résultats scientifiques facilement. Pour plusieurs raisons, la complexité du workflow et des structures d'exécution du workflow est en augmentation au fil du temps, ce qui a un impact évident sur la réutilisation des workflows scientifiques.L'objectif global de cette thèse est d'améliorer la réutilisation des workflows en fournissant des stratégies visant à réduire la complexité des structures de workflow tout en préservant la provenance. Deux stratégies sont introduites. Tout d'abord, nous proposons une approche de réécriture de la structure du graphe de n'importe quel workflow scientifique (classiquement représentée comme un graphe acyclique orienté (DAG)) dans une structure plus simple, à savoir une structure série-parallèle (SP) tout en préservant la provenance. Les SP-graphes sont simples et bien structurés, ce qui permet de mieux distinguer les principales étapes du workflow. En outre, d'un point de vue plus formel, on peut utiliser des algorithmes polynomiaux pour effectuer des opérations complexes fondées sur les graphiques (par exemple, la comparaison de workflows, ce qui est directement lié au problème d’homomorphisme de sous-graphes) lorsque les workflows ont des SP-structures alors que ces opérations sont reliées à des problèmes NP-hard pour des graphes qui sont des DAG sans aucune restriction sur leur structure. Nous avons introduit la notion de préservation de la provenance, conçu l’algorithme de réécriture SPFlow et réalisé l’outil associé.Deuxièmement, nous proposons une méthodologie avec une technique capable de réduire la redondance présente dans les workflow (en supprimant les occurrences inutiles de tâches). Plus précisément, nous détectons des « anti-modèles », un terme largement utilisé dans le domaine de la conception de programme, pour indiquer l'utilisation de formes idiomatiques qui mènent à une conception trop compliquée, et qui doit donc être évitée. Nous avons ainsi conçu l'algorithme DistillFlow qui est capable de transformer un workflow donné en un workflow sémantiquement équivalent «distillé», c’est-à-dire, qui est libre ou partiellement libre des anti-modèles et possède une structure plus concise et plus simple. Les deux principales approches de cette thèse (à savoir, SPFlow et DistillFlow) sont basées sur un modèle de provenance que nous avons introduit pour représenter la structure de la provenance des exécutions du workflowl. La notion de «provenance-équivalence» qui détermine si deux workflows ont la même signification est également au centre de notre travail. Nos solutions ont été testées systématiquement sur de grandes collections de workflows réels, en particulier avec le système Taverna. Nos outils sont disponibles à l'adresse: https://www.lri.fr/~chenj/. / Bioinformatics experiments are usually performed using scientific workflows in which tasks are chained together forming very intricate and nested graph structures. Scientific workflow systems have then been developed to guide users in the design and execution of workflows. An advantage of these systems over traditional approaches is their ability to automatically record the provenance (or lineage) of intermediate and final data products generated during workflow execution. The provenance of a data product contains information about how the product was derived, and it is crucial for enabling scientists to easily understand, reproduce, and verify scientific results. For several reasons, the complexity of workflow and workflow execution structures is increasing over time, which has a clear impact on scientific workflows reuse.The global aim of this thesis is to enhance workflow reuse by providing strategies to reduce the complexity of workflow structures while preserving provenance. Two strategies are introduced.First, we propose an approach to rewrite the graph structure of any scientific workflow (classically represented as a directed acyclic graph (DAG)) into a simpler structure, namely, a series-parallel (SP) structure while preserving provenance. SP-graphs are simple and layered, making the main phases of workflow easier to distinguish. Additionally, from a more formal point of view, polynomial-time algorithms for performing complex graph-based operations (e.g., comparing workflows, which is directly related to the problem of subgraph homomorphism) can be designed when workflows have SP-structures while such operations are related to an NP-hard problem for DAG structures without any restriction on their structures. The SPFlow rewriting and provenance-preserving algorithm and its associated tool are thus introduced.Second, we provide a methodology together with a technique able to reduce the redundancy present in workflows (by removing unnecessary occurrences of tasks). More precisely, we detect "anti-patterns", a term broadly used in program design to indicate the use of idiomatic forms that lead to over-complicated design, and which should therefore be avoided. We thus provide the DistillFlow algorithm able to transform a workflow into a distilled semantically-equivalent workflow, which is free or partly free of anti-patterns and has a more concise and simpler structure.The two main approaches of this thesis (namely, SPFlow and DistillFlow) are based on a provenance model that we have introduced to represent the provenance structure of the workflow executions. The notion of provenance-equivalence which determines whether two workflows have the same meaning is also at the center of our work. Our solutions have been systematically tested on large collections of real workflows, especially from the Taverna system. Our approaches are available for use at https://www.lri.fr/~chenj/.
39

SciProv: uma arquitetura para a busca semântica em metadados de proveniência no contexto de e-Science

Valente, Wander Antunes Gaspar 18 January 2011 (has links)
Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-05-05T13:06:54Z No. of bitstreams: 1 wanderantunesgasparvalente.pdf: 18725317 bytes, checksum: 3ee881993096b45e72f9522887e7e2e0 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-17T13:37:14Z (GMT) No. of bitstreams: 1 wanderantunesgasparvalente.pdf: 18725317 bytes, checksum: 3ee881993096b45e72f9522887e7e2e0 (MD5) / Made available in DSpace on 2017-05-17T13:37:14Z (GMT). No. of bitstreams: 1 wanderantunesgasparvalente.pdf: 18725317 bytes, checksum: 3ee881993096b45e72f9522887e7e2e0 (MD5) Previous issue date: 2011-01-18 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A e-Science se caracteriza pela manipulação de um vasto volume de dados e utilização de recursos computacionais em larga escala, muitas vezes localizados em ambientes distribuídos. Nesse cenário, representado por alta complexidade e heterogeneidade, torna-se relevante o tratamento da proveniência de dados, que tem por objetivo descrever os dados que foram gerados ao longo da execução de um experimento científico e apresentar os processos de transformação pelos quais foram submetidos. Assim, a proveniência auxilia a formar uma visão da qualidade, da validade e da atualidade dos dados produzidos em um ambiente de pesquisa científica. O SciProv consiste em uma arquitetura cujo objetivo é interagir com sistemas de gerenciamento de Workflows científicos para promover a captura e a gerência dos metadados de proveniência gerados. Para esse propósito, o SciProv adota uma abordagem baseada em um modelo abstrato para a representação da proveniência. Esse modelo, denominado Open Provenance Model, confere ao SciProv a capacidade de prover uma infraestrutura homogênea e interoperável para a manipulação dos metadados de proveniência. Como resultado, o SciProv permite disponibilizar um arcabouço para consulta às informações de proveniência geradas em um cenário complexo e diversificado de e-Science. Mais importante, a arquitetura faz uso de tecnologia web semântica para processar as consultas aos metadados de proveniência. Nesse contexto, a partir do emprego de ontologias e máquinas de inferências, o SciProv provê recursos para efetuar deduções sobre os metadados de proveniência e obter resultados importantes ao extrair informações adicionais além daquelas que encontram-se registradas de forma explícita nas informações gerenciadas. / E-Science is characterized by manipulation of huge data set and large scale computing resources usage, often located in distributed environments. In this scenario, represented by high complexity and heterogeneity, it becomes important to treat data provenance, which aims to describe data that were generated during a scientific experiment execution and presents processes of transformation by which underwent. Thus, lineage helps to form a quality, validity and topicality vision of data produced in a scientific research environment. SciProv consists of an architecture that aims to interact with scientific workflows management systems for capture and manipulation of generated provenance metadata. For this purpose, SciProv adopts an approach based on an abstract model for representing the lineage. This model, called Open Provenance Model, provides to SciProv the ability to set up a homogeneous and interoperable infrastructure for handling provenance metadata. As a result, SciProv is able to provide a framework for query data provenance generated in a complex and diverse e-Science scenario. More important, the architecture makes use of semantic web technology to process metadata provenance queries. In this context, using ontologies and inference engines, SciProv provides resources to make inferences about lineage and to obtain important results in allowing the extraction of information beyond those that are registered explicitly from managed data.
40

Provenance Analysis of the Sperm Bluff Formation, southern Victoria Land, Antarctica

Savage, Jeni Ellen January 2005 (has links)
Beacon Supergroup rocks of probable Devonian age, containing conglomerate clasts of lithologies unknown in outcrop in southern Victoria Land (SVL) occur in the St Johns Range to Bull Pass Region, SVL, Antarctica. The Lower Taylor Group sedimentary rocks, herein called the Sperm Bluff Formation, unconformably rest on the regionally extensive Kukri Erosion Surface that truncates local basement. The basement complex includes three Plutonic Suites, Dry Valley (DV) 1a, DVIb and DV2 of the Granite Harbour Intrusives that intrude metasedimentary rocks of the Koettlitz Group. Allibone et al. (1993b) suggested a SVL terrane accretion event may have occurred about the same time as accretion of a terrane known as the Bowers terrane in northern Victoria Land (NVL) based on changing chemistry of the CambroOrdovician granitoids. Further, it is suggested that conglomerate clasts of the Sperm Bluff Formation may have been derived from this postulated terrane (Allibone et al., 1993b; and Turnbull et al., 1994). Following extensive fieldwork provenance studies and basin analysis of the sedimentary Sperm Bluff Formation are used here to test these ideas. The Sperm Bluff Conglomerate of Turnbull et al. (1994) is re-interpreted as the Sperm Bluff Formation and described using a lithofacies-based approach. The Sperm Bluff Formation is divided into six lithofacies including 1) Conglomerate Lithofacies; 2) Pebbly Sandstone Lithofacies; 3) Crossbedded Sandstone Lithofacies; 4) Parallelbedded Lithofacies; 5) Low-angle Crossbedded Lithofacies; and 6) Interbedded Siltstone/Sandstone Lithofacies. The intimate field association of the Conglomerate, Pebbly Sandstone and Crossbedded Sandstone Lithofacies ties them to the Conglomerate Lithofacies Association whereas the other three units are independent. The Conglomerate Lithofacies Association is interpreted to represent a wavedominated deltaic environment, based on the presence of broad channels, pervasive crossbedding, paleocurrent and trace fossil data. Both Parallel-bedded and Low-angle Crossbedded Sandstone Lithofacies are interpreted as a foreshore-shore face shallow marine setting on the basis of low-angle crossbeds and trace fossil assemblages. The Interbedded Siltstone and Sandstone Lithofacies is interpreted as an estuarine environment based on alternating siltstone/sandstone beds and the presence of flaser and lenticular bedding, small crossbedded dune sets, mud drapes, syneresis cracks and diverse paleocurrent directions. An estuarine setting is tentatively favoured over a lagoonal setting due to the presence of syneresis cracks small channels and the proximity to a river delta. I suggest that the Sperm Bluff Formation is likely a lateral correlative of the Altar Mt Formation of the Middle Taylor Group, in particular the Odin Arkose Member. This interpretation is based on arkosic nature of the sedimentary rocks, regional paleocurrent patterns, the presence of salmon pink grits at Gargoyle Turrets and trace fossil assemblages. The upper most lithofacies at Mt Suess, the Low-angle Crossbedded Sandstone Lithofacies that only occurs at this site is- suggested as a lateral correlative to the Arena Sandstone, which stratigraphically overlies the Altar Mt Formation, based on quartzose composition, clay matrix, stratigraphic position and trace fossils present. Provenance analysis was carried out on sedimentary rocks and conglomerate clasts using clasts counts of conglomerates, petrographic analysis of clasts, point counts of sandstones and clasts, geochemistry and V-Pb detrital zircon analysis. Conglomerate clasts lithologies include dominantly silicic igneous clasts and finely crystalline quartzite clast amongst other subordinate lithologies such as vein quartz, schist, schorl rock, gneiss and sandstone. Despite past identification of granitoid clasts in the Sperm Bluff Formation (Turnbull et al., 1994), none were found. Rhyolitic clasts of the Sperm Bluff Formation have compositions typical of highly evolved subduction related rocks, although they have undergone post-emplacement silicification. Wysoczanski et al. (2003) date rhyolite and tuff clasts between 497±17 Ma and 492±8 Ma, placing them within error of all three Dry Valley Magmatic Suites and removing the likelihood of correlation to NVL volcanic rocks. Petrographic analysis suggests they are components of a silicic magmatic complex. Chemically the volcanic clasts appear to represent a single magmatic suite (Sperm Bluff Clast Suite), and are clearly related to the Dry Valley Plutonic Suites. Although clasts are not constrained beyond doubt to one Suite, DV2 is the best match. Quartzite clasts of the Sperm Bluff Formation are too pure and old to be derived from a local source. Detrital zircon V-Pb ages for the quartzite suggest zircons were derived from the East Antarctic Craton, and that the quartzite source rocks were deposited prior to the Ross-Delamarian Orogeny. Quartzite with a similar age signature has not been identified; however, the Junction Formation sandstone of northwest Nelson has a similar age spectrum. Sandstones from the Sperm Bluff Formation indicate derivation from a felsic continental block provenance, which contain elements of volcanic, hyperbyssal and plutonic rocks. They are arkosic to quartzose in composition and conspicuously lack plagioclase. Detrital zircon analyses give a strong 500 Ma peak in all 3 samples, characteristic of a Ross-Delamarian Orogen source, with few other peaks. The dominance of a single peak is highly suggestive oflocal derivation. The sedimentary rocks of the Sperm Bluff Formation are interpreted to be derived predominantly from the basement rocks they now overlie. The presence of the regionally extensive Kukri Erosion Surface at the lower contact of the Beacon Supergroup rocks implies an intermediate source must have existed. This most likely contained all components of the formation. I suggest that the DV2 Suite was emplaced in a subsiding, extensional intra-arc setting. Erosion of the uplifted arc region probably occurred from Late Ordovician to Silurian times with deposition of sediments in a subsiding intra-arc basin. Erosion of the rhyolitic complex in this region probably occurred, however, it is likely that some was preserved. Inversion of this basin prior to the Devonian probably provided the means for these sediments to be deposited as the Sperm Bluff Fonnation.

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