451 results
Search Results
2. PbIso: an R package and web app for calculating and plotting Pb isotope data.
- Author
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Armistead, Sheree E., Eglington, Bruce M., and Pehrsson, Sally J.
- Subjects
WEB-based user interfaces ,ISOTOPES ,RADIOISOTOPES ,CANADIAN provinces - Abstract
The package PbIso is a free and open R toolbox for commonly used calculations and plots of Pb–Pb isotope data and for generating Pb evolution models. In this paper, we review Pb isotope systematics and the calculations that are commonly used, such as model age, model source μ (
238 U/204 Pb), time-integrated κ (232 Th/238 U), and initial Pb isotope ratios. These equations are implemented into R functions in the package PbIso. In addition, functions are provided for generating Pb evolution models, paleoisochrons, and isochrons. This allows users to apply calculations to their data in a straightforward way while providing transparency and flexibility of the calculations used. We have implemented some basic features of the PbIso package into an online shiny R application (see https://shereearmistead.github.io/software/pbiso), which makes it easy for users without any R experience to use these calculations with their own data and to generate plots. We have provided a case study from the Superior Province in Canada, showing how different Pb evolution models can be generated in PbIso and compared to Pb isotope data. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
3. Canada's maritime frontier: the science legacy of Canada's extended continental shelf mapping for UNCLOS.
- Author
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Mosher, David C., Dickson, Mary-Lynn, Shimeld, John, Jackson, H. Ruth, Oakey, Gordon N., Boggild, Kai, Campbell, D. Calvin, Travaglini, Paola, Rainey, Walta-Anne, Murphy, Alain, Dehler, Sonya, and Ells, John
- Subjects
GEOMORPHOLOGY ,CONTINENTAL shelf ,UNITED Nations Convention on the Law of the Sea (1982) ,GEOSTROPHIC currents ,SUBMARINE fans ,CONTINENTAL slopes ,CONTINENTAL margins - Abstract
Canada ratified the United Nations Convention on the Law of the Sea (UNCLOS) in 2003. With that ratification is an obligation to submit data and information to the U.N. pertaining to the limits of the country's extended continental shelf (ECS); the portion of the juridical continental shelf that extends beyond 200 nautical miles. A team of Canadian scientists, managers, and legal experts that included representation from three Federal Departments (Natural Resources Canada, Fisheries and Oceans Canada, and Global Affairs Canada) with additional support from other departments, spent 13 years compiling and acquiring data to provide the scientific evidence to support delineation of Canada's seaward most maritime limit. The submission has the potential to provide Canada with 2.4 million km
2 of additional submarine landmass in the Atlantic and the Arctic oceans over which Canada exercises sovereign rights for the purpose of exploring and exploiting its natural resources. Specific information such as the tectonic framework of the continental margin, the geomorphology of the margin and in particular the continental slope, the geologic nature of adjoined ridges, rises, and plateaux, and sediment thickness within adjacent basins are examples of fundamental pieces of geoscientific information needed to substantiate Canada's outermost maritime limits. This paper highlights a number of segments of Canada's continental margins to showcase this scientific evidence and how it is applied in the UNCLOS context. In doing so, the paper demonstrates the geologic complexity of Canada's margins as illustrated in scientific publications that have resulted from these new data collections, while at the same time presenting new scientific evidence and interpretations. This collection of data and information provides a wealth of new knowledge in Canada's offshore regions. The massive data compilation in the Atlantic led to conception of continental margins, in a source-to-sink scenario, as having an equilibrium base level or graded form, comparable to river systems. Departures from this shape relate to the interplay of sedimentary processes and in particular to those processes that do not fit the source-to-sink paradigm. For example, a significant part of the Atlantic margin is shown to be heavily influenced by along-slope geostrophic currents that generated massive contourite drift deposits. These deposits reflect lateral transport of sediment that had a significant impact on the morphology of the margin. The role of mass transport processes in shaping continental margins is also highlighted, and in particular the collapses of entire segments of the margin were observed. The prominent role mass failure processes play in delivering sediment to the adjacent abyssal plain is also critical in the ECS context. These observations challenge the entrenched notion of a continental margin comprising a shelf, slope, and rise and in particular the concept of the "continental rise". Prior to 2006, regions of the Arctic Ocean seaward of the Canadian landmass had fewer than 5000 km of seismic reflection data. The massive efforts of Arctic coastal States to map their margins for ECS purposes have led to a leap in technological advances to acquire data in ice-covered seas and have led to a wealth of new geoscientific knowledge. Perhaps foremost amongst this knowledge is demonstration that Canada Basin is indeed a fully developed ocean basin, albeit significantly infilled with sediment. Based on this knowledge and identification of related structures, new realistic tectonic scenarios for opening of the Amerasia Basin are proposed that include a significant component of transform or strike-slip motions. With seismic velocity and rock sample information, the continental nature of Alpha and Mendeleev ridges has been substantiated. Even bathymetric data were lacking in the Arctic and new editions of seafloor maps now support grids of 500 m spacing; although some regions remain sparse. Once thought to be relatively stagnant, sedimentary processes such as found in many ocean basins were discovered in the Arctic Ocean. Evidence of geostrophic currents, sediment mass failures, and deep-sea turbidity current channels were found to be ubiquitous, even in the deepest parts of the Arctic's basins. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
4. Late Wisconsinan buildup and wastage of the Innuitian Ice Sheet across southern Ellesmere Island, Nunavut.
- Author
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England, John H., Atkinson, Nigel, Dyke, Arthur S., Eans, David J. A., and Zreda, Marek
- Subjects
ICE sheets ,ICE fields ,ABSOLUTE sea level change ,GEOLOGY ,GEOMORPHOLOGY - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2004
- Full Text
- View/download PDF
5. Crustal eduction and slab-failure magmatism in an Orosirian (2.05–1.80 Ga) postcollisional cratonic foredeep: geochronology of Seton volcanics and Compton laccoliths, Tu Cho (Great Slave Lake), NWT, Canada.
- Author
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Hoffman, Paul F., Macdonald, Francis A., Bowring, Samuel A., Ramezani, Jahandar, Buchwaldt, Robert, Hildebrand, Robert S., and Whalen, Joseph B.
- Subjects
VOLCANOLOGY ,GEOLOGICAL time scales ,THRUST belts (Geology) ,MAGMATISM ,OROGENIC belts ,VOLCANISM ,LAKES - Abstract
Three Orosirian basins and associated foreland thrust-fold belts are preserved on the margins of the Slave craton. All three are related to orogenic belts where oceans opened and later closed, uniting new crustal partners. The Great Slave basin differs from the Kilhigok and Coronation basins in ways that have defied explanation. It lacks a passive margin sequence and hosts two discrete igneous suites, separated by large-scale thrusting, that occurred well after the adjacent paleocean had closed. Here we report U–Pb zircon geochronology by chemical abrasion isotope dilution thermal ionization mass spectrometry for a member of each suite to constrain the age and origin of postcollisional thrusting. A widespread pulse of mainly phreatic alkaline volcanism, coeval with renewed foredeep flexure, occurred at 1889.0 ± 0.7 Ma (2σ internal error). A quartz-monzodiorite body, one of a belt-parallel chain of laccoliths that postdate thrusting, was emplaced at 1866.9 ± 0.9 Ma. These ages bracket renewed foredeep sedimentation and thrusting that telescoped major facies zones and was rooted within the basin. The older age is 70 and 30−60 Myr younger than collision in the Thelon and Taltson orogens, respectively. We attribute postcollisional thrusting and foredeep subsidence to "eduction"—the upward and outward ejection of partly subducted crust—and postulate that the top of the ejected wedge was a normal-sense detachment fault projecting beneath the Nonacho basin. We infer that eduction was triggered by slab failure, producing alkaline volcanism, and ended with delamination and laccolith emplacement. Eduction was facilitated by tradewind-driven erosion. Delamination was enabled by crustal transfer to the educted wedge, reducing footwall buoyancy. Slab failure and/or delamination removed the passive margin. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
6. Postglacial emergence of Amund and Ellef Ringnes islands, Nunavut: implications for the northwest sector of the Innuitian Ice Sheet.
- Author
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Atkinson, Nigel and England, John
- Subjects
HOLOCENE stratigraphic geology ,ICE sheets ,GLACIAL landforms ,HOLOCENE paleoceanography ,ABSOLUTE sea level change - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2004
- Full Text
- View/download PDF
7. Recent sedimentation in three adjacent fjord-lakes on the Québec North Shore (eastern Canada): facies analysis, laminae preservation, and potential for varve formation.
- Author
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Nzekwe, Obinna P., Francus, Pierre, St-Onge, Guillaume, Lajeunesse, Patrick, Fortin, David, Gagnon-Poiré, Antoine, Philippe, Édouard G.H., and Normandeau, Alexandre
- Subjects
LAKE sediments ,SEDIMENTATION & deposition ,FACIES ,FJORDS ,VARVES ,LAKE hydrology - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2018
- Full Text
- View/download PDF
8. John Tuzo Wilson: a Canadian who revolutionized Earth Sciences1.
- Author
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Polat, Ali
- Subjects
SCIENTISTS ,EARTH sciences ,PLATE tectonics ,CONTINENTAL drift - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2014
- Full Text
- View/download PDF
9. Introduction to the Special issue of the Canadian Journal of Earth Sciences, "Magmatic and metallogenic processes associated with large igneous provinces".
- Author
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Williamson, Marie-Claude and Saumur, Benoit M.
- Subjects
IGNEOUS provinces ,EARTH sciences ,MINES & mineral resources ,IGNEOUS rocks ,GEOCHEMISTRY ,PETROLOGY - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
- View/download PDF
10. Introduction to the Grenville Province: a geological and mineral resources perspective derived from government and academic research initiatives.
- Author
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Corriveau, Louise and Clark, Thomas
- Subjects
MINES & mineral resources ,METALS ,MINERALS ,PRECIOUS metals ,MINING camps ,EARTH sciences ,GEOLOGY ,MINERALOGY ,ORE deposits - Abstract
Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2005
- Full Text
- View/download PDF
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