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Connecting Cape Breton Island and Newfoundland, Canada Geophysical Modeling of Pre-Carboniferous ‘Basement’ Rocks in the Cabot Strait Area Sandra M

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Connecting Cape Breton Island and Newfoundland, Canada Geophysical Modeling of Pre-Carboniferous ‘Basement’ Rocks in the Cabot Strait Area Sandra M Document generated on 09/24/2021 5:32 p.m. Geoscience Canada Journal of the Geological Association of Canada Journal de l’Association Géologique du Canada Connecting Cape Breton Island and Newfoundland, Canada Geophysical Modeling of pre-Carboniferous ‘Basement’ Rocks in the Cabot Strait Area Sandra M. Barr, Sonya A. Dehler and Louis Zsámboki Volume 41, Number 2, 2014 Article abstract Magnetic and gravity data from northeastern Cape Breton Island, URI: https://id.erudit.org/iderudit/1025341ar southwestern Newfoundland, and the intervening Cabot Strait area were compiled and used to generate a series of maps displaying magnetic (filtered See table of contents total field, first and second derivative) and gravity (Bouguer anomaly onshore, free-air anomaly offshore) information to enhance the anomaly pattern associated with regional geology. With further constraints from previously Publisher(s) published seismic reflection interpretations and detailed maps of onshore geology, five two-dimensional subsurface models were generated. Potential The Geological Association of Canada field anomalies in the offshore can be correlated with onshore faults, rock units, and pre-Carboniferous terranes. In Newfoundland, the Cabot – Long ISSN Range Fault separates Grenvillian basement to the northwest from peri-Gondwanan Port aux Basques subzone basement in the southeast and can 0315-0941 (print) be traced to the Wilkie Brook Fault on Cape Breton Island. The Cape Ray 1911-4850 (digital) Fault/Red Indian Line merges offshore with the Cabot – Long Range Fault so that Notre Dame subzone rocks do not extend across the Cabot Strait area. The Explore this journal Port aux Basques – Exploits subzone boundary crosses the strait but is likely buried by younger rocks onshore in Cape Breton Island. Magnetic halos in the Exploits subzone are probably caused by Silurian – Devonian plutons like those Cite this article in the Burgeo Intrusive Suite. The Exploits – Bras d’Or terrane boundary is located within the Ingonish magnetic anomaly, which was resolved into four Barr, S. M., Dehler, S. A. & Zsámboki, L. (2014). Connecting Cape Breton Island overlapping components representing basement sources intruded into and Newfoundland, Canada: Geophysical Modeling of pre-Carboniferous metasedimentary rocks and dioritic and granodioritic plutons of the Bras d’Or ‘Basement’ Rocks in the Cabot Strait Area. Geoscience Canada, 41(2), 186–206. terrane. The Bras d’Or terrane can be traced to the Cinq-Cerf block and Grey River areas in southern Newfoundland. The interpretations suggest that Bras d’Or terrane ‘basement’ may underlie all of Exploits subzone, and that the Aspy terrane of Cape Breton Island is part of that subzone. All Rights Reserved © The Geological Association of Canada, 2014 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ 186 Volume 41 2014 HAROLD WILLIAMS SERIES and used to generate a series of maps pretations suggest that Bras d’Or ter- displaying magnetic (filtered total field, rane ‘basement’ may underlie all of first and second derivative) and gravity Exploits subzone, and that the Aspy (Bouguer anomaly onshore, free-air terrane of Cape Breton Island is part anomaly offshore) information to of that subzone. enhance the anomaly pattern associat- ed with regional geology. With further SOMMAIRE constraints from previously published Les données magnétométriques et seismic reflection interpretations and gravimétriques du nord-est de l’île du detailed maps of onshore geology, five Cap-Breton, dans le sud-ouest de two-dimensional subsurface models Terre-Neuve, et de la région du détroit were generated. Potential field anom- de Cabot contigu, ont été compilées et Connecting Cape Breton alies in the offshore can be correlated utilisées pour produire une série de Island and Newfoundland, with onshore faults, rock units, and cartes affichant les particularités mag- pre-Carboniferous terranes. In New- nétiques (champ total filtré, dérivé pre- Canada: Geophysical foundland, the Cabot – Long Range mière et seconde) et gravimétriques Modeling of pre-Carbonifer- Fault separates Grenvillian basement to (anomalie de Bouguer de la côte, ous ‘Basement’ Rocks in the northwest from peri-Gondwanan anomalie à l’air libre extracôtière) pour Port aux Basques subzone basement in ajouter à la compréhension des motifs the Cabot Strait Area the southeast and can be traced to the d’anomalie de la géologie régionale. Wilkie Brook Fault on Cape Breton En tenant compte des limitations Sandra M. Barr1, Sonya A. Dehler2, Island. The Cape Ray Fault/Red Indi- imposées par les interprétations de and Louis Zsámboki1, 3 an Line merges offshore with the données de levés de sismique réflexion Cabot – Long Range Fault so that déjà publiées et de cartes détaillées de 1Department of Earth and Notre Dame subzone rocks do not géologie continentale, cinq modèles 2D Environmental Science extend across the Cabot Strait area. du sous-sol ont été produits. Des Acadia University The Port aux Basques – Exploits sub- anomalies de champ potentiel en zone Wolfville, NS, Canada, B4P 2R6 zone boundary crosses the strait but is extracôtière peuvent être corrélées avec E-mail: [email protected] likely buried by younger rocks onshore des failles, des unités lithologiques et in Cape Breton Island. Magnetic halos des terranes pré-carbonifères sur la 2Natural Resources Canada in the Exploits subzone are probably côte. Sur l’île de Terre-Neuve, la faille Geological Survey of Canada (Atlantic) caused by Silurian – Devonian plutons de Cabot-Long Range qui sépare le Dartmouth, NS, Canada, B2Y 4A2 like those in the Burgeo Intrusive socle grenvillien au nord-ouest de la Suite. The Exploits – Bras d’Or terrane sous-zone de socle péri-gondwanienne, 3Current address: boundary is located within the Ingo- de Port-aux- Basques au sud-est, peut 63 Barnesdale Ave S nish magnetic anomaly, which was être reliée à la faille de Wilkie Brook Hamilton, ON resolved into four overlapping compo- sur l’île du Cap-Breton. La faille du L8M 2V3 nents representing basement sources Cap Ray et la linéation de Red Indian intruded into metasedimentary rocks se fondent au large avec la faille de SUMMARY and dioritic and granodioritic plutons Cabot – Long Range, ce qui signifie Magnetic and gravity data from north- of the Bras d’Or terrane. The Bras que les roches de la sous-zone de eastern Cape Breton Island, southwest- d’Or terrane can be traced to the Cinq- Notre-Dame ne traversent pas la ern Newfoundland, and the interven- Cerf block and Grey River areas in région du détroit de Cabot. La limite ing Cabot Strait area were compiled southern Newfoundland. The inter- de la sous-zone de Port aux Basques- Geoscience Canada, v. 41, http://dx.doi.org/10.12789/geocanj.2014.41.041 © 2014 GAC/AGC® GEOSCIENCE CANADA Volume 41 2014 187 Exploits traverse le détroit, mais elle LLaurentia and peri- a Quebec LLaurentianu terranes est vraisemblablement enfouie sous des a r u e Grenville Orogen r n NL e tia Long roches plus jeunes sur l’île du Cap-Bre- n tia a Range n n ton. Les halos magnétiques dans la PEI d Inlier CBI te p NB r e sous-zone Exploits sont probablement ra r Ganderia50°00´N n i- USA e causés par des plutons siluro-dévoniens NS s RIL Line comme c’est le cas de ceux de la Indian séquence intrusive de Burgeo. La lim- Red St. Lawrence Central NDS Gander ite du terrane Exploits-Bras d’Or est Promontory Mobile Zone Central CF Belt située dans l’anomalie magnétique DHBF Ingonish, laquelle s’est révélée être Mobile HF AAvaloniavalonia Belt BRI ?? Cabot constituée de quatre composantes Notre DameGanderia subzone ?? ?? Strait Blair River superposées représentant des sources A ?? Inlier Bras de socle engoncées dans des roches AAvaloniavalonia Aspy B d’Or métasédimentaires, et dans des plutons M dioritiques et granodioritiques du ter- MMegumaeguma rane de Bras d’Or. On peut suivre le Mira terrane de Bras d’Or jusque dans les 200 km régions du bloc de Cinq-Cerf et de 60°00´W 40 km Grey River dans le sud de Terre- Neuve. Les interprétations permettent Figure 1. Components of the northern Appalachian orogen after Hibbard et al. de penser que le « socle » du terrane de (2006) showing the location of the study area centred on the Cabot Strait between Bras d’Or pourrait constituer l’assise Cape Breton Island and Newfoundland. Abbreviations: DHBF, Dover – Her- rocheuse de la sous-zone Exploits, et mitage Bay Fault; HF, Hermitage Flexure; NDS, Notre Dame subzone; RIL, Red que le terrane Aspy de l’île du Cap- Indian Line. Inset map on upper left shows political areas in northeastern United Breton ferait partie de cette sous-zone. States (USA) and Canada: CBI, Cape Breton Island; NB, New Brunswick; NS, Nova Scotia; NL, Newfoundland; PEI, Prince Edward Island. Lower right inset INTRODUCTION map shows an enlarged view and key to abbreviations for subdivisions in Cape On his pioneering map emphasizing Breton Island. along-orogen correlations of pre-Car- boniferous rocks in the Appalachian orogen in Cape Breton Island com- focused on Carboniferous units and mountain belt, Williams (1978) inferred pared to Newfoundland (Lin et al. faults affecting those units. They that all of Cape Breton Island is part 1994), making it unsurprising that showed pre-Carboniferous basement of the Avalon Zone. In contrast, fewer components have been pre- on their interpretations, but did not Newfoundland, only a few 10s of kilo- served in the relatively small area of speculate on the nature of that base- metres away across the Cabot Strait, Cape Breton Island.
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