Correlations and fault systematics in the Passamaquoddy Bay area, Southwestern New Brunswick
DOI:
https://doi.org/10.4138/1658Abstract
Three distinct fault-bounded litho-tectonic units have been recognized on Campobello Island in southern Passamaquoddy Bay. These units are the Upper Silurian Wilsons Beach beds, the Lower Silurian Quoddy Formation and the Upper Precambrian Coldbrook Group. Contact relationships between these units and their correlations in the Passamaquoddy Bay area resolve correlation problems between coastal Maine and New Brunswick, and demonstrate the nature of the junction between the Avalon Platform and the Acadian mobile belt. The Wilsons Beach beds are a remnant of the Acadian belt on northeastern Campobello Island, whereas the Coldbrook Group and the Quoddy Formation represent a fault block of the Avalon Platform. The Coldbrook Group, probably overlain unconformably by the Quoddy Formation, plunges to the southwest beneadi the Quoddy Formation of southeastern Maine. The Siluro-Devonian basins formed in a tensional tectonic regime in response to normal(?) faulting. These faults formed along pre-existing zones of crustal weakness that were generated during the late Precambrian by major strike-slip faulting. The present geological configuration of the area was basically established by episodic reactivation of northeast-trending faults (high-angle reverse movements) during the compressional regime of the Acadian Orogeny, RÉSUMÉ On reconnait trois unités litho-techniques bordérs par des failles sur l'ile de Campobello dans le sud de la baie-de Passamaquoddy. Ce sont les lits de Wilson Beach (Silurien supérieur), la Formation de Quoddy (Silurien inférieur) et le Groupe de Coldbrook (Précambrien supérieur). La corrélation de ces unités et de leurs contacts dans la baie de Passamaquoddy résout les problèmes de corrélation entre la côte du Maine et le Nouveau-Brunswick et démontre la nature de la jonction entie la Plate-Forme d'Avalon et la ceinture mobile acadienne. Les lits de Wilson Beach sont un residu de la ceinture acadienne sur le nord-cst de l'ile de Campobello. Par contre, le Groupe de Coldbrook et la Formation de Quoddy représentent un bloc faillé de la Plate-Forme d'Avalon. Le Groupe de Coldbrook est probablement recouvert avec discordance par la Formation de Quoddy et plonge vers le sud-ouest sous la Formation de Quoddy dans le sud-est du Maine. Les bassins siluro-dévoniens se formèrent dans un régime tectonique de tension en résponse à un mouvement normal(?) de failles. Ces failles se créerent le long de zones de faiblcsse crustale déjà établies et issues d'un important coulissement tardi-précambrien. La configuration géologique actuelle de la région s'établit principalement par réactivation épisodique de failles à tendance nord-est (mouvements inverses à fort pendage) durant le régime compressif de l'orogénèse acadienne, [Traduit par le journal]Downloads
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