Abstracts
Abstract
A modified, surface-towed, sub-bottom profiler, the boomer-based “Seistec” system, was deployed in an area offshore of eastern Oak Island, Mahone Bay, Nova Scotia, in May 2017. Several grids of lines were surveyed around eastern Oak Island. Subsequently, the sub-bottom profiler data were interpreted from a geological perspective after being processed, scaled, aligned and merged with a previously collected multibeam bathymetric data set. This exercise resulted in the first integration of multibeam bathymetry and high resolution sub-bottom profile data from offshore Oak Island and provides insight into the subsurface stratigraphy of the bedrock and glacial and postglacial sediments. The seabed is mostly composed of boulder-covered till drumlins and Holocene mud. Subsurface sediments include till and glaciomarine and lacustrine sediments, and a regional unconformity developed in response to postglacial transgression was revealed. Anthropogenic features include a shipwreck and unusual coast-normal seabed gravel ridges. Seabed natural features include sinkholes and pockmarks that are likely connected by channels in the bedrock to sinkhole features on adjacent land.
Résumé
Un sondeur de vase remorqué en surface, le système profileur à boumeur « Seistec », a été déployé dans un secteur au large à l’est de l’île Oak, dans la baie Mahone, en Nouvelle-Écosse, en mai 2017. Plusieurs grilles de lignes ont été sondées à l’est de l’île Oak. Les données du sondeur de vase ont ensuite été interprétées selon une perspective géologique après avoir été traitées, mises à l’échelle, alignées et fusionnées avec un ensemble de données bathymétriques par secteurs précédemment recueillies. L’exercice a abouti à la première intégration de données sur le profil du sous-sol du fond haute résolution et de données bathymétriques par secteurs du large de l’île Oak, et il livre un aperçu de la stratigraphie en faible profondeur du substrat rocheux et des sédiments glaciaires et postglaciaires. Le fond océanique est principalement composé de boue de l’Holocène et de drumlins de till recouverts de gros blocs rocheux. Les sédiments de subsurface comprennent du till et des sédiments glaciomarins et lacustres, et une discordance régionale apparue en réponse à une transgression postglaciaire a été mise au jour. Les particularités anthropiques incluent une épave et des dorsales de gravier sur un fond océanique littoral normal. Les particularités naturelles du fond comprennent des sinkholes et des marques d’échappement qui sont vraisemblablement reliés par des canaux dans le substrat rocheux aux sinkholes présents sur les terres adjacentes.
Appendices
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