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TitreMapping the sea floor beneath the world's highest tides: preliminary surficial geology of the Bay of Fundy, Canada
AuteurTodd, B J; Shaw, J; Parrott, D R; Kostylev, V E
SourceNGF Abstracts and proceedings of the Geological Society of Norway no. 2, 2009 p. 83
Séries alt.Secteur des sciences de la Terre, Contribution externe 20080705
Réunion8th International Conference, GeoHab - marine geological and biological habitat mapping; Trondheim; NO; mai 5-7, 2009
ProvinceRégion extracotière de l'est
Lat/Long OENS-67.5000 -64.5000 45.5000 44.2500
Sujetstopographie du fond océanique; topographie du fond océanique; bathymétrie; glaciation; topographie glaciaire; dépôts glaciaires; retrait de la glace; écoulement glaciaire; géologie des dépôts meubles/géomorphologie; géologie marine; Cénozoïque; Quaternaire
Résumé(disponible en anglais seulement)
The Bay of Fundy is an estuarine embayment in the northeast Gulf of Maine between the Canadian provinces of Nova Scotia and New Brunswick. The largest tides in the world occur here; the tidal range is 4 m at the mouth of the bay where it joins the Gulf of Maine and attains a maximum of 17 m at the head. In 2006, the Geological Survey of Canada, in cooperation with the Canadian Hydrographic Service and the University of New Brunswick, instituted a broad-scale regional mapping program to map the entire sea floor of the Bay of Fundy. To date, 12,466 square kilometres of multibeam sonar coverage have been acquired. The resulting sea floor map demonstrates the impact of glaciation on the Bay of Fundy and the influence of the modern high tidal range, and associated currents, on sediment transport and deposition. In the Pleistocene Epoch, glacial ice flowed from the head of the bay in the northeast to the Gulf of Maine in the southwest. In the southwest, a topographically controlled ice stream existed in the bedrock trough between Brier and Grand Manan islands. Streamlined subglacial landforms (drumlins and megaflutes) are prominent on the flanks of the trough. Prominent lobate ridges, convex to the southwest, are widespread in the central portion of the bay. It is not clear if these ridges are subglacial or ice-front in origin; in any case they appear to mark a complex pattern of ice retreat to the northeast. During retreat, icebergs calved from the floating ice front; iceberg keels incised a dense pattern of scours and pits into the sea floor sediment and this pattern is used to infer paleocurrent patterns. Superimposed on the glacial landforms are Holocene Epoch sedimentary bedforms that reflect the modern current regime in the Bay of Fundy. Banner banks flank prominent headlands where currents are accelerated. The majority of the banner banks are composed of sand but gravel banks also occur. Fields of star dunes in the central bay suggest dominant and subordinate current directions. In Minas Passage, where currents reach 7 - 8 knots (13 - 15 km/hr), approximately 4 km3 of post-glacial sediment has been eroded, exposing 44 km2 of bedrock at the seafloor. Private sector interests are undertaking an engineering study for in-stream tidal power in Minas Passage. A thorough understanding of Bay of Fundy substrates and benthic habitat is required before full-scale tidal power
development proceeds.