ABSTRACT: Seabed processes and geological structure of the Northwest Passage.

CGRG Bibliography of Canadian Geomorphology
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Abstract

In August-October 2006, multibeam echosounder and subbottom profiler data were collected by the CCGS Amundsen and multibeam launch Heron through the Northwest Passage as part of ArcticNet project 1.6. These data were acquired to address seabed issues pertaining to the future opening of the NW Passage including resource development, safe navigation, sovereignty andsecurity of the waterways that make up the Passage. Geoscience research for project 1.6 has been focused on investigating geoenvironmental issues related to offshore development and transportation including ice scour, seafloor instability, shallow gas and the impact of geological processes on the distribution of ecologically and biologically significant benthic ecosystems. Gas vents and oil seeps have been observed using multibeam imagery in several locations in the Northwest Passage including the Beaufort Shelf, Amundsen Gulf, Barrow Strait, and entrance to Lancaster Sound. Understanding these features is important to establishing a baseline of natural hydrocarbons present in the waters of the Northwest Passage. Amundsen data are being used to identify vent and seep location and to assess the amount of activity. Ice Scours with irregular travel paths and scour depths up to 3.6m deep have been observed in water depth of 410m in Amundsen Gulf. The present day sea-ice regime is believed to generate ice scours to water depths of only ~55 to 60 m. The ice scours in 410m water depth may have been caused by large icebergs calving from retreating glaciers approximately 14,000 to 12,000 years ago. Ice scours occurring in water depths greater than 60m may be the products of a more extreme sea-ice regime in the past. Differentiating modern vs. relict ice scour regimes is required to constrain engineering design of offshore pipeline trenching depths. In addition, an understanding of relict ice scours may provide insights into past ice regimes including ice streams, icebergs and thicker sea-ice regimes. Seabed instability research continued with the acquisition of additional multibeam/subbottom data to define the geographic extent of the massive submarine landslide partially mapped in 2004. Clearly defining the age and failure mode of the shelf edge feature could have an impact on Beaufort Sea hydrocarbon development. The Amundsen conducted multibeam and subbottom profile transects across the outer Beaufort Shelf to assess geological processes influencing benthic ecosystems. Seabed topography and sediment stratigraphy provide the basis for identifying seabed processes affecting benthic communities such as ice scouring and sediment transport disturbance effects. Integration of these data with seabed imagery and biological sample analyses is an integral component of this assessment.

Bibliography of Canadian Geomorphology