Abstract

The seismic stratigraphy and architecture of the Beaufort Sea shelf and slope are investigated using a comprehensive grid of high-resolution two-dimensional seismic reflection data. Three cross-shelf troughs, representing locations of former ice streams draining a 1000-km-long section of the Laurentide Ice Sheet (LIS) are examined: the Mackenzie, Amundsen Gulf, and M’Clure Strait systems. Dynamics of these paleo-ice streams influenced ice-sheet configuration and may have forced abrupt climatic change through delivery of ice and freshwater to the Arctic Ocean. A comprehensive understanding of their geometry and dynamics is crucial for constraining numerical models of the LIS. Evidence for two Quaternary ice advances to the shelf break is interpreted from the Mackenzie Trough. By contrast, seismic stratigraphy of the Amundsen Gulf Trough, 400 km east of the Mackenzie Trough, records at least nine Quaternary ice advances. Here, the outer shelf consists of stacked till sheets, extending to the shelf break and forming a trough-mouth fan. The contrasting glacial histories of these neighboring ice streams are explained by their positions within the LIS; the Mackenzie Trough ice stream was situated at the extreme northwest ice-sheet margin, whereas the Amundsen Gulf ice stream had a more central location and larger drainage basin, supplying significant quantities of ice and sediment to the Arctic Ocean through much of the Quaternary. The M’Clure Strait Trough probably possesses a similar architecture to the Amundsen Gulf Trough, and an even larger trough-mouth fan.

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