Landform-sediment assemblages in a fjord and cross-shelf trough system: Scott Inlet and Trough (NE Baffin Island, Canada)

English Abstract:

Multibeam echosounder, subbottom profiler and sediment core data acquired since 2003 by the CCGC Amundsen together with seismic records and core samples from the Geological Survey of Canada allow the reconstruction of Late-Quaternary ice flow and glacial history in the fjords and cross-shelf trough of the Scott Inlet area (northeastern Baffin Island, Arctic Canada). These combined datasets also provide a great opportunity to document a high-latitude fjord-to- continental slope glacial landsystem that has been strongly influenced by ice streaming during the last glacial episode.

The study area can be divided into two physiographic regions: the Clark and Gibbs fjords and the Scott cross-shelf trough. In the fjords, multibeam mapping reveals a morphology that alternates between sills (bedrock or morainic) and sedimentary basins, with the presence of moraines from the side valley glaciers. Offshore Scott Inlet, a deep (800 m) and large (30 km) cross-shelf trough incise the continental shelf. This trough is characterized by traces of a large paleo-ice-stream with an onset zones located off Clark and Gibbs fjords. Five sedimentary units have been identified on the seismic data: 1- A basal unit with a non-penetrable reflector that can be either bedrock or a basal till; 2- A unit with a series of parallel horizontal high amplitude reflections (observed in Clark Fjord); 3- A semi-transparent unit having little or no parallel reflections (Davis Strait silt); 4- A transparent unit corresponding to hemipelagic deposits that is present in the shelf trough (Tiniktartuq mud); 5- A series of parallel horizontal high amplitude reflections interpreted as estuarine sedimentation.

During the last glaciation, the Scott cross-shelf trough favored the formation of an ice-stream that extended upstream into the inner sections of Clark and Gibbs transferring large volume of glacial ice and glacigenic sediments to the continental slope to form an extensive trough-mouth fan. Deglaciation of the continental shelf from a late Foxe glacial maximum was completed by 15 ka BP. Ice retreat within the fjord occurred by steps as moraines sills represent periods of ice stabilisation during deglaciation. Ice retreat to the fjord heads is thought to have been completed by 8-9 ka BP. Sedimentation similar to present-day conditions have then been reached.