|Title||Sill evolution in marine inundated basins, Sachs Harbour, Banks Island, NWT|
|Author||Martin, B G; Bell, T; Smith, I R; Forbes, D L|
|Source||ArcticNet 2007, annual science meeting, programme/ArcticNet 2007, programme, réunion scientifique annuelle; 2007 p. 75|
|Links||Poster - Affiche|
|Alt Series||Earth Sciences Sector, Contribution Series 20070456|
|Meeting||ArcticNet Annual Science Meeting; Collingwood, ON; CA; December 11-14, 2007|
|Media||paper; on-line; digital|
|Related||This publication is related to Martin, B G; Bell, T; Smith,
I R; Forbes, D L; (2010). Sill stratigraphy and sedimentology in marine inundated basins, Sachs Harbour, Northwest Territories: implications for sea-level reconstruction, Geological Survey of Canada, Scientific Presentation no. 6|
|Area||Sachs Harbour; Banks Island|
|Lat/Long WENS||-125.0000 -124.5000 72.0000 71.7500|
|Subjects||surficial geology/geomorphology; coastal environment; coastal erosion; coastal studies; erosion; shorelines; shoreline changes; sea level changes; sea level fluctuations; sills|
|Program||Enhancing resilience in a changing climate|
|Abstract||Realistic projections of future relative sea-level rise are critical for assessing future erosion and flooding impacts, and thus are necessary components of an integrated regional impacts study (IRIS)
involving coastal communities and habitats. One of the goals of ArcticNet Project 1.2 is to refine the record of past sea-level change and validate model projections for future change across the Canadian Arctic. This presentation focuses on the
interpretation of past sea-level records, specifically the process of marine inundation of former freshwater basins on coastal lowlands in the western Arctic, although it is broadly applicable to submerging coasts elsewhere. |
The inundation basin
approach in sea-level studies relies on the accurate determination of the former height of the basin sill over which the marine water flooded, but this can be particularly challenging due to post-inundation erosion and deposition altering sill
morphology and elevation. Shallow seismic profiles and core samples of sills from marine-inundated basins at Sachs Harbour, Banks Island, are being used to identify key processes in the remodeling of sill morphology following submergence and to
define a range of attributes that may be used to characterize sill reworking.
The former glacial outwash plain that terminates at Sachs Harbour is dotted with kettle lakes that have gradually been inundated by rising sea level. Basin sills
(1.3-5.0 m depth) progressively shallow from west to east, reflecting the sequential inundation of higher basins. Sills have steep slopes and relatively flat tops, which in places are incised by channels that are interpreted to be palaeo-basin
outlets. The local Sachs River terminates in an estuarine basin 12 km farther east, but its drowned palaeo-channel can be traced to a submerged delta in front of the community.
Thirteen sediment cores, retrieved through vibracoring and percussion
coring from the sea-ice surface in 2006 and 2007, vary in length from 46 to176 cm. X-rays and textural analysis of the cores reveal pervasive fine to very fine laminated mud and fine sand. Three sedimentary units have been identified across all
cores, although their stratigraphic position and prominence may vary between cores. One unit consists mostly of mud with minor amounts of fine sand and appears to infill former outlet channels and the submerged Sachs River channel. Organic carbon is
generally highest in this unit, varying between 10 and 15% with a relatively low (3-5%) inorganic carbon content. Unit two is composed largely of fine to very fine sand with small amounts of mud and varying amounts of medium to coarse sand. This unit
is divided into three sub-units, one very finely laminated with a higher (5%+) mud content, one coarsely laminated, and the other more massive. Unit three is composed of medium to coarse sand and characterized by the lowest organic and inorganic
carbon content (as low as 2%) in the cores.
The next stages of the project are to correlate the acoustic and core stratigraphy to reconstruct the broad architecture of the sills and to formulate a depositional and erosional history for the
observed sedimentary sequences.