|Titre||Preliminary notes on the marine geology off southwest Newfoundland, based on a merged multibeam/LIDAR data set|
|Source||Commission géologique du Canada, Dossier public 6977, 2012, 24 pages, https://doi.org/10.4095/290202 (Accès ouvert)|
|Éditeur||Ressources naturelles Canada|
|Media||en ligne; numérique|
|Référence reliée||Cette publication est reliée Shaw, J; Courtney, R
C; Christian, H; Dehler, S; (1999). Cruise Report 97060, CCGS Matthew, Ground-truthing of multibeam bathymetry data in western Newfoundland: Bonne Bay, Bay of Islands, Port au Port region, and St. George's Bay, Commission géologique du Canada,
Dossier public 3789|
|Province||Région extracotière de l'est|
|SNRC||12B; 12G/01; 12G/02; 12G/08; 12G/09; 12H/12|
|Lat/Long OENS||-59.5000 -57.5000 49.7500 48.2500|
|Sujets||plate-forme continentale; levés géophysiques; interprétations géophysiques; Holocène; sonar latéral; bathymétrie; plate-forme continentale; roches sédimentaires; tills; sables; antecedents glaciaires;
dépôts glaciaires; lithologie; Faille de Cabot ; géologie des dépôts meubles/géomorphologie; géophysique; géologie marine; Paléozoïque; Carbonifère|
|Illustrations||location maps; profiles; images|
|Programme||La géoscience pour les développements extracôtiers de la côte est, Géoscience en mer|
|Diffusé||2012 06 19|
|Résumé||(Sommaire disponible en anglais seulement)|
1) For purposes of description the area is divided into three areas (1-3). In the absence of seismics, grab samples, and photographs, estimates of
sediment type and thickness are based on bathymetric cross-sections and backscatter. Backscatter data were extracted but there are levelling differences between backscatter collected by CCGS Matthew and that collected by launches.
2) The coastline
consists of coastal bluffs composed of glacial sediments, resting on bedrock that is generally exposed at or above sea level.
3) Generally speaking the inner shelf is wave-dominated area in which bedrock is exposed at the sea floor adjacent to the
coast. Two main types of bedrock occur: 1) Carboniferous sedimentary bedrock in the north, recognized by numerous parallel ridges 1-2 m high; and 2) older, more-resistant bedrock with complex patterns of joints in the south. These two types are
separated by the offshore extension of a major structural lineation, the Cabot Fault. This runs southwest from the vicinity of Little Codroy.
4) Several large sand sheets are present on the inner shelf, usually above a depth of 50 m. These sand
bodies are mostly thin (2-3 m at most) and, with two exceptions, do not reach the modern coast, are not linked with modern sediment sources, and can be considered relict.
5) In the north of the mapped area, crescentic bars on the barrier beach at
Little Codroy (vicinity of site 7) connect with offshore sand bodies. The bars are mobile during storm conditions. In the extreme south (near site 1) the large nearshore bar immediately offshore from a large barrier beach connects with a sand sheet
that runs many kilometres offshore. This bar also is mobile in response to changing wave conditions.
6) Farther offshore from the sand/bedrock zone the topography is muted, and bedrock disappears below a cover of Quaternary sediment, probably
till. This is characterised by high backscatter. Till in the extreme northwest of Area 1 is marked by relict iceberg furrows.
7) Areas of low backscatter between the inner shelf bedrock/sand zone and the outer glacial sediment zone probably
comprise postglacial sandy mud of unknown thickness.
8) A dominant feature in the survey area is a previously unrecognized submarine canyon, hereby informally named the Cape Ray Submarine Canyon. It comprises a headwall area, and a series of
shallow (~5 m) channels that continue into deeper water. This feature adjoins one of the large sand sheets. The sand sheet shows signs of sediment starvation where it adjoins the canyon. Based on published information on canyons on the outer
continental shelves, it is suspected that this canyon was created by resuspension of sediment near the shelf edge by oceanographic processes. There is no information on modern activity in this canyon. The hazard potential of canyons on the outer
continental shelves with respect to submarine pipelines has been discussed by Campbell and MacDonald (2006).