Submarine landslides on the Hovgaard Ridge, central Fram Strait – preliminary results
Presented by Matthias FORWICK on 23 Sep 2013 from 17:15 to 19:15
Type: Poster presentation
Session: Poster session
Track: Poster presentations
The Hovgaard Ridge is located in the central Fram Strait between Greenland and Svalbard, approx. 80 km southwest of the Molloy Fracture Zone that separates the Molloy and Knipovich spreading ridges. It is approx. 110 km long, rises up to ~1800 m above the surrounding sea floor, and has a triangular shape narrowing from ~20 km in the SE to <4 km in the NW. The dip of its southern slope is ~10-40° and the gradients of the western and eastern slopes decrease gradually from up to 30° in the south to <15° in the north. The ridge top is an up to 10 km wide, northward-narrowing, “convex plateau” with a gradient typically below 5°. The bathymetry of the western and eastern slopes provides multiple evidence of sediment failure and downslope sediment transport. This includes channels incising the southern and central parts of the western slope. Here, the largest channels are approx. 130 m deep, up to 1.5 km wide and maximum 8 km long. They originate in areas of increasing in slope angle at the margins of the plateau, below 1300 m water depth. The northern parts of the western and eastern slopes contain multiple slide scars with up to ~20 m high headwalls. Single scars are up to 5 km wide, and the lateral extent of merged multiple scars is up to 12 km. The absence of internal escarpments on the western slope is interpreted to be due to failures limited to one stratigraphic level. However, a staircase-like morphology on the eastern slope suggests slope failures affecting multiple stratigraphic levels. The relatively high width-to-depth ratio of these scars is assumed to indicate failures of sediment slabs. Up to 130 m deep and 3 km wide slide scars with rough internal morphology occur in the central parts of the eastern slope. The width of the slide scars is either constant or it narrows towards the foot of the slope. The irregular internal morphology suggests that the slides affected multiple stratigraphic levels, and/or that evacuation of failed sediments from the slide scars was incomplete. The following processes may have led to sediment failure and channel formation on the Hovgaard Ridge: 1) The scars on the northern part of the western slope, as well as along the entire eastern slope are assumed to be the result of failure of weak layers triggered by seismicity related to seafloor-spreading along the nearby Molloy and Knipovich Ridges and/or tectonic adjustments along the Molloy Fracture Zone. The failures probably developed retrogressively due to initial sediment removal from the steepest parts close to the foot of the ridge leading to undercutting and removal of support. 2) Channel formation on the southern and central parts of the western slope may have resulted from a) cascading water masses of the Return Atlantic Current (RAC) crossing the Hovgaard Ridge in south-westerly direction, and/or b) sediment-gravity flows originating from failure at the slope break due to deposition of sediments winnowed from the plateau by the RAC.
Location: GEOMAR East shore
Address: Wischhofstr. 1-3 / D-24148 Kiel