Mapping the South Queensland margin: collapses, depressions and general instability
Presented by Dr. David VöLKER, Ms. Samantha CLARKE on 23 Sep 2013 from 17:15 to 19:15
Type: Poster presentation
Session: Poster session
Track: Poster presentations
Continental margins characterized by low seismic activity and low sedimentation rate like the continental slopes offshore East Australia are often not considered as being subject to significant submarine landsliding and related tsunami hazard. Recent observations of the R/V Southern Surveyor expeditions however call for a re-evaluation of the stability of the continental slopes off East Australia as they documented ubiquitous landslides. Gravity core samples from slide planes of three upper slope slides presented almost historical ages of 15,000 and 20,000 years whereas sedimentary geotechnical testing and numerical slope stability estimations resulted in the puzzling conclusion that these submarine slopes should be stable against sliding The need to better unserstand the mechanisms of these landlsides was the rationale to man a third expedition on the R/V Southern Surveyor in Jan. 2013, the first results of which are presented here.
We investigated the shelf edge, upper slope, and submarine canyons along the margin of southern Queensland between latitudes 25°S and 27°S (Fig. 1a) by echo-sounding, dredging and gravity coring. As an additional objective, we mapped submarine canyon systems that act as major transport ways of sediment from the shelf to the abyss. The submarine morphology of the shelf and slope offshore Fraser Island documents ongoing detachment of chunks of the upper slope along a tension crack that extends for some 100 km. If we take the last bit of unaffected continental slope as the original morphology, we calculate a loss of material due to submarine landsliding of ~30 km3 per km of coastline.
Location: GEOMAR East shore
Address: Wischhofstr. 1-3 / D-24148 Kiel