Title

Sediment Characteristics of Submarine Landslides on the Upper East Australian Continental Margin--Preliminary findings

Abstract

A large number of recent submarine landslides on the Eastern Australian continental slope were investigated during voyages aboard the RV Southern Surveyor in 2006 and 2008. Preliminary sedimentological analysis, geotechnical and radiocarbon data resulting from the examination of twelve gravity cores recovered from upper-slope slides showed that at least three of the twelve cores penetrated large, geologically-recent, submarine landslide failures. The failure surfaces lay within slide scars at distances of between 60 cm and 200 cm beneath the present-day seabed. Sediment present on the upper slope comprises mixtures of calcareous and terrigenous sand and mud. Distinct differences in physical properties (bulk unit density, water content, grain-size distribution) were recorded across the slide-plane boundaries. Slope stability modelling using classical soil mechanics techniques and measured sediment shear-strengths indicates that the slopes should be stable. However, the ubiquity of slides on this margin indicates that their occurrence is a relatively common event and that submarine-sliding should be considered to be a normal characteristic of this continental margin. While this presents something of an interpretational paradox, it nevertheless indicates that an unidentified mechanism acts to reduce the shear resistance of these sediments to very low values which enables the slope failures to occur. Preliminary bulk dates confirm Boyd et al's (2009) conclusion based on sedimentation rates, that some of the landslide masses were mobilised during the most recent glacial-interglacial cycle. Penecontemporaneous dates recorded for separate but adjacent slides are consistent with the slides being triggered by a single event such as an earthquake. Boyd, R., J. Keene, Hubble T.C.T et al. (2009). Southeast Australia: A Cenozoic Continental Margin Dominated by Mass Transport. Submarine Mass Movements and Their Consequences, Advances in Natural and Technological Hazards Research. D. C. Mosher, et al. 28: 491-502.

Publication Date

12-2010

Journal or Conference Title

Fall Meeting, American Geophysical Union (AGU)

Conference Date

Dec 13 - Dec 17, 2010

Publisher Place

San Francisco, CA, USA

Publisher

American Geophysical Union Publications

Document Type

Conference Proceeding