Physical Properties and Age of Continental Slope Sediments Dredged from the Eastern Australian Continental Margin – Implications for Timing of Slope Failure

Sedimentology, structure and age estimate of five continental slope submarine landslides, eastern Australia

“…These deposits are generally less than one-kilometre thick and commonly less than 500 m thick (Conolly, 1969;Keene et al, 2008;Ringis, 1972), which is thin in comparison with other passive margin deposits such as those of the North Atlantic (Heezen, 1974) whose sediments are commonly an order of magnitude thicker. Previous studies are few, but they consistently indicate that these upper slope sediments are mixed siliciclastic-carbonate muds (Glenn et al, 2008;Hubble & Jenkins, 1984a, b;Hubble et al, 2012;Troedsen & Davies, 2001). …”

“…If the rates were representative or similar to the long-term Neogene average surface accumulation then sediment removal has been a consistently occurring event since the formation of the margin at 60 Ma. Given that the sediment wedge deposit is generally less than 500 m thick (Boyd et al, 2004(Boyd et al, , 2010 and there is abundant evidence for submarine landsliding (Boyd et al, 2010;Clarke et al, 2012;Hubble et al, 2012;Hubble et al 2016;and this work) then it follows that the main mechanism for sediment removal on this section of the margin is the eastern Australian current and mass wasting. Assuming constant sedimentation rates of between 0.02-0.20 mka -1 on the margin since its formation, a sediment deposit between ~1-3 km is "missing" from the margin, suggesting that much of the sediment has moved off the shelf and slope and down to the abyssal plain.…”

“…The margin is relatively narrow and typically presents a steep, thinly sedimented upper and middle slope with continental bedrock exposed on its lower slope ( Figure 5) (Boyd et al, 2010;Keene, Baker, Tran & Potter, 2008;Marshall, 1978Marshall, , 1979. The present day morphology of the slope is dominated by erosion and mass wasting (Boyd et al, 2010;Clarke et al, 2012;Glenn et al, 2008;Hubble et al, 2012).…”

“…Subsequent mapping of this margin with the next generation of high resolution, multibeam echo-sounding equipment between 2006 and 2013, has provided sufficient information and morphological data to establish that there are a surprisingly large number of submarine landslides evident on the continental slope (Boyd et al, 2010;Glenn et al, 2008;Hubble, Airey, Sealey, De Carli & Clarke, 2013) given this margin's well-recognised low sedimentation rates (Boyd, Ruming & Roberts, 2004) and passive margin tectonic setting. Instead of the relative quiescence and stability that might be expected, recent studies have demonstrated that submarine sliding should be considered to be a common and ongoing characteristic of the continental slope offshore eastern Australia (EA) south of Fraser Island (Boyd et al, 2010;Clarke et al, 2012;Hubble et al, 2012). This paper presents a study of upper continental slope sediments collected from the EACM and is part of a larger body of work intended to determine the frequency and consequences of submarine landsliding in this part of the margin (c.f.…”

“…This paper presents a study of upper continental slope sediments collected from the EACM and is part of a larger body of work intended to determine the frequency and consequences of submarine landsliding in this part of the margin (c.f. Boyd et al, 2010;Clarke, 2014;Clarke et al, 2012;Hubble et al, 2012Hubble et al, , 2016. This paper aims to establish the geological and sedimentological characteristics of the materials in which geologically recent (<25 ka) submarine landsliding has occurred (Boyd et al, 2010;Clarke et al, 2012) and examines material sampled from ten gravity cores from the upper slope between 2-5 m long that were collected onboard RV Southern Surveyor in November 2008 (SS2008-V12; Boyd et al, 2010).…”