Southeast Australia: A Cenozoic Continental Margin Dominated by Mass Transport

Abstract

This book, "Submarine Mass Movements and Their Consequences IV", is dedicated to the memory of two colleagues whose wide-ranging field studies did so much to advance our understanding of deep-water sedimentation systems: Drs. Bill Normark and Bruno Savoye. I had the good fortune to count them among my closest professional and personal friends. Both were sea-going scientists par excellence, both were warm and supportive individuals, who always had time for students, and both were modest about their own accomplishments. Although many will remember Bill for his work on turbidites and submarine fans, he made important early contributions to our understanding of submarine mass movements. Large slides are a significant component of deep-water terrigenous basins and thus did not escape Bill's curiosity. In 1968, during his Ph.D. work, he acquired seabed imagery and sub-bottom profiles with the Scripps deeptow system over Ranger slide off Baja California. His 1974 and 1990 papers on this slide are classic Normark: meticulous use of multiple data sets and a clear mind as to what were the important issues. As Chief Scientist of the gloria cruise that mapped the seafloor around the Hawaiian islands, he was the first to appreciate the full extent of the flank-collapse debris avalanches, using the terms "prodigious" and "humongous" in the literature (and "giant" when reined in by editors).Likewise, Bruno is remembered by many for his work on turbidite systems, but he too worked on submarine slides, particularly earlier in his career. The first paper that he and I worked on together described a slide near the wreck of the Titanic, where his colleagues at ifremer had collected a magnificent survey with the next generation of deep-tow technology, the ifremer sar, but just missed the wreck. He is well known for his contributions on the 1979 Nice landslide, which triggered both a tsunami and a turbidity current. Bruno brought his enthusiasm and energy, together with his organisational and analytical skills as an engineer, to the science of turbidites and mass movements. He combined the technological expertise of ifremer, industry funding and his own instinct of what was necessary to make significant scientific advances at sea.Mass movements are an important part of the turbidite story. For Bill and Bruno, during much of their careers, mass movements were regarded as the predominant cause of turbidity currents. Both played an important role in challenging that dogma in recent years. Those who study mass movements from the comfort of the seismic work-station or by numerical modelling owe a lot to seagoing scientists like Bruno and Bill who laid the groundwork of where, why and how submarine mass-movements occur in the field.

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

“…These features are representative of slope failures that occurred in the two dominant slope morphologies present in the study area (see Figure 3) identified by Boyd et al (2010), Clarke et al (2012), and Clarke (2014): a) the relatively steep (3-7°) and canyon-incised slope (Bribie Bowl Slide and Bryon Slide); and b) the relatively gentle slope (1-3°) of the Nerang Plateau (Coolangatta-1, -2 slides and Cudgen Slide). Ten gravity cores from the upper continental slope (<1200 m) were examined in this work (Figure 2), with at least one gravity core recovered from each of the five submarine landslide scars investigated.…”

“…It extends 1500 km from the Great Barrier Reef to Bass Strait and forms the western continental physiographic boundary of the Tasman Sea. 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).…”

“…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). Five cores that contain boundary surfaces are identified by a sharp, colour-change boundary, small increases in sediment stiffness, slight increases in sediment density, and distinct gaps in AMS 14 C age of at least 25 ka.…”

“…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).…”