Mass-transport deposits, olistostromes and soft-sediment deformation in modern and ancient continental margins, and associated natural hazards

Mass-transport deposits (MTDs), olistostromes and related softsediment deformation structures represent significant components of the geological architecture of both modern and ancient continental margins, including active, passive and hybrid margin types (Dilek and Rowland, 1993; Stoker et al., 1998; Dilek and Robinson, 2003; Lamarche et al., 2008; Madon, 2010; Ratzov et al., 2010; Anma et al., 2011; Pini et al., 2012; Festa et al., 2013), and are commonly associated with earthquakes and tsunamis (e.g., Tappin et al., 2008). These tsunamic events adversely affected the human populations, engineering infrastructures and global economy, and inflicted severe and locally irrecoverable damages on the coastal ecosystems (e.g., Yamada et al., 2012 and references therein). Improving our understanding of the mechanisms and processes of slope failure andMTDdevelopment, their spatial and temporal relationships with seismic events, and the dynamic equilibrium of active, passive and hybrid continental margins is one of the most urgent and challenging tasks faced by modern Earth science. To that end, a key approach to increase our scientific knowledge on these topics of both great scientific and societal importance is a comparative analysis of modern and ancient examples of MTDs, chaotic rock bodies and olistostromes (sensu Flores, 1955 or “sedimentary melanges” sensu Bettelli and Panini, 1985; Festa et al., 2012), and the processes of their formation. Interdisciplinary investigations in the last 30 years of modern passive and active continental margins through 3D-seismic reflection, multibeam sonar and submersible studies (including drilling, coring and in situ sampling) and analogue modeling played a major role in our comprehension of the mode, nature and scale of the formation of modern submarine MTDs with respect to their causative events. On the other hand, on-land studies of exhumed, ancient MTDs (or olistostromes) have provided useful information on their internal structure and stratigraphy at scales (meters to hundreds of meter) that are commonly difficult to obtain through marine studies mainly because of poor acoustic transparency below the standard seismic resolution. Hence, studies of modern and ancient MTDs/olistostromes are highly complementary and essential.