Submarine Landslides

Subaqueous Mass Transport Deposits from Outcrops to Seismic Profiles

Kei Ogata, Andrea Festa, Gian Andrea Pini, Kei Ogata, Andrea Festa, Gian Andrea Pini

• Publisher: American Geophysical Union
• Year: 2019
• Print ISBN: 9781119500582
• eBook ISBN: 9781119500636
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Geophysics

An examination of ancient and contemporary submarine landslides and their impact

Landslides are common in every subaqueous geodynamic context, from passive and active continental margins to oceanic and continental intraplate settings. They pose significant threats to both offshore and coastal areas due to their frequency, dimensions, and terminal velocity, capacity to travel great distances, and ability to generate potentially destructive tsunamis.

Submarine Landslides: Subaqueous Mass Transport Deposits from Outcrops to Seismic Profiles examines the mechanisms, characteristics, and impacts of submarine landslides.

Volume highlights include:

• Use of different methodological approaches, from geophysics to field-based geology
• Data on submarine landslide deposits at various scales
• Worldwide collection of case studies from on- and off-shore
• Potential risks to human society and infrastructure
• Impacts on the hydrosphere, atmosphere, and lithosphere

Part I
Submarine Landslide Deposits in Orogenic Belts

1
Submarine Landslide Deposits in Orogenic Belts: Olistostromes and Sedimentary Mélanges

Kei Ogata¹, Andrea Festa², Gian Andrea Pini³, and Juan Luis Alonso⁴

¹ Faculty of Science, Department of Earth Sciences, Free University of Amsterdam, Amsterdam, The Netherlands

² Department of Earth Sciences, University of Turin, Turin, Italy

³ Department of Mathematics and Geosciences, University of Trieste, Trieste, Italy

⁴ Department of Geology, University of Oviedo, Oviedo, Spain

ABSTRACT

Olistostrome and sedimentary mélange are two synonymous genetic terms referring to the “fossil” products of ancient submarine mass‐transport processes exhumed in orogenic belts. Lithology, stratigraphy, lithification degree, and structural anatomy of these units reflect the synergic and combined action of different mass‐transport processes leading to composite deposits developed through multistage deformation phases. The general depositional physiography, tectonic setting, and the type, scale, and rate of slide mass transformation mechanisms during the downslope motion and emplacement and postdepositional processes are the main factors controlling the final internal anatomy of olistostromes and sedimentary mélanges. These features are commonly progressively reworked by subsequent burial, diapiric, and tectonic processes and may be eventually almost completely obliterated by metamorphic processes during orogenic belt and/or subduction complex evolution. The correct recognition of olistostromal units and their intrinsic features in different orogenic belts needs extensive and careful fieldwork and ultimately provides excellent proxies for the timing of various tectonic‐sedimentary events interacting during the Wilson cycle. The basic concepts of structural geology, sedimentology, stratigraphy, and basin analysis should be jointly applied in studying the internal structure, lithological arrangement, and formation‐deformation mechanisms of olistostromes and sedimentary mélanges.

1.1. INTRODUCTION

Major sedimentary accumulations (basin wide) originated from large‐scale submarine landslides and slope failures crop out widely within the sedimentary record of mountain belts throughout the world (Figure 1.1). These ancient “fossil” counterparts of the mass‐transport deposits (MTDs) and mass‐transport complexes (MTCs), which are commonly observed in the geophysical profiles of present‐day continental margins (see, e.g., Hampton et al., 1996; Weimer & Shipp, 2004, and further discussed in Part II), are also known by the synonymous names “olistostrome” or “sedimentary mélange.” Such units are invaluable tools for the study of the internal anatomy of submarine landslide deposits across different scales (Lucente & Pini, 2008; Ogata et al., 2012a; Festa et al., 2016).

Present‐day MTDs are commonly characterized by great internal heterogeneity and deformation, resulting in two‐dimensional (2D) and three‐dimensional (3D) seismic imagery characterized by acoustic artifacts and transparent zones. For this reason, apart from some exceptions (see, e.g., Gamboa et al., 2010; Strasser et al., 2012; Ogata et al., 2014a; Alves, 2015), including the most representative ones discussed in this book, the complex internal structure of MTDs usually has been overlooked. Detailed studies combining high‐resolution marine geophysical data, outcrop‐based surveys, and core analysis show systematic partitions of the internal structural arrangement of MTDs and MTCs into discrete deformation domains, suggesting (i) differential movement of discrete bodies of mass during translation and emplacement, (ii) episodic pulses during the same depositional event(s), and (iii) interplay of different synchronous mass‐transport processes (King et al., 2011; Vanneste et al., 2011; Ogata et al., 2012a, 2014b; Omosanya & Alves, 2012; Joanne et al., 2013).

Figure 1.1 (a) Geographical distribution of major olistostromes and sedimentary mélanges and some examples

(Source: Modified from Festa et al. (2016)).

(b) Oligocene‐Miocene Val Tiepido‐Canossa olistostrome, Northern Apennines, Italy. (c) Athalassa member olistostrome in the Pliocene Nicosia Formation, Cyprus. (d) Eocene Fanlo unit olistostrome, south central Pyrenees, Spain. (e) Detail of intrabasinal blocks enclosed in the Paleogene megabeds of the Friuli‐Julian Basin, NE Italy. (f) Basalt slide block in one of the Miocene Taranaki Basin olistostromes, New Zealand. (g) Fluid escape structure cutting a carbonate slide block in the Eocene Hecho Group “megaturbidites,” Pyrenees, Spain. (h) Folded slide blocks in one of the Miocene Rudeis Formation olistostromes, Sinai, Egypt. (i) Plio‐Pleistocene Chikura Group olistostrome, Japan. (j) Eastern Argentine Precordillera sedimentary mélange(s) in the Silurian La Rinconada Formation, San Juan Province, Argentina. Dashed lines indicate bedding (e.g., crude lamination, subunit boundaries, base and roof contacts). Circled person(s) for scale.

From the point of view of the internal structures and kinematics, both the lower detachment surface and the shear zones separating the individual masses inside the body are characterized by features reflecting different mechanisms of movement (e.g., Pini et al., 2010a, 2010b, 2012). Among these mechanisms are the dispersive forces due to the grain‐to‐grain acoustic resonance interactions (Melosh, 1987) and the interstitial fluid overpressure in a matrix with the characteristics of a hyperconcentrated suspension (Mutti, 1992; Mutti et al., 1999, 2006; Ogata et al., 2012a, 2012b).

Recent outcrop‐based studies, such as those discussed in Part I, document that fluid overpressure can enable slide‐flow transformation from discrete coherent movement to uniform cohesive flow, along with progressive disruption of sediment blocks and seafloor (e.g., Ogata et al., 2012a, 2014b). These studies confirm the concept of evolution of mass‐transport processes, from sliding slumping to blocky flow, debris flow, and eventually turbidity flow and deposition (Mutti et al., 2006; Festa et al., 2016).

Field‐based studi...

Table of contents

• COVER
• TABLE OF CONTENTS
• LIST OF CONTRIBUTORS
• PREFACE
• ACKNOWLEDGEMENTS
• Part I: Submarine Landslide Deposits in Orogenic Belts
• Part II: Submarine Landslide Deposits in Current Active and Passive Margins
• INDEX
• END USER LICENSE AGREEMENT