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Oceanographic Processes and Morphosedimentary Products Along the Iberian Margins: a New Multidisciplinary Approach

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Oceanographic Processes and Morphosedimentary Products Along the Iberian Margins: a New Multidisciplinary Approach Marine Geology 378 (2016) 127–156 Contents lists available at ScienceDirect Marine Geology journal homepage: www.elsevier.com/locate/margo Oceanographic processes and morphosedimentary products along the Iberian margins: A new multidisciplinary approach F. Javier Hernández-Molina a,⁎, Anna Wåhlin b,MiguelBrunoc, Gemma Ercilla d, Estefanía Llave e, Nuno Serra f, Gabriel Rosón g,PerePuigd, Michele Rebesco h, David Van Rooij i,DavidRoquej, César González-Pola k, Francisco Sánchez l,MaríaGómezm,BenedictPreun, Tilmann Schwenk o, Till J.J. Hanebuth p,q, Ricardo F. Sánchez Leal r, Jesús García-Lafuente s, Rachel E. Brackenridge t,u,CarmenJuand,i, Dorrik A.V. Stow t,JoséMaríaSánchez-Gonzálezg a Dept. Earth Sciences, Royal Holloway Univ. London, Egham, Surrey TW20 0EX, UK b Department of Earth Sciences, University of Gothenburg, PO Box 460, SE 405 30 Göteborg, Sweden c CACYTMAR. Univ. Cádiz, Avda República Saharaui S/N, Puerto Real, 11510, Cádiz, Spain d CSIC, ICM, Paseo Marítimo de la Barceloneta, 37-49, 08003 Barcelona, Spain e Instituto Geológico y Minero de España Ríos Rosas, 23, 28003, Madrid, Spain f Institut für Meereskunde, Univ. Hamburg, Bundesstr. 53, 20146, Hamburg, Germany g Facultad de Ciencias do Mar, Univ. Vigo, 36200 Vigo, Spain h OGS, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Borgo Grotta Gigante 42/C, 34010 Sgonico, TS, Italy i Renard Centre of Marine Geology, Dept. of Geology and Soil Science. Ghent University, Krijgslaan, 281 S8 B-9000 Gent, Belgium j CSIC, ICMAN, Campus Universitario Rio San Pedro s/n. Puerto Real, Cádiz, CP 11510, Spain k Instituto Español de Oceanografía, C.O. Gijón. c/ Príncipe de Asturias 70 Bis., CP 33212, Gijón, Spain l Instituto Español de Oceanografía, C.O. de Santander, Promontorio San Martín s/n, Apdo 240, 39080 Santander, Spain m Instituto Español de Oceanografía, c/Corazón de María 8, 28002, Madrid, Spain n Chevron Upstream Europe, Chevron North Sea Limited, Seafield House, Aberdeen AB15 6XL, UK o MARUM — Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany p School of Coastal and Marine Systems Sciences, Coastal Carolina University, P.O. Box 261954, Conway, SC 29528, USA q Marine Sedimentation Systems Group, MARUM — Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359, Bremen, Germany r Instituto Español de Oceanografía, C.O. de Cádiz, Muelle de Levante s/n, P.O. Box 2609, 11006 Cádiz, Spain s Physical Oceanography Group, University of Malaga, ETSI Telecomunicación, Campus de Teatinos, s/n 29071 Málaga, Spain t Institute of Petroleum Engineering, Heriot-Watt Univ., Edinburgh EH14 4AS, Scotland, UK u Shell International Exploration & Production, B.V. Carel van Bylandtlaan 05.0B.03, 2596, HR, The Hague, Netherlands article info abstract Article history: Our understanding of bottom-currents and associated oceanographic processes (e.g., overflows, barotropic tidal Received 6 June 2015 currents) including intermittent processes (e.g., vertical eddies, deep sea storms, horizontal vortices, internal Received in revised form 13 November 2015 waves and tsunamis) is rapidly evolving. Many deep-water processes remain poorly understood due to limited Accepted 17 December 2015 direct observations, but can generate significant depositional and erosional features on both short and long Available online 20 December 2015 term time scales. This paper represents a review work, which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the Iberian continental margins. Keywords: Iberian margins This review explores the implications of the studied processes, given their secondary role relative to other factors Oceanographic processes such as mass-transport and turbiditic processes, and highlights three major results: a) contourite depositional Bottom currents and erosional features are ubiquitous along the margins, indicating that bottom currents and associated oceano- Sedimentary processes graphic processes control the physiography and sedimentation; b) the position of interfaces between major Contourites water masses and their vertical and spatial variation in time specifically appears to exert primary control in de- termining major morphologic changes along the slope gradient, including the contourite terraces development; and c) contourites deposits exhibit greater variation than the established facies model suggests. Therefore, a con- sistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development. An integrated interpretation of these oceanographic processes requires an understanding of contourites, seafloor features, their spatial and temporal evolution, and the near-bottom flows that form them. This approach will synthesize oceanographic data, seafloor morphology, sediments and seismic images to improve our knowledge of permanent and intermittent processes around Iberia, and evaluate ⁎ Corresponding author. E-mail address: [email protected] (F.J. Hernández-Molina). http://dx.doi.org/10.1016/j.margeo.2015.12.008 0025-3227/© 2015 Elsevier B.V. All rights reserved. 128 F.J. Hernández-Molina et al. / Marine Geology 378 (2016) 127–156 their conceptual and regional role in the margin's sedimentary evolution. Given their complexes, three- dimensional and temporally-variable nature, integration of these processes into sedimentary, oceanographic and climatological frameworks will require a multidisciplinary approach that includes Geology, Physical ocean- ography, Paleoceanography and Benthic Biology. © 2015 Elsevier B.V. All rights reserved. 1. Introduction generally exhibit persistent net flow along-slope (following the local bathymetry), but can considerably vary in direction and velocity Deep-marine settings have been considered until 1980s as relatively (Stow et al., 2009). Overflows, tides, including internal tides and other low energy and quiescent depositional environments where deep- intermittent processes such as bottom reaching (vertical) eddies, deep water masses flow as relatively slow-moving tabular bodies and depo- sea storms, (horizontal) vortices, internal waves, solitons, tsunami re- sition is episodically interrupted by down-slope gravity driven process- lated currents, rogue waves and cyclonic waves (during storms and hur- es. However, since the 1990s it has been demonstrated that deep-water ricanes) can also affect bottom currents (Fig. 1) (e.g., Shanmugam, masses can exhibit relatively high velocity and play a dominant deposi- 2012a, 2013a, 2013b, 2014; Rebesco et al., 2014). These processes mod- tional role in certain areas (e.g., Rebesco et al., 2014). These conditions ulate the bottom currents and their speed, instantaneous direction, and hold especially when water masses interact with local seafloor irregu- tend to develop local and regional hydrodynamic structures (e.g., cores, larities (i.e., seamounts, ridges, hills, mounds, banks, scarps). Flow branches, filaments, eddies, vortices, local turbulence, internal waves, through deep oceanic gateways, straits or basins can also generate helicoidal flows, vertical columns). Many of these oceanographic high velocity and turbulent flows, resulting in regional-scale erosional, deep-water processes are poorly understood but can generate pervasive depositional and mixed morphological features. Understanding these depositional and erosional features over both short- and long-term time seafloor features therefore requires a more detailed model of bottom scales (Shanmugam, 2013b; Rebesco et al., 2014 and reference therein). current effects. Contourites are defined as sediments deposited or substantially The general term ‘bottom current’ refers to deep-water currents reworked by the persistent action of bottom currents (e.g., Stow et al., capable of eroding, transporting, and depositing sediments along the 2002a; Rebesco, 2005; Rebesco et al., 2014). The term “contourites” seafloor (Rebesco and Camerlenghi, 2008). Background bottom was originally intended to define sediments deposited in the deep sea currents are the result of both the ocean thermohaline circulation by contour-parallel thermohaline currents (Hollister and Heezen, (THC) and the ocean wind-driven circulation (Rahmstorf, 2006). They 1967). Usage of the term has subsequently widened to include a larger Fig. 1. 3D sketch depicting the possible oceanographic processes in deep-water environments. In addition to density currents and overflows, the velocity at the seafloor can also be affected by barotropic currents or intermittent processes like cascading, giant eddies, deep sea storms, vortices, internal waves, internal tides, tsunamis, cyclone waves and rogue waves. (From Rebesco et al., 2014, with permission from Elsevier). F.J. Hernández-Molina et al. / Marine Geology 378 (2016) 127–156 129 range of deposits affected by different types of currents (Rebesco et al., formation is closely associated with convection in a few localities. 2014). Bottom currents are capable of building thick and extensive ac- These mainly occur in the subpolar convergence zone of the Northern cumulations of sediments referred to as “contourite drifts”. The term Hemisphere and the convergence zone of the Antarctic polar front in “contourite depositional system” (CDS) refers to large contourite de- the Southern Hemisphere. The principal deep-water masses forming posits (drifts) associated with erosional features in an environment part of
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