Contourite characterization and its discrimination from other deep-water deposits in the Gulf of Cadiz contourite depositional system

• Published in: Sedimentology
• Main Authors: De Castro, Sandra, Hernández Molina, Francisco Javier, De Weger, Wouter, Rodríguez-Tovar, Francisco Javier, Jiménez-Espejo, Francisco J., Mena, Anxo, Llave, Estefanía, Sierro, Francisco Javier
• Other Authors: Ministerio de Ciencia e Innovación (España), Junta de Andalucía, Ministerio de Economía y Competitividad (España)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: John Wiley & Sons 2021
• Subjects: Contourites; Deep-water processes; Gulf of Cadiz; Hemipelagites; Mixed-systems; Turbidites; Holloway; McArthur; North Atlantic
• Online Access: http://hdl.handle.net/10261/258983; https://doi.org/10.1111/sed.12813

Despite numerous efforts to properly differentiate between contourites and other deep-water deposits in cores and outcrops, reliable diagnostic criteria are still lacking. The co-occurrence of downslope and along-slope sedimentary processes makes it particularly difficult to differentiate these relatively homogeneous deposits. The main aim of this paper is to identify differences in deep-water sediments based on Principal Component Analysis of grain size and geochemistry, sedimentary facies, and reinforced by microfacies and ichnofacies. The sediments studied were obtained from two International Ocean Drilling Program Expedition 339 sites in mounded and sheeted drifts in the Gulf of Cadiz. The statistical approach led to the discernment of hemipelagites, silty contourites, sandy contourites, bottom current reworked sands, fine-grained turbidites and debrites over a range of depositional and physiographic elements. These elements are linked to contourite drifts, the drift-channel transition, the contourite channel and distal upper slope. When bottom currents or gravity-driven flows are not the dominant depositional process, marine productivity and continental input settling forms the main depositional mechanism in deep-water environments. This is reflected by a high variability of the first principal component in hemipelagic deposits. The stacked principal component variability of these deposits evidences that the contourite drift and the adjacent contourite channel were influenced by the interrelation of hemipelagic, gravitational and bottom current induced depositional processes. This interrelation questions the paradigm that a drift is made up solely of muddy sediments. The interrelation of sedimentary processes is a consequence of the precession-driven changes in the intensity of the Mediterranean Outflow Water related to Mediterranean climate variability, which are punctuated by millennial-scale variability. Associated vertical and lateral shifts of the Mediterranean Outflow Water, and therefore of its interface with the East North Atlantic Central Water, controlled sediment input and favoured turbulent sediment transport in the middle slope. During the interglacial precession maxima/insolation minima, a more vigorous upper core of the Mediterranean Outflow Water and the enhanced impact of the East North Atlantic Central Water – Mediterranean Outflow Water interface allowed for the development of the sandier contourite deposits. his project was funded through the Joint Industry Project supported by BP, ENI, ExxonMobil, TOTAL, Wintershall Dea and TGS, within the framework of “The Drifters” Research Group at Royal Holloway University of London (RHUL), in conjunction with the projects CTM 2012‐39599‐C03, CGL2015‐66835‐P, CTM2016‐75129‐C3‐1‐R, CGL2016‐80445‐R (AEI/FEDER, UE) and B‐RNM‐072‐UGR18. This research used data and samples collected by IODP Expedition 339 aboard the Joides Resolution. Data was acquired at the XRF Core Scanner Lab at MARUM – Center for Marine Environmental Sciences, University of Bremen, Germany. Our thanks to Dr Javier Dorador (RHUL, UK) for the high‐resolution core imaging treatment, to Dr David Roque (ICMAN‐CSIC, Spain) for his help in the hydrographic panels from Fig. 2 , and to Dr Ángel Puga‐Bernabéu (University of Granada, Spain) for revision that helped to improve the original version of the manuscript before submission. This study significantly benefited from discussions with all who attended the IODP Exp. 339 MOW meeting in Heidelberg (Germany) in January 2019. We would like to thank Associate Editor Dr Adam McArthur and the three reviewers, Dr Rachel Brackenridge, Dr Giancarlo Davoli and Dr Adriano Viana, for their positive and constructive comments that helped us improve the manuscript.