Deep-sea sedimentation offshore eastern Taiwan: Facies and processes characterization Rémi Lehu a,b, ⁎, Serge Lallemand a,c , Shu-Kun Hsu b,c , Nathalie Babonneau d,c , Gueorgui Ratzov e , Andrew T. Lin b,c , Laurent Dezileau a,c a Université de Montpellier, Géosciences Montpellier, 34090 Montpellier, France b Department of Earth Sciences, National Central University, Zhongli, Taiwan c LIA, ADEPT, France–Taiwan d Université de Brest, UMR 6538 Domaines Océaniques, 29280 Plouzané, France e GéoAzur, Université de Nice/Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06560 Valbonne, France abstract article info Article history: Received 19 May 2014 Received in revised form 20 May 2015 Accepted 25 May 2015 Available online 26 June 2015 Keywords: Active margin Morphosedimentary mapping Slope instabilities Turbidites Recent sedimentary facies and processes along the offshore slope of east Taiwan are investigated using a large set of geophysical and sedimentological data. The Taiwan orogen is often considered as one of the most tectonically active regions in the world and also suffers important climatic activity with an average of four typhoons per year. We have mapped in details the morphosedimentary features and characterized the sedimentary facies along offshore eastern Taiwan. There, we show that the slope is driven by a variety of erosional processes from mass wasting to turbidity current. Mass movements such as slides or mass transport deposits (MTDs) are ubiquitous and affect the whole east coast off Taiwan. Detailed core investigations, such as grain size analysis, chemical and mineralogical composition, revealed that turbidite facies range from thin fine-grained turbidites to thick massive turbidite facies. The detailed analysis of turbidite beds allow us to discuss the controlling factors of turbidity current generation. Turbidity currents represent an important sedimentary process that governs the slope morphology off east Taiwan. Triggering mechanisms likely range from slope instabilities related to earth- quakes shaking to failure relative to climatic-controlled pulses of sediment supply. We propose that at least two end-members are characteristics in our turbidite records in term of controlling factor: 1) Turbidity currents likely generated by tectonic activity and earthquakes shaking in particular; and 2) Turbidity currents likely generated by climatic activity such as typhoon-induced floods. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Along active margins, gravity flows represent the main erosional process that controls slope morphology and governs sediment dispersal in the oceanic realm (Masson et al., 2006). Gravity flows include mas- sive debris avalanches (Collot et al., 2001), slide/slumps, cohesive debris flows, fluidized flows (Mulder and Cochonat, 1996; Mulder and Alexander, 2001) and turbulent flows such as turbidity currents (Bouma, 1962; Mulder and Alexander, 2001). These sedimentary pro- cesses result in a variety of deposits (slumps, MTDs, Turbidites) and are triggered or facilitated by a wide range of factors including tectonic forcing (uplift and slope oversteepening, earthquakes) and climatic forcing (catastrophic floods, sea-level variations, wave loading, storms, sediment overloading), or a combined effect of both (Einsele, 1996; Locat and Lee, 2002; Piper and Normark, 2009). Additionally, long- shore currents may also locally rework, transport and accumulate shelf material or the one supplied by rivers (Romans et al., 2009; Covault and Graham, 2010). The Taiwan mountain belt, represents a peculiar place to investigate such sedimentary processes because it displays a variety of morphological settings, an intense tectonic and seismic activity, and high sedimentation rates (Huh et al., 2004, 2006). Since the last decades, the Taiwan area has been studied through abun- dant tectonic and geophysical investigations but it appears that only few studies focused on morphosedimentary processes (Huang et al., 1992; Dadson et al., 2005; Ramsey et al., 2006). Because of a lack of “ground- truth” data it is still uncertain to provide a clear assessment about the erosional processes that shape the seafloor offshore eastern Taiwan and their controlling factors. Using a compilation of a large pre-existing geophysical dataset and newly acquired sedimentological data, we aim to characterize the variability of sedimentary facies in such an active context. This work will provide new considerations on Marine Geology 369 (2015) 1–18 ⁎ Corresponding author at: Géosciences Montpellier, Montpellier, France. E-mail address: lehu.remi@gmail.com (R. Lehu). http://dx.doi.org/10.1016/j.margeo.2015.05.013 0025-3227/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Marine Geology journal homepage: www.elsevier.com/locate/margeo