ORIGINAL Persistent quasi-periodic turbidite activity off Saharan Africa and its comparability to orbital and climate cyclicities C. Zühlsdorff & T. J. J. Hanebuth & R. Henrich Received: 21 June 2006 / Accepted: 15 August 2007 / Published online: 22 September 2007 # Springer-Verlag 2007 Abstract Based on a high-resolution sediment record from a submarine meandering canyon system offshore the present- day hyperarid Saharan Africa, two phases of turbidity-current activity can be distinguished during the past 13,000 years. Frequent, siliciclastic turbidity currents can be related to deglacial sea-level history, whereas rhythmically recurring fine-grained and carbonate-rich turbidity currents with recur- rence times of roughly 900 years are inferred for the Holocene. Various trigger mechanisms can be considered to initiate turbidity currents, but only a few can explain a peri- odic turbidite activity. A comparison of Holocene turbidite recurrence times and basic cycles of 900 and 1,800 years found in various Holocene paleoclimate studies suggests that a previously unrecognized climate-related coupling may be active. Introduction Besides normal marine sedimentation, terrigenous sediment supply, and alongslope sediment transport processes, continental margins are often influenced by gravity flows. Significant amounts of sediments are thereby transported from the ocean margins into deep-sea basins, sometimes involving voluminous sediment packages, and/or rapid sediment flows due to slope failures, which bear the po- tential for natural hazards. Examples of mechanisms that are generally considered to initiate slope instability in the marine domain include seismic and volcanic activity, rapid sediment accumulation and oversteepening, gas charging, gas hydrate dissociation, seepage, tidal or storm waves, and sea-level fluctuation. Distinct times for turbidity-current emplacement do not seem to exist; the initiation of turbidity currents de- pends rather on the prevailing forcing mechanism in a given system. Nevertheless, most channel systems appear to have been active during low sea levels (Shanmugam and Moiola 1982; Stow et al. 1985), whereas high stand turbidites (Zaragosi et al. 2000; Khripounoff et al. 2003) are less common. However, sediment records indicate that turbi- dity-current activity is also initiated at oxygen isotope stage boundaries, i.e., during periods of rapid, major sea-level rise or fall (Weaver and Kuijpers 1983; Wynn et al. 2002). The abovementioned forces are frequently proposed as responsible for the initiation of gravity flow events and turbidity currents. Some of these forces are climate- controlled. A climatically forced aggradation pattern of fan lobes in a turbiditic system completely concealed from glacioeustatic effects was shown by Weltje and de Boer (1993) for Pliocene times. However, relations between turbidite activity and Holocene climate variability have, to our knowledge, never been described before. Within this context, this study presents a high-resolution record of Cap Timiris Canyon offshore Mauritania, and associated turbidity-current activity over the past 13 cal. ka BP (calibrated thousands of years before present; i.e., 1950). Study area Along the passive continental margin off NW Africa, downslope sediment transport into the deep sea is prom- Geo-Mar Lett (2008) 28:87–95 DOI 10.1007/s00367-007-0092-0 C. Zühlsdorff (*) : T. J. J. Hanebuth : R. Henrich Faculty of Geosciences, Bremen University, Klagenfurter Straße, 28359 Bremen, Germany e-mail: christine.zuehlsdorff@geo.uib.no Present address: C. Zühlsdorff Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway