Provenance and Pathways of Late Quaternary Turbidites in the Deep-Water Agadir Basin, Northwest African Margin

Int J Earth Sci (Geol Rundsch) (2009) 98:721–733 DOI 10.1007/s00531-008-0313-4 ORIGINAL PAPER Provenance and pathways of late Quaternary turbidites in the deep-water Agadir Basin, northwest African margin Michael Frenz Æ Russell B. Wynn Æ Aggeliki Georgiopoulou Æ Vera B. Bender Æ Gayle Hough Æ Douglas G. Masson Æ Peter J. Talling Æ Bryan T. Cronin Received: 29 January 2007 / Accepted: 11 March 2008 / Published online: 28 March 2008 Ó Springer-Verlag 2008 Abstract A series of individual turbidites, correlated volume volcaniclastic turbidites are attributed to a Canary over distances[100 km, are present in the recent fill of the Islands landslide source, while several small mud-domi- Agadir Basin, offshore northwest Africa. The aim here is to nated turbidites are interpreted to be locally sourced from unravel multiple turbidite source areas and flow pathways, hemipelagic-draped seamounts (e.g. Turbidite AB10). and show how turbidite provenance studies contribute to Finally, Turbidite AB1 (*1 ka) is only present in the interpretation of flow processes. Agadir Basin turbidites are western Agadir Basin, and is linked to recent ‘‘re-activa- sourced from four main areas, with the majority originating tion’’ of the Sahara Slide headwall. The muddy suspension from the siliciclastic Morocco Shelf; their sand-mud dis- clouds of three large-volume flows, all linked to large-scale tribution is strongly controlled by flow sediment volume, landslides, have covered huge areas of seafloor and flowed with relatively low-volume flows dying out within the along or even slightly upslope for long distances. It is Agadir Basin and large-volume flows bypassing significant proposed that northeastwards-flowing bottom currents have sediment volumes to basins further downslope. Two large- aided transport of these dilute flow fractions into and across the Agadir Basin. Keywords Agadir Basin Á Morocco Shelf Á Canary Islands Á Turbidites Á Sediment provenance M. Frenz Á R. B. Wynn (&) Á G. Hough Á D. G. Masson National Oceanography Centre, European Way, Southampton, Hampshire SO14 3ZH, UK e-mail: [email protected] Introduction and aims M. Frenz The Moroccan Turbidite System (Wynn et al. 2002) con- e-mail: [email protected] sists of three interlinked deep-water basins: the Agadir A. Georgiopoulou Basin, Seine Abyssal Plain and Madeira Abyssal Plain School of Earth, Ocean and Planetary Sciences, (Fig. 1a). The Agadir Basin and Seine Abyssal Plain, both Cardiff University, Park Place, Cardiff CF10 3YE, UK at water depths of *4,400 m, are separated by the Casa- V. B. Bender blanca Ridge situated west of the Casablanca Seamount. Department of Sedimentology and Paleoceanography, The Agadir Basin and Madeira Abyssal Plain (water depth University of Bremen, Klagenfurter Strasse, of *5,400 m) are connected by a 600-km long network of 28334 Bremen, Germany shallow channels termed the Madeira Distributary Channel P. J. Talling System (Masson 1994; Wynn et al. 2000a). The Agadir Department of Earth Sciences, University of Bristol, Basin, situated most proximal to the Moroccan continental Queens Road, Bristol BS8 1RJ, UK margin, is confined by the volcanic Madeiran archipelago to the north, and a group of volcanic seamounts (including B. T. Cronin Deep Marine, 9 North Square, Footdee, Dacia Seamount and the Selvage Islands) to the south Aberdeen AB11 5DX, UK (Fig. 1a, b). 123 722 Int J Earth Sci (Geol Rundsch) (2009) 98:721–733 36°N a every 10,000 years (Weaver and Kuijpers 1983; Weaver et al. 1992; Wynn et al. 2002) individual turbidites are Seine Abyssal Plain 34°N usually separated by discrete hemipelagic intervals. Min- Madeira Rise D13 eralogical and geochemical analysis of turbidites in the Madeira Madeira Abyssal Plain has previously revealed three main Abyssal 32°N Plain DS Ag C ad source areas (de Lange et al. 1987; Jarvis and Higgs 1987; MDCS Fig. 1b an ir s C yo Atla an n ary D SI Weaver and Rothwell 1987): (1) Relatively organic-rich eb 30°N ris F Agadir s low Fig. 1c in turbidites (0.3–3% TOC) are derived from the northwest Canary nta ou Islands M African margin. (2) Turbidites rich in volcaniclastic com- 28°N ponents are attributed to the volcanic Canary and Madeiran Northwest Africa Islands. (3) Turbidites with high carbonate contents origi- Fig. 5 26°N nate from a pelagic-draped seamount source west of the Sahara Slide ~500 km Madeira Abyssal Plain. The connection of volcaniclastic 24°N turbidites to the Canary Islands has subsequently been ° ° ° ° ° ° ° ° ° ° 26 W 24 W 22 W 20 W 18 W 16 W 14 W 12 W 10 W 8 W reinforced by the recognition and interpretation of a num- b ber of Quaternary submarine landslides in the archipelago (Holcomb and Searle 1991; Watts and Masson 1995; Masson 1996; Urgeles et al. 1997; Masson et al. 1998, 2002, 2006; Wynn and Masson 2003, Fig. 1c). The turbidite succession and stratigraphy in the Madeira Abyssal Plain (Weaver et al. 1992) and Seine Abyssal Plain D13071 (Davies et al. 1997) has been tied in to the Agadir Basin sequence by Wynn et al. (2002). They used a variety of techniques, including magnetic susceptibility, sand fraction mineralogy and coccolith stratigraphy, to correlate indi- C vidual turbidites in a sequence spanning the last *200 ka. Their study recognised four main groups of turbidites in the Agadir Basin: (1) Turbidites with very low magnetic susceptibility and a basal sand fraction dominated by terrigenous clastic and shelfal biogenic constituents; these are sourced from the Moroccan margin and are introduced via the Agadir Canyon. (2) Turbidites with very high magnetic susceptibility and volcaniclastic sand bases; these are sourced from the submarine slopes of the Canary Islands. (3) Turbidites in the northeast Agadir Basin with Fig. 1 a General study area location map (inset) and shaded 3D very low magnetic susceptibility and a carbonate-rich bathymetry of the northwest African continental margin, showing (microfossil) composition; these are interpreted to be features that are referred to in the text. Locations of Figs. 1b, c and 5 sourced from the flanks of the Casablanca Seamount. (4) are indicated. Small black circles show locations of cores used in this Turbidites that could not be attributed to a specific source study. MDCS Madeira Distributary Channel System, SI Selvage Islands, DS Dacia Seamount. b Shaded 3D bathymetry map of the (based on available data). Here, we follow the Agadir Agadir Basin, showing locations of cores used in this study; those in Basin stratigraphy of Wynn et al. (2002), whereby the black and labelled are referred to in the text, while core CD166/12 youngest turbidite in the studied sequence is termed AB1 (shown in Fig. 2) is highlighted in red. c Shaded 3D bathymetry map and the oldest AB14. of the western Canary Islands, showing the location of mapped 3 landslides on the flanks of El Hierro, La Palma and Tenerife (redrawn Several large-volume turbidites ([100 km sediment from Masson et al. 2002). Dark colours highlight landslides that are volume), originating from both the Moroccan margin and connected to two prominent volcaniclastic turbidites in the studied the Canary Islands, have been found in all three basins of sequence of the Agadir Basin: El Golfo turbidite AB2 and Icod the Moroccan Turbidite System, e.g. turbidites AB5, AB12 turbidite AB14 and AB14. This indicates that large turbidity currents from both sources are able to negotiate the 40–80 m high Casablanca Ridge between the Agadir Basin and the Seine The sedimentary fill of basins in the Moroccan Turbidite Abyssal Plain (Davies et al. 1997; Wynn et al. 2002, System comprises turbidites interbedded with hemipelag- Fig. 1a, b). To the west, the Madeira Distributary Channel ites. Due to a relatively low turbidite frequency of *1 System acts as a conduit for large-volume turbidity 123 Int J Earth Sci (Geol Rundsch) (2009) 98:721–733 723 currents flowing westwards from the Agadir Basin and Turbidite provenance and flow pathways western Canary Islands to the Madeira Abyssal Plain (Masson 1994, Fig. 1a). Volcaniclastic turbidites During cruise CD166, in late 2004, 50 piston cores were recovered from the Agadir Basin, of which 31 were Multi-sensor core logging of Agadir Basin cores is espe- located on the basin floor. The increased core coverage cially useful for picking out turbidites with relatively high provides greater confidence (compared to previous studies MS values, e.g. turbidites AB2, AB8 and AB14 (Fig. 2). in the area) when correlating individual turbidite beds The high MS values contrast strongly with all other Agadir over several hundred kilometres, and allows a more Basin turbidites, which generally show very low MS (see detailed evaluation of turbidite source areas and flow below). The high MS values are due to elevated ferro- pathways. This study aims to integrate analyses of the magnetic mineral contents, resulting from a dominance of new CD166 cores with previous results (e.g. Wynn et al. volcanic glass and basaltic rock fragments (Wynn et al. 2002), to better constrain source areas for individual 2002). These volcanic components are responsible for turbidites in the Agadir Basin over the last *200 ka. The other characteristics of these turbidites, including the dark results are intended to improve understanding of recent grey or black colour and high Fe and Ti contents (Fig. 2). deep-water basin fill successions in areas with multiple sources, and to highlight some of the associated com- Turbidite AB2 plexities. It should be noted that detailed analysis of gravity flow processes, deposit geometry and architecture, Previous investigation of mass wasting deposits around the and landslide-turbidite linkages in the Agadir Basin will western Canary Islands suggested a link between the El be covered by separate contributions (e.g.

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