The diversity of deep-water sinuous channel belts and slope valley-fill complexes M. Janocko a, * , W. Nemec a , S. Henriksen b , M. Warcho1 c a Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway b Statoil Research Centre, Arkitekt Ebbels Veg 10, Rotvoll, 7005 Trondheim, Norway c Statoil Research Centre, Sandsliveien 90, Sandsli, 5020 Bergen, Norway article info Article history: Received 2 August 2011 Received in revised form 11 June 2012 Accepted 26 June 2012 Available online 6 July 2012 Keywords: Continental slope Offshore West Africa 3D seismics Turbidite Meandering Levée Point bar Lateral accretion package Channel-bend mound abstract The study combines interpretation of 3D seismic imagery of submarine sinuous channel belts in offshore West Africa with observations from a range of outcrop analogues. Five main architectural elements of slope channel belts are recognized: lateral-accretion packages (LAPs), channel-bend mounds, levées, non-turbiditic mass-transport deposits (MTDs) and last-stage channel-fills. Channel belts differ in their planform, cross-section and the range of architectural elements involved. Four end-member types of sinuous channel belts are distinguished, formed by meandering non-aggradational channels, levéed aggradational channels, erosional cut-and-fill channels and hybrid channels. Analysis indicates that meandering channels form when system is near its potential equilibrium profile. They evolve from nearly straight to highly sinuous by increasing first the bend amplitude and then the conduit length. Levéed channels are thought to evolve from incipient meandering conduits perturbed by aggradation and erosional channels to evolve from either levéed or meandering conduits, inheriting their sinuosity. Hybrid channels signify a failed or incomplete transformation. The channel belts occur isolated or stacked into multi-storey complexes, unconfined or formed within incised valleys. Unconfined complexes, composed of levéed channel belts, are relatively uncommon. Valley-confined complexes predominate and are overlain by isolated channel belts, often confined by the valley external levées. Valley-fill complexes are characterized by an upward fining and a general decrease in sandstone net/ gross. The majority of slope valley-fills in the study area and other reported cases show a development from deep incision to a transient equilibrium state recorded by the deposition of coarse sediment lag or non-aggradational channel belts, which are commonly overlain by MTDs emplaced when the valley reached its maximum relief. The middle to upper part of valley-fill consists of levéed channel belts recording aggradation, with possible development of non-aggradational meandering channel belts in the uppermost part prior to the valley abandonment. Similar meandering channel belts may also occasionally occur in the middle part of valley-fill succession. It is suggested that the variation among valley-fills can be due to external factors, such as slope tectonics and salt movements, or to an internal forcing through the interplay of valley incision depth, base-level change, turbiditeesystem equilibrium profile and slope general aggradation rate. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The last decade saw significant advances in the sedimentolog- ical understanding of deep-water sinuous channels and their features. Detailed studies of side-scan sonar and 3D seismic- reflection imagery have revealed a range of architectural elements associated with sinuous channels, such as lateral- accretion packages (LAPs) (Abreu et al., 2003; Mayall et al., 2006; Kolla et al., 2007; Labourdette, 2007), nested mounds (Clark and Pickering, 1996; Peakall et al., 2000), outer-bank bars (Nakajima et al., 2009), non-turbiditic mass-transport deposits (Deptuck et al., 2003; Samuel et al., 2003; Heiniö and Davies, 2007; Armitage et al., 2009), levées (Clemenceau et al., 2000; Skene et al., 2002; Babonneau et al., 2004; Hubbard et al., 2009), crevasse splays (Demyttenaere et al., 2000; Mayall and Stewart, 2000; Posamentier and Kolla, 2003; Cross et al., 2009) and last- stage channel-fills (Kneller, 2003; Wynn et al., 2007). Most of these elements have been recognized in outcrops as sandy to gravelly deposits (e.g., Morris and Normark, 2000; Lien et al., 2003; Dykstra and Kneller, 2009; Kane et al., 2009; Kane and Hodgson, 2011) and are considered to be important components of hydro- carbon reservoirs (Prather, 2003; Mayall et al., 2006). * Corresponding author. Present address: Statoil Research Centre, Sandsliveien 90, Sandsli, 5020 Bergen, Norway. Tel.: þ47 94166972; fax: þ47 55996076. E-mail addresses: mjan@statoil.com, mikejanocko@hotmail.com (M. Janocko). Contents lists available at SciVerse ScienceDirect Marine and Petroleum Geology journal homepage: www.elsevier.com/locate/marpetgeo 0264-8172/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marpetgeo.2012.06.012 Marine and Petroleum Geology 41 (2013) 7e34