Carbonate mound development in contrasting settings on the Irish margin Cees van der Land a,n , Markus Eisele b , Furu Mienis a , Henk de Haas a , Dierk Hebbeln b , John J.G. Reijmer c , Tjeerd C.E. van Weering a,d a Royal Netherlands Institute for Sea Research, Department of Marine Geology, P.O. Box 59,1790 AB Den Burg, The Netherlands b MARUM, Center for Marine Environmental Sciences, University of Bremen, Leobener Str., 28359 Bremen, Germany c Faculty of Earth and Life Sciences, Department of Sedimentology, VU University Amsterdam, De Boelelaan 1085,1081 HV, Amsterdam, The Netherlands d Faculty of Earth and Life Sciences, Department of Paleoclimatology and Geo-morphology, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands article info Available online 15 October 2013 Keywords: Cold-water coral mound Rockall Trough Porcupine Seabight North-Atlantic Deep-sea corals Carbonate content Cementation abstract Cold-water coral carbonate mounds, formed by framework building cold-water corals, are found in several mound provinces on the Irish margin. Differences in cold-water coral mound development rates and sediment composition between mounds at the southwest Rockall Trough margin and the Galway Mound in the Porcupine Seabight are investigated. Variations in sediment composition in the two mound provinces are related to the local environmental conditions and sediment sources. Mound accumulation rates are possibly higher at the Galway Mound probably due to a higher influx of hemipelagic fine grained non-carbonate sediments. In both cold-water coral mound areas, mound growth has been continuous for the last ca 11,000 years, before this period several hiatuses and unconformities exist in the mound record. The most recent unconformity can be correlated across multiple mounds and mound provinces at the Irish margin on the basis of apparent age. On the southwest Rockall Trough margin these hiatuses/unconformities are associated with post-depositional aragonite dissolution in, and lithification of, certain intervals, while at Galway Mound no lithification occurs. This study revealed that the influx and types of material transported to cold-water coral mounds may have a direct impact on the carbonate mound accumulation rate and on post-depositional processes. Significantly, the Logachev Mounds on the SW Rockall Trough margin accumulate slower but, because they contain lithified layers, are less susceptible to erosion. This net effect may account for their larger size compared to the Belgica Mounds. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Cold-water corals are widely distributed and thrive on continental shelves, continental margins, on seamounts in fjords and on canyon walls around the world (Cairns, 2007; Freiwald and Roberts, 2005; Roberts et al., 2006; Roberts et al., 2009). Under specific environmental conditions framework building cold-water corals such as Lophelia pertusa and Madrepora oculata can form elevated structures, so called cold-water coral mounds. Vital for reef and mound growth is the presence of a dense coral frame- work, creating local low energy environments, promoting the accumulation of hemipelagic and bedload sediment between the coral branches (De Haas et al., 2009; Dorschel et al., 2007; Mienis et al., 2009; Roberts et al., 2006; Wheeler et al., 2005a). Several carbonate mound provinces are reported from the Irish margin (Dorschel et al., 2010; Wheeler et al., 2007), on both sides of the Rockall Trough (RT) (Akhmetzhanov et al., 2003; De Haas et al., 2009; Kenyon et al., 2003; Van Weering et al., 2003a; Wheeler et al., 2005b), on the western Rockall Bank (RB) (Wienberg et al., 2008) and in the Porcupine Seabight (PS) (De Mol et al., 2002; Henriet et al., 1998; Hovland et al., 1994; Huvenne et al., 2002; Huvenne et al., 2003)(Fig. 1). Carbonate mounds in the PS and along the SW Rockall Trough (SW RT) margin occur in a confined depth zone, where strong currents enhance the food supply to the corals and prevent the living corals from getting smothered by sediment (Dorschel et al., 2007; Duineveld et al., 2007; Mienis et al., 2007; White et al., 2005). However, some significant differences exist between the two areas, in mound morphology (Wheeler et al., 2007), local near-bed hydrodynamics (Huvenne et al., 2005; White and Dorschel, 2010), cold-water coral facies distribution (De Haas et al., 2009; Dorschel et al., 2007; Rüggeberg et al., 2007) and the composition of mound sediments (Dorschel et al., 2005; Eisele et al., 2008; Mienis et al., 2009; Titschack et al., 2009). The latter is the focus of this paper. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dsr2 Deep-Sea Research II 0967-0645/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dsr2.2013.10.004 n Corresponding author. Current address: Newcastle University, School of Civil Engineering and Geosciences, Drummond Building, Newcastle upon Tyne NE1 7RU, UK. Tel.: þ44 191 208 6513. E-mail address: cees.van.der.land@ncl.ac.uk (C. van der Land). Deep-Sea Research II 99 (2014) 297–306