The Holocene occurrence of cold water corals in the NE Atlantic: Implications for coral carbonate mound evolution

U-series dating of constructional cold-water corals is a powerful tool to reconstruct the evolution of corals on carbonate mounds. Here we have investigated the time framework of corals such as Lophelia pertusa and Madrepora oculata on five different mound settings of the eastern North Atlantic (on Rockall Bank and in Porcupine Seabight), sampled at variable depth and location (610-880 m water depth). We have found that the past 11 ka reflect a period generally favourable for coral development. We further determined local mound growth rates and identified mound surface erosion (framework collapse) during times of active coral framework construction. "Local" vertical mound growth rates vary between less than 5 cm ka(-1) and up to 220 cm ka(-1). We interpret rates exceeding 15 cm ka(-1) as representative of densely populated coral reefs. During times of reduced or absent coral development, mound evolution rates are by far smaller (0 to <5 cm ka(-1)). The time resolution achieved here furthermore provides first evidence for reduced coral (ecosystem) activity at 1.8-2.0 ka, 4.2-4.8 ka and between 6 and 8.2 ka within the Holocene that may be related to climate driven changes of the coral growth environments. During Glacial periods coral growth in those areas seems apparently extremely reduced or is even absent on mounds. (C) 2009 Elsevier B.V. All rights reserved.