Rüggeberg, Andres (2003) Environmental Control on Growth and Development of a Deep-Water Carbonate Mound from the Porcupine Seabight. (PhD/ Doctoral thesis), Christian-Albrechts-Universität, Kiel, Germany, 202 pp.

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Abstract

The objective of this study is to reconstruct past environmental settings locked in the sediments of a carbonate mound in the northern Porcupine Seabight, west off Ireland. Benthic foraminiferal assemblages were investigated on two sediment cores, one located on top of the mound and a second one from an off-mound position further north as control site. The off-mound samples reveal two different assemblages: (1) an Interglacial group dominated by infaunal species, and (2) a Glacial group, dominated by cassidulinid species. Due to an incomplete stratigraphic record in the on-mound core, same species of the off-mound assemblages were grouped in on-mound samples. The Interglacial group dominates and the Glacial group is less abundant throughout the entire core indicating the lack of glacial time intervals in the on-mound core, which is coherent with stable oxygen isotope data and U/Th dates on coral fragments. A third assemblage is abundant in samples of the on-mound core showing elevated epibenthic species. This Mound group shows a great affinity to strong currents, high nutrient availability and is supposed to indicate Mediterranean Outflow Water in the northern Porcupine Seabight, as well as a higher coral cover on Propeller Mound in an earlier interglacial period. A Late Pleistocene decline in mound growth for Propeller Mound is suggested by the decrease of the Mound group towards the Holocene. Finally, the reconstructed environmental setting portrays the boundary conditions of the habitable range for the cold-water corals. Their growth occurred during interglacial and interstadial periods, whereas a glacial retreat of corals is documented in the absence of glacial sediments in the on-mound core. These conclusions are summarised in a model which efficiently accounts for the mound development covering the period of the Northern Hemisphere Glaciation.

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