Variability on Pleistocene to recent sedimentation from the Porcupine Seabight, northeastern Atlantic: Implications for Carbonate mound growth and development
The Porcupine Seabight (PSB) on the Irish continental margin contains three distinct carbonate mound provinces with many of the individual mounds being colonised by the cold-water azooxanthellate corals Lophelia pertusa and Madrepora oculata. The oceanographic regime in the PSB is one of the main co...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universität Bremen
2006
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| Online Access: | https://media.suub.uni-bremen.de/handle/elib/2361 https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000106894 |
| Summary: | The Porcupine Seabight (PSB) on the Irish continental margin contains three distinct carbonate mound provinces with many of the individual mounds being colonised by the cold-water azooxanthellate corals Lophelia pertusa and Madrepora oculata. The oceanographic regime in the PSB is one of the main controls on the location and development of these mounds. For these sea floor structures bottom currents play an important role and nowadays in the PSB the Mediterranean Outflow Water (MOW) appears to be crucial for the living cold-water coral ecosystems on these carbonate mounds. The variability in present-day bottom current speeds on Propeller Mound were studied from modern sedimentation. The dominant current direction in the PSB is from south to north, although at Propeller Mound the currents aredeflected in a southwesterly direction. Grain size and compositional analyses of box core surfaces taken from the seafloor adjacent to and from Propeller Mound in theHovland Mound Province show that the intensity of these currents varies locally. Highest current speeds occur to the west of the mound and on the mound surface, winnowing away finer sediment fractions (clay-fine silt) and leaving coarse sortable silt and sand lag deposits. Coarse grains are absent from the seafloor to the east of the mound. Local forcing of bottom currents is likely due to the elevated topography of the mound and tidal currents in the area. Sediments from Propeller Mound contain elevated calcium carbonate contents (50 percentage) compared to background sediments (39 percentage)what is proportional to the volume of coarse bioclastic material present. The hydrodynamic variability recorded in Pleistocene drift sediments was studied in a more southerly mound province. Analysis of core MD-01-2450 from the BelgicaMound Province documents drift sedimentation in an off-mound location reaching far beyond 200 kyr B.P. An hiatus representing >160 kyr is present, separating an upper silty drift body containing abundant coarse ice rafted debris IRD) from a ... |
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