Formation of carbonate mounds in the Porcupine Basin, offshore Ireland: Evaluating transport of substrates for microbial processes from deep sources using numerical simulation and organic geochemistrty

• Main Author: Naeth, Jochen
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Forschungszenrum Jülich GmbH Zentralbibliothek, Verlag 2004
• Subjects: Iceland; North Atlantic
• Online Access: https://juser.fz-juelich.de/record/42596; https://juser.fz-juelich.de/search?p=id:%22PreJuSER-42596%22

The goal of this study is to assess whether deep coral mound growth on the continental slope of the north Atlantic is related to active hydrocarbon leakage. The objects of interest are numerous buried and non-buried carbonate mounds in the Porcupine Basin, 200 km offshore Ireland. Mounds with a size of up to 3 km length and a maximum height of about 600 m have been found in two mound provinces, the Hovland-Magellan mound province on the northern slope and the Belgica mound province on the eastern slope of the basin. The shape of the mounds varies from mostly elongated to circular and mounds consist mainly of corals, carbonate crusts and fine grained clastic sediments. To evaluate the possible link between hydrocarbon leakage and mound growth 2D basin modelling in combination with geochemical analysis of sediments from gravity cores was used. Two north-south trending seismic lines with an intersecting east-west line cover the Hovland-Magellan mound province and reach the border of the Belgica mound area. Six close by exploration wells were used for calibration of the burial and thermal history using vitrinite reflectance, bottom hole temperatures and apatite fission track data. The temperature history was defined based on the geologic evolution of the Porcupine basin, assuming heat flow peaks in Jurassic/Cretaceous times (rifting) and in the Paleocene (Iceland plume). The magnitude of the heat flow peaks was determined using the stretching factor beta for each point of the basin. Calibration of the thermal history indicated that both the rifting and plume effects were required in order to reproduce all calibration data satisfactorily. For fluid flow simulation a correct geometric reconstruction of the modelled sections was required. The paleo-geometry was defined by means of estimated paleo-water depth profiles for each time step, which were then introduced to the model to prevent unrealistic structures during burial. Possible source rocks in the Porcupine Basin are found in the Jurassic and older strata ...