Bioturbation and Resource Quality: A Case Study from the Upper Cretaceous Lysing and Nise Formations, Ellida and Midnatsoll Fields, Norwegian Sea
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Abstract
Nine cores (approx. 156 m) within the Upper Cretaceous Lysing and Nise formations (Møre Basin, Norwegian continental shelf) are studied in order to assess the relationship between bioturbate fabric and the resulting permeability distribution. Overall, the Lysing and Nise formations strata comprise unburrowed to completely bioturbated very-fine to fine sandstones and mudstones containing a highly-diverse trace fossil assemblage that represent parts of the proximal through distal Cruziana ichnofacies. X-ray microtomography (Micro-CT) imaging, spot-, bulk-permeability measurements and petrographic assessments show that permeability distributions are strongly influenced by the location and nature of bioturbation. Spot permeability data taken from core-plugs indicates that the burrow permeability can be up to two orders of magnitude greater than the matrix. Therefore, it proffers a biogenically influenced dual-permeability flow media. These modifications constitute selective fluid flow networks that occur through the imposition of coarser grained sediment within burrows in otherwise fine-grained strata