Magnetic Fabric of Surficial Deep-Sea Sediments in the Hebbie Area (Nova Scotian Continental Rise)

摘要

The anisotropy of magnetic susceptibility (AMS) of surficial sediments in the HEBBLE area (depth 4820 m Nova Scotian continental rise) has been measured to study the fabric of these sediments and to relate the sediment fabric to depositional conditions. Previous investigators have established that strong but variable bottom currents are important agents in redistributing bottom sediment fabric to depositional conditions. Previous investigators have established that strong but variable bottom currents are important agents in redistributing bottom sediments in the area. We observe that the upper 1.5 cm of the sediments has a primary fabric (dominantly foliar with horizontal bedding) created by bottom-current activity while sediments deeper than 2.5 cm have a predominantly secondary fabric due to bioturbation. The magnitude of the AMS signal in these sediments is generally low making it difficult to the regional bathymetric contours, but there is also a significant grouping of alignments perpendicular to the contours. Primary fabrics are observed in a few of the samples from the bioturbated sediments with the magnetic grains oriented parallel to the contours. Some of the variability of depositional conditions within the region. An analysis of the magnitude of the AMS fabric suggests that the parameter F sub s often used to denote bottom-current fabrics, is strongly dependent on the total anisotropy and only weakly dependent on the lineated nature of the fabric. Both primary and secondary fabrics can have relatively large F sub s values. Thus F sub s does not appear sufficient for delineating bottom current activity in the deep sea. Keyword: HEBBLE (High Energy Benthic Boundary Layer Experiment).