Composition and origin of sediments on the mid-oceanic Kolbeinsey Ridge, north of Iceland

Abstract

In order to characterize the sediments of the South Kolbeinsey Ridge and to determine the influence of morpho- and hydrodynamic conditions in this area, a comprehensive sedimentological investigation was combined with detailed geochemical analyses. Lithological composition and grain size are mainly controlled by the input from two different sources: the submarine, active mid-ocean ridge and Iceland. Coarse-grained volcanic material dominates in the ridge area, whereas fine-grained detritus from Iceland characterizes the adjacent basin. Further, the distribution of these sediments is largely influenced by hydrodynamic conditions and redeposition processes. Strong bottom-water currents indicated by the benthic foraminifer species Cibicides lobatulus prevent extensive deposition of fine-grained material on the top of the ridge. The ridge slope is characterized by redeposited sediments of various grain sizes. Bulk-sediment chemical analyses show element distribution patterns that are strongly correlated with the ratio of volcanic vs. detritic particle composition. This ratio reflects particle input and distribution processes. Two element associations are notable: elements coupled with (1) ridge-derived volcanic particles and (2) the detrital <2 μm fraction which reflects weathered material from Iceland.