Structural description and paleomagnetic directions of ODP Hole 152-917A

During Ocean Drilling Program Legs 152 and 163, we recovered core from the offshore East Greenland volcanic province. The basaltic core recovered included a set of structural elements reflecting the history of extrusion, cooling, postdeposition alteration, and minor tectonism. Brittle features in the basaltic core include faults and several generations of veins. Several minicore samples from the lower sections of core from Hole 917A were taken for paleomagnetic analysis, primarily to test whether there were any significant postdepositional tectonic rotations or whether the core could be reoriented using paleomagnetic techniques. The characteristic magnetization direction was used to estimate the in situ orientation of measured structural features within the core. Although significant uncertainty is associated with the analysis, the corrected attitudes of veins in basalt at Site 917 dip moderately west, with a smaller, conjugate group of veins dipping moderately east-southeast, parallel to other seaward-dipping faults in the area, which were interpreted from seismic lines.

Controls of sediment dynamics on the Galician slope reconstructed from three sediment cores (GeoB11035-1, GeoB130206-1, GeoB13071-1)

Controls of sediment dynamics at the Galician continental slope (NW Iberia) during the past 30 ka were reconstructed from three new gravity cores (GeoB11035-1, 130206-1, 13071-1) based on sedimentological (e.g. sortable silt, IRD), micropalaeontological (e.g. coccoliths), geochemical (AMS 14C, XRF) and geophysical (e.g. magnetic susceptibility) diagnostics. The data are consistent with existing regional knowledge that, during marine isotope stages 3-1, variations in detrital input, marine productivity and sea level were the essential drivers of sediment availability on the slope, whereas deep-water current velocities controlled sediment deposition: (1) the period prior to 30 cal ka BP is characterized by minor but systematic variations in various proxies which can be associated with D-O cycles; (2) between 30 and 18 cal ka BP, high detrital input and steady slope-parallel currents led to constant sedimentation; (3) from the LGM until 10 cal ka BP, the shelf-transgressive sea-level rise increased the detrital particle flux; sedimentation was influenced by significantly enhanced deep-water circulation during the Bølling/Allerød, and subsequent slowing during the Younger Dryas; (4) an abrupt and lasting change to hemipelagic sedimentation at ca. 10 cal ka BP was probably due to Holocene warming and decelerated transgression; (5) after 5 cal ka BP, additional input of detrital material to the slope is plausibly linked to the evolution of fine-grained depocentres on the Galician shelf, this being the first report of this close shelf-slope sedimentary linkage off NW Iberia. Furthermore, there is novel evidence of the nowadays strong outer shelf Iberian Poleward Current becoming established at about 15.5 cal ka BP. The data also demonstrate that small-scale morphologic features and local pathways of sediment export from the neighbouring shelf play an important role for sediment distribution on the NW Iberian slope, including a hitherto unknown sediment conduit off the Ría de Arousa. By implication, the impact of local morphology on along- and down-slope sediment dynamics is more complex than commonly considered, and deserves future attention.