Detrital and early diagenetic processes in Late Pleistocene and Holocene sediments from the SW Galicia Bank inferred from high-resolution enviromagnetic and geochemical records

Abstract

U-channel-based high-resolution magnetic and geochemical measurements supported by scanning electron microscopy, X-ray diffraction and fluorescence, and grain-size analyses of discrete samples were carried out on six sediment cores recovered from the SW flank of the Galicia Bank, at the Prestige' s wreck area. Five magnetochemical facies, reflecting the different sedimentary environments (i.e. hemipelagic, contouritic, turbiditic), sediment provenances and early diagenetic redoxomorphic processes (i.e. Mn peaks) are defined on the basis of a cluster analysis. The records showed climatically forced detrital signatures of regional importance, associated with continental slope sedimentary processes. The chronostratigraphy and correlation of the cores is based on 20 14C AMS-dating, recognition of Heinrich like Events H1 to H3 and well-documented Holocene climatic features. From a geochemical and enviromagnetic perspective, the Late Pleistocene to Holocene evolution of the area shows two different sedimentation contexts. MIS 2 is dominated by down-slope depositional processes. The highest sedimentation rates (9.1 cm/ky) were achieved during this interval. The major turbidite activity is recorded between ≈ 31 000 yr BP and ≈ 13 500 yr BP. Successive arrivals of IRD (H1 to H3) are also identified during this period. In contrast, Holocene sedimentation was dominated by a mixture of pelagic, hemipelagic and along-slope depositional processes and presented considerable lower sedimentation rates (3 cm/ky). Bottom-currents intensification at 7000 yr BP and 4500 yr BP coinciding with Late Holocene warm events are also recognised during this stage.