caa a22 4500 477064167 CHVBK 20180405111407.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/BF02369007 doi (NATIONALLICENCE)springer-10.1007/BF02369007 Late Quaternary sedimentation on the Mid-Atlantic Reykjanes Ridge: clay mineral assemblages and depositional environment [Elektronische Daten] [B. Gehrke, K. Lackschewitz, H. Wallrabe-Adams] Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses. The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary. Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts of illite, chlorite, and kaolinite characterize ice-rafted sediments of the "Heinrich layers”. In these sediments smectite crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order, similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18-16 ka), indicating a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase in fine-grained quartz (<2µm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated at around 10 ka, where a strong increase in smectite of low crystallographic order is detected. Springer-Verlag, 1996 Clay mineralogy nationallicence Mid-Atlantic Reykjanes Ridge nationallicence Quaternary sediments nationallicence Source areas nationallicence Deep-water circulation nationallicence Iceland-Scotland Overflow Water (ISOW) nationallicence Ice-rafted sediment nationallicence Gehrke B. GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, D-24148, Kiel, Germany aut Lackschewitz K. GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, D-24148, Kiel, Germany aut Wallrabe-Adams H. GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, D-24148, Kiel, Germany aut Geologische Rundschau Springer-Verlag 85/3(1996-09-01), 525-535 0016-7835 85:3<525 1996 85 531 https://doi.org/10.1007/BF02369007 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF02369007 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Gehrke B. GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, D-24148, Kiel, Germany aut NATIONALLICENCE 700 1- Lackschewitz K. GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, D-24148, Kiel, Germany aut NATIONALLICENCE 700 1- Wallrabe-Adams H. GEOMAR Research Center for Marine Geosciences, Wischhofstr. 1-3, D-24148, Kiel, Germany aut NATIONALLICENCE 773 0- Geologische Rundschau Springer-Verlag 85/3(1996-09-01), 525-535 0016-7835 85:3<525 1996 85 531 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer