RV POSEIDON Fahrtbericht / Cruise Report P457 [POS457]: Iceland Hazards ; Volcanic risks from Iceland and climate Change: the late Quaternary to anthropogene development, Reykjavík / Iceland – Galway / Ireland, 7.-22. August 2013

Abstract

R/V POSEIDON cruise P457 aimed further development of detailed marine tephrochronology of Iceland by sediment coring in order to improve our knowledge of the spatio-temporal evolution of Icelandic volcanism and related hazards. In addition, the marine record contains paleoclimatic information, which may relate recurrent glacier advances and land degradation periods to ocean and atmospheric circulation changes. A minor sub-project should contribute to a better understanding of Surtsey volcanism by investigations of marine Surtsey tephra. P457 conducted extensive sediment echosounding (11 surveys with a total length of c. 425 nm) in order to identify undisturbed sediment sequences for coring. At 20 appropriate sites, P457 deployed gravity and/or gaint box corers to recover ultra-high resolution sediment cores from < 100 m to ~1,600 m water depth at the south-western, southern and eastern sectors of the Icelandic shelf and slope. Of these deployments, 9 gravity corers yielded altogether 59.5 m core recovery and 11 box corers recovered surface sediment samples. Additionally 7 CTD/rosette water sampling stations have been performed at shallow sites close to Iceland and at deep sites further offshore in order to determine the REE distributions and the Nd and Hf isotope compositions of the sea water. No equipment was lost or significantly damaged. Cruise P457 was particularly successful in the working areas southwest and south of Iceland but failed to recover long sediment cores in the eastern working areas and at Surtsey. Sand, clayey silt, clayey sandy silt, sandy clayey silt, and volcanic ashes are the dominant lithologies in the P457 sediment cores. Preliminary studies of selected sedimentary records along the Iceland margin from ca. 24°W to 12°W on both sides of Reykjanes Ridge suggest that a correlation of these cores is possible, implying that sedimentary records are undisturbed and of high quality. Notably, distinct volcanic ash layers can apparently be traced in the P457 cores across the working area. Preliminary age models of selected cores show that the sedimentation rates around Iceland are low with only a thin Holocene. Sediment records cover approximately 120.000 years at most.