Re-evaluation and extension of the Marine Isotope Stage 5 tephrostratigraphy of the Faroe Islands region: The cryptotephra record

PMA, SMD, WENA and NJGP are supported by NERC through the SMART project (NE/F020600/1, NE/F02116X/1, NE/F021445/1). The research leading to the results for the MIS 4 and 5a tephra horizons has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° [259253]. PMA, SMD and NJGP acknowledge the support of the Climate Change Consortium of Wales (C3W). JB is funded by the Research Council of Norway through the INTERACT project (project no. 221999).Abstract Previous studies of marine sequences from the Faroe Islands region have identified a series of coarse-grained tephra horizons deposited during Marine Isotope Stage (MIS) 5. Here we reassess the MIS 5 tephrostratigraphy of the Faroe Islands region and focus on the cryptotephra deposits preserved within the fine-grained fraction of marine core LINK 16. We also extend the record to encompass the late MIS 6 and early MIS 4 periods. A density separation technique, commonly used for tephra investigations in lacustrine settings but rarely applied to marine sediments, is utilised to explore the fine-grained material and EPMA and LA-ICP-MS are employed to determine the major and trace element composition of individual tephra shards. In total, 3 basaltic and 3 rhyolitic Icelandic cryptotephra deposits with homogeneous geochemical compositions are identified — all of which have the potential to act as isochronous tie-lines. Geochemical results highlight that the Grímsvötn volcanic system of Iceland is the predominant source of the basaltic horizons and the Öraefajökull or Torfajökull systems are the likely sources of the rhyolitic deposits. Three of the horizons have been previously recognised in Faroe Islands region marine sequences, with two of these deposits traceable into a Norwegian Sea sequence. An early MIS 4 rhyolitic horizon is the most widespread deposit as it can be traced into the Norwegian Sea and to the south into a record from the Rockall Trough. Basaltic and rhyolitic horizons deposited during late MIS 6 have not been recognised in other sequences and represent new additions to the regional tephrostratigraphy.Publisher PDFPeer reviewe

Ice rafted debris of ODP Holes 104-642B and 104-644A in the Vøring Plateau

Studies of ice-rafted detritus in ODP holes from the Norwegian Sea document a series of glacial episodes in the surroundings of the Norwegian - Greenland Sea from the late Miocene (5.45 Ma) through the Pliocene. These glacial events were of smaller magnitude than those of the period postdating the major onset of large scale northern hemisphere glacial cyclicity at 2.57 Ma. A further amplification of the glaciations took place after 1.2 Ma. Oxygen isotope records from benthic foraminifers indicate high-frequency global ice volume fluctuations since the late Miocene. A major glacial episode took place at 5.1 – 5 Ma, which lowered eustatic sea-level by about 80 m below the present. Similar lowerings of sea-level are also documented for some glacials in the Pliocene (3.7 – 3.1 Ma). These glacials indicate substantially larger Antarctic ice volumes than at present. The glacial episode at 5 Ma is correlated with the upper evaporite sequence of the Messinian salinity crisis in the Mediterranean. The Norwegian Sea was a net exporter of deep-water during most of the last 6 Myr. Periods of carbonate dissolution lasting several 100 kyr indicate intervals of reduced ventilation and a more stable water column in the Norwegian Sea in both the late Miocene — Pliocene and the early Quaternary. There is no clear evidence for reduced deep-water formation during the upper Messinian event. High-frequency variation in δ 13C indicates that changes in deep-water ventilation rate were coupled with orbital forcing. While the ventilation and deep-water chemistry of the Norwegian Sea has varied during the late Neogene, the δ 18O results indicate that Norwegian Sea deep-waters were denser and colder than those of the Atlantic during major portions of the last 6 Myr

Degradation of phytate by the 6-phytase from Hafnia alvei: a combined structural and solution study

Phytases hydrolyse phytate (myo-inositol hexakisphosphate), the principal form of phosphate stored in plant seeds to produce phosphate and lower phosphorylated myo-inositols. They are used extensively in the feed industry, and have been characterised biochemically and structurally with a number of structures in the PDB. They are divided into four distinct families: histidine acid phosphatases (HAP), β-propeller phytases, cysteine phosphatases and purple acid phosphatases and also split into three enzyme classes, the 3-, 5- and 6-phytases, depending on the position of the first phosphate in the inositol ring to be removed. We report identification, cloning, purification and 3D structures of 6-phytases from two bacteria, Hafnia alvei and Yersinia kristensenii, together with their pH optima, thermal stability, and degradation profiles for phytate. An important result is the structure of the H. alvei enzyme in complex with the substrate analogue myo-inositol hexakissulphate. In contrast to the only previous structure of a ligand-bound 6-phytase, where the 3-phosphate was unexpectedly in the catalytic site, in the H. alvei complex the expected scissile 6-phosphate (sulphate in the inhibitor) is placed in the catalytic site