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Color (lightness), organic carbon content, total nitrogen content, carbonate content, and bulk and clay mineralogy were determined for most of the sapropelic sediments recovered by Leg 42A and for some of their adjacent normal sediments.Maximum values of organic carbon and nitrogen reach 16.7% and 1%, respectively. Carbon/nitrogen ratios generally increase with greater organic carbon content and with increasing age. Very high ratios of some sapropel material suggest a considerable supply of terrigenous organic material.The color of the sediment becomes darker with increasing organic carbon content. This is interpreted as the result of monosulfide formation which is controlled by the original content of finely dispersed organic matter. In contrast, the formation of pyrite in sapropels seems to depend upon the presence or absence of lumps of organic matter.Total carbonate content ranges between almost zero and 78% in the sapropels. In comparison to normal sediments, no major carbonate dissolution could be observed. Calcite is the dominant carbonate mineral, while the content of detrital dolomite reaches a maximum of 16%. Occasionally, appearances of calcite and aragonite are attributed to turbiditic supply of shallow water carbonates. In the Messinian evaporitic sequence of Site 374, primary or early diagenetic dolomite is the only carbonate mineral.Calcite, mainly derived from the tests of foraminifers and coccolithophorids; has no relation to the content of organic carbon. This, together with the abundance of plant debris, suggests that the main part of the organic material in sapropels does not originate from plankton.Gypsum is a common component of sapropels, while anhydrite is restricted to the evaporitic sediments of Messinian age. For these strata, contemporaneous formation of sulfides (pyrite) and sulfates (gypsum, anhydrite) is assumed.The clay mineralogy of the sapropel shows considerable differences from that of the normal host sediments: greater contents of organic matter result in increased mineral alteration. The alteration leads to a degradation of the minerals towards mixed-layer types or chlorite, or to their complete destruction. The process increases in the series: kaolinite, illite, chlorite, smectite, attapulgite. The degree of alteration is greatest at the bases of sapropels. It appears to occur when a rich supply of detrital fragile materials has been available to sites in the center of the sapropelic area in the deeper parts of the basin. It is clear that the mechanisms of sapropel formation operate at the sediment/seawater interface and do not depend on depth of burial.

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The deglaciation history and Holocene environmental evolution of northern Wijdefjorden, Svalbard, are reconstructed using sediment cores and acoustic data (multibeam swath bathymetry and sub‐bottom profiler data). Results reveal that the fjord mouth was deglaciated prior to 14.5±0.3 cal. ka BP and deglaciation occurred stepwise. Biomarker analyses show rapid variations in water temperature and sea ice cover during the deglaciation, and cold conditions during the Younger Dryas, followed by minimum sea ice cover throughout the Early Holocene, until c. 7 cal. ka BP. Most of the glaciers in Wijdefjorden had retreated onto land by c. 7.6±0.2 cal. ka BP. Subsequently, the sea‐ice extent increased and remained high throughout the last part of the Holocene. We interpret a high Late Holocene sediment accumulation rate in the northernmost core to reflect increased sediment flux to the site from the outlet of the adjacent lake Femmilsjøen, related to glacier growth in the Femmilsjøen catchment area. Furthermore, increased sea ice cover, lower water temperatures and the re‐occurrence of ice‐rafted debris indicate increased local glacier activity and overall cooler conditions in Wijdefjorden after c. 0.5 cal. ka BP. We summarize our findings in a conceptual model for the depositional environment in northern Wijdefjorden from the Late Weichselian until present.

RNA regulation can be performed by a second targeting RNA molecule, such as in the microRNA regulation mechanism. Selective 2’-hydroxyl acylation analyzed by primer extension (SHAPE) probes structure of RNA molecules and can resolve RNA:protein interactions, but RNA:RNA interactions have not yet been addressed with this technique. Here, we apply SHAPE to investigate RNA-mediated binding processes in RNA:RNA and RNA:RNA-RBP complexes. We use RNA:RNA binding by SHAPE (abbreviated RABS) to investigate microRNA-34a (miR-34a) binding its mRNA target, the silent information regulator 1 (mSIRT1), both with and without the Argonaute protein, constituting the RNA-induced silencing complex (RISC). We show that the seed of the mRNA target must be bound to the microRNA-loaded into RISC to enable further binding of the compensatory region by RISC, while the naked miR-34a is able to bind the compensatory region without seed interaction. The method presented here provides complementary structural evidence for the commonly performed luciferase-assay-based evaluation of microRNA binding-site efficiency and specificity on the mRNA target site and could therefore be used in conjunction with it. The method can be applied to any nucleic acid-mediated RNA- or RBP-binding process, such as splicing, antisense RNA binding, or regulation by RISC, providing important insight into the targeted RNA structure.

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