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Rano Raraku, the crater lake constrained by basaltic tuff that served as the primary quarry used to construct themoaistatues on Rapa Nui (Easter Island), has experienced fluctuations in lake level over the past centuries. As one of the only freshwater sources on the island, understanding the present and past geochemical characteristics of the lake water is critical to understand if the lake could have been a viable freshwater source for Rapa Nui. At the time of sampling in September 2017, the maximum lake depth was ~1 m. The lake level has substantially declined in the subsequent years, with the lake drying almost completely in January 2018. The lake is currently characterized by highly anoxic conditions, with a predominance of ammonium ions on nitrates, a high concentration of organic carbon in the water-sediment interface and reducing conditions of the lake, as evidenced by Mn/Fe and Cr/V ratios. Our estimates of past salinity inferred from the chloride mass balance indicates that it was unlikely that Rano Raraku provided a viable freshwater source for early Rapa Nui people. The installation of an outlet pipe around 1950 that was active until the late 1970s, as well as grazing of horses on the lake margins appear to have significantly impacted the geochemical conditions of Rano Raraku sediments and lake water in recent decades. Such impacts are distinct from natural environmental changes and highlight the need to consider the sensitivity of the lake geochemistry to human activities.

The work was made at the northern shore of the Santa Catarina Island, Florianopolis-SC. This area is enclosed in a shoreline sands plain environment, which is composed by sand deposits placed in a succession of troughs and ridges, lengthened and strait, continuous and discontinuous and parallel to the actual coastline. At the troughs, it is observed fine organic matter enriched in fine sediments, that allowed the development of a more exuberant vegetation, motivated the classification, previously, as shallow lagoon zone. However, the type of the sediments found is the area and the occurrence of shoreline sands put in question this interpretation. The use of GPR was proposed to obtain a better underground visualization of the structures related to the sedimentation environment at the studied areas. The profiles were made in perpendicular directions to the shoreline sands and the coastline.

Abstract Neutron diffraction is well suited for the analysis of archaeological findings and museum objects if drilling, cutting or coring for material sampling is unacceptable. Quantitative information on the phase composition and on the microstructure of an intact and valuable object can be non-destructively obtained in order to assess its properties, to support its authenticity, or to reconstruct details of the process of its production. The present paper surveys on recent work carried out on the time-of-flight diffractometer ROTAX at ISIS. Particular attention is given to the multi-phase analysis of 18th-century stoneware ceramics and to the texture analysis of 16th-century Ag/Cu coins.

Despite International Union of the Geological Sciences (IUGS) ratification of the International Commission on Stratigraphy recommendation that the base of the Parakidograptus acuminatus zone be the base of the Silurian and that the boundary stratotype be at Dob's Linn, Scotland, numerous concerns continue to be expressed over the timing of the selection as well as the boundary and its stratotype. The richness of both graptolite and non-graptolite biostratigraphic data in numerous stratigraphic sections from many areas in China published at about the same time that the boundary and stratotype were approved formally and shortly after approval suggest the possibility that boundary designation may have been somewhat premature. The new data from China document clearly the major extinction of characteristic Late Ordovician taxa significantly below the presently accepted System boundary. The new data indicate that the re-radiation of graptolites after the extinction took place in the Glyptograptus persculptus zone, the graptolite zone subjacent to the P. acuminatus zone. New geochemical data from Dob's Linn reveal a change in chemistry in strata subjacent to the base of the G. persculptus zone that could be used as an aid in correlation. The new data suggest the possibility that the base of the G. persculptus zone, the relatively traditional base of the Silurian, could be as appropriate a System boundary as the base of the P. acuminatus zone.

Abstract The article presents a physical and mathematical model of the propagation of air shock waves in the network of coal mine workings after an instant explosion of the methane-air mixture in a given area. An approach to the implementation of a method for solving problems on the propagation of air shock waves in a branched network of mine workings is presented, taking into account arbitrary angles of their conjugation. The results of calculating the propagation of air shock waves in the model networks of mine workings are presented.