Global flood risk could increase five-fold with a 4-degree C temperature rise

A new report looks at flood risk and economic damages under different global warming scenarios with temperature increases of 1.5 degrees Celsius, 2 degrees Celsius and 4 degrees Celsius. It concludes that, if global temperatures rise by 4 degrees Celsius, the flood risk in countries representing more than 70 percent percent of the global population and global GDP will increase by more than 500 percent.

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Origin of red beds and paleosols in the Palaeoproterozoic Transvaal and Olifansthoek Supergroups of South Africa: provenance versus metasomatic controls

The Palaeoproterozoic Transvaal and Olifantshoek Supergroups of South Africa contain some of the earliest hematite‐rich sedimentary rocks (red‐beds) and paleosols on record. The origin of these rocks has been variously attributed to surface processes under an oxygenated atmosphere that post‐dated the ca. 2.3 Ga Great Oxidation Event (GOE). Interpretations of their geochemical signatures, however, have been inconclusive with respect to the causes of the apparent K‐enrichment that these rocks record. Here, we re‐visit the basal Mapedi Formation of the Olifantshoek Supergroup and the unconformably underlying Drakenstein palaeo‐weathering profile that develops against the Ongeluk Formation of the upper Transvaal Supergroup, and present new petrographic and geochemical data in an attempt to constrain the burial metasomatic history of these rocks. Apart from the strong hematitic nature and K‐metasomatic overprint seen in both the Mapedi Formation and Ongeluk paleosol, a curious and hitherto unexplored enrichment in high‐field strength elements (HFSEs: Ti, Nb, Y, Zr, REE, etc.) by several orders of magnitude higher than average shale characterizes the lower part of the Mapedi Formation as examined here. We show that such enrichments cannot be explained by normal source‐to sink weathering processes, unless an unlikely provenance of special geochemical composition (i.e. alkali igneous rocks) is to be invoked. We conclude that the HFSE enrichment, K‐metasomatism and evidently transgressive Fe‐oxidation effects in the Mapedi shales can only be accounted for via post‐depositional fluid‐rock interaction, possibly involving F‐bearing diagenetic brines. This opens the distinct possibility that such fluids may have also been implicated in alteration processes, enhanced Fe mobility and development of epigenetic hematitic iron‐ores as seen at the Transvaal‐Olifantshoek unconformity on regional scales. Copyright © 2017 John Wiley & Sons, Ltd.

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Sedimentary environment and geomorphic development of the uppermost Siwalik molasse in Kumaun Himalayan Foreland Basin, North India

An area of about 250 sq. km. around Ramnagar and Garjiya within the Siwalik molasse in the Kumaun foothills was mapped for geomorphic evolution and sedimentation pattern. The area, bounded by Himalayan Frontal Thrust (HFT) in the south and Main Boundary Thrust (MBT) in the north, consists of the sediments of uppermost part of the Pinjor and overlying Boulder Conglomerate Formations. Sedimentologically, three facies associations (FAA–FAC) were recognized with their order of superposition as FAA → FAB, FAA → FAC, FAB → FAC and FAC → FAB with variability in depositional setting. Lithofacies FAA–FAC were seemingly deposited in sand‐dominated fluvial channel belt, gravelly braided channel belt and cut‐off channel settings, respectively. The sediment dispersal in the basin was influenced by active basinal tectonics that caused frequent avulsions during the Bounder Bed times. The compositions of the clasts of these lithofacies reveal a shift in the primary provenance from pre‐Tertiary Himalayan hinterlands during the emplacement of FAA (of the Pinjor Formation) to evolving frontal Siwalik highlands during the emplacement of FAB and FAC (of the Bouldder Conglomerate Formation). This temporal shift in the provenance indicates exhumation of the older Siwalik sequences during the later phases of Himalayan orogeny. A number of subordinate faults, oblique to above mentioned intracrustal boundary thrusts and formed after the sedimentation was seized, were likely responsible for displacement between the sediments of different associations. The neotectonic rejuvenation is also reflected by the upliftment of two sister basins in opposite direction, rapid uplift in V‐shaped valleys, fault escarpments, three levels of terrace development and displacement of rock types along the subordinate faults as well as deflection and entrenchment in the course of lower order streams. Copyright © 2017 John Wiley & Sons, Ltd.

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