[1] In the Bengal Basin, the land surface exposed during the last lowstand of sea level around 20 ka, and now buried by Holocene sediment, is capped by an effectively impermeable clay paleosol that we term the Last Glacial Maximum paleosol (LGMP). The paleosol strongly affects groundwater flow and controls the location of arsenic pollution in the shallow aquifers of our study site in southern West Bengal and, by implication, in shallow aquifers across the Bengal Basin and As-polluted deltaic aquifers worldwide. The presence of the LGMP defines paleointerfluvial areas; it is absent from paleochannel areas. A paleosol model of pollution proposed here predicts that groundwater in paleochannels is polluted by arsenic, while that beneath paleointerfluvial areas is not: paleointerfluvial aquifers are unpolluted because they are protected by the LGMP from downward migration of arsenic and from downward migration of organic matter that drives As-pollution via reductive dissolution of As-bearing iron oxyhydroxides. Horizontal groundwater flow carries arsenic from paleochannels toward paleointerfluvial aquifers, in which sorption of arsenic minimizes the risk of pollution.

Results of one of the most comprehensive paleomagnetic and supporting geological programs ever carried out in offshore SE Asia on North Luzon, northern Philippines, are reported. Six new results, based on 66 sites, are reported from a total collection of 243 individual sites. Declinations in the data subset are sometimes scattered, likely reflecting combinations of major plate and local rotations in both clockwise and counterclockwise directions, and thus have a somewhat limited value for tectonic modeling. The inclination data are, however, much more valuable and can be best explained if North Luzon traveled as part of the Philippine Sea Plate for most of its history, a scenario which is compatible with the known geology of the eastern Philippines and broader region. In the proposed model, for all of its Eocene‐Pliocene history, North Luzon is placed on the western edge of the Philippine Sea Plate, effectively always just to the west of the site where the Benham Plateau formed ∼40 Ma. The paleomagnetic data indicate a substantial northward migration of the area since the start of the Neogene, with an earlier interval stretching back to at least the mid‐Early Cretaceous when this part of the plate occupied equatorial latitudes. Post‐15 Ma motion of the plate has involved the indentation of the Palawan microcontinental block into the western side of the Philippine Archipelago. Deformations induced by this process offer the most likely explanation for the scattered declinations observed in North Luzon and areas a short distance to the south.

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The sea floor around eastern New Guinea is divided into a number of deep basins, separated by submarine ridges which are capped in places by islands of metamorphic, volcanic or coralline rock. The area has been subject to phases of extension since at least the Palaeocene, when the Coral Sea basin was formed. There have also been major compressive events, including the thrust emplacement of an ophiolite, the Papuan Ultramafic Belt, on to the Papuan Peninsula in the Oligocene. This peninsula, on the E of New Guinea, has been volcanically active from the Middle Miocene to the present day, and there have been eruptions on many of the surrounding islands and in the marine basins. Extension-related volcanic rocks include low-K tholeiites dredged from the floor of the Woodlark Basin and a peralkaline rhyolite association on islands near the E end of the peninsula. Volcanic rock types usually regarded as indicators of subduction, including andesites and high-K trachybasalts (shoshonites), are common.During the Neogene, two phases of extension with associated igneous activity can be interpreted; the first in the Middle and Late Miocene, and the second from the Middle Pliocene to the present day. Only in the first phase was the formation of marginal basins related to subduction. The later phase is seen as part of the response of the complexly fragmented Melanesian area to changes in relative motions of the surrounding major plates. Sea-floor spreading is currently occurring in the Woodlark Basin, and the post-Miocene calc-alkaline and shoshonitic rocks of the Papuan Peninsula and offshore islands reflect reactivation of subduction-modified mantle under this tensional regime, and not renewed subduction.