ABSTRACT
Phosphorite nodules occurring along the biologically productive continental margin of Peru have been dated by uranium-series methods. The radiometric ages range from late Pleistocene to Recent, indicating that phosphorities are currently forming in this area.
ABSTRACT
Radiocarbon and thorium-230 dates of uplifted coral reef terraces on New Guinea appear to support theories of glaciation which utilize Milankovitch cycles as a controlling trigger mechanism. In addition to high sealevel stands recognized by other workers, the New Guinea data clearly indicate a marine transgression between 50,000 and 35,000 years before the present. A eustatic sea level curve reconstructed from field observations and radiometric dates shows a close correlation with temperature fluctuations in high latitudes as predicted by astronomical data.
ABSTRACT
Investigation of 33 islands, scattered widely across the Caroline and Marshall Island groups in the Central Pacific revealed no emerged reefs in which corals had unquestionably formed in situ, or other direct evidence of postglacial high stands of sea level. Low unconsolidated rock terraces and ridges of reefflat islands, mostly lying between tide levels, were composed of rubble conglomerates; carbon-14 dating of 11 samples from the conglomerates so far may suggest a former slightly higher sea level (nine samples range between 1890 and 3450 and one approaches 4500 years ago). However, recent hurricanes have produced ridges of comparable height and material, and in the same areas relics from World War II have been found cemented in place. Thus these datings do not in themselves necessarily indicate formerly higher sea levels. Rubble tracts are produced by storms under present conditions without any change in datum, and there seems to be no compelling evidence that they were not so developed during various periods in the past.
