The central part of the Piave River valley in the Venetian pre-Alps of NE Italy exposes an expanded and continuous marine sediment succession that encompasses the Paleocene series and the Paleocene to Eocene transition. The Paleocene through lowermost Eocene succession is >100 m thick and was deposited at middle to lower bathyal depths in a hemipelagic, near-continental setting in the central western Tethys. In the Forada section, the Paleocene succession of limestone-marl couplets is sharply interrupted by an ~3.30 m-thick unit of clays and marls (clay marl unit). The very base of this unit represents the biostratigraphic Paleocene-Eocene boundary, and the entire unit coincides with the main carbon isotope excursion of the Paleocene-Eocene thermal maximum event. Concentrations of hematite and biogenic carbonate, delta 13C measurements, and abundance of radiolarians, all oscillate in a cyclical fashion and are interpreted to represent precession cycles. The main excursion interval spans five complete cycles, that is, 105 ± 10 k.y. The overlying carbon isotope recovery interval, which is composed of six distinct limestone-marl couplets, is interpreted to represent six precessional cycles with a duration of 126 ± 12 k.y. The entire carbon isotope excursion interval in Forada has a total duration of ~231 ± 22 k.y., which is 5%–10% longer than previous estimates derived from open ocean sites (210–220 k.y.). Geochemical proxies for redox conditions indicate oxygenated conditions before, during, and after the carbon isotope excursion event. The Forada section exhibits a nonstepped sharp decrease in delta 13C (-2.35‰) at the base of the clay marl unit. The hemipelagic, near-continental depositional setting of Forada and the sharply elevated sedimentation rates throughout the clay marl unit argue for continuous rather than interrupted deposition and show that the initial nonstepped carbon isotope shift was not caused by a hiatus. A single sample at the base of the unit lacks biogenic carbonate. Preservation of carbonate thereafter improves progressively up-section in the clay marl unit, which is consistent with a prodigiously abrupt and rapid acidifi cation of the oceans followed by a slower, successive deepening of the carbonate compensation depth. Increased sedimentation rates through the clay marl unit (approximately the main interval of the carbon isotope excursion) are consistent with an intensified hydrological cycle driven by supergreenhouse conditions and enhanced weathering and transport of terrigenous material to this near-continental, hemipelagic environment in the central western Tethys. The sharp transition in lithology from the clay marl unit to the overlying limestone-marl couplets in the recovery interval and the coincident shift toward heavier delta 13C values suggest that the silicate pump and continental weathering, the cause of the enhanced terrigenous flux to Forada, stopped abruptly. This implies that the source of the light CO2 ceased to be added to the ocean-atmosphere system at the top of the cla...

No abstract

The geological and archaeological signatures al the site of Kupona na Dari on the Willaumez Peninsula, West New Britain provide important new data about human colonisation of the Bismarck Archipelago. Analyses of the stratigraphy and weathering of paleosols and manuporls. when combined with fission track. radiocarbon, and luminescence dating, indicate that the site was first occupied at about 35-45.000 years ago. During the whole peri(Kl of occupation, people were exposed to a series of volcanic events which varied in terms of tbeir potential impacts on the local environment. A PIXE-PIGME characterisation study of the obsidian artefacts at tbe site demonstrates that from the earliest period stone resources were acquired from outcrops located across a relatively large region. When compared with Early-Middle Holocene assemblages from nearby localities, the Pleistocene stone tool technology differs in only a few minor respects. From this analysis we infer tbat groups were mobile in both periods, but slightly different strategies for tbe procurement and maintenance of tbe stone tools were required for tbe more extensive ranges exploited during the Pleistocene. The inter-disciplinary study of Kupona na Dari concludes that colonisation comprised a long term process of settling into this volcanically active environment. Due to variability in the environments tbat people encountered, the pattern of colonisation may not have been similar across the entire Bismarck Archipelago, RT: Anthropology. Tbe Australian Museum,

No abstract

Analytical measurements of the 28 Si crystal used for the determination of the Avogadro constant are essential to prevent biased results or under-estimated uncertainties. A review of the existing data confirms the high-purity of silicon with respect to a large number of elements. In order to obtain a direct evidence of purity, we developed a relative analytical method based on neutron activation. As a preliminary test, this method was applied to a sample of the Avogadro crystal WASO 04. The investigation concerned twenty-nine elements. The mass fraction of Au was quantified to be (1.03 ± 0.18) × 10 -12 . For the remaining twenty-eight elements, the mass fractions are below the detection limits, which range between 1 × 10 -12 and 1 × 10 -5 .