A Vendian-Cambrian boundary succession from the northwestern margin of the Siberian Platform: stratigraphy, palaeontology, chemostratigraphy and correlation

Siberia contains several key reference sections for studies of biological and environmental evolution across the Proterozoic-Phanerozoic transition. The Platonovskaya Formation, exposed in the Turukhansk region of western Siberia, is an uppermost Proterozoic to Cambrian succession whose trace and body fossils place broad limits on the age of deposition, but do not permit detailed correlation with boundary successions elsewhere. In contrast, a striking negative carbon isotopic excursion in the lower part of the Platonovskaya Formation permits precise chemostratigraphic correlation with upper-most Yudomian successions in Siberia, and possibly worldwide. In addition to providing a tool for correlation, the isotopic excursion preserved in the Platonovskaya and contemporaneous successions documents a major biogeochemical event, likely involving the world ocean. The excursion coincides with the palaeontological breakpoint between Ediacaran- and Cambrian-style assemblages, suggesting a role for biogeochemical change in evolutionary events near the Proterozoic Cambrian boundary.     

c-Reactive protein levels as a biomarker of inflammation and stress in the Atlantic sharpnose shark (Rhizoprionodon terraenovae) from three southeastern USA estuaries

Circulating c-reactive protein (CRP) levels can be used as a bioindicator of the acute phase inflammatory response and as a possible biomarker of inflammation and neurogenic stress in vertebrates. Currently, there are no data describing the ranges of CRP levels in sharks living in different habitats, especially habitats of differing degrees of pollution. Developing antibodies against CRP is a first and critical step towards developing sensitive methods for quantifying CRP, and thus inflammatory and stress responses in sharks. Sharpnose shark, Rhizoprionodon terraenovae, serum C-reactive protein was purified sequentially over AH-sepharose 4B-PC and sepharose CL-4B columns and used to immunize balb/c mice for generating stocks of polyclonal anti-sera. Serum samples from 131 sharpnose sharks were collected from three different geographical regions along the coast of SC and GA, USA between June and November 2002. Total CRP concentrations were quantified by ELISA and found to be highest in the sharpnose shark population collected in the summer from Charleston, SC, compared to Beaufort, SC and Brunswick, GA. Seasonal comparisons indicated a higher CRP concentration in the summer of the Charleston, SC population compared to the fall. These data suggest that sharks living in the Charleston, SC harbor estuary may be exposed to a suite of pathogens or other stressors that are different than those found in the Beaufort, SC and Brunswick, GA estuaries. These data support the use of CRP as a bioindicator of health status in elasmobranchs.     

Linkages between cellular biomarker responses and reproductive success in oysters--Crassostrea virginica

The purpose of these studies was to evaluate if there were relationships between lysosomal destabilization or glutathione concentrations and gamete viability of oysters, Crassostrea virginica. Oysters were collected from field sites during the peak spawning period (May-June) during 2001 and 2002. Lysosomal destabilization rates and glutathione concentrations of hepatopancreas tissues (e.g. digestive gland) were determined. Eggs and sperm from the same adults were also used to conduct embryo development assays with reference seawater collected from a clean site, site water, and also a range of Cd concentrations (the Cd exposures were used to determine if there were differences in susceptibility to pollutants). Baseline embryo development success (e.g. percent normal development when the assays were conducted with reference seawater or site water) was related to lysosomal destabilization, but not glutathione status. However, the susceptibility of embryos to metal toxicity was related to glutathione status, i.e., sensitivity to Cd exposures increased with decreasing glutathione levels. These studies support the hypotheses that there are linkages between embryo development success and susceptibility to pollutant stress and cellular biomarker responses. These kinds of effects on reproductive success could lead to subtle but significant long-term effects on recruitment and viability of oyster populations.     

Sizing up the sub-Tommotian unconformity in Siberia

Sedimentary rocks in the western Anabar region, northwestern Siberia, preserve an exceptional record of evolution and biogeochemical events near the Proterozoic-Cambrian boundary. Carbon isotopic data on petrographically and geochemically screened samples collected at 1 to 2 m intervals support correlation of the lower Anabar succession (Staraya Reckha and lower Manykai Formations) with sub-Tommotian carbonates of the Ust'-Yu-doma Formation in southeastern Siberia. In contrast, the upper Manykai and most of the overlying Medvezhya Formation appear to preserve a sedimentary and paleontological record of an evolutionary important time interval represented in southeastern Siberia only by the sub-Tommotian unconformity. Correlation of the Anabar section with other northern Siberian successions that contain well-dated volcanic rocks permits the estimate that the sub-Tommotian unconformity in southeastern Siberia spans approximately 3 to 6 m.y. Diverse small shelly fossils (but not archaeocyathans) previously thought to mark the base of the Tommotian Stage evolved sequentially throughout this earlier interval.     

Stable isotopic compositions of carbonates from the Mesoproterozoic Bangemall Group, northwestern Australia

Marine carbonate rocks from the Mesoproterozoic Bangemall Group of northwestern Australia show little deviation (+/-1.3%) in whole-rock delta 13C(carb)-values about a mean of -0.5%. This narrow range persists despite close sampling (every 10-20 m) through long sections (up to 2500 m) that are geographically widespread (up to 250 km apart), over many depositional environments (supralittoral to outer shelf), sediment sources (stromatolitic bioherms to detrital calcilutites) and rock types (pure limestones to dolomitic shales). The only major excursions from the norm seem related to unusual environmental or post-depositional processes, as they are correlated with large enrichments (to -3%) or depletions (to -16%) in 18O. Relatively heavy delta 13C-values, up to +2.5%, occur in a single bed of brecciated ferruginous dolostone at a single locality; these abnormal values may result from local evaporitic conditions. Limey and shaley nodular dolostones have delta 13C-values as low as -4.3%, probably caused by remineralization of organic matter during late and patchy dolomitization. Most notably, sharp negative excursions in delta 13C, up to -8.4%, occur in bleached kerogen-free rocks with mineral assemblages of dolomite + quartz + calcite +/- tremolite + talc, reflecting isotopic re-equilibration in thick metamorphic aureoles around dolerite intrusions. General environmental variations are minor, with delta 13C-values of peritidal facies tending to be slightly positive whereas those of subtidal facies are slightly negative. There are no strong secular trends, but subtle fluctuations within the range -2 to +l% can be correlated along the northwestern margin of the basin. This resembles the pattern seen in other Mesoproterozoic successions, but is markedly unlike the heavy background (> +5%) and extreme variations (up to l0%) in delta 13C evident in Neoproterozoic successions of similar thickness and environmental setting. Hence, in contrast to the Neoproterozoic, the global rate of organic carbon burial was probably fairly constant during deposition of the Bangemall Group, and perhaps generally during the Mesoproterozoic, as was the redox state of the atmosphere and hydrosphere.     

岩浆氧逸度及其研究进展

岩浆熔体的氧逸度是岩石学研究中的一个重要物理化学参数。本文从氧逸度的概念、估算方法、影响因素等方面综述了近年来基性及酸性岩浆氧逸度的研究成果。     

Migration and the transformation of employment and household structures

Data collected in Colombia and Thailand in 1977 are used to "compare the employment and household characteristics of migrants before and after the move in order to assess the degree of change which accompanies migration. Moreover, these comparisons [are] made for migration streams between places at different levels in the urban hierarchy with the intention of determining within which streams the greatest transformations occur."     

红拟石首鱼的中间培育和养成技术

目前，红拟石首鱼的养殖业正在发展，前景看好。该鱼的亲鱼可以在圈养条件下进行培育，可根据需要进行产卵，生产仔鱼。中间培养生产包括饵料生物培养以及仔鱼长到全长２５ｍｍ养成生产包括池塘养殖、网 箱养殖和闭合循环水槽系统密集养殖。