The formation of Pliocene sapropels and carbonate cycles in the Mediterranean: diagenesis, dilution, and productivity

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Compositional variation in Roman colourless glass objects from the Bocholtz burial (The Netherlands)

We investigated the major and trace element composition and Pb and Sr isotope characteristics of a series of about 20 colourless glass objects from a single high-status Roman burial from the Netherlands (Bocholtz). The major elements show a relatively homogeneous group, with one outlier. This is corroborated by the Sr isotopes. Based on the Sb and Pb content, three major groups can be discerned, with two other outliers. This grouping is corroborated by the contents of the trace elements Bi, Sn, Ag, As and Mo, and by variations in lead isotopic ratios. On the basis of these results, we conclude that the glass of all objects was probably made with sand and lime from the same source. The variation in trace elements and lead isotope composition is most likely the result of variations in the composition of the sulphidic antimony ore(s) that were used to decolourize the glass. The composition of the Bocholtz glass is compared with that of other Roman glass, and implications for production models, trade and use of colourless glass objects are discussed. On the basis of isotopic and major element variation, we conclude that the antimony ore presumably originated from different mines.status: publishe

Identification of quantitative trait loci regulating haematopoietic parameters in B6AKRF2 mice

The haematopoietic system is a complex organised tissue with a hierarchical structure. Identification of organisational pathways within the haematopoietic system is relevant for a better understanding of haematopoiesis in health and disease. We have analysed numerous haematopoicticm parameters in two panels of a total of 157 genetically distinct B6AKRF2 mice, derived from an intercross between AKR and C57B1/6 mice, strains known to differ in various stem cell traits. The major objective of our study was to assess the extent to which various haematopoietic parameters, such as stem cell numbers, progenitor cell cycling, progenitor cell mobilisation and neutrophil numbers in blood and bone marrow are coregulated. The genotypes of these mice were used to search for genetic loci that regulate these parameters. We found significant quantitative trait loci (QTL) associated with the number of stem cells (CAFC-35) in the bone marrow and the number of neutrophils in the blood. However, most haematopoietic parameters appeared to be controlled by non-heritable (epigenetic) factors, or by multiple QTLs. Our study reveals striking differences in structure of the haematopoietic hierarchy between individual mice. Surprisingly, stem and progenitor cell pool size and proliferation rate, as well as peripheral blood cell counts are all independently regulated

The role of mat-forming diatoms in formation of Mediterranean sapropels

The origins of sapropels (sedimentary layers rich in organic carbon) are unclear, yet they may be a key to understanding the influence of climate on ocean eutrophication, the mechanisms of sustaining biological production in stratified waters and the genesis of petroleum source rocks. Recent microfossil studies of foraminifera and calcareous nannofossils have focused attention on a deep chlorophyll maximum as a locus for the high production inferred for sapropel formation, but have not identified the agent responsible. Here we report the results of a high-resolution, electron-microscope-based study of a late Quaternary laminated sapropel in which the annual flux cycle has been preserved. We find that much of the production was by diatoms, both mat-forming and other colonial forms, adapted to exploit a deep nutrient supply trapped below surface waters in a stratified water column. Reconstructed organic-carbon and opal fluxes to the sediments are comparable to those at high-productivity sites in today's oceans, and calculations based on diatom Si/C ratios suggest that the high organic-carbon content of sapropels may be entirely accounted for by sedimenting diatoms. We propose that this style of production may have been common in ancient Palaeogene and Cretaceous seas, environments for which conventional appeals to upwelling-driven production to account for the occurrence of diatomites, and some organic-carbon-rich sediments, have never seemed wholly appropriate.<br/