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| Grégoire, Ch.. |
| 1. This paper is an electron microscope study of the alterations produced by temperatures in range of 100°C to 900°C in mother-of-pearl of the modern <i>Nautilus</i> shell. 2. Fragments of nacreous layers of the shell wall in the living chamber were exposed for 5 minutes to 21 days to dry heat in open vessels and in quartz tubes sealed under vacuum or argon. Other fragments were boiled in sea mud and sea water. 3. In open vessels and in sealed tubes, conversion of aragonite into calcite took place in the samples heated at 400 °C and above. In the 600 °C-900 °C samples, calcite was mixed with varying amounts of calcium oxide. With elevation of temperature, the original hard, compact and stratified mother-of-pearl became progressively brittle,... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Diagenesis; Metamorphism; Nacre; Nautilus. |
| Ano: 1968 |
URL: http://www.vliz.be/imisdocs/publications/294745.pdf |
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| Blanchet, C. L.; Kasten, S.; Vidal, L.; Poulton, S. W.; Ganeshram, R.; Thouveny, N.. |
| In order to evaluate the influence of diagenetic and post-sampling processes on the stable oxygen and carbon isotope compositions of biogenic carbonates, we conducted a multiproxy study of organic-rich sediments from the eastern Pacific oxygen minimum zone. Core MD02-2520, which was retrieved from the Gulf of Tehuantepec (Mexico), has seasonal laminations and covers the last 40 kyr. Together with the presence of gypsum crystals and inorganic calcite aggregates, the occurrence of large excursions in the stable oxygen and carbon isotope records of both planktonic and benthic foraminifera (as large as +3 parts per thousand in delta O-18 and -5 parts per thousand in delta C-13) point to significant secondary transformations. Storage-related gypsum... |
| Tipo: Text |
Palavras-chave: Diagenesis; Gypsum; Inorganic calcite; Laminations; Oxygen minimum zone; Sulfur reoxidation. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00139/25049/23173.pdf |
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| Ge, Can; Zhang, Weiguo; Dong, Chenyin; Dong, Yan; Bai, Xuexin; Liu, Jinyan; Thi Thu Hien, Nguyen; Feng, Huan; Yu, Lizhong. |
| The inner shelf of the East China Sea is a river-dominated margin characterized by fine-grained mud deposits and a rapid sedimentation rate. Three short sediment cores (similar to 2.7m in length) were examined to characterize spatial variations in magnetic mineral diagenesis. The sediment cores were analyzed for sedimentation rates, magnetic properties, particle size distribution, organic carbon, and total sulfur content. The two more proximal cores with higher sedimentation rates (similar to 2.2cm/yr and similar to 0.96cm/yr) do not exhibit obvious effects of reductive dissolution of magnetite with increasing depth, which is consistent with their lower total sulfur content. The offshore core, A12-4, which has a lower sedimentation rate, contains clear... |
| Tipo: Text |
Palavras-chave: Magnetic properties; Diagenesis; Organic matter reactivity; Sedimentation rate; River-dominated margin; East China Sea. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00351/46256/46079.pdf |
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| Boussetta, Soumaya; Kallel, Nejib; Bassinot, Franck; Labeyrie, Laurent; Duplessy, Jean-claude; Caillon, Nicolas; Dewilde, Fabien; Rebaubier, Helene. |
| We generated a high-resolution SSTMg/Ca record for the surface-dwelling planktonic foraminifera Globigerina bulloides from the core MD99-2346 collected in the Gulf of Lion, and compared it to that obtained using modern analogue techniques applied to fossil foraminiferal assemblages (SSTMAT). The two temperature records display similar patterns during the last 28,000 years but the SSTMg/Ca estimates are several degrees warmer (similar to+4 degrees C) than SSTMAT. The temperature shift between SSTMg/Ca and SSTMAT remained relatively constant over time. This seems to exclude a bias on the Mg/Ca record associated with salinity or secondary Mg-rich calcite encrustation on the foraminiferal tests during early diagenesis. Therefore, anomalously high Mg/Ca... |
| Tipo: Text |
Palavras-chave: Mediterranean; Mg/Ca; Planktonic foraminifera; Sea surface Temperature; Salinity; Diagenesis; Vital effect. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00139/25047/23181.pdf |
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| Bankole, Olabode M.; El Albani, Abderrazak; Meunier, Alain; Rouxel, Olivier; Gauthier-lafaye, Francois; Bekker, Andrey. |
| Red beds are extensively used as evidence for an oxygenated atmosphere in the Paleoproterozoic. Red beds in the unmetamorphosed, ca. 2.15 Ga FA Formation of the Franceville Basin, Gabon were geochemically, petrographically, and mineralogically characterized to constrain the process of their formation and their relationship to atmospheric oxygenation in the early Paleoproterozoic. Petrographic observations indicate that ferric oxides are dispersed in clay filling intergranular pores and along platy cleavage in altered phyllosilicates. Grain-coating hematite is generally rare to absent in most samples suggesting hematite precipitation after sediment deposition and during burial diagenesis. Textures and geochemical data suggest that iron was likely sourced... |
| Tipo: Text |
Palavras-chave: Red beds; Atmospheric oxygenation; Diagenesis; Iron isotopes; Franceville Basin; Oldest sandstone-type U deposit. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00358/46966/48278.pdf |
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| Leutert, Thomas J.; Sexton, Philip F.; Tripati, Aradhna; Piasecki, Alison; Ling Ho, Sze; Nele Meckler, A.. |
| Applying the clumped isotope (Δ47) thermometer to foraminifer microfossils offers the potential to significantly improve paleoclimate reconstructions, owing to its insensitivity to the isotopic composition of seawater (unlike traditional oxygen isotope (δ18O) analyses). However, the extent to which primary Δ47 signatures of foraminiferal calcites can be overprinted during diagenesis is not well known. Here, we present Δ47 data as well as high-resolution (∼10 kyr) δ18O and δ13C middle Eocene time series, measured on benthic and planktic foraminifera from ODP/IODP Sites 1408, 1409, 1410, 1050, 1260 and 1263 in the Atlantic Ocean. The sites examined span various oceanographic regimes, including the western tropical to mid-latitude North Atlantic, and the... |
| Tipo: Text |
Palavras-chave: Clumped isotopes; Foraminifera; Diagenesis; Eocene; Stable-isotope geochemistry; Preservation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00495/60683/64757.pdf |
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