Stable carbon and oxygen isotopic compositions of recent charophyte oosporangia and water from Malham Tarn,U.K.: palaeontological implications |
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Authors: | Timothy P. Jones Steven M. Fortier Allan Pentecost Margaret E. Collinson |
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Affiliation: | (1) Institut und Museum für Geologie und Paläontologie, Universität Tübingen, Sigwartstraße 10, D-72076 Tübingen, Germany;(2) Present address: Department of Earth Sciences, University of Wales Cardiff, Cardiff, CF1 3YE, Wales, UK;(3) Institut für Mineralogie, Petrologie und Geochemie, Universität Tübingen, Wilhelmstraße 56, D-72076 Tübingen, Germany;(4) Present address: Chemical & Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6110, USA;(5) Division of Life Sciences, King"s College London, University of London, Campden Hill Road, London, W8 7AH, UK;(6) Geology Department, Royal Holloway, University of London, Egham Hill, Egham, Surrey, TW20 0EX, UK |
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Abstract: | Charophyte oosporangia and water samples from a highly calcareous lake were measured for stable carbon and oxygen isotopic composition. The time period over which the oosporangia calcify is short, thus any biochemical relationship between the water and oosporangia"s calcite represents only one time window (late Summer in Malham Tam). This important temporal restraint must also apply to interpretations of all fossil material measured. The 18Oc of the charophyte oosporangia is deduced to be in equilibrium with the 18O of the water for a given temperature. The 13 Cc of the charophyte oosporangia was approximately 2.5 per mil lower than the 13CDIC in the water we measured. With the release Of CO2 with phosphoric acid from the charophyte oosporangia, there was no significant difference in the 18Oc values obtained, regardless of whether or not the carbonate was separated from the organic center, however 13Cc values were marginally lower for carbonate plus organic center measurements. Our results indicate that fossil charophyte gyrogonites can be used to elucidate the geochemistry of the ancient water body in which they lived. |
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Keywords: | Chara charophytes gyrogonites carbon oxygen stable isotopes palaeolimnology |
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