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首页> 外文OA文献 >Dinosaur eggshell isotope geochemistry as tools of paleoenvironmental reconstruction for the upper Cretaceous from the Tremp Formation (Southern Pyrenees).
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Dinosaur eggshell isotope geochemistry as tools of paleoenvironmental reconstruction for the upper Cretaceous from the Tremp Formation (Southern Pyrenees).

机译：恐龙蛋壳同位素地球化学作为特里普组（南比利牛斯）上白垩统古环境重建的工具。

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The isotopic compositions (δ13C and δ18O) of dinosaur eggshells have beenwidely used in palaeoenvironmental studies, although the geochemical signatures of eggshells are not usually contrasted with other proxies. In this work, the isotopic signatures of eggshells from a large Maastrichtian succession from the Tremp Formation (Southern Pyrenees, Spain) are compared to those of carbonate pedogenic nodules occurring in the same levels. The isotopic signatures of eggshells vary according to the stratigraphic unit and geographical location. A group of samples from several localities corresponding to eggshells without significant diagenetic imprints has isotopic values differing from the associated nodules; The Late Cretaceous isotopic composition record from the Tremp Fm. is consistent that is, the eggshells have distinct primary signatures preserved. However, the eggshells from another locality, which exhibit neomorphed textures, display isotopic signatures similar to the associated pedogenic carbonate, which suggests a diagenetic isotopic signature and confirms alteration in the eggshells. Both microscopic and geochemical data suggest that an early meteoric diagenesis (pedogenesis) is responsible for the secondary signatures. The δ13C values in the carbonate pedogenic nodules indicate a carbon isotopic composition typical of C3 plants, although the slight difference in δ13C between the palaeosol carbonate of coeval successions may be due to slightly different palaeoenvironmental conditions. The small discrepancy in the δ13C calculated for C3 plants, from carbonate nodules and from eggshells may be because the palaeosol carbonate gives the isotopic composition of the vegetation grown at a local site whereas the δ13C fromeggshells is a proxy for the ingested food in the area in which the dinosaurs lived. The oxygen isotopic compositions frompalaeosol carbonate nodules have been used for calculation of the air temperature, and we may conclude that the mean air temperature in the studied area during the Late Cretaceous was approximately 21 °C. The use of this temperature gives rational results in the calculation of the oxygen isotopic composition of palaeosol carbonate by means of the isotopic composition of the eggshell carbonate. Additionally, a relatively continuous isotopic record of nodules shows an overall vertical trend towards negative δ13C values and a high relative and steady δ18O content throughout the Maastrichtian. The K/Pg boundary was recorded by a negative excursion in δ13C in the carbonate nodules
机译：恐龙蛋壳的同位素组成（δ13C和δ18O）已被广泛用于古环境研究，尽管蛋壳的地球化学特征通常不与其他代理人进行对比。在这项工作中，将来自特伦普组（西班牙南比利牛斯）的大型马斯特里赫特演替过程中的蛋壳的同位素特征与相同水平出现的碳酸盐成岩结核的同位素特征进行了比较。蛋壳的同位素特征根据地层单位和地理位置而变化。一组来自几个地点的，与蛋壳相对应的样本，没有明显的成岩作用印记，其同位素值不同于相关结节。 Tremp Fm记录的晚白垩世同位素组成。这是一致的，即蛋壳保留了不同的主要特征。但是，另一个地方的蛋壳表现出新的质地，显示出与相关的成岩碳酸盐相似的同位素特征，表明成岩同位素特征并证实了蛋壳中的改变。微观和地球化学数据都表明，早期的快速成岩作用（成岩作用）是造成次生特征的原因。碳酸盐岩成虫小结节中的δ13C值表明了C3植物的典型碳同位素组成，尽管同期演替的古土壤碳酸盐之间的δ13C略有差异可能是由于古环境条件略有不同。从碳酸盐结节和蛋壳中计算出的C3植物的δ13C差异很小，可能是因为古土壤碳酸盐给出了当地生长的植被的同位素组成，而卵壳中的δ13C代表了该地区所摄取食物的替代物。恐龙居住的地方。来自古土壤碳酸盐结节的氧同位素组成已用于计算气温，我们可以得出结论，白垩纪晚期研究区域的平均气温约为21°C。该温度的使用通过蛋壳碳酸盐的同位素组成，在计算古土壤碳酸酯的氧同位素组成方面给出了合理的结果。此外，结核的相对连续同位素记录显示，整个马斯特里赫特地区的总体垂直趋势为负δ13C值和较高的相对和稳定δ18O含量。通过碳酸盐结节中δ13C的负偏移记录了K / Pg边界

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