Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils
Paleoenvironmental conditions and strontium isotope stratigraphy in the Paleogene Gafsa Basin (Tunisia) deduced from geochemical analyses of phosphatic fossils
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根据磷酸盐化石地球化学分析得出的古近纪加夫萨盆地（突尼斯）古环境条件和锶同位素地层
DOI：
10.1007/s00531-012-0845-5
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发表时间：
2012
影响因子：
2.3
通讯作者：
Kocsis L
中科院分区：
文献类型：
--
作者：
Kocsis L
来自加夫萨盆地三个主要磷块岩矿点的化石鲨鱼牙齿和粪化石（突尼斯西南部）的地球化学成分进行了调查，以改善当地的地层和更好地评估古环境条件。根据Maastrichtian早期El哈里亚组和始新世早期Métlaouis.s.组鲨鱼牙齿的~（86）Sr同位素比值，得到的Sr同位素年龄分别为68 ± 1和47.9 ± 1.3 Ma，与这些沉积物的预期地层位置雅阁。相反，鲨鱼牙齿从古新世始新世Chouabine组有很大的变化，即使在个别层的Sr同位素比值。经过统计处理，然后消除某些离群样本，三个年龄模型的建议和讨论。最合理的解包括IX层、VIII-V层和IV-0层的三个后续Sr年龄，分别为61.8 ± 2.2Ma、57.2 ± 1.8和54.6 ± 1.6。讨论了三种解释异常值存在的情况：（1）成岩作用，（2）改造和（3）局部控制的海水Sr同位素比值。一些化石中相对于全球海洋较高的87 Sr/86 Sr比值最合理的解释是由于低海平面导致的增强的盆地内再加工。而87 Sr/86 Sr比值低于全球海水的样品可能与成岩作用或受晚白垩世海相碳酸盐岩风化作用影响的海水有关，后者也得到了模型计算的支持。这些化石的ε Nd值与古近纪和晚白垩世特提斯海水的ε Nd值非常相似，与上述解释一致。Chouabine地层最顶部磷酸盐层的鲨鱼牙齿中相对较低的氧同位素值以及Sr同位素结果表明，与公海的联系正在恢复。这些δ 18 O数据反映了环境温度的升高，这可能与早始新世气候最佳期有关。
Fossil shark teeth and coprolites from three major phosphorite occurrences in the Gafsa Basin (southwestern Tunisia) were investigated for their geochemical compositions to improve local stratigraphy and to better assess paleoenvironmental conditions.87Sr/86Sr isotope ratios of shark teeth from the Early Maastrichtian El Haria Formation and from the Early Eocene Métlaouis.s.Formation yielded Sr isotope ages of 68 ± 1 and 47.9 ± 1.3 Ma, respectively, which accord with the expected stratigraphic positions of these sediments. Conversely, shark teeth from the Paleocene–Eocene Chouabine Formation have large variation in Sr isotope ratios even within individual layers. After statistical treatment and then elimination of certain outlier samples, three age-models are proposed and discussed. The most reasonable solution includes three subsequent Sr ages of 61.8 ± 2.2 Ma, 57.2 ± 1.8 and 54.6 ± 1.6 for layer IX, layers VIII–V and layers IV–0, respectively. Three scenarios are discussed for explanation of the presence of the outliers: (1) diagenesis, (2) re-working and (3) locally controlled seawater Sr isotope ratio. The most plausible account for the higher87Sr/86Sr ratios relative to the global ocean in some fossils is enhanced intrabasinal re-working due to low sea level. Conversely, the sample with lower87Sr/86Sr than the global seawater may link to diagenesis or to seawater influenced by weathering of Late Cretaceous marine carbonates, which latter is supported by model calculation as well. The εNdvalues of these fossils are very similar to those reported for Paleogene and Late Cretaceous Tethyan seawater and are compatible with the above interpretations. The relatively low oxygen isotope values in shark teeth from the topmost phosphate bed of the Chouabine Formation, together with the Sr isotope results, point toward recovering better connections with the open sea. These δ18O data reflect elevated ambient temperature, which may link to the Early Eocene Climatic Optimum.
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利用鱼牙化石中的锶同位素对深海粘土进行高分辨率测年
影响因子：
5.3
作者：
B. Ingram
通讯作者：
B. Ingram
DOI：
10.1144/gsl.sp.1998.132.01.21
发表时间：
1998
期刊：
Geological Society, London, Special Publications
影响因子：
--
作者：
A. Zaïer;A. Beji;S. Sassi;R. Moody
通讯作者：
R. Moody
突尼斯南部撒哈拉浅地台白垩纪-第三纪过渡
影响因子：
1.6
作者：
G. Keller;T. Adatte;W. Stinnesbeck;D. Stüben;U. Kramar;Z. Berner;Liangquan Li;K. Perch
通讯作者：
K. Perch
影响因子：
5
作者：
E. Martin;B. Haley
通讯作者：
E. Martin;B. Haley
上古新世-下始新世地层记录和古新世-始新世边界碳同位素偏移：对地质年代学的影响
DOI：
10.1144/gsl.sp.1996.101.01.18
发表时间：
1996
期刊：
Geological Society, London, Special Publications
影响因子：
--
作者：
M. Aubry;W. Berggren;L. Stott;A. Sinha
通讯作者：
A. Sinha