Ca isotopic compositions of dolomite, phosphorite and the oldest animal embryo fossils from the Neoproterozoic in Weng'an, South China
Ca isotopic compositions of dolomite, phosphorite and the oldest animal embryo fossils from the Neoproterozoic in Weng'an, South China
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华南瓮安新元古代白云岩、磷矿及最古老动物胚胎化石的Ca同位素组成
DOI：
10.1016/j.gr.2007.10.004
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发表时间：
2008-08
影响因子：
6.1
通讯作者：
Suga, Akinobu
中科院分区：
文献类型：
--
作者：
Hirata, Takafumi;Yamamoto, Shinji;Li, Yong;Guo, Junfeng;Ohno, Tsuyoshi;Komiya, Tsuyoshi;Han, Jian;Suga, Akinobu
破译新元古代雪球地球事件后地表环境的剧烈变化和动物的出现，对于认识地表环境的变化及其对整个地质时期生命演化的影响具有重要意义。特别是新元古代晚期动物胚胎化石、刺胞动物或海绵动物两类后生动物和埃迪卡拉动物群的出现，是生物进化的关键转折点之一。钙是大多数动物生长所必需的元素之一。为了评价新元古代的Ca旋回，我们利用电感耦合等离子体质谱仪（MC-ICP-MS）测量了磷矿、白云岩和磷化动物胚胎化石的Ca同位素比值（44Ca/42Ca和43ca /42Ca）。通过与NIST SRM915a （δ44/42CaNIST915）比值的相对偏差，确定了磷灰岩和白云岩的44ca /42Ca比值在0.83 ~ 0.95‰之间，说明磷灰岩/白云岩与海水的分馏作用很小。这表明，在瓮安生物群出现时，可能由于磷矿/白云岩的大量沉积和钙生物矿化的开始，海水中缺乏钙。3种磷化动物胚胎化石的δ44/42Ca值均低于磷灰岩和白云岩，说明磷化动物胚胎化石的前体能够通过钙生物矿化作用分馏出Ca同位素，与海洋腹足类动物相一致。
Deciphering the drastic changes of surface environment and the emergence of animals after the Neoproterozoic Snowball Earth event are important for understanding the changes of surface environment and its influence on the evolution of life through geologic time. Especially, the emergence of two types of Metazoan animals such as animal embryo fossils, cnidarians or sponges, and Ediacaran fauna in the late Neoproterozoic was one of the critical turning points in the biological evolution. Calcium is one of the essential elements for the growth of most animals. In this study, in order to evaluate the Ca cycles in the Neoproterozoic, we have measured Ca isotopic ratios (44Ca/42Ca and43Ca/42Ca) for phosphorite, dolostone and phosphatic animal embryo fossils with a multiple collector, inductively coupled plasma-mass spectrometer (MC-ICP-MS). The resulting44Ca/42Ca ratio defined by the relative deviation from the ratio of NIST SRM915a (δ44/42CaNIST915) for phosphorite and dolostone ranges from 0.83 to 0.95‰, demonstrating that the fractionation between phosphorite/dolostone and seawater was very small. This evidence indicates that at the emergence of the Weng'an biota seawater was deficient in Ca probably due to mass deposition of phosphorite/dolostone and to the beginning of Ca-biomineralization. Three phosphatic animal embryo fossils have lower δ44/42Ca values than the phosphorite and dolomite, implying that the precursor of the phosphatic embryo fossils was able to fractionate Ca isotopes through Ca-biomineralization, consistent with marine gastropods.
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影响因子：
1.4
作者：
Yue Zhao
通讯作者：
Yue Zhao
影响因子：
6.1
作者：
J. Meert;B. Lieberman
通讯作者：
J. Meert;B. Lieberman
DOI：
10.1016/j.palaeo.2004.09.005
发表时间：
2005-01
期刊：
Palaeogeography, Palaeoclimatology, Palaeoecology
影响因子：
--
作者：
A. Immenhauser;T. Nägler;T. Steuber;D. Hippler
通讯作者：
A. Immenhauser;T. Nägler;T. Steuber;D. Hippler
DOI：
10.1666/0022-3360(2000)074
发表时间：
2000-09
期刊：
--
影响因子：
--
作者：
S. Xiao;A. Knoll
通讯作者：
S. Xiao;A. Knoll
影响因子：
2.7
作者：
Chen, JY;Oliveri, P;Davidson, EH
通讯作者：
Davidson, EH