Intra-tooth variations in δ18O (PO4) of mammalian tooth enamel as a record of seasonal variations in continental climate variables
Intra-tooth variations in δ18O (PO4) of mammalian tooth enamel as a record of seasonal variations in continental climate variables
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DOI：
10.1016/s0016-7037(98)00114-8
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发表时间：
1998-06-01
影响因子：
5
通讯作者：
O'Neil, JR
中科院分区：
文献类型：
--
作者：
Fricke, HC;Clyde, WC;O'Neil, JR
自从首次观察到哺乳动物牙釉质磷酸盐的 delta(18)O 值 (delta(18)O(p)) 以来，牙齿内的定期变化就被认为是大陆气候变量季节变化的潜在衡量标准。为了更详细地研究这种可能性，对生活在不同地理位置、生态环境和气候条件（爱荷华州、佛罗里达州、怀俄明州、冰岛、英国、克罗地亚和菲律宾）的许多哺乳动物食草动物（绵羊、牛、麋鹿和猪）的牙齿进行了分析。饮用自来水的牛的牙齿缺乏齿内 delta(18)O(p) 变异，这提供了强有力的证据，表明观察到的齿内变异的根本原因主要是摄入水的同位素组成的变化。与这种解释相一致，每个地点的齿内 delta(18)O(p) 值及其绝对值的范围反映了观察到的当地降水 (delta(18)O(pt)) 范围和绝对 delta(18)O 值以及气候变量的差异。因此，齿内 delta(18)O(p) 值确实可以被视为大陆环境中季节性气候变化的定性测量。定量使用齿内 delta(18)O(p) 值作为气候指标是可能的，但由于缺乏哺乳动物生理学、行为以及可能在影响 delta(18)O(p) 中发挥作用的当地水文方面的详细信息而受到阻碍。英国约克附近同一地点的绵羊和牛测量的 delta(18)O(p) 值的不同范围（分别为千分之 3.4 和千分之 2.6）就说明了这个问题。观察到的差异很可能反映了两个物种摄入的叶水相对量的差异。未来需要对约束良好的样本进行研究，以测试生理模型并建立准确地将 delta(18)O(p) 与 delta(18)O(pt) 联系起来的经验关系。除了用作季节性指标外，牙齿内 delta(18)O(p) 值的变化还为长期气候变化和古生物学研究提供了有价值的信息。版权所有 (C) 1998 爱思唯尔科学有限公司
Regular intra-tooth variations in the delta(18)O value of mammalian tooth enamel phosphate (delta(18)O(p)) have been considered a potential measure of seasonal changes in continental climate variables since they were first observed. In order to investigate this possibility in more detail, analyses were made of teeth from a number of mammalian herbivores (sheep, cattle, elk, and pigs) that lived over a wide range of geographic locations, ecological settings, and climatic conditions (Iowa, Florida, Wyoming, Iceland,. England, Croatia, and the Philippines). The lack of intra-tooth delta(18)O(p) variations in teeth of cattle that were given tap water to drink provides strong evidence that the underlying cause of observed intra-tooth variations is primarily a change in the isotopic composition of ingested water. In concert with this interpretation, the range of intra-tooth delta(18)O(p) values and their absolute values from each locality mirror observed differences in the range and absolute delta(18)O values of local precipitation (delta(18)O(pt)) and in climate variables. Thus intra-tooth delta(18)O(p) values can indeed be considered a qualitative measure of seasonal climate change in continental settings. Quantitative use of intra-tooth delta(18)O(p) values as a climate proxy is possible, but is hindered by lack of detailed information on aspects of mammalian physiology, behavior, and perhaps local hydrology that may also play a role in influencing delta(18)O(p). This problem is exemplified by the different range in delta(18)O(p) values measured for sheep and cattle from the same locality around York, UK (3.4 vs. 2.6 parts per thousand, respectively). The observed difference most likely reflects a difference in the relative amount of leaf water ingested by the two species. Future studies of well-constrained samples are required to test physiological models and to develop empirical relations that accurately relate delta(18)O(p) to delta(18)O(pt). In addition to their use as indicators of seasonality, intra-tooth variations in delta(18)O(p) values provide valuable information for longer-term climate change and paleobiological investigations. Copyright (C) 1998 Elsevier Science Ltd.