Use of stable oxygen isotope determinations from brachiopod shells in palaeoenvironmental reconstruction
Use of stable oxygen isotope determinations from brachiopod shells in palaeoenvironmental reconstruction
复制标题
DOI：
10.1016/s0031-0182(01)00456-4
复制
发表时间：
2002-07-01
影响因子：
3
通讯作者：
Fallick, AE
中科院分区：
文献类型：
--
作者：
Curry, GB;Fallick, AE
对新西兰上更新世（约80 ka）浅海沉积物中的腕足类壳化石进行了稳定氧同位素分析，作为古环境调查的一部分。对卡洛里亚整个壳的大量分析产生了高度可变的结果（范围为千分之2.30），使得这些数据作为古环境指标的用途有限。试图通过去除被认为容易受到氧同位素不平衡效应（“重要效应”）影响的腕足动物外壳区域来获得一致的氧同位素值，结果显示，来自同一个体的腹侧和背侧瓣膜的匹配前部（同时分泌）也产生了不同的氧同位素比率。与同一个体的腹侧瓣膜相比，背侧瓣膜的VO值更高，变化更少。然后将调查扩展到来自新西兰南岛类似浅水栖息地的同一物种的活体代表。在8个被调查的个体中，有7个重复了背瓣膜产生比腹瓣膜匹配区域更高和更少变化的氧同位素值的模式，尽管不同标本之间的绝对值有相当大的差异。因此，与通常的做法相反，在这个物种中，似乎是更薄更轻的背阀提供了更一致的同位素测量。如果转换成绝对温度估计，背阀测量值对应于该物种在其现今栖息地经历的年平均温度和最高温度之间的温度，这可能使其成为可接受的古环境指标。个体之间的高度差异（包括从一个腹阀推断的温度高于平均最高温度）表明，在任何古环境调查中，都需要对一系列个体进行调查，以避免误导性的解释。然而，标本内和标本间同位素组成的变化可能提供有关过去生长速率、代谢和可能的病理状况的有价值的古生物学信息。(C) 2002 Elsevier Science B.V.版权所有
Stable oxygen isotope analyses were obtained from fossil brachiopod shells from a shallow marine deposit of Upper Pleistocene age (approximately 80 ka) in New Zealand as part of a palaeoenvironmental investigation. Bulk analyses of entire shells of Calloria inconspicua yielded highly variable results (a range of 2.30parts per thousand), rendering these data of limited use as palaeoenvironmental proxies. Attempts to obtain consistent oxygen isotope values by removing areas of the brachiopod shell thought to be prone to oxygen isotope disequilibrium effects ('vital effects') revealed that the matching anterior portions of ventral and dorsal valves from the same individual (which were secreted at the same time) also yielded different oxygen isotope ratios. The dorsal valve VO values were higher and less variable than those obtained from the ventral valve of the same individual. The investigation was then extended to living representatives of the same species from a similar shallow water habitat from the South Island of New Zealand. The pattern of dorsal valves yielding higher and less variable oxygen isotope values than matching areas of the ventral valves was repeated in seven out of eight individuals investigated, although there was considerable variation in the absolute values from specimen to specimen. Contrary to common practice therefore, it seems that in this species it is the much thinner and lighter dorsal valve that provides a more consistent isotopic measurement. If converted into absolute temperature estimates, the dorsal valve measurements correspond to a temperature midway between the mean and maximum annual temperature experienced by this species in its present-day habitat, which may make it acceptable as a palaeoenvironmental indicator. The high level of variation between individuals (including an inferred temperature from one ventral valve above the mean maximum temperature experienced) indicates that a range of individuals needs to be investigated in any palaeoenvironmental investigation to avoid misleading interpretations. However, intra- and inter-specimen variation in isotopic composition may provide valuable palaeobiological information on growth rates, metabolism and possibly also pathological conditions in the past. (C) 2002 Elsevier Science B.V. All rights reserved.