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首页> 外文期刊>Geochimica et Cosmochimica Acta: Journal of the Geochemical Society and the Meteoritical Society >Paleogene paleoclimate reconstruction using oxygen isotopes from land and freshwater organisms: the use of multiple paleoproxies
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Paleogene paleoclimate reconstruction using oxygen isotopes from land and freshwater organisms: the use of multiple paleoproxies

机译：利用来自陆地和淡水生物的氧同位素进行古气候古气候重建：多种古气候的使用

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摘要

Understanding past climate change is critical to the interpretation of earth history. Even though relative temperature change has been readily assessed in the marine record, it has been more difficult in the terrestrial record due to restricted taxonomic distribution and isotopic fractionation. This problem could be overcome by the use of multiple paleoproxies. Therefore, the delta(18)O isotopic composition of five paleoproxies (rodent tooth enamel, delta(18)O(Phosphate) + 17.7 +/- 2.0parts per thousand n = 74 (VSMOW); fish scale ganoine delta(18)O(Phosphate) = + 19.7 +/- 0.7parts per thousand n = 20 (VSMOW); gastropod shell delta(18)O(Calcite) = -1.7 +/- 1.3parts per thousand n = 50 (VPDB); charophyte gyrogonite delta(18)O(Calcite) = -2.4 +/- 0.5parts per thousand n = 20 (VPDB); fish otolith delta(18)O = -3.6 +/- 0.6parts per thousand n = 20 (VPDB)) from the Late Eocene (Priabonian) Osborne Member (Headon Hill Formation, Solent Group, Hampshire Basin, UK) were determined. Because diagenetic alteration was shown to be minimal the phosphate oxygen component of rodent tooth enamel (as opposed to enamel carbonate oxygen) was used to calculate an initial delta(18)O(Local water) value of 0.0 +/- 3.4parts per thousand. However, a skewed distribution, most likely as a result of the ingestion of evaporating water, necessitated the calculation of a corrected delta(18)O(Local water) value of -1.3 +/- 1.7parts per thousand (n = 62). This delta(18)O(Local water) value corresponds to an approximate mean annual temperature of 18 +/- 1degreesC Four other mean paleotemperatures can also be calculated by combining the delta(18)O(Local water) value with four independent freshwater paleoproxies. The calculated paleotemperature using the fish scale thermometry equations most likely represents the mean temperature (21 +/- 2degreesC) of the entire length of the growing season. This should be concordant with the paleotemperature calculated using the Lymnaea shell thermometry equation (23 +/- 2degreesC). The lack of concordance is interpreted to be the result of diagenetic alteration of the originally aragonitic Lymnaea shell to calcite. The mean paleotemperature calculated using the charophyte gyrogonite thermometry equation (21 +/- 2degreesC), on the other hand, most likely represents the mean temperature of a single month toward the end of the growing season. The fish otolith mean paleotemperature (28 +/- 2degreesC) most likely represents the mean temperature of the warmest months of the growing season. An approximate mean annual temperature of 18 +/- 1degreesC, in addition to a mean growing season paleotemperature of 21 +/- 2degreesC (using fish scale only) with a warmest month temperature of 28 +/- 2degreesC, and high associated standard deviations suggest that a subtropical to warm temperate seasonal climate existed during the deposition of the Late Eocene Osborne Member. Copyright (C) 2003 Elsevier Ltd. [References: 64]
机译：了解过去的气候变化对于解释地球历史至关重要。尽管在海洋记录中已经可以轻松评估相对温度的变化，但由于有限的生物分类分布和同位素分馏，在陆地记录中却更加困难。这个问题可以通过使用多个古近摄度来克服。因此，五个古近界（啮齿动物牙釉质，δ（18）O（磷酸盐）+ 17.7 +/- 2.0份/千n（74）（VSMOW）;鱼鳞甘氨酸delta（18）O）的delta（18）O同位素组成（磷酸盐）= + 19.7 +/- 0.7份/千n = 20（VSMOW）;腹足动物壳δ（18）O（方解石）= -1.7 +/- 1.3份/千n = 50（VPDB）;硅藻土陀螺石δ （18）O（方解石）= -2.4 +/- 0.5份每千n = 20（VPDB）;鱼耳石δ（18）O = -3.6 +/- 0.6份每千n = 20（VPDB））确定了晚始新世（Priabonian）奥斯本成员（英国汉普郡盆地Solent Group的Headon Hill地层）。因为显示出成岩作用的改变很小，所以啮齿动物牙釉质的磷酸氧成分（与牙釉质碳酸氧相反）被用来计算初始δ（18）O（局部水）值为0.0 +/- 3.4份/千。但是，偏斜的分布很可能是由于吸收了蒸发的水而导致的，因此必须计算出校正的delta（18）O（局部水）值为-1.3 +/- 1.7千分之一（n = 62）。该delta（18）O（Local water）值对应于大约18 +/- 1°C的年平均气温，也可以通过将delta（18）O（Local water）值与四个独立的淡水古气候相结合来计算其他四个平均古温度。使用鱼鳞测温方程计算的古温度很可能代表了整个生长季节的平均温度（21 +/- 2摄氏度）。这应与使用Lymnaea壳测温方程（23 +/- 2℃）计算的古温度一致。缺乏一致性被解释为最初的松香属Lymnaea壳成方解石成岩作用的结果。另一方面，使用风化菱铁矿测温方程（21 +/- 2摄氏度）计算出的平均古温度很可能代表着生长季节快结束时一个月的平均温度。鱼耳石的平均古温度（28 +/- 2℃）很可能代表了生长期最温暖月份的平均温度。年平均气温约为21 +/- 2摄氏度（仅使用鱼鳞），最温暖的月份温度为28 +/- 2摄氏度，且相关标准偏差较高，因此年平均气温约为18 +/- 1摄氏度。始新世奥斯本成员沉积期间存在亚热带至温暖的温带季节性气候。版权所有（C）2003 Elsevier Ltd. [参考：64]

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