Oxygen isotopes and MgCO3 in brachiopod calcite and a new paleotemperature equation
Oxygen isotopes and MgCO3 in brachiopod calcite and a new paleotemperature equation
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DOI：
10.1016/j.chemgeo.2013.09.014
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发表时间：
2013-11-14
期刊：
影响因子：
3.9
通讯作者：
Ruggiero, E.
中科院分区：
文献类型：
--
作者：
Brand, Uwe;Azmy, K.;Ruggiero, E.
现代腕足动物及其周围的海水，从34个地方，涵盖从极地到热带浅水汇编分析了他们的氧同位素组成，SrCO 3和MgCO 3的含量。如果在计算中考虑常规海水δ O-18组成和对氧同位素的“MgCO 3效应”，则钙化温度与测得的环境海水温度一致。现代腕足动物的SrCO_3含量与环境温度无关，而MgCO_3含量与温度和生长速率有一定的关系，部分受环境生产力或清除率或局部环境的控制，并受分类上的亲缘关系如盲肠的存在与否等的影响。其对壳MgCO 3含量进行调整，并覆盖水温范围为-2度至+32摄氏度的栖息地：T摄氏度= 16.192-3.468（δ（c）-δ（SW）-Mg-c）（N = 319; R-2 = 0.98）。Mg效应调整基于壳方解石δ O-18每摩尔%MgCO3变化+0.17份千分之一（Jimenez-Lopez等人，2004年）。这种调整对于确定现代铰接腕足动物的钙化温度至关重要，特别是来自冷水和温水栖息地的腕足动物，和/或具有异常低或高MgCO 3含量的腕足动物，否则可能会被抵消（更低或更高）高达7摄氏度。此外，这种调整可能是至关重要的化石腕足动物和其他海洋方解石无脊椎动物与可变的MgCO 3含量，当使用他们的三角洲O-18和三角洲（47）确定古代海水三角洲O-18的组成和温度。(C)2013年爱思唯尔B。V.保留所有权利。
Modern brachiopods and their ambient seawater, compiled from 34 localities, covering shallow-waters from the poles to the tropics were analyzed for their oxygen isotopic compositions, and SrCO3 and MgCO3 contents. If the routine seawater delta O-18 composition and the 'MgCO3 effect' on oxygen isotopes are considered in calculations, calcification temperatures are concordant with measured ambient seawater temperatures. The SrCO3 contents of modern brachiopods appear to be unrelated to ambient growth temperatures, while their MgCO3 contents exhibit some relationship with temperature and growth rate, controlled, in part, by ambient productivity or clearance rates or local environment, and by taxonomic affinity such as presence or absence of caeca.Linear least-squares regression analysis yields a new oxygen isotope paleotemperature equation for brachiopod calcite, which makes adjustment for shell MgCO3 contents, and covers habitats with water temperatures ranging from -2 degrees to +32 degrees C:T degrees C = 16.192-3.468(delta(c)-delta(SW)-Mg-c) (N = 319; R-2 = 0.98).The Mg-effect adjustment is based on the change in shell-calcite delta O-18 by +0.17 parts per thousand per mol% MgCO3 (Jimenez-Lopez et al., 2004). This adjustment is critical to the determination of calcification temperatures for modern articulated brachiopods, especially the ones from cold and warmwater habitats, and/or the ones with exceptionally low or high MgCO3 contents, which otherwise may be offset (lower or higher) by as much as 7 degrees C. Furthermore, this adjustment may be critical for fossil brachiopods and other marine calcitic invertebrates with variable MgCO3 contents, and when using their delta O-18 and Delta(47) for determining ancient seawater delta O-18 compositions and temperatures. (C) 2013 Elsevier B. V. All rights reserved.