Growth and high-resolution paleoenvironmental signals of rhodoliths (coralline red algae): A new biogenic archive
Growth and high-resolution paleoenvironmental signals of rhodoliths (coralline red algae): A new biogenic archive
复制标题
DOI：
10.1029/1999jc000128
复制
发表时间：
2000-09-15
影响因子：
3.6
通讯作者：
Zachos, JC
中科院分区：
文献类型：
--
作者：
Halfar, J;Zack, T;Zachos, JC
我们调查了rhodoliths（珊瑚红藻）从一个亚热带地区在加州海湾（Lithothammonium crassiusculum）和一个亚北极地区在纽芬兰（Lithothammonium glaciale）的潜在古环境档案，使用微量分析地球化学技术测量三角洲（18）O，Mg和Ca的变化。红柱石是潜在的非常适合作为浅水古环境信号的记录器，因为它们（1）从热带到极地地区分布在世界各地，（2）寿命从几十年到几百年，（3）显示出发育良好的生长带。我们的研究结果表明，红柱石生长带保存了古海洋-古气候变化的超高分辨率记录，并可能构成重建这些藻类所在的滨浅海地区古环境历史的重要新档案。crassiusculum和-3.2至-0.3份千分之一的L，冰川。在这两种情况下，δ（18）O值的范围表明，海洋表面温度的变化幅度略低于两个研究地点在海洋中实际测量的幅度。crassiusculum和glaciale都表现出负的同位素平衡偏移。生长带中镁和钙的电子探针分析揭示了循环变化，其值范围在7.7-18.5摩尔% MgCO 3之间。glaciale和13.2- 22.5mol%MgCO_3。厚叶藓此外，电子探针元素图突出了个别的生长带，提供了一个强大的方法来研究红柱石的形成，并表明，我们分析的标本有250-450亩米/年的垂直增长率。
We investigated rhodoliths (coralline red algae) from a subtropical locality in the Gulf of California (Lithothamnium crassiusculum) and a subarctic locality in Newfoundland (Lithothamnium glaciale) for their potential as paleoenvironmental archives using microanalytical geochemical techniques to measure variations in delta(18)O, Mg, and Ca. Rhodoliths are potentially well suited as recorders of shallow water paleoenvironmental signals because they (1) have worldwide distribution from the tropics to polar regions, (2) are long lived from decades to centuries, and (3) display well-developed growth bands. Our results indicate that rhodolith growth bands preserve ultrahigh-resolution records of paleoceanographic-paleoclimatic change and likely constitute an important new archive for reconstructing the paleoenvironmental history of littoral-neritic areas in which these algae are found. The delta(18)O content of individually sampled rhodolith growth bands ranges from -2.4 to -4.6 parts per thousand in L. crassiusculum and from -3.2 to -0.3 parts per thousand in L, glaciale. In both cases, the range of delta(18)O values suggests a slightly lower amplitude of variation in sea surface temperature than that actually measured in the ocean at the two study sites. Both L, crassiusculum ann L, glaciale show a negative offset from isotopic equilibrium. Electron microprobe analysis of magnesium and calcium in growth bands reveals cyclic variations with values ranging between 7.7-18.5 mol % MgCO3 in L. glaciale and 13.2-22.5 mol % MgCO3 in L. crassiusculum. In addition, electron microprobe element maps highlight individual growth bands, provide a powerful approach to study rhodolith formation, and indicate that the specimens we analyzed have Vertical growth rates of 250-450 mu m/yr.