Critical Studies of Uranium and Trace Element Coral- Geochemistry to Determine their Reliability as Paleoclimate Recorders

该提案寻求进行基础研究，以确定U、Be、Sr和其他阳离子在新老珊瑚中的位置。这项工作的一个具体目标是确定这些元素是部分或主要以吸附在有机物上的形式存在，还是完全位于晶格中。这一知识是利用珊瑚作为广泛地球物理和地球化学信息的古记录器的必要先决条件，这些信息包括海洋234U/238U和10Be/9Be比值、海水金属浓度和大气14C/12C比值。我们的研究将试图评估珊瑚成分是否可用于检测感兴趣的地球物理参数(S)的变异性，并应有助于确定珊瑚14C/12C比值的可靠性，并提出以可靠的方式提取此类信息的适当方法，而不受成岩作用的影响。例如，如果我们的研究表明，珊瑚中的某些阳离子主要吸附在有机物上，那么这些阳离子的浓度将受到与环境交换的影响。为了将这些元素用于古环境研究，只需从文石晶格中提取阳离子即可。我们还建议研究珊瑚在过去确定表层海洋10Be/9Be比值的适宜性。10Be是由大气中的宇宙线核相互作用产生的。10Be半衰期为1.5My承诺允许通过对50克重量的样本进行分析来确定数百万年前的珊瑚的年龄。该提案显然是探索性的，旨在加强珊瑚作为全球古气候和古海洋参数记录器的潜力。

The proposal seeks to carry out basic studies to determine the siting of U, Be, Sr and other cations in recent and old corals. A specific aim of the work is to determine whether these elements exist partly or primarily as adsorbed onto organic matter, or are exclusively sited within the lattice. This knowledge is an essential prerequisite for using corals as paleorecorders of wide- ranging geophysical and geochemical information, e.g., oceanic 234U/238U and 10Be/9Be ratios, seawater metal concentrations and atmospheric 14C/12C ratios. Our studies will attempt to assess whether coral compositions can be used for examining variability in the geophysical parameter(s) of interest, and should help determine the reliability of coral 14C/12C ratios, and also suggest suitable methods to extract such information in a reliable manner, free of effects due to diagenesis. For example, if our studies show that certain cations in corals are primarily adsorbed on organic matter, the concentrations of those cations would be subject to exchange with the environment. To use such elements for paleoenvironment studies, it would be necessary to extract cations from the aragonite lattice only. We also propose to examine the suitability of corals for determining surface oceanic 10Be/9Be ratios in the past. 10Be is produced by cosmic ray nuclear interactions in the atmosphere. The 10Be half-life of 1.5 my promises to allow dating corals of several millions of years' age from analyses of samples of 50 gm weight. The proposal is clearly exploratory in character, aiming at enhancing the potential of corals as recorders of global paleoclimatic and paleo-oceanographic parameters.