Lagoonal facies, ages, and sedimentation in three atolls in the Pacific
Lagoonal facies, ages, and sedimentation in three atolls in the Pacific
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DOI：
10.1016/s0025-3227(02)00188-3
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发表时间：
2002-06
期刊：
影响因子：
2.9
通讯作者：
H. Yamano;H. Kayanne;F. Matsuda;Y. Tsuji
中科院分区：
文献类型：
--
作者：
H. Yamano;H. Kayanne;F. Matsuda;Y. Tsuji
为了研究太平洋环礁泻湖相和时间演化，我们收集并分析了三个不同大小和深度的太平洋环礁泻湖(帕劳群岛的卡扬赫尔、马绍尔群岛的埃尼韦塔克和马朱罗)的表层和岩心沉积物。将泻湖划分为三种相：钙骨岩相、钙钙岩-杂骨岩混合相和杂骨岩相。其依据是有无两种较大的底栖有孔虫--Calcarina和Heterstegina，分别作为礁坪和深泻湖环境的指示物。Calcarina相由异地礁源物质组成，Calcarina-Heterstegina混合相是礁源物质和原位泻湖物质的混合体，而Heterstegina相主要由原位泻湖物质组成。由于这两种有孔虫广泛分布于西太平洋至中太平洋地区，本研究提出的相分类方法也适用于其他太平洋环礁。根据对马朱罗湖岩心样品的放射性碳测年结果，估算了泻湖沉积物的累积速率为0.65mKyr−1。根据沉积物的累积速率和密度计算出碳酸钙产量为710gCaCO3m−2yr−1。
In order to investigate Pacific atoll lagoonal facies and temporal evolution, we collected and analyzed surface and core sediments from three Pacific atoll lagoons of various sizes and depths (Kayangel of Palau Islands, Enewetak and Majuro of the Marshall Islands). The lagoons were divided into three facies: Calcarina facies, Calcarina–Heterostegina mixed facies and Heterostegina facies. These were based on the presence or absence of the tests of two larger benthic foraminifera, Calcarina and Heterostegina, as indicators of reef flat and deep lagoon environments, respectively. The Calcarina facies is composed of allochthonous reef-derived materials, the Calcarina–Heterostegina mixed facies is a mixture of reef-derived and in situ lagoonal materials, and the Heterostegina facies is composed mainly of in situ lagoonal materials. As both foraminifera are widely distributed in the Western to Central Pacific region, the facies classification presented in this study can be applicable to other Pacific atolls. Based on the results of radiocarbon dating on samples obtained from cores at Majuro lagoon, the accumulation rates of the lagoonal sediments were estimated as 0.65 m kyr−1. Calcium carbonate production was calculated on the basis of the accumulation rates and density of sediments to be 710 g CaCO3m−2yr−1.