Abstract Modern sedimentary facies in the shallow platform interior of the almost-atoll of Aitutaki, Cook Islands, is significant, because abundant non-skeletal grains have been discovered in this Pacific location and also in some adjacent carbonate platforms. Abundant non-skeletal carbonate grain occurrences have been classically placed in the western Atlantic and the Arabian/Persian Gulf, but not in the Indo-Pacific realm. In order of decreasing abundance, non-skeletal grains in Aitutaki include peloids, aggregate grains, and ooids. Peloids are largely cemented fecal pellets, and their occurrence is controlled by the occurrence of mollusk and crustacean producers in the interior platform. Ooids, which are characterized by thin and irregular cortices, and aggregate grains appear to be more common at the platform margin in environments of somewhat elevated depositional energy. In general, high alkalinity in this part of the south Pacific seems to be another precondition of non-skeletal grain formation. The fine grain-size fraction reaches an abundance of 70% in the platform interior (average 41.5%) and is largely of skeletal origin. Based on the quantitative analysis of texture and composition of samples, two groups of sediment types may be distinguished including coralgal grainstones and packstones that occur at the platform margin as well as peloidal and mixed skeletal-peloidal wackestones and packstones in the platform interior. These two types may be further differentiated into eight sedimentary facies including (1) peloidal wackestone, (2) peloidal packstone, (3) mud-rich skeletal-peloidal packstone, (4) skeletal-peloidal packstone, (5) skeletal-peloidal grainstone, (6) coralgal packstone, (7) coralgal grainstone, and (8) coralgal-aggregate grainstone. Sediment texture is correlated with water depth, which is considered a good proxy for depositional energy. Considerable bathymetric overlap exists, however, between sedimentary facies. Also, facies distribution in the platform interior appears to be fragmentary rather than being characterized by laterally extensive units. These observations have to be considered when using sedimentary facies distribution in modern reefs and carbonate platforms as models for ancient systems in the fossil record.

中文翻译：

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几乎环礁的艾图塔基、库克群岛、南太平洋的沉积物

摘要 库克群岛艾图塔基近环礁浅台台内部现代沉积相具有重要意义，因为在该太平洋位置以及一些相邻的碳酸盐台地中发现了丰富的非骨骼颗粒。丰富的非骨架碳酸盐颗粒产地通常位于西大西洋和​​阿拉伯/波斯湾，但不在印度太平洋地区。按照丰度递减的顺序，Aitutaki 中的非骨骼颗粒包括 peloids、聚集颗粒和 ooids。Peloids 主要是胶结的粪便颗粒，它们的发生受内部平台中软体动物和甲壳类动物生产者的控制。Ooids，其特征是皮质薄且不规则，在沉积能有所升高的环境中，聚集颗粒似乎更常见于台地边缘。一般来说，南太平洋这一部分的高碱度似乎是非骨骼颗粒形成的另一个先决条件。平台内部的细粒度部分达到 70% 的丰度（平均 41.5%），并且主要来自骨骼。根据样品质地和成分的定量分析，可以区分出两组沉积类型，包括出现在台地边缘的珊瑚状颗粒岩和灰岩，以及台地内部的球状和混合骨架-球状灰岩和灰岩。这两种类型可进一步区分为八种沉积相，包括（1）球状泥灰岩，（2）球状泥灰岩，(3) 富含泥浆的骨架-球状粒状砂岩，(4) 骨架-球状粒状粒状砂岩，(5) 骨架-球状粒状粒状砂岩，(6) 珊瑚状粒状粒状砂岩，(7) 珊瑚状粒状粒状砂岩，和 (8) 珊瑚状粒状粒状粒状粒状砂岩。沉积物质地与水深相关，水深被认为是沉积能量的良好代表。然而，沉积相之间存在相当大的测深重叠。此外，台地内部的相分布似乎是零散的，而不是以横向扩展单元为特征。当使用现代珊瑚礁和碳酸盐台地的沉积相分布作为化石记录中古代系统的模型时，必须考虑这些观察结果。(8) 珊瑚粒粒状砂岩。沉积物质地与水深相关，水深被认为是沉积能量的良好代表。然而，沉积相之间存在相当大的测深重叠。此外，台地内部的相分布似乎是零散的，而不是以横向扩展单元为特征。当使用现代珊瑚礁和碳酸盐台地的沉积相分布作为化石记录中古代系统的模型时，必须考虑这些观察结果。(8) 珊瑚粒粒状砂岩。沉积物质地与水深相关，水深被认为是沉积能量的良好代表。然而，沉积相之间存在相当大的测深重叠。此外，台地内部的相分布似乎是零散的，而不是以横向扩展单元为特征。当使用现代珊瑚礁和碳酸盐台地的沉积相分布作为化石记录中古代系统的模型时，必须考虑这些观察结果。台地内部的相分布似乎是零散的，而不是以横向广泛的单元为特征。当使用现代珊瑚礁和碳酸盐台地的沉积相分布作为化石记录中古代系统的模型时，必须考虑这些观察结果。台地内部的相分布似乎是零散的，而不是以横向广泛的单元为特征。当使用现代珊瑚礁和碳酸盐台地的沉积相分布作为化石记录中古代系统的模型时，必须考虑这些观察结果。