Field observations and hydrogeological drilling investigations carried out in Reunion and Mauritius Islands revealed marine coral-rich carbonate deposits interbedded with or trapped into lavas flows and (or) volcanic detritus in coastal sites. The times of deposition of these carbonates are inferred mainly from K/Ar dating and relative age estimates of associated volcanic rocks. In Reunion, three coral deposits were found beneath the western slopes of the older Piton des Neiges shield volcano. These were dated at 0.28–0.27 million years (Ma), 0.25 Ma, and about 37,000 years respectively, indicating that marine deposition occurred during Marine Isotope Stage (MIS) 8 low stand, MIS 7.5 high stand, and MIS 3.2 low stand. On Mauritius, seven marine carbonate units were identified, located in western and northern areas. The oldest are believed to be late Miocene (older than 5 Ma) to early Pliocene (4–4.5 Ma) in age. The younger were assigned to MIS 11 (0.44–0.35 Ma), MIS 9–8 (older than 0.26 Ma), and MISs 7.5 and 5.5 respectively. While the Piton des Neiges shield would have remained relatively stable since the earlier eruptive phases, Mauritius is shown to have experienced low rates of subsidence (0.015–0.033 mm/year). Identification and point-counting of the main skeletal components—including foraminiferal assemblages—from each carbonate unit, combined with statistical treatment (principal component analysis) of the relevant dataset, allowed different biological associations to be delineated, typified respectively by alcyonarians, ectoprocts, corals, coralline algae and foraminifera. By analogy with the compositional patterns of modern reefal sediments, these associations are shown to be referable to the outer-reef zones (i.e. lower fore-reef and upper fore-reef) and reef-crest to reef-flat zones. By contrast, in Reunion, coral gravels and boulders deposited during MIS 7.5 are interpreted as coastal, storm-generated sediments. The lack of recognized backreef deposits in drillholes in either Reunion or Mauritius suggest that the reef tracts represented may not have possessed well-differentiated backreef environments, but developed in the form of coralgal carpets or narrow fringing reefs such as those present along the west side of Reunion and western and northern Mauritius.

中文翻译：

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留尼汪岛和毛里求斯盾状火山（西印度洋）建造期间的偶发珊瑚生长事件

在留尼汪岛和毛里求斯群岛进行的实地观察和水文地质钻探调查显示，富含海洋珊瑚的碳酸盐沉积物与沿海地区的熔岩流和（或）火山碎屑夹杂或困在其中。这些碳酸盐的沉积时间主要是从 K/Ar 测年和相关火山岩的相对年龄估计中推断出来的。在留尼汪岛，在较旧的 Piton des Neiges 盾状火山的西坡下发现了三个珊瑚沉积物。它们的年代分别为 0.28-027 万年 (Ma)、0.25 Ma 和约 37,000 年，表明海相沉积发生在海洋同位素阶段 (MIS) 8 低位、MIS 7.5 高位和 MIS 3.2 低位。在毛里求斯，确定了七个海相碳酸盐单元，位于西部和北部地区。最古老的被认为是中新世晚期（大于 5 Ma）到上新世早期（4-4.5 Ma）。较年轻的被分配到 MIS 11（0.44-0.35 Ma）、MIS 9-8（大于 0.26 Ma）和 MIS 7.5 和 5.5。虽然 Piton des Neiges 地盾自早期喷发阶段以来一直保持相对稳定，但毛里求斯的下沉率较低（0.015-0.033 毫米/年）。对每个碳酸盐单元的主要骨骼成分（包括有孔虫组合）进行识别和点计数，结合相关数据集的统计处理（主要成分分析），可以描绘出不同的生物关联，分别以海藻、外生动物、珊瑚为代表、珊瑚藻和有孔虫。类比现代珊瑚礁沉积物的组成模式，这些关联被证明是指外礁区（即下前礁和上前礁），而礁顶则是指礁滩区。相比之下，在留尼汪岛，MIS 7.5 期间沉积的珊瑚砾石和巨石被解释为沿海风暴产生的沉积物。在留尼汪岛或毛里求斯的钻孔中缺乏公认的后礁沉积物表明，所代表的珊瑚礁区域可能不具有分化良好的后礁环境，而是以珊瑚毯或狭窄的边缘礁的形式发育，例如沿着西侧存在的那些。留尼汪岛和毛里求斯西部和北部。5 被解释为沿海、风暴产生的沉积物。在留尼汪岛或毛里求斯的钻孔中缺乏公认的后礁沉积物表明，所代表的珊瑚礁区域可能不具有分化良好的后礁环境，而是以珊瑚毯或狭窄的边缘礁的形式发育，例如沿着西侧存在的那些。留尼汪岛和毛里求斯西部和北部。5 被解释为沿海、风暴产生的沉积物。在留尼汪岛或毛里求斯的钻孔中缺乏公认的后礁沉积物表明，所代表的珊瑚礁区域可能不具有分化良好的后礁环境，而是以珊瑚毯或狭窄的边缘礁的形式发育，例如沿着西侧存在的那些。留尼汪岛和毛里求斯西部和北部。