In French Polynesia, low-lying, reef islands, composed of unconsolidated skeletal material rest on cemented conglomerate platforms. These are regarded as mainly generated by storm activity during the mid-late Holocene. Field observations and coral sampling were carried out on conglomerates from three atolls located in the north-western Tuamotu, namely, Takapoto, Takaroa and Fakarava. There, fifty-seven samples were dated using the uranium‑thorium (U/Th) method. The lateral age distribution of clasts indicates that conglomerate platforms have accreted from lagoon sides seawards.

In addition to U/Th dating, the coral clast-age datasets include eighteen calibrated radiocarbon ages from Takopoto and other Tuamotu atolls – Takapoto, Mataiva, Rangiroa, Arutua, Apataki, Marokau, Hao, Pukarua, Nukutavake. As a matter of comparison, another seventy-seven, previously published radiometric conglomerate ages from various French Polynesian islands (Society, Tuamotu, Gambier) were incorporated in the present study. It appears that the formation of conglomerate platforms has taken place principally during a 2000-year interval, between 3000 and 1000 yr BP when sea level dropped from about +0.60 m to its present position. Before and after these periods, lower amounts of coral detritus have been provided to conglomerates, possibly due to clast deposition in adjacent lagoons and to trapping into reef rim-islands respectively.

Age discrepancies of most coral clasts collected from multiple stacked layers at Takapoto and Fakarava do not exceed 500 years, strongly suggesting limited clast reworking before final stabilization. The superimposition of two to four firmly cemented conglomeratic layers at the same place gives evidence that marine cementation has operated shortly after clast deposition. This event is regarded as having taken place within both phreatic and vadose environments. Rubble sheets found seawards at some atoll-rim sites are interpreted to be conglomerates in the making, emplaced over the last centuries.

Dating of atoll-islet material indicates clearly that, over the 2500–1000 yr-BP span, the building of conglomerates and overlying islets has interplayed. The former have evolved within subtidal to supratidal zones while the latter have been accreted subaerially. This may explain the firmly consolidated state of platforms and the unconsolidated state of islets. Due to their firmness, conglomerate platforms are assumed to be key structures for the maintenance of atoll islands subjected to sea level rise and increasing storminess in the coming centuries.

在法属波利尼西亚，由未固结骨骼材料组成的低洼礁岛位于胶结的砾岩平台上。这些被认为主要是由全新世中期晚期的风暴活动产生的。在位于Tuamotu西北部的三个环礁，即塔卡波托，塔卡罗阿和法卡拉瓦，对砾岩进行了实地观察和珊瑚取样。那里使用铀‑（U / Th）方法确定了57个样品的年代。碎屑的侧向年龄分布表明砾岩平台从泻湖两侧向海增生。

除U / Th年代外，珊瑚的裂谷年龄数据集还包括来自Takopoto和其他Tuamotu环礁（Takapoto，Mataiva，Rangiroa，Arutua，Apataki，Marokau，Hao，Pukruua，Nukutavake）的18个校准的放射性碳年龄。作为比较，本研究纳入了来自各个法属波利尼西亚群岛（Society，Tuamotu，Gambier）的另外77个先前发布的辐射计集团年龄。似乎主要是在海平面从约+0.60 m下降到现在位置的2000年间隔（3000至1000 BP）之间发生了砾岩平台的形成。在这些时期之前和之后，可能是由于邻近泻湖中的碎屑沉积和分别被捕捞到礁石边缘岛中而导致的砾岩沉积物中珊瑚碎屑的含量较低。

从塔卡波托和法卡拉瓦的多层堆积层收集的大多数珊瑚碎屑的年龄差异不超过500年，强烈表明在最终稳定之前，有限的碎屑返工。同一位置上两到四个牢固胶结的砾岩层的叠加提供了证据，表明在碎屑沉积后不久，海洋胶结作用就开始了。该事件被认为是在潜水和渗流环境中发生的。在某些环礁边缘地点发现向海的碎石片被解释为是在整个生产过程中形成的大集团。

环礁小岛材料的年代清楚地表明，在2500-1000 yr-BP跨度中，砾岩的建设和上覆的小岛相互影响。前者已在潮下至上膜区发展，而后者已在地下膜下增生。这可以解释平台的牢固合并状态和胰岛的未合并状态。由于其坚固性，砾岩平台被认为是维护环礁岛的关键结构，该环礁岛在未来几个世纪中会受到海平面上升和暴风雨增加的影响。