The impact of global environmental change on coral reef islands is uncertain, with few studies having resolved the critical controls on island formation and change. Based on detailed, topographic surveys, sediment analysis and radiometric dating, we present a multi-phase model of the formation of two reef islands in Jaluit atoll, Republic of the Marshall Islands. The initial phase of island building occurred 1300 years ago, later than elsewhere in the Marshall Islands and during a period of relative sea level fall from the mid-Holocene sea level highstand. Initial accumulation occurred as a consequence of relative emergence of the reef flat that forced a transition in reef flat ecology and dominant foraminifera sediment producers that contributed to island building. Distinctive sets of progradational ridges and their coarse sediment character provide evidence for the importance of extreme wave events in island expansion from an initial core. Expansion occurred in two principle phases, 650–350 years ago and 200 years ago to the present, each coincident with known phases of increased storminess in the central Pacific. Results highlight the complexity of island formation and show that future change will depend not only on sea level but storm processes that have been a major influence on island development over the past 650 years. Anticipated reduction in cyclogenesis in the southern Marshall Islands region suggests a near-future period of geomorphic stasis of the islands of Jaluit. An increase in cyclogenesis in the central Pacific and higher latitudes may enhance opportunities for storm-driven island accumulation events over the next century where coral growth is able to be maintained.

全球环境变化对珊瑚礁岛屿的影响尚不确定，很少有研究解决了对岛屿形成和变化的关键控制。基于详细的地形调查、沉积物分析和辐射测年，我们提出了马绍尔群岛共和国贾鲁伊特环礁两个礁岛形成的多阶段模型。岛屿建造的初始阶段发生在 1300 年前，比马绍尔群岛的其他地方晚，并且是在全新世中期海平面高位相对海平面下降的时期。最初的积累是由于礁滩的相对出现，迫使礁滩生态和占主导地位的有孔虫沉积物生产者发生转变的结果，这有助于岛屿建设。独特的进积山脊及其粗糙的沉积物特征为极端波浪事件在岛屿从初始核心扩张中的重要性提供了证据。扩张发生在两个主要阶段，即 650-350 年前和 200 年前至今，每个阶段都与已知的中太平洋暴风雨增加的阶段相吻合。结果突出了岛屿形成的复杂性，并表明未来的变化不仅取决于海平面，还取决于过去 650 年来对岛屿发展产生重大影响的风暴过程。预计马绍尔群岛南部地区的气旋发生减少表明 Jaluit 群岛在不久的将来会出现地貌停滞。