The Iapetus Ocean opened during the fission of the supercontinent Rodinia, from the breakup of three of its core continental constituents: Laurentia, Baltica and Amazonia. The timing of Iapetus opening is still much debated, with estimates ranging from 700 to 550 Ma. Similarly debated is exactly how Laurentia, Baltica and Amazonia were positioned relative to each other immediately before their breakup. In this study, we reconsider the timing and framework of Iapetus opening by integrating the fragmentary mid-Neoproterozoic to early Cambrian observational records from these continents. We first demonstrate that paleomagnetic data, despite being both sparse and probably contaminated by some global-scale, non-uniformitarian process in Ediacaran time, support the existence of a wide ocean between these continents by 575 Ma. However, the paleomagnetic data alone are insufficient to allow the formulation of more specific conclusions concerning the timing and paleogeography of Iapetus opening. We therefore conduct an extensive review of the mid-Neoproterozoic to Cambrian geology of eastern Laurentia, western Baltica and western Amazonia which, jointly interpreted with the paleomagnetic constraints, allow us to construct a self-consistent and geodynamically feasible plate tectonic model. In this model, the breakup of Laurentia, Baltica and Amazonia was polyphase, involving the spalling of multiple marginal terranes from Laurentia and the successive opening of several oceans, including a composite ‘Iapetus Ocean’. The first phase of continental breakup occurred between eastern Laurentia and western Amazonia at 750–700 Ma, leading to the opening of the Puncoviscana Ocean. This was followed by the opening of the eastern branch of the Iapetus Ocean, between Laurentia and Baltica, at ~590 Ma, which may have been instigated by emplacement of the Central Iapetus Magmatic Province. The western branch of Iapetus subsequently opened at ~550 Ma by the detachment of marginal terranes from eastern Laurentia, following a protracted phase of rifting. We contend that our preferred scenario is the simplest solution given the presently available evidence but throughout this review we underline key outstanding questions and the attendant uncertainties in our preferred model.

Iapetus Ocean 在超大陆 Rodinia 裂变期间开放，其三个核心大陆成分：Laurentia、Baltica 和 Amazonia 分裂。Iapetus 开放的时间仍然存在很多争议，估计在 700 到 550 Ma 之间。同样争论不休的是 Laurentia、Baltica 和 Amazonia 在他们分手之前是如何相对彼此定位的。在这项研究中，我们通过整合来自这些大陆的零碎的中新元古代和早寒武纪观测记录来重新考虑土卫一开放的时间和框架。我们首先证明，尽管古地磁数据既稀少又可能受到埃迪卡拉纪某些全球规模的非均一过程的污染，但在 575 Ma 之前，这些大陆之间存在广阔的海洋。然而，仅靠古地磁数据不足以得出关于土卫一开放的时间和古地理的更具体的结论。因此，我们对劳伦西亚东部、波罗的海西部和亚马逊西部的中新元古代至寒武纪地质进行了广泛的审查，结合古地磁约束进行解释，使我们能够构建自洽和地球动力学可行的板块构造模型。在这个模型中，劳伦大陆、波罗的海和亚马逊流域的分裂是多相的，包括来自劳伦大陆的多个边缘地体的剥落和几个大洋的连续开放，包括一个复合的“Iapetus Ocean”。大陆分裂的第一阶段发生在 750-700 Ma 的东劳伦西亚和西亚马逊之间，导致 Puncoviscana 洋的开放。随后在 Laurentia 和 Baltica 之间的 Iapetus 洋东部分支在约 590 Ma 开放，这可能是由中央 Iapetus 岩浆省的进驻引起的。Iapetus 的西部分支随后在 550 Ma 左右开放，在经历了长期的裂谷之后，边缘地体从 Laurentia 东部脱离。我们认为，鉴于目前可用的证据，我们的首选方案是最简单的解决方案，但在整个审查过程中，我们强调了我们首选模型中的关键未决问题和随之而来的不确定性。Iapetus 的西部分支随后在 550 Ma 左右开放，在经历了长期的裂谷之后，边缘地体从 Laurentia 东部脱离。我们认为，鉴于目前可用的证据，我们的首选方案是最简单的解决方案，但在整个审查过程中，我们强调了我们首选模型中的关键未决问题和随之而来的不确定性。Iapetus 的西部分支随后在 550 Ma 左右开放，在经历了长期的裂谷之后，边缘地体从 Laurentia 东部脱离。我们认为，鉴于目前可用的证据，我们的首选方案是最简单的解决方案，但在整个审查过程中，我们强调了我们首选模型中的关键未决问题和随之而来的不确定性。