Cyclostratigraphy is a powerful tool in chronostratigraphic studies, and has shown its potential in Precambrian time. The Cryogenian Period is one of the most dynamic and intriguing intervals in Earth history and it is a witness to the most extreme climate changes on the planet, known as two Snowball Earth events. However, a robust chronostratigraphic framework is still lacking especially for the younger Marinoan Snowball Earth event, hampering the stratigraphic correlation and comparison among geographically separated records, as well as the understanding of the initiation and termination of this global-scale glaciation. The Cryogenian Fiq Formation in Oman is thought to be Marinoan-equivalent. The duration of the nonglacial units in the Fiq Formation could provide a conservative age constraint on the previously not well-determined onset age of the Marinoan glaciation. In this work, a cyclostratigraphic study has been conducted on three drill cores of the Fiq Formation. The multi-taper method (MTM) spectral analysis, the correlation coefficient (COCO), and the evolutionary correlation coefficient (eCOCO) analyses were performed on the high-resolution gamma-ray (GR) data from the three cores. A hierarchy of Milankovitch cycles (eccentricities, obliquities, and precessions) has been identified, which was used to estimate the optimal sedimentary accumulate rates and the duration of the Fiq Formation in each core. Based on the cyclostratigraphic results, the time scale of the Fiq Formation is at least ~6 Myr. Integrating the radiometric ages and the cyclostratigraphic data from other continents, the onset age of the Marinoan glaciation is suggested to be 650–641 Ma. This new result helps improve the chronostratigraphic framework for the Cryogenian Period and also provides critical temporal constraints for the geological and numerical models that explore the possible mechanisms for the Snowball Earth events.

旋回地层学是年代地层学研究的有力工具，并在前寒武纪显示了其潜力。低温纪是地球历史上最具活力和最有趣的时期之一，它见证了地球上最极端的气候变化，被称为两次雪球地球事件。然而，特别是对于较年轻的 Marinoan Snowball Earth 事件，仍然缺乏强大的年代地层框架，阻碍了地理上分离记录之间的地层相关性和比较，以及对这种全球尺度冰川作用的开始和终止的理解。阿曼的 Cryogenian Fiq 地层被认为是 Marinoan 地层。Fiq 组中非冰川单元的持续时间可以为先前未明确确定的 Marinoan 冰川开始年龄提供保守的年龄限制。在这项工作中，对 Fiq 组的三个钻芯进行了旋回地层研究。对来自三个岩心的高分辨率伽马射线 (GR) 数据进行了多锥度法 (MTM) 光谱分析、相关系数 (COCO) 和演化相关系数 (eCOCO) 分析。已经确定了米兰科维奇旋回的层次结构（离心率、倾斜度和岁差），用于估计每个岩心中最佳沉积堆积速率和 Fiq 地层的持续时间。根据旋回地层结果，Fiq 组的时间尺度至少约为 6 Myr。综合辐射年龄和其他大陆的旋回地层数据，建议马里诺冰川的起始年龄为650-641 Ma。这一新结果有助于改善低温纪的年代地层框架，并为探索雪球地球事件可能机制的地质和数值模型提供关键的时间约束。