Deep Earth Origin of the Great Unconformity – Datasets and Scripts

The Great Unconformity marks a globally extensive erosive surface (with gaps of more than ~200 million years in the geological record) that preceded the Cambrian Explosion of life. The processes proposed for the formation of the Great Unconformity include glacial erosion during the Snowball Earth, rifting and plume activity, sea-level fall, and mantle-driven dynamic topography. However, the dynamics of these processes have not been tested. Using a series of paleogeographically constrained mantle-flow models from one billion years ago, we show that continental-scale uplift and subsidence associated with long-wavelength dynamic topography driven by mantle convection drove the formation and preservation of the Great Unconformity. Our models predict prolonged continental-scale Precambrian uplift and long-term Phanerozoic subsidence for Laurentia, Baltica and North China. This vertical-motion scenario is ideal for the formation and preservation of the Great Unconformity, a first-order surface expression of deep-Earth processes. The large area of Laurentia and limited deformation at its margins explain why the Great Unconformity is best preserved and documented there. Our models predict cycles of dynamic topography that are broadly reflected in the preserved sediment volume across continents. The 'Deep Earth Origin of the Great Unconformity – Datasets and Scripts' contains data, Jupyter notebooks, and Python scripts that were created to post-process outputs (mantle temperature, velocity vectors, and dynamic topography) from mantle flow models and to investigate the role of dynamic topography in the formation and preservation of the Great Unconformity.大不整合面（Great Unconformity）是全球广泛分布的侵蚀面，对应地质岩石记录中约2亿至12亿年的沉积缺失，形成于生命寒武纪大爆发之前。目前针对大不整合面的成因提出的机制包括雪球地球（Snowball Earth）时期的冰川侵蚀、裂谷作用与地幔柱活动、海平面下降，以及地幔驱动的动态地形。但上述过程的动力学机制尚未得到验证。基于一系列从10亿年前开始、受古地理约束的地幔流动模型，本研究证明：由地幔对流引发的长波长动态地形所伴随的大陆尺度隆升与沉降，驱动了大不整合面的形成与保存。我们的模型预测，劳伦大陆（Laurentia）、波罗的大陆（Baltica）与华北地块将经历大陆尺度的前寒武纪长期隆升，以及显生宙长期沉降。这种垂直运动模式是大不整合面形成与保存的理想条件，而大不整合面正是深部地球过程的一级地表响应。劳伦大陆广袤的面积与其边缘有限的变形程度，解释了为何大不整合面在该区域保存最为完好且研究记录最为详尽。我们的模型预测的动态地形周期，可在全球各大陆的沉积物保存体积中得到广泛反映。 “大不整合面的深部地球成因-数据集”（Deep Earth Origin of the Great Unconformity-Datasets）包含用于后处理地幔流动模型输出结果（地幔温度、速度矢量与动态地形）的Jupyter笔记本与Python脚本，旨在探究动态地形在大不整合面形成与保存过程中所发挥的作用。