Corinth Virtual Site Survey: Integrating Geophysical Data for Syn-rift Stratigraphy, Fault and Basin Evolution and Advancing IODP Proposed Drilling

大陆的分裂形成了延伸的大陆边缘，最终形成了海洋盆地，这是一个可能持续数千万年的过程。这一裂谷过程的开始被认为对其结束时形成的大陆边缘的结构和沉积分层做出了重大贡献。在最初的几百万年中，裂谷如何开始和发展的细节常常被大陆边缘下复杂的变形和厚厚的沉积层所掩盖。为了理解早期阶段，我们必须研究裂谷最近才开始形成的地区，希腊科林斯湾是其最初数百万年历史中的一个关键例子。在整个墨西哥湾，裂缝的两侧每年以高达20毫米的速度移动，这种高伸展速度导致了无数次地震，这在历史上是非常具破坏性的。快速伸展还导致了一个快速发展的裂谷盆地，该盆地部分淹没在海中，并充斥着沉积物。在墨西哥湾内，收集了大量海洋地球物理数据，包括详细的海底地图，以及利用声源提供海底物质横截面的地震数据。地震数据使我们能够直接对累积的沉积层进行成像，并识别偏离这些层并形成盆地的断层。该项目将综合这些数据，对沉积层(及其可能的年龄)和断裂面进行非常详细的解释。通过与气候和海平面变化模型进行比较，成像并指定地层的年龄，使我们能够确定盆地是如何随着时间的推移而发展的。数据拍摄的断裂面产生了裂谷的伸展和下沉，它们的活动历史控制着盆地的发展。这些结果将被用来生成第一个高分辨率的裂谷发展模型，在裂谷历史的最初数百万年里，并将有助于解决大陆如何分裂的一些悬而未决的问题。该模型将被一系列科学家使用，包括那些试图了解构造、地形地貌和气候如何相互作用，导致沉积物从一个地方移动到另一个地方的科学家：裂谷盆地是沉积物的主要汇之一，我们将计算输送到科林斯盆地的沉积物的体积如何随着时间、断层的移动和气候的变化而变化。世界上大多数石油资源都是在古老的裂谷中发现的，但裂谷是如何发展的，以及现在发现石油的岩石单元的详细几何形状，往往被其他地质过程和较浅的沉积层所掩盖。了解早期的裂谷过程对于确定随时间在盆地不同部分沉积的地点和类型是很重要的。我们还将分析单个断层如何生长以及如何与裂谷中的其他断层相互作用的细节：这个过程会影响沉积物进入裂谷盆地的位置，因此对识别石油储集层也很重要。裂谷断层是希腊中部破坏性地震的罪魁祸首，因此这个项目对断层位置和滑动速度的分析也将帮助我们更好地了解潜在的危险，增加减少相关风险的可能性。最终，该项目将通过综合海洋钻探计划，选择用于钻探和采样裂谷地带沉积物的地点。这些样本将提供：沉积层的实际年龄，因此每个活动断裂的滑动速率都得到了很好的解析，并对这里产生的裂谷模型进行了检验；以及沉积物的类型，它将告诉我们更多关于过去数百万年的区域气候，以及通常形成油气藏的沉积物在北海等较古老的裂谷系统中所处的类似位置。

The breaking apart of a continent to form extended continental margins and ultimately ocean basins is a process that can last for 10s of millions of years. The start of this process of rifting is thought to contribute significantly to the structure and sedimentary layering of the continental margins that have formed by its end. Often the details of how rifting initiates and develops in the first few million years are lost in the complexities of deformation and thick sediment layers beneath the continent's edges. To understand the early phases, we have to study areas where rifting has only recently started, and the Gulf of Corinth, Greece, is a key example in its first few millions of years of history. Across the Gulf, the two sides of the rift are moving apart at up to 20 mm every year and this high rate of extension results in numerous earthquakes which historically have been very destructive. The rapid extension also results in a rapidly developing rift basin which is partially submerged beneath the sea and filling with sediments. Within the Gulf, a large volume of marine geophysical data has been collected, including detailed maps of the seabed, as well as seismic data that use sound sources to give cross-sections of material beneath the seabed. The seismic data allow us to directly image the accumulated sediment layers and to identify faults that offset the layers and create the basin. This project will integrate these data to make a very detailed interpretation of the sediment layers (and their likely age) and fault planes. Imaging and assigning ages to the layers, by comparing with models of climate and sea level change, allows us to determine how the basin has developed through time. The fault planes imaged by the data generate the extension and subsidence of the rift, and their history of activity controls how the basin develops. The results will be used to generate the first high resolution model of rift development over the initial few million years of a rift's history and will help to address some of the unanswered questions of how continents break apart. The model will be used by a range of scientists, including those trying to understand how tectonics, landscape morphology and climate all interact to cause sediments to move from one place to another: rift basins are one of the main sinks for sediments and we will calculate how the volume of sediment delivered to the Corinth basin has changed with time, as faults move and as climate changes. The majority of the world's petroleum resources are found in old rifts, but often details of how the rift developed and the detailed geometry of the rock units in which the oil is now found are masked by other geological processes and by shallower sediment layers. Understanding the early rift processes is important for determining where and what kind of sediments will be deposited in different parts of the basin with time. We will also analyse details of how individual faults grow and interact with other faults in the rift: this process affects where sediments enter a rift basin and is therefore also important for identifying petroleum reservoirs.The rift faults are responsible for the destructive earthquakes in central Greece, so this project's analysis of fault location and rate of slip will also help us to better understand the potential hazard, increasing the potential for reduction of associated risk.Ultimately, the project will be used to select sites for drilling and sampling the sediments of the rift zone, through the Integrated Ocean Drilling Program. These samples would provide: the actual age of sediment layers, and hence well resolved slip rates for each active fault and a test for the rift models generated here; and the types of sediments, that will tell us more about the regional climate of the last few millions of years and where sediments that typically form hydrocarbon reservoirs are located in this analogue for older rift systems like the North Sea.