Collaborative Research: Rifting, Magmatism, and Lithospheric Sutures; Crustal Imaging of the South Georgia Basin and Suwanee Suture

格鲁吉亚沿海平原下的岩石是形成北美东部的最基本的构造事件的中心：大约2.9亿年前大陆碰撞形成盘古大陆;大约2.3亿年前大陆分裂导致大西洋形成;以及大约2亿年前地球历史上最大的岩浆事件之一，大西洋中部岩浆区。 这些事件的记录和它们之间可能的关系被保存在格鲁吉亚南部地壳的结构中，包括两种不同类型大陆之间的缝合线，北美东海岸沿着最大的断裂盆地和大西洋中部岩浆区的火成岩。 这些研究人员和一个由研究生和本科生组成的大型团队正在收集地震数据，这些数据可用于对地壳结构进行成像，以了解这些构造事件。 沿着横跨缝合带和盆地的两个约300公里长的剖面部署了数百个地震检波器，它们记录了间隔约20公里的一系列爆炸装药产生的声波。地震检波器也被部署在一个集中在盆地的盒子里，以记录按网格排列的爆炸物。 声波在岩石中传播的速度随成分、孔隙度和其他岩石特性而变化。调查人员正在利用旅行时间层析成像技术建立速度模型，以揭示火成岩的分布、地壳厚度的变化和地壳成分的变化。除了更好地了解基本构造过程外，该计划的其他好处包括培训和教育学生，以及可能成为碳封存良好目标的盆地和火成岩的表征。

The rocks beneath the coastal plain of Georgia were at the center of the most fundamental tectonic events to shape eastern North America: continental collision around 290 million years ago to form the super continent of Pangea; continental breakup leading to the formation of the Atlantic Ocean beginning around 230 million years ago; and one of the biggest magmatic events in Earth's history around 200 million years ago, the Central Atlantic Magmatic Province. A record of these events and possible relationships between them is preserved by structures in the crust of southern Georgia, including a suture between two different types of continent, the largest failed rift basin along the east coast of North America and igneous rocks from the Central Atlantic Magmatic Province. These investigators and a large team of graduate and undergraduate students are collecting seismic data that can be used to image structures in the crust to understand these tectonic events. Hundreds of geophones are being deployed along two ~300-km-long profiles across the suture and the basin, which record sound waves generated by a series of explosive charges spaced ~20 km apart. Geophones are also being deployed in a box focused on the basin to record explosive charges arranged in a grid. The speed that sound waves travel through rocks varies with composition, porosity, and other rock characteristics. The investigators are using travel-time tomography to create velocity models that reveal the distribution of igneous rocks, variations in the thickness of the crust and variations in crustal composition. Besides a better understanding of fundamental tectonic processes, other benefits of this program include training and education of students, and characterization of basins and igneous rocks that might be good targets for carbon sequestration.