Anatomy of a Passive Continental Margin: Deep Structure of Transitional Crust and the Source of the East Coast MagneticAnomaly

许多MCS、磁力和重力调查都集中在确定美国东海岸大陆边缘的基本结构特征上。不幸的是，对裂谷、构造沉陷、变薄和早期火山活动性质的严格限制，都受到了对几个边缘平行盆地下最深的“裂谷阶段”地壳成像的困难。最近的一项MCS计划描绘了卡罗莱纳州的海槽，沿着两条边缘垂直的线部署了8个OBH。霍尔布鲁克博士和珀迪博士已经开始处理这些数据。此次获奖将允许他们继续进行全波场成像和2D射线跟踪建模，以改善垂直入射MCS剖面的速度结构和成像。此外，还提供了支持，以准备沿切萨皮克湾近海类似的边缘横断面进行额外的一系列OBH部署。这项活动暂定在1990年春或夏举行。这两个实验的具体目标都是确定莫霍面几何形状、基底深度和介于裂谷阶段的地壳的各种特征。后者的例子包括裂谷阶段地壳的厚度、宽度和速度沿走向的变化，以及与“正常”大陆和洋壳的横向边界的内部结构、反射特征和性质。

Numerous MCS, magnetic and gravity surveys have concentrated on determining fundamental structural features of the US East Coast continental margin. Unfortunately, firm constraints on the nature of rifting, tectonic subsidence, thinning and early volcanism have all been hampered by the difficulty of imaging the deepest "rift-stage" crust that underlies several margin- parallel basins. A recent MCS program profiled the Carolina Trough, and 8 OBHs were deployed along two margin-perpendicular lines. Drs. Holbrook and Purdy have begun processing these data. The present award will allow them to continue full wavefield imaging and 2D ray trace modeling that will improve velocity structure and imaging of the vertical-incidence MCS profiles. In addition, support is provided to prepare for an additional series of OBH deployments along a similar margin transect offshore Chesapeake Bay. This is tentatively scheduled for the Spring or Summer of 1990. Specific goals of both experiments are to determine Moho geometry, basement depths, and various features of the intervening rift-stage crust. Examples of the latter include along-strike variations in thickness, width, and velocity of rift-stage crust, as well as internal structure, reflection character, and nature of the lateral boundaries with "normal" continental and oceanic crust.