Correlation of Geologic and Seismic Structures in the Southern MARK Area: Surface Manifestations of Normal Faulting on the Mid-Atlantic Ridge

缓慢扩张的中大西洋脊（MAR）由对称和不对称的裂谷段或扩张单元组成，这些裂谷段或扩张单元由转换断层和“非转换偏移”或调节带端到端连接，与许多大陆裂谷的结构相似。在MAR构造的各个组成部分中，最重要的断裂发生在不对称（半地堑）扩张单元的主要边界断裂和连接它们与相邻单元的容纳带。这些特征的典型例子出现在MARK地区（大西洋中脊23”N）， 1992年Alvin可以对其进行调查。美国/法国（F.A.R.A.）联合计划将尝试进行20次潜水，以调查凯恩变换以南约100公里处MARK地区南部伸展构造的地表表现。将研究两个主要的地球物理上确定的结构。1)。主要目标将是沿陡峭的东部中谷壁约22′30′n的远震和微震活动带（Toomey et al., 1985; 1988）。这被解释为一个地震活跃断裂带，可能是一个幼年分离断层。2)。第二个目标将是同一传播单元北端的住宿区。这位于同一扩散单元北端区域的表面交叉处。在最近的多通道地震反射研究中发现，这可能是一个低角度斜滑断层（侧向斜坡），位于一个主要的北倾地壳内反射面的表面交叉处。阿尔文潜水将允许对变形基底岩石露头的各种特征（断层面、剪切带、片理、线理、堤防和流动等）进行详细的测绘和结构测量。目标是利用地震和地质数据之间的相关性，帮助弥合构造过程和近轴测深特征之间的差距。

The slow-spreading Mid-Atlantic Ridge (MAR) consists of both symmetrical and asymmetrical rift valley segments or spreading cells that are linked end-to-end by transform faults and "non- transform offsets" or accommodation zones and is similar to the structure of many continental rifts. Of the various components of MAR architecture the most important faulting occurs at the major border faults of asymmetrical (half-graben) spreading cells and at the accommodation zones that link them to adjacent cells. Typical examples of these feature are present in the MARK Area (23"N on the Mid-Atlantic Ridge) and can be investigated by Alvin in 1992. A joint U.S./French (F.A.R.A.) program of 20 dives to will be attempted investigate the surface manifestations of extensional tectonics in the southern part of the MARK Area about 100 km south of the Kane Transform. Two major geophysically defined structures will be investigated. 1.) The primary target will be the zone teleseismic and microseismic activity along the steep eastern median valley wall at about 22'30'N (Toomey et al., 1985; 1988). This is interpreted as a seismically active fault zone and perhaps a juvenile detachment fault. 2.) The secondary target will be the accommodation zone at the north end of the same spreading cell. This lies at the surface intersection of a zone at the north end of the same spreading cell. This lies at the surface intersection of a major north-dipping intra-crustal reflector identified in recent multichannel seismic reflection studies that may be a low-angle oblique-slip fault (lateral ramp). The Alvin dives will permit detailed mapping and structural measurement of various features (fault surfaces, shear zones, foliations, lineations, dikes and flows, etc.) in outcrops of deformed basement rocks. The goal is to use the correlation between seismic and geologic data to help bridge the gap between tectonic processes and the creation of near-axial bathymetric features.