Annotated record of the detailed examination of Mn deposits from DSDP Leg 48 (Holes 400A, 401, 402)

Unlike many cruises of the Deep Sea Drilling Project, Leg 48 was scientifically planned to drill a number of sites to systematically address the problems of passive margin evolution. Site 400 was drilled at the foot of the Meriadzek Escarpment of North Biscay in 4399 meters depth. The site was located in a half-graben forming part of a succession of tilted and rotated fault blocks near the continent/ocean boundary. Site 401 was situated on the planated edge of a tilted fault-block underlying the southern edge of the Meriadzek Terrace on the north Biscay margin. Site 402 was located on the upper slope of the northern continental margin of the Bay of Biscay. The main objectives were to establish the presence or absence of shallow water Upper Cretaceous beds, and to penetrate pre-Aptian synrift sediments and the upslope equivalent of the deep water Albian-Aptian carbonaceous mudstones penetrated at Hole 400A.

与多数深海钻探计划（Deep Sea Drilling Project）航次不同，第48航次（Leg 48）系经科学规划，通过钻探多个站位以系统探究被动大陆边缘演化相关问题。400号站位布设于比斯开湾北部梅里亚德克陡崖（Meriadzek Escarpment）脚下，水深4399米，该站位位于半地堑内，而该半地堑是大陆-大洋边界附近一系列倾斜旋转断块的组成部分。401号站位位于比斯开湾北部边缘梅里亚德克台地（Meriadzek Terrace）南侧下方的倾斜断块夷平边缘之上。402号站位则位于比斯开湾北部大陆边缘的上陆坡区域。本次钻探的主要目标为两项：一是探明浅水型上白垩统地层是否存在，二是钻穿阿普第期前同裂谷沉积物，以及400A钻孔（Hole 400A）所钻遇的深水阿尔布-阿普第期碳质泥岩的上斜坡对应地层。