Annotated record of the detailed examination of Mn deposits from DSDP Leg 64 (Holes 474, 474A, 475, 479, 480, 481A)1982

The origin and evolution of passive continental margins are of great scientific interest and economic importance. During DSDP Leg 64 the Glomar Challenger drilled at eight sites (474-481) in the Gulf of California region. The Gulf of California presented a singular example of tectonics and sedimentation in a very young ocean, being formed by translation and oblique rifting. The sedimentation of the region is hemipelagic, rapid, and largely dominated by siliceous microfossils.Sites 474, 475, and 476 form a transect from oceanic crust to continental crust at the southern tip of Baja California in order to define passive-margin subsidence during the early post-rifting phase. Sites 477, 478, and 481 investigate of the nature of young ocean crust in the Guaymas Basin, where high accumulation rates are common and variable high heat flow indicates active rifting and hydrothermal activity. Sites 479 and 480, are situated on the Guaymas Basin Slope above the proto-Gulf sequences. Interest focused on the paleoceanography of laminated, homogeneous diatom-rich, anoxic sediments within the zone of low oxygen.

被动大陆边缘（passive continental margins）的起源与演化兼具重大科学研究价值与经济意义。在深海钻探计划（Deep Sea Drilling Project, DSDP）第64航次中，“格洛玛·挑战者号”（Glomar Challenger）钻探船于加利福尼亚湾海域的8个站位（474至481）开展了钻探作业。加利福尼亚湾是极年轻海洋中构造活动与沉积作用的典型范例，其形成机制为平移作用与斜向裂谷作用。该区域的沉积作用以半远洋沉积为主，沉积速率较快，且沉积物主要由硅质微化石构成。站位474、475与476在下加利福尼亚半岛南端形成了一条从洋壳到陆壳的剖面，用于厘定裂谷作用早期后阶段的被动大陆边缘沉降过程。站位477、478与481旨在研究瓜伊马斯盆地（Guaymas Basin）内年轻洋壳的性质；该盆地普遍存在较高的沉积堆积速率，且多变的高热流特征指示了活跃的裂谷作用与热液活动。站位479与480位于原海湾沉积序列之上的瓜伊马斯盆地斜坡区域。本次研究的重点聚焦于低氧带内纹层状、均质且富硅藻的缺氧沉积物的古海洋学特征。