(Table 1) Age and description, showing diagenetic changes with depth at DSDP Site 80-550@en

Leg 80 of the Deep Sea Drilling Project drilled four coreholes through syn- and postrift sediments on the seaward edge of the Goban Spur in the Bay of Biscay. A relatively thin sedimentary veneer composed of nannofossil chalk and calcareous and siliceous mudstone was cored, providing the opportunity to document the effects of burial depth and other factors on the porosity of chalks by means of the scanning electron microscope. Four diagenetic \"fades\" were described from SEM analysis of the chalks; in order of increasing depth they are (1) mechanical compaction facies, (2) a transitional facies with both mechanical and chemical compaction features, (3) a chemical compaction facies, and (4) a cement-inhibited facies. It appears that advanced stages of cementation and lithification can occur in pure chalks at relatively shallow depths of burial (100-700 m) but can be inhibited by the presence of clays and coarser grained detritus.深海钻探计划（Deep Sea Drilling Project）第80航次在比斯开湾戈班海台的向海边缘，于同裂谷期与后裂谷期沉积物中钻取了4个钻孔岩芯。本次获取了一套由超微化石白垩、钙质泥岩与硅质泥岩组成的薄层沉积盖层，为借助扫描电子显微镜（scanning electron microscope, SEM）阐明埋藏深度及其他因素对白垩孔隙度的影响提供了研究契机。通过对白垩的SEM分析，本次研究识别出4种成岩相，按埋藏深度递增顺序依次为：(1) 机械压实相；(2) 兼具机械与化学压实特征的过渡相；(3) 化学压实相；(4) 胶结抑制相。研究表明，纯净白垩可在相对较浅的埋藏深度（100~700米）下进入胶结与岩石化的高级阶段，但黏土与粗粒碎屑的存在会抑制这一过程。