Lithology, stratigraphy, organic carbon content, extract and liquid chromatography yields, and Rock-Eval pyrolysis at DSDP Holes 75-530A and 75-532

Seventeen sediment samples of Albian-Cenomanian to early Pliocene age from DSDP Hole 530A in the Angola Basin and six sediment samples of early Pliocene to late Pleistocene age from the Walvis Ridge were investigated by organic geochemical methods, including organic carbon determination, Rock-Eval pyrolysis, gas chromatography and combined gas chromatography/mass spectrometry of extractable hydrocarbons, and kerogen microscopy. The organic matter in all samples is strongly influenced by a terrigenous component from the nearby continent. The amount of marine organic matter present usually increases with the total organic carbon content, which reaches an extreme value of more than 10% in a Cenomanian black shale from Hole 530A. At Site 530 the extent of preservation of organic matter in the deep sea sediments is related to mass transport down the continental slope, whereas the high organic carbon contents in the sediments from Site 532 reflect both high bioproductivity in the Benguela upwelling regime and considerable supply of terrigenous organic matter. The maturation level of the organic matter is low in all samples.

本研究采用有机地球化学分析手段，对安哥拉盆地深海钻探计划（Deep Sea Drilling Project, DSDP）530A孔中17件阿尔布阶-森诺曼阶至上新世早期的沉积物样品，以及沃尔维斯海岭采集的6件上新世早期至更新世晚期的沉积物样品开展了系统测试。测试方法涵盖有机碳含量测定、Rock-Eval热解（Rock-Eval pyrolysis）、气相色谱法，以及可抽提烃类的气相色谱-质谱联用法与干酪根显微分析。所有样品中的有机质均显著受邻近大陆陆源组分的影响，海相有机质占比通常随总有机碳（total organic carbon, TOC）含量升高而增加；其中530A孔的一件森诺曼阶黑色页岩中，总有机碳含量极值超过10%。在530站位，深海沉积物内有机质的保存程度与大陆坡物质搬运过程密切相关；而532站位沉积物的高总有机碳含量，则同时反映了本格拉上升流区极高的生物生产力，以及陆源有机质的大量补给。所有样品的有机质成熟度均处于较低水平。