Organic carbon and nitrogen, sediment composition, and clay mineralogy of Deep Sea Drilling Project Site 603, western Atlantic Ocean

Sediment and interstitial water samples recovered during DSDP Leg 93 at Site 603 (lower continental rise off Cape Hatteras) were analyzed for a series of geochemical facies indicators to elucidate the nature and origin of the sedimentary material. Special emphasis was given to middle Cretaceous organic-matter-rich turbidite sequences of Aptian to Turanian age.
Organic carbon content ranges from nil in pelagic claystone samples to 4.2% (total rock) in middle Cretaceous carbonaceous mudstones of turbiditic origin. The organic matter is of marine algal origin with significant contributions of terrigenous matter via turbidites. Maturation indices (vitrinite reflectance) reveal that the terrestrial humic material is reworked. Maturity of autochthonous material (i.e., primary vitrinite) falls in the range of 0.3 to 0.6% Carbohydrate, hydrocarbon, and microscopic investigations reveal moderate to high microbial degradation. Unlike deep-basin black shales of the South and North Atlantic, organic-carbon-rich members of the Hatteras Formation lack trace metal enrichment. Dissolved organic carbon (DOC) in interstitial water samples ranges from 34.4 ppm in a sandstone sample to 126.2 ppm in an organic-matter-rich carbonaceous claystone sample. One to two percent of DOC is carbohydratecarbon.

对深海钻探计划（Deep Sea Drilling Project, DSDP）第93航次于哈特拉斯角外下大陆隆603站位获取的沉积物与间隙水样品，开展了一系列地球化学相指标分析，以阐明沉积物质的性质与成因。研究重点聚焦于阿普第期至土仑期的白垩纪中期富有机质浊积岩序列。
有机碳含量范围为远洋黏土岩样品中的未检出值，至白垩纪中期浊积成因碳质泥岩中的4.2%（全岩）。该有机质为海洋藻类起源，同时通过浊积作用接收了大量陆源物质贡献。镜质体反射率等成熟度指标显示，陆地腐殖质物质经历了再沉积作用。原地有机质（即原生镜质体）的成熟度处于0.3%至0.6%区间。
碳水化合物、烃类检测与显微观察结果表明，有机质存在中等至高强度的微生物降解作用。与南、北大西洋的深盆黑色页岩不同，哈特拉斯组的富有机质岩层并不具备微量元素富集特征。
间隙水样品中的溶解有机碳（DOC）含量范围为砂岩样品中的34.4 ppm，至富有机质碳质黏土岩样品中的126.2 ppm。其中1%至2%的溶解有机碳为碳水化合物碳。