Abstract The Albian-Santonian sedimentary sequence in the Ndeaboh-Nenwe area of Enugu, Southern Benue Trough, were analysed for foraminifera and integrated with ostracod and palynofacies analyses to comprehensively appraise the age and depositional environment of the sediments. This is paramount since the studied formations have intermittent series of non-marine sedimentary influences throughout the basin. The results of foraminifera evaluation indicate that the Abakaliki Formation is barren of foraminifera species, whereas the Eze-Aku and Awgu formations have preponderance of planktonic foraminifera assemblages over benthic forms. The Eze-Aku Formation records an abundance of species of Hedbergella and a peak for Heterohelix. The co-occurrence of Whiteinella archeocretacea, Hedbergella planispira, Heterohelix delrieonsis and the ostracod species Ovocytherida symmetrica, suggests a Late Cenomanian to Early Turonian age. Rare species of short-ranging and keeled planktonic taxa are present in Awgu Formation, which has a preponderance of Heterohelix reussi, Heteroheix globulosa, Heterhelix pulchra, Whiteinella baltica, and the ostracods Brachycythere ekpo and Cythereis sp. The Awgu Formation is Middle Turonian to Santonian. The percentage of amorphous organic matter and lithologic characteristics suggest a marine environment for the Abakaliki Formation, although the water depth cannot be ascertained. In the Eze-Aku Formation, the prevalence of Hedbergella and its co-occurrence with Whiteinella and associated palynofacies data (amorphous organic matter, black debris, few structured terrestrial phytoclasts) and dinoflagellate cysts suggest a fairly deep (200–300 m) marine environment with occasional terrestrial input. The low diversity of agglutinated benthic foraminifera assemblage in the Awgu Formation indicates deposition at a minimum paleo-water depth. The paucity of benthic foraminifera, rare occurrence of keeled planktonic species, and the dominance of Hedbergella and Heterohelix; low oxygen tolerant species, in the studied interval are attributed to anaerobic bottom conditions possibly caused by poor bottom water circulation and high organic productivity in the oceans and seas during the Cenomanian-Santonian.

中文翻译：

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尼日利亚南贝努埃海槽 Albian 至 Santonian 沉积物沉积的有孔虫生物地层学、孢粉相和古环境

摘要 对南贝努埃海槽Enugu Ndeaboh-Nenwe地区Albian-Santonian沉积层序进行有孔虫分析，并结合介形虫和孢粉相分析，综合评价沉积物的年龄和沉积环境。这是最重要的，因为研究的地层在整个盆地中具有间歇性的一系列非海洋沉积影响。有孔虫评估结果表明，Abakaliki 组是贫瘠的有孔虫物种，而 Eze-Aku 和 Awgu 组浮游有孔虫组合优于底栖形式。Eze-Aku 组记录了丰富的 Hedbergella 物种和 Heterohelix 的峰值。Whiteinella archeocretacea、Hedbergella planispira、Heterohelix delrieonsis 和介形虫种 Ovocytherida symmetrica，表明晚 Cenomanian 到早 Turonian 时代。Awgu组存在稀有的短程和龙骨浮游类群，其中Heterohelix reussi、Heteroheix globulosa、Heterhelix pulchra、Whiteinella baltica和介形动物Brachycythere ekpo和Cythereis sp。Awgu 组是中土伦阶到桑托阶。尽管无法确定水深，但无定形有机质的百分比和岩性特征表明 Abakaliki 组存在海洋环境。在 Eze-Aku 组中，Hedbergella 的流行及其与 Whiteinella 的共生以及相关孢粉相数据（无定形有机质、黑色碎片、很少有结构的陆地植株）和甲藻囊肿表明一个相当深（200-300 m）的海洋环境，偶尔有陆地输入。Awgu 组中粘附的底栖有孔虫组合的低多样性表明沉积在最小的古水深度。底栖有孔虫的稀少，龙骨浮游物种的罕见出现，以及 Hedbergella 和 Heterohelix 的优势；研究区间内的低耐氧物种归因于底部厌氧条件，这可能是由于 Cenomanian-Santonian 期间海底水循环不良和海洋中的高有机生产力造成的。Awgu 组中粘附的底栖有孔虫组合的低多样性表明沉积在最小的古水深度。底栖有孔虫的稀少，龙骨浮游物种的罕见出现，以及 Hedbergella 和 Heterohelix 的优势；研究区间内的低耐氧物种归因于底部厌氧条件，这可能是由于 Cenomanian-Santonian 期间海底水循环不良和海洋中的高有机生产力造成的。Awgu 组中粘附的底栖有孔虫组合的低多样性表明沉积在最小的古水深度。底栖有孔虫的稀少，龙骨浮游物种的罕见出现，以及 Hedbergella 和 Heterohelix 的优势；研究区间内的低耐氧物种归因于底部厌氧条件，这可能是由于 Cenomanian-Santonian 期间海底水循环不良和海洋中的高有机生产力造成的。