Dinoflagellate cyst biostratigraphy and palaeoecology of the early Paleogene Landana reference section, Cabinda Province, Angola

Forty-four rock samples from the Landana section, belonging to the historical Dartevelle collection of the Royal Museum for Central Africa (RMCA) at Tervuren, Belgium, were palynologically processed and analysed. Systematic analysis of the samples from the Landana sea cliff locality has revealed 90 dinoflagellate cyst taxa spanning an interval that ranges at least from the middle Paleocene to the late Eocene/early Oligocene. This locality represents the first extensive sub-equatorial African Paleogene dinoflagellate cyst record. Dinoflagellate cyst occurrences were calibrated and evaluated against newly revised foraminiferal ranges. This novel dinoflagellate cyst biostratigraphic record was compared and correlated with contemporaneous records relatively close by in the Gulf of Guinea, as well as with records from more distant locations such as Antarctica, Australia and New Zealand. A preliminary dinoflagellate cyst zonation is here proposed comprising three zones and five unzoned yet otherwise distinct intervals. The lower part of the Landana section records a large portion of the early to middle/late Selandian, which is made apparent by the presence of taxa such as <i>Isabelidinium cingulatum</i>, <i>Isabelidinium</i>? <i>viborgense</i>, and <i>Spinidinium densispinatum</i>. The Thanetian through Lutetian part of the section is more fragmentary and is devoid of any significant marker taxa normally typical for this time interval elsewhere. The upper part of the record is largely devoid of dinoflagellate cysts, with the few dinoflagellate cyst-bearing samples pointing to an Eocene to early Oligocene age. Dinoflagellate cyst assemblages are relatively variable and often largely dominated by a single particular taxon or complex. We record remarkably abundant peridinioid cysts signalling high palaeoproductivity for protracted periods of time, resulting from either heightened terrestrial influence or enhanced upwelling.

采自比利时特尔武伦市中非皇家博物馆（Royal Museum for Central Africa, RMCA）达特维尔历史馆藏的44块兰达纳剖面岩样，已完成孢粉学处理与分析。对兰达纳海崖剖面样品的系统研究共鉴定出90个沟鞭藻囊孢（dinoflagellate cyst）类群，其产出层位的时代跨度至少从中古新世延伸至始新世晚期/渐新世早期。该剖面为非洲近赤道区域首个大规模古近纪（Paleogene）沟鞭藻囊孢化石记录。本次研究以最新修订的有孔虫（foraminifera）延限范围为参照，对沟鞭藻囊孢的产出层位进行了定年与评估。将这套全新的沟鞭藻囊孢生物地层记录，与几内亚湾附近同期的化石记录以及南极洲、澳大利亚、新西兰等远距地区的相关记录开展了对比与地层关联。本文提出一套初步的沟鞭藻囊孢生物地层分带方案，包含3个化石带以及5个尚未分带但特征显著的间隔区间。兰达纳剖面的下部层位记录了塞兰阶（Selandian）早-中/晚期的大部分时段，这一结论可通过*环纹伊莎贝尔啶藻（Isabelidinium cingulatum）*、*疑似 viborgense 伊莎贝尔啶藻（Isabelidinium? viborgense）*以及*密刺刺甲藻（Spinidinium densispinatum）*等类群的出现得到佐证。剖面中达宁阶（Thanetian）至吕特阶（Lutetian）的部分保存较为破碎，缺乏其他地区该时段常见的标志性类群。该记录的上部层位几乎不含沟鞭藻囊孢，仅有的含囊孢样品的时代指向始新世至渐新世早期。沟鞭藻囊孢组合相对多变，且常以单个类群或类群复合体占据绝对优势。本次研究发现极为丰富的类多甲藻囊孢（peridinioid），指示研究区长期处于高古生产力水平，这一现象可能由增强的陆源输入或上升流活动所驱动。