Fossil plant remains in DSDP Leg 80 holes

The lower part of the syn-rift Barremian-?Hauterivian section at Site 549 contains a large amount of acid-resistant land-derived organic matter that, as elsewhere in the Cretaceous sediments of the IPOD Leg 80 sites, is thermally immature. This plant debris was derived from a vegetation made up of many species of pteridophytes and gymnosperms. The palynofacies indicate that the sediments were deposited in shallow marginal and nonmarine environments and that the climate was probably warm temperate and fairly moist at the time. Source potential for gas is suggested at some horizons. Most of the younger Lower Cretaceous sediments at this and the other sites were deposited in more open marine conditions. Although they generally contain less organic matter, land plant remains continue to comprise a major part of the palynofacies. The Upper Cretaceous sediments were mainly deposited in well oxygenated conditions and are organically lean. However, stratigraphically restricted dark-colored shales at Sites 549 to 551 contain relatively large quantities of amorphous detritus of at least partly marine origin. These characteristics are suggestive of deposition during periods of restricted circulation and also of source potential for oil and gas if maturation levels had been higher.

549站位同裂谷期巴雷姆阶—疑似豪特里维阶剖面的下部层段，赋存大量抗酸陆源有机质。与初始大洋钻探计划（Initial Ocean Drilling Program, IPOD）第80航次其他站位的白垩纪沉积物一致，该套有机质的热成熟度未达成熟阶段。该植物碎屑源自以多种蕨类植物（pteridophytes）和裸子植物（gymnosperms）为主要类群的古植被。孢粉相（palynofacies）分析表明，这套沉积物沉积于浅海陆缘及非海洋环境，当时的气候大概率为暖温带且相对湿润。部分层位具备天然气生成潜力。
该站位及其他多数站位的下白垩统较年轻沉积物，均沉积于更为开阔的海洋环境中。尽管此类沉积物的有机质含量普遍较低，但陆源植物残体仍是孢粉相的主要组成部分。
上白垩统沉积物主要沉积于富氧环境，整体有机质含量偏低。不过在549至551站位，存在层位分布受限的暗色页岩，其中赋存相对大量的无定形碎屑，这些碎屑至少部分源自海洋。上述特征指示其沉积时期处于环流受限的环境，且若沉积物的热成熟度水平更高，这些层位将具备可观的油气生成潜力。