Carbon contents of lower Cretaceous sediments from ODP Hole 198-1213B (Table 1)

ODP Leg 198 drilling on Shatsky Rise recovered a lower Aptian porcellanite (~120.5 Ma) deposited during oceanic anoxic event (OAE) 1a that contains C36-C39 alkadienones: C37:2 and C39:2 alkadien-2-ones and C36:2 and C38:2 alkadien-3-ones. This alkenone distribution differs from that typical of contemporary sediments and haptophyte algae, but resembles that of Cretaceous sediments from the Blake-Bahama basin. The discovery of alkenones in the early Aptian extends their sedimentary record by 15 M.y. to 120.5 M.y. and demonstrates the potential for long-term survival of these diagnostic functional lipids under favorable depositional conditions and subsequent shallow burial. It also contributes to the understanding and reconstruction of evolutionary developments in alkenone distributions and biosynthesis over geologic time.

大洋钻探计划（Ocean Drilling Program, ODP）第198航次在沙茨基海隆（Shatsky Rise）实施的钻探作业，采获了形成于海洋缺氧事件（Oceanic Anoxic Event, OAE）1a期间的阿普第阶早期瓷岩，其沉积年代约为120.5 Ma，该岩样中含有碳链长度为C36至C39的二烯酮类化合物：包括C37:2与C39:2型2-二烯酮，以及C36:2与C38:2型3-二烯酮。此类烯酮类化合物的分布特征既区别于同期沉积物及定鞭金藻（haptophyte algae）的典型分布模式，却又与布莱克-巴哈马盆地（Blake-Bahama basin）白垩纪沉积物的烯酮分布特征高度相似。本次在阿普第阶早期沉积物中发现烯酮类化合物，将其沉积记录的时间跨度向前延伸了15百万年（15 M.y.）至120.5 Ma，同时证实了这类标志性功能脂质在适宜沉积环境及后续浅埋藏条件下可长期留存的可能性。该发现还有助于深化对地质时间尺度下烯酮类化合物分布与生物合成演化历程的理解与重建。