古新世-始新世极热时期的微化石印痕
瑞典自然历史博物馆古生物学部Sam M. Slater的团队发现了古新世—始新世极热时期的微化石印痕。相关论文于2024年2月2日发表在《地质学》杂志上。
研究人员通过寻找保存在有机物上的微型浮游生物的印痕化石来测试掩埋后溶解的证据。该团队研究了美国东部马里兰州南Dover桥(SDB)岩芯的PETM序列，并将其印痕记录与先前发表的传统采样CaCO3保存的微型浮游生物体化石数据进行了比较。在缺乏CaCO3的地层中，留下的大量印痕表明，埋藏后的溶蚀作用将大部分CaCO3从岩石记录中去除。
多数样品均有印痕记录，但印痕数量少，多样性低。生物体化石的数量和种类要多得多，更完整地记录了贯穿PETM现存的微型浮游生物群落。SDB层序记录了PRTM开始时的溶蚀带/低碳酸盐层段，通过该层段的微型浮游生物体化石较少。在这段时间内没有发现微型浮游生物的印痕，表明生物体化石的稀有性不太可能是埋藏后溶解的结果。相反，他们的研究结果表明，在SDB，PETM的CaCO3含量下降是以下原因造成的：(1)生物对该事件期间发生的变化的响应，和/或(2)CaCO3在岩化之前溶解(即在水柱或海底)。
据了解，古新世-始新世极热时期(PETM;ca. 56Ma)的地质间隔记录了海底沉积物中碳酸钙(CaCO3)的显著下降，这可能反映了深海(也可能是浅水)海洋酸化的事件。然而，由于CaCO3易受埋藏后溶蚀作用的影响，这一过程对PETM地质记录的影响程度仍不确定。
附：英文原文
Title: Nannofossil imprints across the Paleocene-Eocene thermal maximum
Author: Sam M. Slater, Paul R. Bown, Phillip E. Jardine
Issue&Volume: 2024-02-02
Abstract: The Paleocene–Eocene thermal maximum (PETM; ca. 56 Ma) geological interval records a marked decline in calcium carbonate (CaCO3) in seafloor sediments, potentially reflecting an episode of deep- and possibly shallow-water ocean acidification. However, because CaCO3 is susceptible to postburial dissolution, the extent to which this process has influenced the PETM geological record remains uncertain. Here, we tested for evidence of postburial dissolution by searching for imprint fossils of nannoplankton preserved on organic matter. We studied a PETM succession from the South Dover Bridge (SDB) core, Maryland, eastern United States, and compared our imprint record with previously published data from traditionally sampled CaCO3-preserved nannoplankton body fossils. Abundant imprints through intervals devoid of CaCO3 would signify that postburial dissolution removed much of the CaCO3 from the rock record. Imprints were recorded from most samples but were rare and of low diversity. Body fossils were substantially more numerous and diverse, capturing a more complete record of the living nannoplankton communities through the PETM. The SDB succession records a dissolution zone/low-carbonate interval at the onset of the PETM, through which nannoplankton body fossils are rare. No nannoplankton imprints were found from this interval, suggesting that the rarity of body fossils is unlikely to have been the result of postburial dissolution. Instead, our findings suggest that declines in CaCO3 through the PETM at the SDB location were the result of: (1) biotic responses to changes that were happening during this event, and/or (2) CaCO3 dissolution that occurred before lithification (i.e., in the water column or at the seafloor).
DOI: 10.1130/G51746.1
来源：科学网 小柯机器人
