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首页> 外文期刊>Journal of nannoplankton research: A publication of the International Nannoplankton Association >Calcareous nannofossil and foraminiferal evidence for a PETM pre-onset excursion, Atlantic Coastal Plain, USA
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Calcareous nannofossil and foraminiferal evidence for a PETM pre-onset excursion, Atlantic Coastal Plain, USA

机译：帕特马帕菲斯特钙质Nannofossil和对美国大西洋沿海平原的Petm的对amniferal证据

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The Paleocene-Eocene thermal maximum (PETM) in coastal plain sediments of Maryland is marked by a carbon isotope excursion (CIE) of approximately-5 per mil in normal marine sediments, and as much as a-23 per mil shift in marine sediments with a large terrestrial input (Self-Trail et al., 2014). Carbon and oxygen isotope analyses of the South Dover Bridge (SDB) and Mattawoman Creek Billingsley Road (MCBR) cores in Maryland revealed the presence of a PETM pre-onset excursion (POE) in both cores in the Aquia Formation (Robinson et al., 2014). The POE in the SDB core began ~2m below the CIE, is 0.9 m thick, and was characterized by a-2 per mil shift in carbon isotopes. The POE in MCBR began ~1.13m below the CIE, is 0.88m thick, and was characterized by a ~4 per mil shift. Preliminary analyses of calcareous nannofossils from SDB document assemblage changes across the POE. Overall species richness declined during the POE, and the percent abundances of Discoaster spp., Semihololithus biscayae, and Hornibrookina spp. decreased significantly. At the same time, there was a corresponding increase in the percent abundance of Calsiosolenia aperta and Prinsius bisulcus. Several species (i.e., Chiasmolithus bidens and Fasciculithus involutus) began a slow decline in abundance during the POE, which continued to the base of the CIE, and two species,C. aperta and Prinsius bisulcus, began a decline immediately following the POE that ultimately resulted in their extinction at the P/E boundary. Foraminiferal response to the POE included a decrease in both abundance and species richness of planktic foraminifers and an increase in specimens showing visible signs of dissolution, which is similar to the dissolution zone response at the CIE onset but less severe. Foraminifers in both the CIE onset and POE were fully recrystallized due to diagenetic alteration. However, the POE also was characterized by partially dissolved foraminifers that lacked any evidence of surface texture and commonly had collapsed chambers. In addition to changes in foramimferal and nannofossil assemblages, the sediments of the Aquia Formation became more clayey across the POE, decreasing from a baseline weight percent of ~60% sand prior to the event, to 40% during the event, before rebounding to 80% after the event.
机译：马里兰州沿海平原沉积物中的古代 - 何种热量最大（PETM）由普通海洋沉积物中约5米的碳同位素偏移（CIE）标志，并且在海洋沉积物中均为A-23一个大型地面输入（自我跟踪等人。，2014）。马里兰南多佛桥（SDB）和Mattawoman Creek Billingsley Road（MCBR）核心的碳和氧同位素分析在Aquia Chemation中的两座核心（Robinson等人）揭示了PETM预发病巡回（PoE）的存在2014）。 SDB核心的PoE开始于CIE以下〜2M，厚度为0.9米，其特征在于碳同位素的A-2均匀。 MCBR的PoE开始在CIE下方〜1.13米，厚度为0.88米，其特点是〜4米尔偏移。对普遍的SDB文献组合的钙质Nannofossils的初步分析。在PoE期间，整体物种丰富度下降，以及迪斯科斯SPP的丰富百分比。，Semiholithus Biscayae和Hornibrookina SPP。显着下降。与此同时，Calsiosolenia Aperta和Prinsius Busulcus百分比相应增加。几种物种（即Chiasmolithus Bidens和Fasciculithus prescutus）在PoE期间开始缓慢下降，这持续到CIE的基础和两种物种C. Aperta和Prinsius Busulcus，在PoE之后立即衰落，最终导致其在P / E边界处灭绝。对POE的对氨酰胺响应包括综合性传染料的丰富和物种丰富性的减少，并增加了显示可见溶解迹象的标本的增加，这类似于CIE发作的溶出区反应，但不太严重。由于成岩性改变，CIE发作和POE两者的火氨素被完全重结晶。然而，PoE还具有部分溶解的前胺，其缺乏表面纹理的任何证据，并且通常具有折叠的腔室。除了捕捞围场和Nannofossil组合的变化之外，Aquia形成的沉积物在群体之前的基线重量百分比减少到事件前的基线重量百分比，在活动期间为40％，在篮板上反弹至80 ％ 在事件发生后。

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