Quantitative estimates of calcareous nannofossil changes across the Plenus Marls (latest Cenomanian), Dover, England: implications for the generation of the Cenomanian-Turonian Boundary Event
Quantitative estimates of calcareous nannofossil changes across the Plenus Marls (latest Cenomanian), Dover, England: implications for the generation of the Cenomanian-Turonian Boundary Event
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英国多佛 Plenus Marls（最新塞诺曼阶）钙质超微化石变化的定量估计：对塞诺曼阶-图伦阶边界事件产生的影响
DOI：
10.1006/cres.1994.1007
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发表时间：
1994
影响因子：
2.1
通讯作者：
C. Paul
中科院分区：
文献类型：
--
作者：
M. Lamolda;A. Gorostidi;C. Paul
从Abbots悬崖白垩岩顶部，通过Plenus泥灰岩，进入多佛的梅尔伯恩岩石，关于超微化石、不溶性残留物、δ 13 C和δ 18 O的绝对丰度和多样性的定量数据表明，与大多数先前的解释相反，
(1)赛诺曼-土伦边界事件是由海平面的急剧下降引起的，海平面的急剧下降产生了次Plenus侵蚀面，随后在10万年的时间里逐渐恢复到最后的赛诺曼阶段的更高水平，如通过Plenus泥灰岩的陆源碎屑积累速率下降所示。
(2)生产力，反映了超微化石丰度和多样性，百分比Watznaueria barnesae（溶解的措施）和总碳酸盐和完整的超微化石的积累率，下降通过Plenus泥灰岩和恢复微弱的梅尔伯恩岩石。这些趋势中没有一个，也没有先前报道的dinocyst丰度的下降（Jarvis等人，1988年b），与岩性相关，它们反映了主要的，而不是埋藏后的影响。
(3)在Plenus泥灰岩和基底梅尔伯恩岩中，δ 13 C和δ 18 O显示出与岩性同相的明显的、有节奏的波动，反映了米兰科维奇的控制，叠加在它们的主要偏移上。
我们认为，主要的δ 13 C偏移是由于有机碳的埋藏速率增加，从而隔离了营养物质并导致生产力下降，在多佛观察到的δ 18 C值与通过Plenus泥灰岩4-8层的海水温度下降一致。
Quantitative data on absolute abundance and diversity of nannofossils, insoluble residues, δ13C and δ18O from the top Abbots Cliff Chalk, through the Plenus Marls and into the Melbourn Rock at Dover, England suggest, contrary to most previous interpretations, that:
(1) The Cenomanian-Turonian Boundary Event was initiated by a sharp fall in sea level which produced the sub-plenus erosion surface, followed by a gradual recovery over 100 000 years to a higher level in the latest Cenomanian, as shown by declining rates of accumulation of terrigenous clastics through the Plenus Marls.
(2) Productivity, as reflected by nannofossil abundance and diversity, percentage of Watznaueria barnesae (a measure of dissolution) and by accumulation rates of total carbonate and intact nannofossils, declined through the Plenus Marls and recovered weakly in the Melbourn Rock. None of these trends, nor the previously reported decline in dinocyst abundance (Jarvis et al., 1988b), correlates with lithology and they reflect primary, not post-burial, effects.
(3) in the Plenus Marls and basal Melbourn Rock δ13C and δ18O show clear, rhythmic fluctuations in phase with lithology which reflect Milankovitch control, superimposed on their major excursions.
We suggest that the major δ13C excursion results from increased rates of burial of organic carbon which sequestered nutrients and caused the decline in productivity observed at Dover, δ18C values are consistent with a decline in sea water temperature through beds 4-8 of the Plenus Marls.