The upper Paleocene-lower Eocene stratigraphic record and the Paleocene-Eocene boundary carbon isotope excursion: implications for geochronology
The upper Paleocene-lower Eocene stratigraphic record and the Paleocene-Eocene boundary carbon isotope excursion: implications for geochronology
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上古新世-下始新世地层记录和古新世-始新世边界碳同位素偏移：对地质年代学的影响
DOI：
10.1144/gsl.sp.1996.101.01.18
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
A. Sinha
中科院分区：
文献类型：
--
作者：
M. Aubry;W. Berggren;L. Stott;A. Sinha
在ODP 690站首次发现的晚古新世碳同位素漂移，是目前研究深海地层与大陆地层在空间和时间上进行精确对比的最佳手段。然而，它的位置相对于生物地层基准在几个露头和深海部分显然是不一致的。通过对北大西洋（DSDP Site 549和550）和南大西洋（ODP Site 690）的磁性地层、生物地层（钙质超微化石和浮游有孔虫）和碳同位素数据的综合分析，我们发现，为了了解古新世晚期至始新世早期生物和同位素事件的时间关系和序列，有必要建立一个复合参考剖面。我们由此推断，除了有据可查的“经典”碳同位素漂移发生在中生物区NP 9，一个年轻的同位素漂移，但没有记录，发生在较低的生物区NP 10。在构建DSDP 550孔的最新地磁极性时标时，用作校准的Chron C24 r（0.66）中的55 Ma年龄估计值位于不整合面（将NP 9带的低层与NP 10带的低层分开），因此，在Chron 24 r中，NP 9/NP 10带/时边界的位置较高/较年轻。由于从DSDP 550和690站点恢复的剖面可能不重叠在NP 9上部-NP 10下部的带性间隔上，并且由于前一个剖面在NP 9/NP 10带性边界处不整合，因此目前没有办法建立令人满意的Chron C24 r的数字年代学，这意味着对古新世上部到始新世下部生物地层和同位素事件的年龄估计有待生物，磁，在连续地层剖面中进行同位素地层学研究。
Abstract The late Paleocene carbon isotope excursion which was first identified at ODP Site 690, is currently regarded as the best means for an exact correlation at a specific point in space and time between deep sea and continental stratigraphies. Yet its position relative to biostratigraphic datums in several outcrop and deep sea sections is apparently inconsistent. Based on the integration of magnetostratigraphic, biostratigraphic (calcareous nannofossils and planktonic foraminifera) and carbon isotopic data from the North (DSDP Sites 549 and 550) and South (ODP Site 690) Atlantic Ocean, we show that in order to understand the temporal relationships and sequence of late Paleocene to early Eocene biotic and isotopic events, it is necessary to construct a composite reference section. We infer from this that in addition to the well documented ‘classic’ carbon isotope excursion which occurs in mid-Biozone NP9, a younger isotopic excursion, yet undocumented, occurs in lower Biozone NP10. The 55 Ma age estimate in Chron C24r (0.66) used as a calibration in the construction of the latest geomagnetic polarity time scale in DSDP Hole 550 lies at an unconformity (separating stratigraphic levels low in Zone NP9 from low in Zone NP10) with the result that the position of the NP9/NP10 zonal/chronal boundary is higher/younger in Chron 24r. Because the sections recovered from DSDP Sites 550 and 690 probably do not overlap over the upper NP9-lower NP10 zonal interval, and because the former section is unconformable at the NP9/NP10 zonal boundary, there is currently no means of establishing satisfactorily a numerical chronology for Chron C24r, which means that the age estimates for the upper Paleocene to lowermost Eocene biostratigraphic and isotopic events await documentation of bio-, magneto-, and isotopic stratigraphy in continuous stratigraphic section(s).