MAGNETOSTRATIGRAPHY OF OLIGOCENE TO PLEISTOCENE SEDIMENTS , SITES 558 AND 563 1
MAGNETOSTRATIGRAPHY OF OLIGOCENE TO PLEISTOCENE SEDIMENTS , SITES 558 AND 563 1
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渐新世至更新世沉积物的磁性地层学，地点558和563 1
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Lamont
中科院分区：
文献类型：
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作者：
M. Khan;D. Kent;K. Miller;Lamont
DSDP 563和558站点（北大西洋西部）的综合磁性地层学和生物地层学研究表明，除了早中新世短暂（~2 Ma）的间断外，两个站点的沉积从海底形成（563站点，异常12和13之间; 558站点，异常13和15之间）到中新世都是连续的。几个生物地层基准面，这已与其他地方的磁极性年代密切相关，允许相关的磁性地层与地磁极性时间尺度。根据这一校准，沉积物积累速率在渐新世-早中新世为低至中等（< 10 m/Ma），在中新世中晚期短暂中断后较高（> 10 m/ Ma）（两个地点均缺失Chron C5 E）。已建立的磁性年代学可用于直接的磁性生物地层对比。对于渐新世-中新世的样品，这些相关性与先前发表的一阶相关性一致。然而，我们的对比不同于早期的间接中上中新世的对比。特别是，间接方法以前被用来相关磁性地层年代11（=区NN 9）与海洋异常5A（年代C5 AN）。然而，NN 9区（= Chron 11）和相关的N16区出现在与海洋磁异常5最相关的563和558站点的长正常间隔中。这种重新分配（年代11 =异常5 =年代C5 N）需要大约1.5-2 Ma的上移超微化石带边界NN 7/NN 8通过NN 10/NN 11。上中新统下部层型（Tortonian）在生物地层学上与NN 9-NN 11带相连。由于NN 9带位于磁异常5相关区（Chron C5 N），中新世中-上界线（托顿基底）可能在Chron C5 N基底附近，估计其磁年代学年龄为10.4Ma。
Integrated magnetostratigraphic and biostratigraphic studies of DSDP Sites 563 and 558 (western North Atlantic) show that, except for a short (~2 Ma) early Miocene hiatus, deposition was continuous from time of seafloor formation (Site 563, between Anomalies 12 and 13; Site 558, between Anomalies 13 and 15) through the Miocene at both sites. Several biostratigraphic datum levels, which have been correlated firmly with magnetic polarity chrons elsewhere, allow correlation of the magnetostratigraphy with the geomagnetic polarity time scale. Based upon that calibration, sediment accumulation rates were low to moderate (< 10 m/Ma) in the Oligocene-early Miocene and higher (> 10 m/ Ma) in the middle-late Miocene after a short hiatus (Chron C5E is missing at both sites). The established magnetochronology is used to make direct magnetobiostratigraphic correlations. For the Oligocenelower Miocene samples, these correlations agree well with previously published first-order correlations. However, our correlations differ from the earlier indirect middle to upper Miocene correlations. In particular, indirect methods were previously used to correlate magnetostratigraphic Chron 11 (= Zone NN9) with marine Anomaly 5A (Chron C5AN). However, Zone NN9 ( = Chron 11) and associated Zone N16 occur in a long normal interval at Sites 563 and 558 that best correlates with marine magnetic Anomaly 5. This reassignment (Chron 11 = Anomaly 5 = Chron C5N) requires an approximately 1.5-2 Ma upward shift in nannofossil zonal boundaries NN7/NN8 through NN10/NN11. The stratotype lower upper Miocene (Tortonian) is biostratigraphically linked with Zones NN9-NN11. Because Zone NN9 occurs in magnetic Anomaly 5 correlative (Chron C5N), the middle-upper Miocene boundary (basal Tortonian) is probably near the base of Chron C5N, with an estimated magnetochronologic age of 10.4 Ma.