Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments
Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments
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DOI：
10.1016/j.epsl.2012.06.050
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发表时间：
2012-10
影响因子：
5.3
通讯作者：
N. Nowaczyk;H. Arz;U. Frank;J. Kind;B. Plessen
中科院分区：
文献类型：
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作者：
N. Nowaczyk;H. Arz;U. Frank;J. Kind;B. Plessen
来自黑海东南部的沉积物岩心提供了Laschamp地磁极性偏移中纬度的高分辨率记录。通过16个AMS14C年龄、坎帕系Ignimbrite tephra（39.28±0.11ka）的鉴定以及黑海沉积物的沉积学参数与格陵兰NGRIP冰芯氧同位素记录的详细调优，提供了年龄约束。根据推导出的年龄模型，Laschamp漂移期间的虚拟地磁极（VGP）位置在南极洲持续了大约440年，使Laschamp漂移成为一个极性方向完全相反的短暂事件。以41.0ka为中心的反相，与之前在~ 50ka处的强场最大值的20%的显著场强恢复有关。记录到的Laschamp偏移的场反转仅持续约250年，其特征是相对古强度低（相对于50ka为5%）。Laschamp漂移的中心，完全相反的阶段被VGP漂移到马尾藻海（~ 41.9ka）和拉布拉多海（~ 39.6ka）所包围。黑海的古地磁结果与法国型地区的VGP数据非常吻合，这有助于对拉斯尚-奥尔比（Laschamp-Olby）出现的非叠加熔岩进行时间排序。此外，在34 ~ 35ka之间的vgp以顺时针的环路到达低北至赤道纬度，推断为Mono湖偏移。
Investigated sediment cores from the southeastern Black Sea provide a high-resolution record from mid latitudes of the Laschamp geomagnetic polarity excursion. Age constraints are provided by 16 AMS14C ages, identification of the Campanian Ignimbrite tephra (39.28±0.11ka), and by detailed tuning of sedimentologic parameters of the Black Sea sediments to the oxygen isotope record from the Greenland NGRIP ice core. According to the derived age model, virtual geomagnetic pole (VGP) positions during the Laschamp excursion persisted in Antarctica for an estimated 440yr, making the Laschamp excursion a short-lived event with fully reversed polarity directions. The reversed phase, centred at 41.0ka, is associated with a significant field intensity recovery to 20% of the preceding strong field maximum at ∼50ka. Recorded field reversals of the Laschamp excursion, lasting only an estimated ∼250yr, are characterized by low relative paleointensities (5% relative to 50ka). The central, fully reversed phase of the Laschamp excursion is bracketed by VGP excursions to the Sargasso Sea (∼41.9ka) and to the Labrador Sea (∼39.6ka). Paleomagnetic results from the Black Sea are in excellent agreement with VGP data from the French type locality which facilitates the chronological ordering of the non-superposed lavas that crop out at Laschamp–Olby. In addition, VGPs between 34 and 35ka reach low northerly to equatorial latitudes during a clockwise loop, inferred to be the Mono lake excursion.