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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Marine magnetic anomalies: evidence that 'tiny wiggles' represent short-period geomagnetic polarity intervals
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Marine magnetic anomalies: evidence that 'tiny wiggles' represent short-period geomagnetic polarity intervals

机译：海洋磁异常：“微小摆动”代表短周期地磁极性间隔的证据

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Since the 1960's, the geomagnetic polarity time scale, which is based on marine magnetic anomalies, has become fundamentally important in geochronology. Despite the importance of marine magnetic anomaly records, there has been longstanding uncertainty about the meaning of the smallest anomalies observed in these records. Small amplitude, short wavelength anomalies are frequently observed in marine magnetic anomaly records across fast-spreading oceanic crust (>50 mm/yr). The origin of these small-scale anomalies (referred to as 'tiny wiggles') has remained controversial over the last 30 years. 'Tiny wiggles' have been interpreted to represent either short-period polarity intervals or largescale fluctuations in the ancient field intensity. We present palaeomagnetic evidence from a sedimentary record from the North Pacific Ocean, which demonstrates that two short, but clearly resolvable, polarity zones, in addition to a probable geomagnetic excursion, occur within Chron C5n.2n (9.92-10.95 Ma) where three 'tiny wiggles' have been reported on marine magnetic anomaly profiles. Relative palaeointensity data indicate that the field collapsed prior to and during the reversals (and during the excursion) but that it recovered to higher field intensities within the polarity intervals before collapsing to low values at the succeeding polarity transition. This indicates that some 'tiny wiggles' represent real short-period geomagnetic polarity intervals, while others may represent geomagnetic excursions. The existence of such short polarity intervals confirms the predictions of statistical analyses of geomagnetic reversal frequency and indicates that 'tiny wiggles' represent the maximum resolution o geomagnetic polarity intervals in marine magnetic anomaly records.
机译：自1960年代以来，基于海洋磁异常的地磁极性时标在地球年代学中已变得至关重要。尽管海洋磁异常记录很重要，但是对于这些记录中观察到的最小异常的含义一直存在不确定性。在快速扩散的大洋地壳（> 50 mm / yr）中，海洋磁异常记录中经常观察到小幅度，短波长的异常。在过去的30年中，这些小规模异常的起源（称为“微小的摆动”）一直存在争议。 “微小的摆动”已被解释为代表短时的极性间隔或古代磁场强度的大规模波动。我们从北太平洋的沉积记录中提供了古地磁证据，表明在Chron C5n.2n（9.92-10.95 Ma）内还发生了两个短而清晰可辨的极性带，以及可能的地磁偏移，其中三个据报道，海洋磁异常剖面上有微小的摆动。相对古强度数据表明，在反转之前和反转期间（以及偏移期间），电场崩溃了，但是在随后的极性转换中塌陷为低值之前，它在极性区间内恢复了较高的电场强度。这表明一些“微小的摆动”代表了真正的短周期地磁极性间隔，而另一些则代表了地磁偏移。这样短的极性间隔的存在证实了地磁反转频率统计分析的预测，并表明“微小的摆动”代表了海洋磁异常记录中地磁极性间隔的最大分辨率。

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