The C27n‐C26r geomagnetic polarity reversal recorded in the west Greenland flood basalt province: How complex is the transitional field?
The C27n‐C26r geomagnetic polarity reversal recorded in the west Greenland flood basalt province: How complex is the transitional field?
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格陵兰西部溢流玄武岩省记录的C27n-C26r地磁极性反转：过渡场有多复杂？
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
A. Pedersen
中科院分区：
文献类型：
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作者：
J. Riisager;P. Riisager;A. Pedersen
我们在西格陵兰洪水玄武岩省Vaigat组的两个独立熔岩层序中采集了C27n-C26r （~ 60.9 Ma）地磁极性反转（GPR）的古地磁记录。这两条剖面相距16公里，分别由45和35个熔岩流样本组成，其中31和23个分别记录了过渡场方向。每个剖面的一个显著特征是存在具有相似古地磁方向的连续流动，根据地质、地球化学和古地磁证据，这些流动被解释为流场（即熔岩在短时间内喷发），而不是地磁场静止的时期。多模式摄影测量显示，Vaigat组泥质熔岩的典型流动长度小于2 km，这解释了为什么两条剖面（相距16 km）的古地磁方向不可能进行流-流对比。因此，这两个剖面记录了相同探地雷达的不同和独立的时间序列，使我们能够阐明从单一记录中产生的一些问题。特别值得注意的是，两个高分辨率古地磁记录没有共同的总体趋势，这清楚地表明C27n-C26r过渡场比任何一个记录都更复杂，变化更快。此外，我们获得了过渡带前C27n和过渡带后C26r的稳定极性古地磁数据，得到了纬度64.8°N，经度141.5°E （N = 14, K = 19.8, A95 = 9.2°）的古地磁极，并通过了反转检验。
[1] We present a paleomagnetic record of the C27n-C26r (∼60.9 Ma) geomagnetic polarity reversal (GPR) sampled in two separate lava sequences in the Vaigat Formation, west Greenland flood basalt province. The two profiles, distanced 16 km apart, consist of 45 and 35 sampled lava flows of which 31 and 23, respectively, record transitional field directions. A prominent feature of each profile is the presence of successive flows with similar paleomagnetic directions, which based on geological, geochemical, and paleomagnetic evidences are interpreted to represent flow fields (i.e., lavas erupted in a short period of time) rather than periods when the geomagnetic field stood still. Multimodel photogrammetry shows that the typical flow length of Vaigat Formation picritic lavas is <2 km, which explains why flow-to-flow correlation of paleomagnetic directions between the two profiles (16 km apart) is not possible. The two profiles therefore record different and independent time series of the same GPR, allowing us to cast light on some of the questions that have arisen from single records. Particularly noteworthy is the fact that the two high-resolution paleomagnetic records share no general trends, clearly indicating that the C27n-C26r transitional field was more complex and faster changing than can be resolved by either record. In addition, we obtained stable polarity paleomagnetic data from both pretransitional C27n and posttransitional C26r yielding a paleomagnetic pole latitude 64.8°N, longitude 141.5°E (N = 14, K = 19.8, A95 = 9.2°) that passes reversal test.