Izvestiya, Physics of the Solid Earth ( IF 1 ) Pub Date : 2021-04-13 , DOI: 10.1134/s1069351321020014 I. E. Lebedev , P. L. Tikhomirov , A. M. Pasenko , B. Eid , F. Lhuillier , V. E. Pavlov
Abstract—Paleomagnetic studies of several Late Cretaceous volcanic sections of the Okhotsk–Chukotka volcanic belt have been carried out in the Bilibino region of the Chukotka Autonomous Okrug and along the Pevek–Egvekenot road. Extensive collections have been acquired and analyzed. The laboratory experiments isolated the ancient characteristic magnetization component reflecting the direction of the geomagnetic field at the time of formation of the studied rocks (~85 Ma ago). The primary character of the revealed characteristic magnetization component is supported by the positive regional fold test and by the coincidence of the paleomagnetic pole calculated from this component with that previously obtained for Chukotka from the rocks of similar age (Stone et al., 2009). The paleomagnetic pole calculated from the combination of the previous and our newly obtained data (Plat = 69.3°, Plong = 180.7°, N = 99, A95 = 5.1°) indicates that the sampled rocks were formed in the immediate vicinity of the geographic pole. The reliability of the existing Late Cretaceous paleomagnetic poles for Eurasia and North America is analyzed, and the refined poles are calculated for these plates for the time of ~85 Ma. The reconstruction of the Chukotka–Kolyma–Omolon block’s position relative to Eurasia and North America allowing for the paleomagnetic poles calculated for that time is proposed. The reconstruction implies that from the formation time of the studied rocks up to the present, the Chukotka–Kolyma–Omolon block has undergone relatively small (tens to first hundreds of km) southward movements relative to the North American plate and has been noticeably shifted (by a few hundred km) relative to the Eurasian plate. Our reconstruction is close to that proposed in (Otofuji et al., 2015) but, in contrast to the latter, it does not require a collision between the Chukotka–Kolyma–Omolon block and Eurasia after 80 Ma ago.
中文翻译:
晚白垩世楚科奇火山火山的新古地磁数据:鄂霍次克—楚科奇火山火山带形成后,楚科奇火山块可能经历了相对于北美和欧亚板块的位移?
摘要—在楚科奇自治区的布鲁比诺地区以及沿佩维克-埃格维克诺特公路沿线进行了鄂霍次克-楚科奇火山带的几个晚白垩纪火山岩段的古磁研究。已收集并分析了广泛的馆藏。实验室实验分离出了古老的特征化磁化分量,该分量反映了研究岩石形成时(〜85 Ma以前)的地磁场方向。显露的特征磁化分量的主要特征由正向区域褶皱试验和由该分量计算出的古磁极与先前从相似年龄的岩石中获得的楚科奇的重合所支持(Stone等,2009)。根据先前和我们新获得的数据(Plat = 69.3°,Plong = 180.7°,N = 99,A95 = 5.1°)的组合计算出的古磁极表明,所采样的岩石是在地理极的附近形成的。分析了欧亚大陆和北美现有的晚白垩纪古磁极的可靠性,并计算了这些板块在〜85 Ma的时间中的精炼磁极。提出了重构楚科奇–科利马–奥莫伦区块相对于欧亚大陆和北美的位置的方法,考虑到了当时计算出的古磁极。重建意味着从研究岩石的形成时间到现在,楚科奇–科利马–奥莫隆地块相对于北美板块经历了相对较小的(几十到几百公里)向南运动,并且相对于欧亚板块发生了明显的偏移(几百公里)。我们的重建与(Otofuji等人,2015)中提出的重建相近,但是与后者相反,它不需要在80 Ma之前楚科奇-科利马-莫莫隆区块与欧亚大陆之间发生碰撞。