New Late Cretaceous paleomagnetic data from volcanic rocks and red beds from the Lhasa terrane and its implications for the paleolatitude of the southern margin of Asia prior to the collision with India
New Late Cretaceous paleomagnetic data from volcanic rocks and red beds from the Lhasa terrane and its implications for the paleolatitude of the southern margin of Asia prior to the collision with India
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DOI：
10.1016/j.gr.2015.11.006
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发表时间：
2017-01-01
影响因子：
6.1
通讯作者：
Zhang, Lei
中科院分区：
文献类型：
--
作者：
Cao, Yong;Sun, Zhiming;Zhang, Lei
为了提高晚白垩世亚洲南缘古纬度的估计，以及印度-亚洲碰撞对亚洲大陆内部会聚的限制，我们对拉萨林州盆地（29.9 ° N/91.1 ° E）晚白垩世红层序列和夹层火山岩进行了联合的年代学和古地磁研究。K-Ar定年结果表明，玄武岩的时代为晚白垩世（68-75 Ma）。分步热退磁成功地分离出10个红层点和11个熔岩流点的高解堵温度特征方向。积极的褶皱和反转测试表明，红层和玄武岩遗址的特征剩磁的主要来源。在红层和玄武岩熔岩流中记录的一致的倾斜表明，在所研究的部分中的红层中没有发生与倾斜相关的显著变浅。倾斜校正的平均方向为D/I = 0.5度/20.2度，α（95）= 6.4度，N = 21个站点，对应于70.5度N，269.6度E，A（95）= 4.9度的古极点。晚白垩世亚洲南缘的古地磁结果为北纬10.4 ± 4.9度。与预期的特提斯喜马拉雅和亚洲的古地磁方向相比，自晚白垩世以来，亚洲南缘和特提斯喜马拉雅之间以及亚洲内部可能分别发生了17.7 +/- 5.5度（1960 +/- 610公里）和9.4 +/- 4.7度（1040 +/- 520公里）的显著地壳缩短。根据拉萨古地磁资料，白垩纪和古新世亚洲南缘的纬度处于一个稳定的古纬度位置（10 ° ~ 15 ° N）。(C)2015年国际冈瓦纳研究协会。Elsevier B. V.出版，保留所有权利。
In order to improve estimation of the paleolatitude of the southern margin of Asia during the Late Cretaceous, as well as the constraints on the intracontinental convergence within Asia due to the India-Asia collision, we performed a combined geochronological and paleomagnetic investigation of Late Cretaceous red bed sequences and intercalated volcanic rocks from the Linzhou Basin in the Lhasa terrane (29.9 degrees N/91.1 degrees E). The results of potassiumargon (K-Ar) dating indicated that the basalt sequences are of Late Cretaceous age (68-75 Ma). Stepwise thermal demagnetization successfully isolated high unblocking-temperature characteristic directions from 10 red bed sites and 11 lava flow sites. Positive fold and reversal tests indicate a primary origin for the characteristic remanence of the red beds and basalt sites. The consistent inclination recorded in the red beds and basalt lava flows indicates that no significant compaction-related inclination shallowing has occurred in the red beds from the studied section. The tilt-corrected mean direction is D/I = 0.5 degrees/20.2 degrees with alpha(95) = 6.4 degrees and N = 21 sites, corresponding to a paleopole at 70.5 degrees N, 269.6 degrees Ewith A(95) = 4.9 degrees. The paleomagnetic results yield a paleolatitude of 10.4 +/- 4.9 degrees N for the southern margin of Asia in the Late Cretaceous. Compared with expected paleomagnetic directions from the Tethyan Himalaya and Asia, significant crustal shortening of 17.7 +/- 5.5 degrees (1960 +/- 610 km) and 9.4 +/- 4.7 degrees (1040 +/- 520 km), respectively, may have occurred between the southern margin of Asia and the Tethyan Himalaya, and within Asia, since the Late Cretaceous. Based on previous Cretaceous and Paleocene data from the Lhasa terrane, the latitude of the southern margin of Asia was located at a stable paleolatitudinal position (10 degrees-15 degrees N) during the Cretaceous and Paleocene. (C) 2015 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.