Open AccessCounter‐clockwise rotation of the eastern part of the Mongolia block: Early Cretaceous palaeomagnetic results from Bikin, Far Eastern Russia
Author(s) -
Otofuji Yoichiro,
Miura Daisuke,
Takaba Koichi,
Takemoto Kazuhiro,
Narumoto Kazutoshi,
Zaman Haider,
Inokuchi Hiroo,
Kulinich Ruslan G.,
Zimin Petr S.,
Sakhno Vladimir G.
Publication year - 2006
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2005.02790.x
Subject(s) - clockwise , paleomagnetism , geology , cretaceous , paleontology , structural basin , fold (higher order function) , block (permutation group theory) , declination , geometry , mathematics , mechanical engineering , physics , astronomy , engineering
SUMMARY We present palaeomagnetic results from Lower Cretaceous rocks in Bikin area of the Alchan basin (46.5°N, 134.7°E), Sikhote Alin orogenic belt, Far Eastern Russia. A high‐temperature magnetization component with maximum unblocking temperatures at about 590°C was isolated from six sites of dacite welded tuffs in the Albian Alchanskaya Formation. The fold tests for these six sites are positive, suggesting that primary magnetization is preserved in the studied rocks. The tilt‐corrected mean direction of D = 309.3°, I = 68.7° (α 95 = 10.1°) , with a corresponding palaeopole position at 57.0°N, 76.8°E ( A 95 = 15.1°) , indicates a counter‐clockwise (CCW) rotation for the studied area. CCW rotation is also indicated from west‐directed declinations ( D = 249.1°, I = 64.1°, α 95 = 11.2°) obtained from secondary magnetization of the Berriasian Kultukha Formation. Combining with the previously reported studies, the west‐directed Cretaceous palaeomagnetic directions cover widely the eastern part of the Mongolia block. Comparison with 100 Ma palaeomagnetic pole for Eurasia shows that the eastern part of the Mongolia block experienced a CCW rotation of over 36° with respect to the Eurasian continent later than Late Cretaceous. This rotation is ascribed to post‐Late Cretaceous extension that affected the continental basins (the Middle Amur, Sanjiang, Razdolnian, Amur‐Zeya and Songliao basins) of the northeast Chinese Plain along the eastern margin of the Mongolia block. Contemporaneous with this CCW rotation, similar extension resulted in clockwise rotation of the eastern part of the North China block.