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Title: A Devonian paleomagnetic pole from red beds of the Tarim Block, China

Abstract

The authors present new Devonian paleomagnetic results from 59 sites in three stratigraphic sections exposed on the northwestern margin of the Tarim Block. At one section, 1,998 m of red sandstone is continuously exposed; the other two sections can be correlated with the first on both magnetostratigraphic and lithologic grounds. Progressive thermal demagnetization reveals three characteristic magnetizations. One is a Late Permian overprint which is isolated below 578C at sites near contacts with Late Permian dikes. The other two components are approximately antipodal, have a much higher unblocking temperature than the overprint, and are directionally distinct from the Late Permian overprint. They believe that these are characteristic Devonian magnetizations. Within the continuous 1,998 m section, results denote a 395 m reversed polarity zone overlying a 1,603 m normal polarity zone. One reversed event is recorded at the base of the section. A paleomagnetic pole calculated by averaging results from 47 normal and reversed sites lies at {lambda}{sub p}=16.5{degree}N, {phi}{sub p}=165.0{degree}E, K=25, and A{sub 95}=4.3{degree}. This pole is statistically distinct from a previously reported Late Devonian pole for Tarim. On the basis of field geologic and rock magnetic studies, they believe that the previously reported pole, in addition to results frommore » one of their three sections, reflects at least partial contamination in the form of a thermal overprint caused by Late Permian igneous activity. An analysis of Devonian to Late Carboniferous polar wander suggests that the Tarim Block was attached to a subducting plate, and moved northward and rotated clockwise during the late Paleozoic. Comparison of the Devonian paleolatitudes of Siberian, Kazakhstan, Tarim and South China Blocks indicates that both the Tarim and South China Blocks were located in equatorial regions and were far south of the northern Angaran plate (Siberia and Kazakhstan).« less

Authors:
; ; ;  [1]; ; ;  [2];  [3];  [4]
  1. Stanford Univ., California (USA)
  2. Geology Bureau of Xinjiang, Urumqi (China)
  3. Chinese Academy of Geological Sciences, Beijing (China)
  4. China Univ. of Geosciences, Beijing (China)
Publication Date:
OSTI Identifier:
5226830
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research; (United States)
Additional Journal Information:
Journal Volume: 95:B12; Journal ID: ISSN 0148-0227
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CHINA; GEOLOGIC FORMATIONS; PALEOMAGNETISM; CARBONIFEROUS PERIOD; CORRELATIONS; DEMAGNETIZATION; DEVONIAN PERIOD; DIKES; GEOMAGNETIC COORDINATES; LITHOLOGY; PALEOZOIC ERA; PERMIAN PERIOD; PLATE TECTONICS; SANDSTONES; STRATIGRAPHY; SUBDUCTION ZONES; ASIA; COORDINATES; GEOLOGIC AGES; GEOLOGIC STRUCTURES; GEOLOGY; MAGNETISM; ROCKS; SEDIMENTARY ROCKS; TECTONICS; 580000* - Geosciences

Citation Formats

Li, Yianping, McWilliams, M, Sharps, R, Cox, A, Li, Yongan, Li, Qiang, Gao, Zhengjia, Zhang, Zhengkun, and Zhai, Yongjian. A Devonian paleomagnetic pole from red beds of the Tarim Block, China. United States: N. p., 1990. Web. doi:10.1029/JB095iB12p19185.
Li, Yianping, McWilliams, M, Sharps, R, Cox, A, Li, Yongan, Li, Qiang, Gao, Zhengjia, Zhang, Zhengkun, & Zhai, Yongjian. A Devonian paleomagnetic pole from red beds of the Tarim Block, China. United States. https://doi.org/10.1029/JB095iB12p19185
Li, Yianping, McWilliams, M, Sharps, R, Cox, A, Li, Yongan, Li, Qiang, Gao, Zhengjia, Zhang, Zhengkun, and Zhai, Yongjian. 1990. "A Devonian paleomagnetic pole from red beds of the Tarim Block, China". United States. https://doi.org/10.1029/JB095iB12p19185.
@article{osti_5226830,
title = {A Devonian paleomagnetic pole from red beds of the Tarim Block, China},
author = {Li, Yianping and McWilliams, M and Sharps, R and Cox, A and Li, Yongan and Li, Qiang and Gao, Zhengjia and Zhang, Zhengkun and Zhai, Yongjian},
abstractNote = {The authors present new Devonian paleomagnetic results from 59 sites in three stratigraphic sections exposed on the northwestern margin of the Tarim Block. At one section, 1,998 m of red sandstone is continuously exposed; the other two sections can be correlated with the first on both magnetostratigraphic and lithologic grounds. Progressive thermal demagnetization reveals three characteristic magnetizations. One is a Late Permian overprint which is isolated below 578C at sites near contacts with Late Permian dikes. The other two components are approximately antipodal, have a much higher unblocking temperature than the overprint, and are directionally distinct from the Late Permian overprint. They believe that these are characteristic Devonian magnetizations. Within the continuous 1,998 m section, results denote a 395 m reversed polarity zone overlying a 1,603 m normal polarity zone. One reversed event is recorded at the base of the section. A paleomagnetic pole calculated by averaging results from 47 normal and reversed sites lies at {lambda}{sub p}=16.5{degree}N, {phi}{sub p}=165.0{degree}E, K=25, and A{sub 95}=4.3{degree}. This pole is statistically distinct from a previously reported Late Devonian pole for Tarim. On the basis of field geologic and rock magnetic studies, they believe that the previously reported pole, in addition to results from one of their three sections, reflects at least partial contamination in the form of a thermal overprint caused by Late Permian igneous activity. An analysis of Devonian to Late Carboniferous polar wander suggests that the Tarim Block was attached to a subducting plate, and moved northward and rotated clockwise during the late Paleozoic. Comparison of the Devonian paleolatitudes of Siberian, Kazakhstan, Tarim and South China Blocks indicates that both the Tarim and South China Blocks were located in equatorial regions and were far south of the northern Angaran plate (Siberia and Kazakhstan).},
doi = {10.1029/JB095iB12p19185},
url = {https://www.osti.gov/biblio/5226830}, journal = {Journal of Geophysical Research; (United States)},
issn = {0148-0227},
number = ,
volume = 95:B12,
place = {United States},
year = {Sat Nov 10 00:00:00 EST 1990},
month = {Sat Nov 10 00:00:00 EST 1990}
}