A Devonian paleomagnetic pole from red beds of the Tarim Block, China
- Stanford Univ., California (USA)
- Geology Bureau of Xinjiang, Urumqi (China)
- Chinese Academy of Geological Sciences, Beijing (China)
- China Univ. of Geosciences, Beijing (China)
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).
- OSTI ID:
- 5226830
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 95:B12; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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