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" The Tertiary tectonic evolution of Southeast Asia: "
B. W. Richter
M. Fuller
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1113365
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| Doc. No
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TLpq304232444
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| Main Entry
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B. W. Richter
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M. Fuller
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| Title & Author
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The Tertiary tectonic evolution of Southeast Asia:\ B. W. RichterM. Fuller
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| College
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University of California, Santa Barbara
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| Date
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1996
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| student score
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1996
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| Degree
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Ph.D.
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| Page No
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247
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| Abstract
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The Tertiary tectonic evolution of Southeast Asia has been controlled by the interaction between Eurasia, India, Australia, and the Pacific and Philippine Sea Plates. Plate circuits provide a framework for understanding the motions of the major plates but paleomagnetic studies provide the only means of measuring motions within Southeast Asia. Data collected from the Shan plateau of Myanmar show CW declinations interpreted to represent usd33\sp\circ\pm7.7\sp\circusd of CW rotation relative to the South China block since the Middle Cretaceous; corresponding to usd15.4\sp\circ\pm5.4\sp\circusd of CW rotation relative to the Indochina block. Paleomagnetic data collected from remagnetized Paleozoic carbonates indicate that similar CW rotations extend southward into northern Malaysia. In contrast, paleomagnetic data collected from the remainder of Peninsular Malaysia show CCW declinations. Similar CCW declinations have been measured by others in Borneo, the Celebes Sea, and Sulawesi, and support the hypothesis that much of this region rotated 35 to 40 CCW as a rigid block, relative to South China, since the Middle Cretaceous. CW rotations are consistent with extrusion tectonics but CCW rotations are not predicted by the present model. A modified model which incorporates continental deformation driven by the India-Eurasia collision with subduction of oceanic crust along the Sumatra, Java, Sulawesi, and Philippine margins may be able to explain both CW and CCW rotations. Southward motion of Indochina is likely co have been limited by young buoyant oceanic crust of the Wharton spreading system (e.g. Investigator FZ) which lay along the Sumatran margin from the Cretaceous to the Eocene. Furthermore, the Java-Australia boundary is likely to have been a passive margin until the Middle Oligocene. Thus, as Australia moved northward in the Late Eocene it pushed Borneo northward. These opposing forces are interpreted to drive the CCW rotation of Borneo and Malaysia. Moreover, the Philippine Sea plate was rotating CW and moving to the northwest throughout much of the Tertiary and volcanic arc fragments of PSP origin progressively collided with Borneo throughout the Tertiary. A series of plate reconstructions are presented showing the evolution of SE Asia within this regional framework.
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Earth sciences
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Geology
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Geophysics
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