Abstract: Evolution of the Tibetan
Plateau Viewed from the Perspective of Eastern Tibet
BURCHFIEL, B. CLARK
Professor of Geology, Massachusetts Institute of Technology, Cambridge,
The tectonics of the eastern part of
the Tibetan plateau and its foreland are key elements to resolve problems
relating to Cenozoic evolution of the plateau and its relation to post-collisional
intracontinental deformation within the India/Eurasia convergent system.
Most fruitful has been the attempt to examine the latest Cenozoic and active
deformation and work backward in time to the inception of the collision.
The youngest and active tectonic framework can be developed more rapidly
from geodesy, seismology, and active deformation than by extensive mapping
of older surface geology where it is more difficult to establish contemporaniety
of structures and events within this vast region. Evidence from young and
active tectonism shows that deformation in the eastern Tibetan plateau
is inhomogeneous and can be divided into three different areas of different
structural style. Geodetic results show that relative to south China velocities
of crustal material within the plateau do not extend beyond the eastern
limit of the plateau and northeast of the plateau show only slow northward
velocity. The velocity structure confirms a three part tectonic division
of the eastern plateau developed from geology. Tectonism in these three
areas can be projected back 6-10 m.y. in different places. Prior to that
time the pattern of deformation shows both similarities and differences
to the young and active deformation. The similarities can be shown to be
related to the continual northward penetration of India into Eurasia, and
the differences may be related to structural controls by crustal anisotropy.
From these data we have developed a hypothesis for crustal evolution of
the plateau that is different from existing models and involves formation
of a fluid lower or middle crust that flows laterally in response to topographically
generated potential energy modifying that part of plateau development that
is related to deformation caused by intracontinental convergence between
India and Eurasia.
AAPG Search and Discovery Article #90927@1999-2000 AAPG Distinguished Lectures