Cenozoic deformation in western Yunnan (China–Myanmar border)

Abstract

In the present paper, we describe ductile and brittle deformation styles in western Yunnan and NE Myanmar, using field data and Landsat 7 imagery. We show that this complex area located at the northern termination of Sunda Plate (Three Rivers area) was wedged during the Tertiary between the left-lateral Ailao Shan/Chong Shan metamorphic belts to the east and the right-lateral Shan scarp/Gaoligong metamorphic belt in west. This triangular region therefore underwent the effects of these continental size ductile strike-slip faults separating major blocks with a dominant EW to ENE compression. Since the Late Miocene, date of the reversal of motion along the RRF, the incipient eastward motion of the Sunda block and the persisting right-lateral motion along its western boundary (Sagaing fault) created N–S compression and E–W to WNW extension underlined by left-lateral transtension along the Wanding/Nanting fault zones. At the same time, the Diangcan Shan, situated along strike the Ailao Shan metamorphic belt, was slightly impinged by the blocks extruded from the syntaxis and exhumed again from the Early Pliocene in accordance with this late and still active state of stress.