SUNDALAND: BASEMENT CHARACTER, STRUCTURE AND PLATE TECTONIC DEVELOPMENT

摘要

Sundaland is a heterogeneous region assembled by closure of Tethyan oceans and addition of Gondwana fragments. Basement structure influenced Cenozoic tectonics. Understanding Cenozoic basins requires a knowledge of the Mesozoic and Early Cenozoic history of Sundaland which is illustrated by a new plate tectonic reconstruction. Continental blocks rifted from Australia during the Late Jurassic and Early Cretaceous are now in Borneo, Java and Sulawesi, not West Burma. The Banda and Argo blocks collided with the SE Asian margin between 110 and 90 Ma. At 90 Ma the Woyla intra-oceanic arc collided with the Sumatra margin and subduction beneath Sundaland terminated. A marked change in deep mantle structure at about 110°E reflects different subduction histories north of India and Australia. They were separated by a transform that was leaky from 90 to 75 Ma and slightly convergent from 75 to 55 Ma. From 90 Ma, India moved rapidly north with north-directed subduction within Tethys and at the Asian margin. It collided with an intra-oceanic arc at about 55 Ma, west of Sumatra, and continued north to collide with Asia in the Eocene. Between 90 and 45 Ma Australia remained close to Antarctica and there was no subduction beneath Sumatra and Java. During this interval Sundaland was largely surrounded by inactive margins with some strike-slip deformation and extension, except for subduction beneath Sumba-Sulawesi. At 45 Ma Australia began to move north; subduction resumed beneath Indonesia and has continued to the present. The deep NW-SE structural trend of Borneo-West Sulawesi was either inherited from Australian basement or Cenozoic deformation. The structure of now-subducted ocean lithosphere influenced the Cenozoic development of eastern Indonesiaincluding important extension that began in the Middle Miocene in Sulawesi and led to the formation of the Banda Arc.