The Permo-Carbonigferous Facies Development in Thailand: A plate tectonic discussion.
Congrès International de Stratigraphie et de Géologie du Carbonifère, 1989, Beijing.
The Permo-Carboniferous sedimentary facies development in Thailand reflects the late
Variscan orogeny in S E Asia.
During the Carboniferous and Permian, a N -S trending trough separated the " S h a n Thai
Craton" and the "Indosinia Craton". In this pelagic basin, deposition of ribbon cherts continued
from pre-Asselian to Kubergandian. I n Lower Permian, carbonatic and tuffitic turbidites
were transported from the neighbouring platforms into the basin.
The Middle Permian flysch sedimentation resulted from a strong orogenic activity. T h e
basin was E-vergent, isoclinally folded and pverthrusted. Parts of the basin are metamorphosed
into the greenschist facies.
I n the eastern marginal parts Kubergandina to Midian; molasse was deposited from the
new rising fold belt.
The intensity of folding of the molasse decreases towards the east or the younger strata.
The total width of the basin was probably not greater than 200 km. T h e pelagic sediments,
flysch and molasse represent a thick pile of a coarsening-upwards sequence, typical of
subduction related sutures. Folding affected a marginal marine basin and was caused by a
westward directed subduction (A-subduction) under the volcanic arc.
West of the arc, pebbly mudstones were laid down on the trench slope or the continental
margin of Paleoeurasia. T h e deposition of these mixtites continued through the Carboniferous
to Lower Permian and came to an end contemporary with the relative uplift of the " S h an
Thai Craton" and the onset of the A-subduction under the Petchabun marginal basin. T h e Benioff-
subduction must have been located west of the depositional area of the pebbly mudstones
and directed towards the east.