Title : "Provenance of Sandstone in the Triassic Nam Pat Group, Northern Thailand"

Researcher : Sampan Singharajwarapan

Office of Researcher : GEOLOGY


The Triassic Nam Pat Group has a lower volcaniclastic conglomerate, the Huai Lat Formation, and an upper marine turbiditic sandstone. The Huai Bo Khong Formation. The sequence has been folded into the large syncline that trends northeast. Petrographic and geochemical data were used to determine the provence and tectonic setting of deposition of the sandstone in the Nam Pat Group.

Nam Pat sandstone beds are characterized by large amount of volcanic rock fragments compared to the amount of quartz and feldspar. Their composition is comparable to sandstone derived from a transitional magmatic are provenance. In an addition to the composition of the framework grains, their immature texture suggests a proximity near to the source of grain. The volcanoes that generated the Permian-Triassic Pak Pat volcanic rocks are inferred to be the main source of the clastic material for the sandstone in the Nam Pat Group. This sandstone was probably deposited in a fore-arc basin.

The relatively high average concentrations of TiO2, Al2O3,Fe2O3 and v, high Zr/Th ratios, low abudance of Th, and low Th/Sc and Ce/V ratios suggest that the sandstone in the Nam Pat Group had an intermidiate igneous rock provenance. It is not certain whether the volcanic source formed in an oceanic island are or in a continental island are setting. However, the compositional similarities between Nam Pat sandstone and the graywacke of the Caples terrane in New Zealand lend strong support for an occanic island are source.

Presented at : International Symposium Shallow Tethys (ST) 5, Chiang Mai, 1-5 February 1999.