RECONSTRUCTING EASTERN GONDWANALAND: DETRITAL HISTORY OF PERMO-CARBONIFEROUS GONDWANAN SEQUENCES FROM SOUTH ASIA
The sandstones from Bangladesh are angular to sub-angular and show greater immaturity compared to the coeval sandstones from India. Several tectonic provenance fields were identified for these mostly poorly sorted arkosic and quartz arenitic sequences. Sandstone modal analysis shows that Gondwanan sediments from Bangladesh area (~Qt66F20L14) plot in the ‘recycled orogenic’ to ‘transitional continental’ provenance fields of Dickinson (1985) whereas Indian Gondwanan samples (~Qt84F3L13) plot in the ‘craton interior’ to ‘recycled orogenic’ fields. Monocrystalline quartz was dominant over polycrystalline quartz in both Indian and Bangladesh samples. Although significant amount of feldspar was observed from the Bangladesh samples and the Talchir Formation from India, no feldspar was found in the samples from the Barakar Formation (India). The highest concentrations of heavy minerals were found in the Barakar Formation. Mud injections in several samples were found to be calcified.
Compositional as well as textural variations suggest different provenance of contrasting source rocks for these sediments of similar depositional age. Ongoing detrital geochronology and mineral chemistry studies will help better understand the provenance of these Permo-Carboniferous sequences.