Abstract: The Cretaceous Ngamring Formation constitutes the main body of the Xigaze forearc basin, southern Xizang. It was deposited in deep-water basin, submarine fan, submarine canyon and slope environments, which provides a good opportunity to study the architecture of submarine lobe. This study conducts stratigraphic and sedimentologic analyses on the easily-accessible, well-outcropped Engongsi section of the Ngamring Formation. Different lithofacies have been described based on lithologies and sedimentary structures, including conglomerate, structureless sandstone, structured sandstone, banded sandstone, debrites, heterolithic packages, siltstone and claystone/limestone. Microfacies of lobe axis, off-axis, fringe and distal fringe have been identified according to assemblages of lithofacies, indicating that the strata were deposits of submarine lobe complex with seven periods of superposed lobes. Different arrangements of microfacies suggest sedimentological variability of each lobe, probably due to the tectonic activities in the source areas.
Keywords: Xigaze forearc basin; Ngamring Formation; sedimentary environment; lobe architecture
合肥工业大学学报自科版