Depositional systems and filling patterns of the Tertiary Qaidam lake basin in the Ganchaigou region, Qinghai

The sediments from the margin-slope zone of the Tertiary Qaidam lake basin in the Ganchaigou region, Qing hai are ex plo red on the basis of surficial investigation and well log s. Five depositional sy stems have been distinguished:fan-delta, submarine pluvial fan-nearshore turbidity current, braided channel-delta, norm al lakedelta and lake depositional systems.The genetic stratigraphic framew ork and model for the lake basin filling are constructed in terms of temporal-spatial distribution and tectonic-stratigraphic sequences in the Ganchaigou region.