Geological times and sedimenrtary facies of the Mesozoic and Cenozoic “red basins” in the Xiushui and Wuning regions, northwestern Jiangxi

The stratigraphic ages have been determinated on the basis of the new palaeontological data for the Wuning, Sandu and Ma'ao Basins in the Xiushui and Wuning regions in northwestern Jiangxi. Twenty-two lithofacies assigned to seven sedimentary types have also been distinguished, including debris flow deposits, mud flow deposits, grain flow deposits, stream-channel (including main channel and distributary channel) deposits, sheet flow deposits, sieve deposits and flood-plain deposits in the basins outlined above. The gravity-flow (deposits) appear in the proximal fan and/or at the base of major depositional cycles. The differences of their sedimentary types may be caused by the variations in lithology in the contiguous provenances. The distributary channel deposits, sheet flow deposits and sieve deposits are concentrated in the mid-fan, where the cross-(beddings), brecciated structures and tractional current marks are extremely conspicuous. The fan fringes are (occupied) by the flood-plain deposits intercalated with minor amount of sandstone and conglomerate lenses of the crevasse-splay origin. The widespread caliche indicates a highly arid palaeoclimate.