Abstract:

The Upper Cretaceous (including Hekou, Tangbian and Lianhe formations) conglomerates are widespread in Yongfeng-Chongren basin, Jiangxi Province, south China, which is the material basis of Danxia landforms. The contingency table analysis of pebble lithology and roundness is an effective approach to provenance interpretation. In this paper, it is the first time that the lithology and roundness of gravels from Yongfeng-Chongren basin are combined to make the contingency table. Gravels are mainly composed of quartzite, granitic rocks, sandstones and metamorphic rocks, and a small amount of mudstones and limestones. For the convenience of counting, the roundness of the gravels are subdivided into three levels including A+B (angular and sub-angular), C (sub-rounded) and D+E (rounded and well-rounded). Normally, when the value of A+B is fewer than expected and the value of D+E is more than expected, pebbles were considered to be transported for long distance. On the contrary, it shows short distance transport. The following conclusions are drawn: the pebbles of Hekou Formation came from more than one source, and they would came from the edge of the basin and Jilongshan, Xiangshan and Yuhuashan mountains and the northwestern Changlong area; the pebbles of Tangbian Formation were mainly derived from Jiandingfengshan and Yuhuashan mountains, and some parts from southeast Fengshan and Xindashan mountains; the Lianhe Formation’s pebbles were mainly derived from Jinhuashan and Zhangling mountains, and some might come from Jilonggang, Songshuling and Lingguling mountains in the northeastern part of the basin. The result of the provenance analysis could provide important basis for the formation and evolution of the Cretaceous red basins in south China.

Key words: provenance, pebble count, roundness, contingency table, Upper Cretaceous