SEDIMENTARY CHARACTERISTICS, BASIN TYPE AND DYNAMIC MECHANISMS DURING LATE TRIASSICJURASSIC IN SOUTHEASTERN HUNAN PROVINCE

There are different standpoints such as para-foreland basin and down-faulted basin about the Late Triassic-Jurassic basin in southeastern Hunan.Distribution of the sediments and lithofacies character show information as follows:there existed marine and marine-terrigenous sedimentary environment during Late Triassic-early Early Jurassic in southeastern Hunan, while continental sedimentary environment during late Early Jurassic-early Middle Jurassic; the Late Triassic basin was a NNE-SN trending narrow and long bay along the east side of Chaling-Chenzhou fault, and the basin expanded to east and west since Early Jurassic; the Late Triassic-Jurassic sediments covered crosswise on older layers.All the above indicated that the Late Triassic-Jurassic basin in southeastern Hunan wasn't a para-foreland depressive basin controlled by NS-compression.Combined with regional tectonic setting, the authors bring forward recognition as follows:the forming of the basin was mainly related with the EW-extention of NNE-trending faults under regional SN-compressional stress field, which confirmed that the lineament trend of Indosinian Movement in southeast Hunan was NNE; above evolution from marine to continental suggested that a EW-trending uplift formed to south of the study area since late Early Jurassic under regional S-N-compression, and that the study area was in a regional depressive tectonic setting when the basin extended in late development stage.These render the complex extensional or compressional space-time variation of tectonic regime when the Late Triassic-Jurassic basins developed in south China.