LINKAGES BETWEEN TECTONICS AND SEDIMENTARY RECORDS OF MESOZOIC INTRACONTINENTAL DEFORMATION IN CENTRAL SOUTH CHINA

The NE-trending Yuan-Ma Basin in Central South China, is situated between the Cathaysia Block in the east and the Yangtze Craton in the west, which is vital for understanding the Mesozoic intracontinental deformation from compressional to extensional setting in South China. However, the evolution and tectonic setting of the Yuan-Ma Basin have been poorly understood. Based on the detailed cross-section along the basin, it has been distinguished that the NW-dipping T₃-J₁ black coal-bearing shale, greyish-green sandstone and brick-red claystone and J₂-J₃ brick-red sandstone, pebble-bearing sandstone and conglomerate are cropped out in the eastern segment of the basin. The Cretaceous brick-red coarse sandstone, pebble-bearing sandstone, siltstone occurred in the western and central segments, as well as the fault breccias and Upper Cretaceous sandstone in the western margin. Detrital zircons are separated from four samples in the eastern segment, seven samples in the central segment and three samples in the western margin. The analysis of these detrital zircons indicates that the magmatic and metamorphic sourced zircons transported and yield major age clusters at 300-150Ma, 500-350Ma and 900-700Ma as well a minor age cluster of 120-100Ma playing a key role in limiting the timing of sedimentary sources and basin formation. Synthesizing these stratigraphic sequence, structures and isotopic dating results, it can be concluded that three evolutionary stages of the Yuan-Ma Basin during T₃-J₁ as the product of the foreland basin that might be related to the orogenesis of the Xuefeng orogeny; during J₂-J₃ it was related to the intracontinental compression of South China and at the end of Early Cretaceous corresponding to the intracontinental extension of eastern China. These three stages have been connected with the early Mesozoic orogenesis of South China, the Middle-Late Jurassic subduction of the Paleo-Pacific Plate and the Cretaceous rollback of the Paleo-Pacific Plate, respectively.