论文部分内容阅读
The Sichuan Basin is one of the largest inland basins in the low latitude region of southern China.The Upper Triassic deposits are terrestrial origin and well developed in this basin.However,the climate conditions of the Late Triassic were poorly understood for a long time.It was supposed to be a warm and humid condition during the entire period of the Late Triassic.Our recent investigations have provided new palaeobotanical evidence showing that a cooling climate event occurred in this region during the Late Triassic episode.The finding of a new Xenoxylon fossil wood taxon in the Xujiahe Formation in Guangyuan,northern Sichuan Basin contributes to a better understanding of the yet poorly documented Xenoxylon early radiation during the Late Triassic.As a palaeobiogeographically significant genus,the occurrence of Xenoxylon in the Sichuan Basin of southern China indicate a short-term cooling event,sandwiched within a period during which warm and wet climate condition largely prevailed over lower latitude regions of the Northern Hemisphere.Such a cooling event is suggested to be indirectly influenced by the temporary onset of a megamonsoon phenomenon during Late Triassic.In addition,palynological data and the Sporomorph Ecogroup Model (SEG) analysis from the Xujiahe Formation support that there some climate perturbations in this time,thus showing congruence for the climate cooling event.