四川江油渔洞子剖面二叠纪—三叠纪界线生物地层及沉积特征

由于在川西北地区二叠纪-三叠纪界线地层的白云岩中一直没有找到可靠的生物化石,长期以来,白云岩就成为划分该地区二叠纪-三叠纪界线的标志。严格来说,这是一条岩石地层界线,而不是真正意义上的生物地层界线。在对四川江油渔洞子剖面进行详细的生物地层和沉积相研究时,在二叠纪长兴组珊瑚层以上的灰质白云岩中发现了微生物岩层并在其中首次找到了牙形刺H.parvus和灾难种有孔虫化石,从而为我们精确划分川北地区二叠纪-三叠纪的界线生物地层及确定该地区白云岩与微生物岩的时代及生态环境变化提供了可靠的生物化石依据。沉积特征的分析有利于了解从晚二叠世长兴组顶部至早三叠世飞仙关组中下部的沉积历史。

PERMIAN-TRIASSIC BOUNDARY BIOSTRATIGRAPHY AND SEDIMENTOLOGY AT THE YUDONZI SECTION OF JIANGYOU,SICHUAN PROVINCE

A dolomite unit near the Permian-Triassic boundary has long been used as the boundary marker in northwestern Sichuan but no biostratigraphically diagnostic fossils have been found in this units.Here we report the discovery of the conodont Hindeodus parvus and foraminifer disaster species from a microbiate bed in the dolomite unit above Permian coral beds at the Yudongzi section in Jiangyou of Sichuan Province.This discovery allows us to determinate the Permian-Triassic boundary in northwestern Sichuan and to understand the ecological and environmental changes across the boundary.We also present a detailed sedimentological analysis of the uppermost Changxing Formation and the lower-middle Feixianguan Formation