Upper Permian to Lower Triassic coastal plain successions of the Sydney Basin in eastern Australia have been investigated in outcrop and continuous drillcores. The purpose of the investigation is to provide an assessment of palaeoenvironmental change at high southern palaeolatitudes in a continental margin context for the late Permian (Lopingian), across the end‐Permian Extinction interval, and into the Early Triassic. These basins were affected by explosive volcanic eruptions during the late Permian and, to a much lesser extent, during the Early Triassic, allowing high‐resolution age determination on the numerous tuff horizons. Palaeobotanical and radiogenic isotope data indicate that the end‐Permian Extinction occurs at the top of the uppermost coal bed, and the Permo‐Triassic boundary either within an immediately overlying mudrock succession or within a succeeding channel sandstone body, depending on locality due to lateral variation. Late Permian depositional environments were initially (during the Wuchiapingian) shallow marine and deltaic, but coastal plain fluvial environments with extensive coal‐forming mires became progressively established during the early late Permian, reflected in numerous preserved coal seams. The fluvial style of coastal plain channel deposits varies geographically. However, apart from the loss of peat‐forming mires, no significant long‐term change in depositional style (grain size, sediment‐body architecture, or sediment dispersal direction) was noted across the end‐Permian Extinction (pinpointed by turnover of the palaeoflora). There is no evidence for immediate aridification across the boundary despite a loss of coal from these successions. Rather, the end‐Permian Extinction marks the base of a long‐term, progressive trend towards better‐drained alluvial conditions into the Early Triassic. Indeed, the floral turnover was immediately followed by a flooding event in basinal depocentres, following which fluvial systems similar to those active prior to the end‐Permian Extinction were re‐established. The age of the floral extinction is constrained to 252.54 ± 0.08 to 252.10 ± 0.06 Ma by a suite of new Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry U‐Pb ages on zircon grains. Another new age indicates that the return to fluvial sedimentation similar to that before the end‐Permian Extinction occurred in the basal Triassic (prior to 251.51 ± 0.14 Ma). The character of the surface separating coal‐bearing pre‐end‐Permian Extinction from coal‐barren post‐end‐Permian Extinction strata varies across the basins. In basin‐central locations, the contact varies from disconformable, where a fluvial channel body has cut down to the level of the top coal, to conformable where the top coal is overlain by mudrocks and interbedded sandstone–siltstone facies. In basin‐marginal locations, however, the contact is a pronounced erosional disconformity with coarse‐grained alluvial facies overlying older Permian rocks. There is no evidence that the contact is everywhere a disconformity or unconformity.

中文翻译：

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澳大利亚东部悉尼盆地二叠纪大陆末期灭绝事件的沉积学

对澳大利亚东部悉尼盆地的上二叠纪至下三叠纪沿海平原演替进行了露头和连续钻探研究。研究的目的是对二叠纪晚期（罗平纪），二叠纪末期灭绝间隔至三叠纪早期的大陆边缘背景下南部边缘古高原的古环境变化进行评估。这些盆地在二叠纪晚期受到爆炸性火山喷发的影响，在三叠纪早期受到较小程度的影响，因此可以在众多凝灰岩层位上以高分辨率确定年龄。古植物和放射性同位素数据表明，二叠纪末期灭绝发生在最上层煤层的顶部，在上覆泥岩层序内或在其后的河道砂岩体中，其二叠系-三叠纪界线，取决于侧向变化所引起的局部性。二叠纪晚期的沉积环境最初是在（五叠坪时期）浅海和三角洲形成的，但在二叠纪晚期，沿海平原平原河床环境逐渐形成了具有广泛成煤作用的泥潭，这反映在许多保存完好的煤层中。沿海平原河道沉积物的河道样式在地理位置上有所不同。然而，除了失去泥炭形成泥潭以外，在二叠纪末期的灭绝过程中没有发现沉积形式（粒度，沉积物构造或沉积物扩散方向）的任何长期长期变化（由古生物的更新确定） ）。尽管这些演习造成煤炭流失，但没有证据表明整个边界都将立即进行干旱化。相反，二叠纪末期的灭绝标志着长期渐进趋势的基础，朝着更好的排水冲积条件进入了早三叠世。确实，花卉更新之后立即在盆地沉积中心发生了洪水事件，此后，与早二叠纪灭绝之前活跃的河流系统相似。通过一套新的化学磨损同位素稀释热电离质谱U-Pb年龄限制了锆石晶粒的花艺灭绝年龄为252.54±0.08至252.10±0.06 Ma。另一个新的年龄表明，在基部三叠纪，河流沉积的恢复与二叠纪末期灭绝之前的相似（251.51±0.14 Ma之前）。在整个盆地之间，将含煤的前二叠纪灭绝与贫瘠的后二叠纪灭绝地层分开的表面特征不同。在盆地中心位置，接触范围从不连续的通道（河床体已被削减到顶煤的水平）到顶面的煤被泥岩和层状砂岩-粉砂岩相覆盖的接触点变化。然而，在盆地边缘位置，这种接触是明显的侵蚀不整合面，其上覆有较老的二叠纪岩石上的粗粒冲积相。没有证据表明接触到处都是不合格或不合格的。接触的范围从不连续的通道通道体已经降到顶煤的水平，到顶煤被泥岩和夹层砂岩-粉砂岩相覆盖的顶替煤变化。然而，在盆地边缘位置，这种接触是明显的侵蚀不整合面，其上覆有较老的二叠纪岩石上的粗粒冲积相。没有证据表明接触到处都是不合格或不合格的。接触的范围从不连续的通道通道体已经降到顶煤的水平，到顶煤被泥岩和夹层砂岩-粉砂岩相覆盖的顶替煤变化。然而，在盆地边缘位置，这种接触是明显的侵蚀不整合面，其上覆有较老的二叠纪岩石上的粗粒冲积相。没有证据表明接触到处都是不合格或不合格的。