论“三叠纪初”的一次海侵

On the“Basal Iriassic”Transgression in China

论述二叠纪末生物大灭绝事件后的一次全球性快速海侵。以往认为该海侵发生在三叠系底部,但新的材料表明属二叠纪末期。在国际标准层型剖面浙江长兴煤山地区海侵高潮(海平面快速上升)见于26层黑色页岩,层内含菊石Hypophiceras组合,双壳类Claraia? baoqingensis和二叠纪牙形刺;在浙江黄芝山剖面海侵见于大灭绝层之上的Claraia cf.bioni层,此层也可与克什米尔Guryul Ravine剖面E_1层(Claraia bioni带)对比;在北极区,海侵层相当于Otoceras Concavum 层。还讨论了康滇古陆东缘和华北古陆南缘此次海侵的影响,这些古陆边缘地区陆相沉积(“卡以头段”和石千峰群)中夹的海相层不是三叠纪,而是二叠纪。

A global rapid transgression after the end-Permian mass extinction is herein discussed. Previously the transgression was considered to occur in the basal Triassic , however, according to the new data it is recognized to happen in the latest Permian. At Meishan section, Changxing, the global stratotype of the Permian-Triassic boundary, the black shale of the bed 26 represents a transgression caused by the rapid sea-level rise. The bed 26 just overlies the mass extinction event bed (bed 25) and yields ammonite Hypophiceras assemblage, bivalve Claraia? baoqingensis and Permian conodonts. At Huangzhishan section of Zhejiang the transgression is defined in the bed of Claraia cf. bioni zone, which also directly overlies the mass extinction bed. In Kashmir, the bed E1 (Claraia bioni zone) of Guryul Ravine section is correlated with the Claraia cf. bioni bed of Huangzhishan section based on bivalves. In the Arctic region the bed of Otoceras concavum zone is most probably corresponding to the ammonite Hypophiceras zone of Meishan. These horizons are regarded as the representative affected by the transgressioa The influence of the transgression is especially remarkable in the marginal areas of some old-lands in China. Marine faunas have been found from the intercalations of the Permian-Triassic boundary beds in the continental sequences, such as in the 'Kayitou beds' in southwest China and in the Shiqianfeng Group in southern part of the North China Continent. The marine intercalations are not of the early Triassic as previously regarded but latest Permian in age according to the fannal correlation.