重庆綦江古剑山上侏罗统蓬莱镇组木化石群的发现及其科学意义

DISCOVERY OF LATE JURASSIC PETRIFIED WOOD FROM THE PENGLAIZHEN FORMATION OF QIJIANG,SOUTHERN CHONGQING AND ITS SCIENTIFIC SIGNIFICANCE

报道在重庆首次发现的晚侏罗世木化石群。化石产地为綦江区古剑山,地层层位为上侏罗统蓬莱镇组上段。化石经磨片后显微镜观察可确定为松柏类植物木材。该木化石群不仅是四川盆地发现的地层层位最高的木化石群,而且应是我国侏罗系层位最高的木化石群。该木化石群可能形成于湖边,反映晚侏罗世该地区可能盛行干旱—半干旱气候。结合之前马桑岩木化石研究可以推断四川盆地从中侏罗世到晚侏罗世虽然沉积相发生了变化,但气候并未发生根本性变化,一直保持干旱—半干旱气候。

Late Jurassic petrified wood is first reported in Chongqing.The buried site is Gujianshan,Qijiang district of Chongqing and the sediment containing the wood is the upper part of Upper Jurassic Penglaizhen Formation. The anatomy of wood shows that it is a conifer.The petrified wood is not only stratigraphically the youngest Jurassic fossil wood in Sichuan Basin,but should be the latest Jurassic petrified wood in age in China.These woods were probably formed near the margin of a lake,suggesting a arid-semiarid climate.It is judged that based on the study of Masangyan petrified wood,although the facies have altered in Sichuan Basin from Middle Jurassic to Late Jurassic,the climate didn＇t change fundamentally but remained arid-semiarid.