贵阳花溪地区下三叠统大冶组遗迹化石及沉积环境分析

Trace Fossils and Their Depositional Environments of the Early Triassic Daye Formation in Huaxi Area,Guiyang

贵阳花溪下三叠统大冶组中富产遗迹化石,产出18个遗迹属:Beaconichnus,Circulichnis,Cosmorhaphe,Dendro-haphe,Glockerichnus,Gyrochorte,Gordia,Maeandropolydora,Micatuba,Mammillichnis,Megagrapton,Planolites,Palaeophycus,Phycodes,Phycosiphon,Rhizocorallium,Thalassinoides和Undichna。自下而上可识别出三个遗迹组构,分别为Phycodes、Phycosiphon-Mammillichnis和Thalassinoidess遗迹组构。根据遗迹化石各属种分布,大冶组自下而上出现四个遗迹相:Cruziana遗迹相、Zoophycoss遗迹相、Nereites遗迹相和Cruziana遗迹相。结合遗迹组构,对大冶组的沉积环境进行了讨论,Phycodes组构属于Cruziana相,指示浅水环境;Phycosiphon-Mammillichnis组构属于Zoophycos遗迹相—Nereites遗迹相,代表台缘下斜坡半深海低能环境;Thalassinoides组构属于Cruziana相,指示早三叠世印度期末的浅水高能环境。

There are lots of trace fossils preserved in the Lower Triassic Daye Formation in Huaxi area of Guiyang. Eighteen ichnogenera have been found in this region： Beaconichnus, Circulichnis, Cosmorhaphe, Dendrohaphe, Glockerichnus, C, yrochorte, Gordia, Maeandropolydora, Micatuba, Mammillichnis, Megagrapton, Planolites, Palaeophycus, Phycodes, Phycosiphon, Rhizocorallium, Thalassinoides and Undichna. Some trace fossils have been found for the first time, and they are Circulichnis, Glockerichnus, Maeandropolydora. Three iehnofabrics have been found in Daye Formation, including： Phycodes iehnofabric, Phycosiphon-Mammillichnis ichnofabric and Thalassinoicles ichnofabric. Based on the relative abundance of the ichnogenera in Daye Formation, four ichnofacies have been distinguished： Cruziana ichnofacies of the first and third member, Zoophycos ichnofacies and Nereites ichnofacies of the second member. Combined with the analysis on ichnofabrics, the ichnofacies research shows that the study area located the front line of carbonate platform slope margin, and reflected less energy and anoxia environment. Phycodes ichnofabric and Thalassinoides ichnofabric can be assigned to Cruziana ichnofaeies, Phycosiphon-Mammillichnis iehnofabric can be assigned to Zoophycos ichnofacies-Nereites ichnofacies.