四川通江诺水河二叠纪-三叠纪界线地层牙形石的发现

川东北地区碳酸盐台地相区二叠系-三叠系界线划分一向存在分歧,因为在二叠系与三叠系之间发育一套40-100m的白云岩的时代缺乏古生物依据。针对这一问题,在四川通江诺水河剖面进行地层古生物研究,在剖面34层和41层的白云岩中首次分别发现了牙形石化石Hindeodus latidentatus、Hindeodus typicalis和Hindeousminutus,Hindeous parvus、Isarcicella cf.staeschei、Isarcicella isacica。根据当前国内外古生物学的研究成果,34层的牙形石属于晚二叠世长兴期的化石,41层中的牙形石为早三叠世印度期的化石。结合两者的之间的岩石地层特点,初步将通江诺水河剖面的二叠系-三叠系的界线置于38层与39层、即白云岩与灰岩之间。

DISCOVERY OF CONODONTS FROM THE PERMIAN-TRIASSIC BOUNDARY BEDS IN NUOSHUIHE SECTION OF TONGJIANG, SICHUAN

There are different views on the Permian-Triassic boundary of the carbonate platform facies of the Northeastern Sichuan area because the 40-100m thick dolostone developed between the Upper Permian Changxing Formation and the Lower Triassic Taye Formation lacks fossil evidence. Based on the stratigraphic and paleontologic studies of the Nuoshuihe section of Tojiang, Sichuan, fossil conodonts Hindeodus latidentatus, H. typicalis, H. minutus, H. parvus, Isarcicella cf. staeschei and I. isacica were found for the first time in the 34th and 41st dolostone beds respectively. According to the results of the stratigraphic studies in the world, the conodonts from the 34th Bed are of the Late Permian Changhsingian age and those from the 41st Bed are Early Triassic Induan in age. Combined with the lithostratigraphic features of both beds, the Permian-Triassic boundary of the Nuoshuihe section of Tojiang is tentatively placed between Beds 38 and 39, that is, between the dolostone and the limestone.