山西的陆相三叠系石千峰群和二马营群

<正> 山西的三叠纪地层1882年李希霍芬(F.V.Richthofen)即有提及,当时通称煤系以上砂岩系;1907年维理士(B.Willis)再把煤系以上砂岩系改称为山西系。将三叠系单独提出,而又研究较为详细者,当自那琳(E.Norin)始。1922,年那琳首先把太原石千峰山、关头村一带,石盒子系以上的巧克力色、紫红色砂岩、泥灰岩层定名为石千峰系(实测厚度约400米)。它包括(1)银杏植物带,(2)石膏泥灰岩带及(3)砂岩带三部分,前两者划为二叠三叠纪,后者归属三叠纪。1924年那琳复谈到:银杏植物带与其下的大羽羊齿带均为温热气侯下沉积,与干燥气侯下的石千峰系堆积显然不同,依沉积环境和室内分析结果,将银杏植物带下移归入上石盒子系。

CONTINENTAL TRIASSIC LITHOSTRATIGRAPHIC UNITS IN SHANXI PROVINCE--SHIQIANFENG GROUP AND ERMAYING GROUP

At the All China Stratigraphic Congress of 1959, the Shanxi Stratigraphic Team of Academia Sinica revised the Shiqianfeng Group, established the Ermaying Group, and gave opinions on their age attributions. It has helped to stydy the other correlated strata ever since. Unfortunately the original report of the Team was not formally published, causing much inconvenience in quoting and consulting.The representative section of the "Shiqianfeng series" named by E. Norin in 1922, is not perfectly exposed. Now the complemented bnd revised Shiqianfeng Group is divided into Sunjiagou formation, Liujiagou formation and Heshanggou formation in an ascending order. They are conformable with each other as well as with the underlying and overlying series. The Ermaying Group makes up the break between the Shiqianfeng and Yanchang Groups which are disconformably overlain by the Jurassic series. Therefore, it links the whole sequence of the continental Triassic succession.The Shiqianfeng Group consists of a purplish red series, including sandstones, mudstones, siltstones and lenticular marlstones which are sediments of desert, shallow salt lakes and easily dried inland rivers under an arid climate condition. And the Ermaying Group is made up of yellowish pink and purplish red with yellowish green color, containing sandstones, mudstones and siltstones, occasionally with some marly beds. Compared with the Shiqianfeng Group it contains a larger amount of mudstones, feldspars in sandstone and fossils and has better sorting grains and a less dry climate.The ages of the Ermaying and the Shiqianfeng Groups were ascribed by the Shanxi Stratigraphic Team to the Middle Triassic and the Lower Triassic respectively. This opinion was confirmed by the discoveries and studies of various kind of fossils (reptiles, amphibians, pisces, ostracods, plants, charoph-yts and spore-pollens). And the Sunjiagou formation ascribed to the early Early Triassic was supported by the correlation with the fossiliferous marine Lower Triassic beds in the neighboring region. But the fossil evidence in. this formation is still insufficient.Since the names of the Ermaying and Shiqianfeng Groups as well as their subdivisions were properly established, their original definitions could not be changed even though there are some different ideas on the age attribution. It is also improper to use the same name for those units of different lithologic character and lithofacies but with corresponding stratigraphic horizon and age.