吉林二道沟组的床板珊瑚型珊瑚

TABULATOMORPHIC CORALS FROM THE ERHTAOKOU FORMATION OF JILIN PROVINCE

二道沟组床板珊瑚型瑚珊群含有常见于欧亚地区下泥盆统的一些重要属种 ,如Favositesmultiplicatus,Squameofavositesgurjevskiensis和Pachyfavositesrariporosus,同时未发现常见于上志留统的分子。据此 ,二道沟组珊瑚群时代应是早泥盆世而不是过去所谓的晚志留世。二道沟组与南天山的阿尔皮什麦布拉克组可能相当 ,同属于下泥盆统下部。描述床板珊瑚和日射珊瑚 8属 1 6种 ,其中 4新种 :Pachyfavositesimpurussp .nov .,Squameo favositesvescussp .nov .,Paraheliolitesobvellatussp .nov .,Pseudoplasmonorayaokengensissp .nov .;2新亚种 :Favositespolarissimilussubsp .nov .,Mesofavositesjilinensisyongjiensissubsp .

For dozens of years, the faunas from the Ertaokou Formation of Jilin have been studied successively by some palaeontologists, such as Yabe H. and Eguchi M. (1944, 1945);Yu Jian zhang and Zhang Wan tong (1951); Mu En zhi (1962); Guo Hong jun (1962); Yu Chan ming and others (1963); Liu Fa and Huang Zhu xi (1997) and others. Their works provided usefully paleeontologic and stratigraphic data about this formation. In 1976 and 1980, Tchi Yong yi worked on some tabulate and heliolitid corals from the Erhtaokou Formation but he assigned the coral bearing formation to Upper Silurian. In 1986, Liao Wei hua and Zheng Chun zi studied some rugosan corals from the same formation and they pointed out that these rugosan corals from this formation were peculiar to early Early Devonian. The corals described here were collected from the Erhtaokou Formation at Yaokeng (Key locality), western Jilin City by Liao Wei hua and Zheng Chun zi in 1984 and they contain both tabulate and heliolid corals (including 8 genus, 16 species) and are listed as follows (cf. Table 1): Favosites multiplicatus Yanet, F. polaris similus subsp. nov., Mesofavosites jilinensis yongjiensis subsp. nov., Pachyfavosites rariporsus Dubatolov, P. impurus sp. nov. , Squameofavosites gurjevskiensis Mironova, S .aff. jilingensis Tchi, S. vescus sp. nov., S. cf. socialisformis Dubatolov, S. sp., Striatopora macroseptata Tchi, Parastriatopora sp., Paraheliolites jilinensis (Tchi, 1980), P . obvellatus sp. nov., Pseudoplasmopora yaokengensis sp. nov., P . aff. aseptata (Regnell, 1941). In the above stated corals, Favosites multiplicatus had been found from Early Devonian strata of Kuznetsk Basin and eastern Ural. In the features of corallites and tabulae, Favosites polaris similus is similar to Favosites polaris known from Early Devonian of western Ural, Kolyma and Xinjiang. Squameofavosites gurjevskiensis had been reported from the Early Devonian strata of Ural and from the Tom Chumysh bed of early Early Devonian of Kuznetsk Basin. Pachyfavosites rariporosus had been also known from the late Early Devonian strata of Kuznetsk Basin. The character of Pachyfavosites impurus may be comparable to Pachyfavosites hamatus occurring in the Monkelu Formation of late Early Devonian strata, nothern Xinjiang. Among the heliolitid corals, Pseudoplasmopora aff. aseptata bears a close resemblance to Pseudoplasmopora aseptata from the Arpishmebulaq Formation of eastern Xinjiang by some features about corallites and coenenchymal tubules but differs from the latter by larger corallites. It is well known that the Arpishmebulaq Formation had been assigned to Upper Silurian (Wang Bao yu, 1980) but it has been assigned to lower Lower Devonian now (Deng Zhan qiu, 1999). Thus, the Erhtaokou Formation may be equivalent to the Arpishmebulaq Formation in geologic age. As stated above, the tabulate and heliolitid corals of the Erhtaokou Formation have close relationship with those of Early Devonian, in other words, the geologic age of the coral bearing formation is not Late Silurian but early Early Devonian, as concluded by Liao and Zheng.TABULATOMOFordozensofyears,thefa