江苏泰县五通组观山段胞石Grahnichitina pilosa的发现及其意义

根据江苏泰县Ｎ－４井五通组观山段顶部的胞石Ｇｒａｈｎｉｃｈｉｔｉｎａ ｐｉｌｏｓａ的发现，确定观山段的时代为中泥盆世吉维特期。据此认为：擂鼓台段的两层暗色泥岩，应分别对比为南洞页岩、长顺页岩；中泥盆世大海侵时，华南海沿苏皖河经皖南、苏南入侵苏北。对Ｇｒａｈｎｉｃｈｉｔｉｎａ ｐｉｌｏｓａ进行描记和讨论。

DISCOVERY OF GRAHNICHITINA PILOSA (CHITINOZOA) FROM THE GUANSHAN MEMBER OF THE WUTUNG FORMATION IN TAIXIAN OF JIANGSU WITH DISCUSSION ON ITS SIGNIFICANCE

There have been three opinions concernig the age of the lower division, the Guanshan Member of the Wutung Formation since the paper by Ting (1919), who then called it the Wutungshan Quatzite, namely 1) Givetian to early Frasnian (Feng, 1987), 2) Frasnian (Li, 1963, 1965; Cai and Li, 1982; Li et al. , 1984), and 3) Strunian (Cai et al. , 1998). However, no reliable age indicators were found within the member. At a depth of 2 358 m of Well N 4 in Taixian of N. Jiangsu gray argillaceous siltstone sandwiched within redbeds yields the chitinozoan species Grahnichitina pilosa (Collinson et Scott, 1958). This species was ever widespread in the world, including U.S.A. (Collinson and Scott, 1958, Dunn, 1959, Morgan,1967, Urban ,1972), Brazil (Boekel, 1968), Ghana (Anan Yorke 1974), Libya (Paris et al. , 1985, Streel et al., 1988), Argentina (Volkheimer et al. , 1988), Algeria (Boumendjel, 1987), and China. It was recorded from the Solon and Lower Rapid members of the Cadar Valley Formation of Illinois and Iowa (Collinson and Scott, 1958, Dunn, 1959, Urban, 1972) where the conodonts are representative of the Middle varcus to hermanni cristatus zones of Givetian age. Therefore, the discovery of G. pilosa confirms a Givetian age for the subsurface Guanshan Member.