云南西部中-晚泥盆世硅质岩相地层及其放射虫动物群

MIDDLE-LATE DEVONIAN STRATA OF CHERTY FACIES AND RADIOLARIAN FAUNAS FROM WEST YUNNAN

本文论述的中晚泥盆世放射虫产于滇西阿里、回库、南雅、里拉、太尔布、晒经坡和长育村等地的硅质岩中 ,包括 1 5属 1 8种 1 0相似种 8未定种 ,其中有 3新种。共发现 3个泥盆纪放射虫动物群 ,它们是 Eoalbaillella lilaensis动物群 ( D2 ) ;H elenifore laticlavium动物群 ( D13) ;H oloeciscusforemanae动物群 ( D23)。文章讨论了 3个问题 :1 Eoalbaillella lilaensis动物群的时代 ;2 H e-lenifore laticlavium的两个形态种 ;3 H oloeciscus foremanae动物群的丰度和分异度。我们认为Eoalbaillella lilaensis动物群的时代置于中泥盆世比早泥盆世更为合宜。H elenifore laticlavium的典型种是 1 983年 Nazarov和 Ormiston建立的 ,标本产自澳大利亚西部卡宁盆地 Gogo组 ,其特点是具有宽而薄的圆形板状环。另一类 H elenifore laticlavium是 1 988年 Ishiga采自澳大利亚东部新英格兰造山带 Hastings地块凝灰质粉砂岩中 ,具有窄而厚的椭圆形板状环。这两个形态种是明显不同的 ,前者称为 m. ( morphotype ) ,后者称为 m. ( morphotype ) ,后者可能是一个新种。在晚弗拉斯期和法门期间 ,在世界各地发生生物群的群体绝灭 ,这就是著名的F- F事件。这一事件造成了许多无脊椎动物 ,例如层孔虫、牙形类、菊石、竹?

Middle Late Devonian radiolarians (15 genera and 18 species, 10 species conformis, 8 species indeterminate, including 3 new species) are found in the Cherts of Ali, Huiku, Nanya, Lila, Tairbu, Saijingpo and Changyuchun of West Yunnan. Three Devonian radiolarian faunas have been identified. They are Eoalbaillella lilaensis fauna (D 2), Helenifore laticlavium fauna (D 1 3), Holoeciscus foremanae fauna (D 2 3). In this paper, we have discussed three problems: ① age of Eoalbaillella lilaensis fauna; ② two morphotypes of Helenifore laticlavium; ③ abundance and diversity of Holoeciscus foremanae fauna. We consider it reasonable to assign a Middle Devonian age than Lower Devonian to the Eoalbaillella lilaensis fauna. The type species Helenifore laticlavium as introduced by Nazarov and Ormiston (1983) from Gogo Formation in the Canning Basin, West Australia, is characterized by wide and thin circular platy ring. Another morphotype of Helenifore laticlavium as reported by Ishiga (1988) from tuffaceous siltstone in Hastings block, New England Fold Belt, east Australia, is characterized by a narrow and thick elliptical platy ring. We regard them as two morphotypes, the former as m.Ⅰ, and the latter as m.Ⅱ which may be a new species. Between the late Frasnian and Famennian, a mass biotic extinction occurred in many areas of the world. This is the famous F F event, which caused numerous invertebrate taxa such as stromatoporids, conodonts, ammonites, tentaculitids, ostracods, brachiopods, corals and trilobites to disappear or decline. About 60% of such taxa became extinct at the end of the Frasnian. However, in our sections from China the above mentioned Famennian radiolarian fauna has a much high total abundance and diversity than that of Frasnian from the same areas. This fact apparently indicates that the F F event only caused some of the reef dwelling biota which live in shallow water and part of the associated fauna and plankton to disappear. It does not appear to have affected the radiolarian fauna which live in deeper water realms. In contrast, during the Famennian the radiolarian fauna was well developed and diversified. It is possible that the F F mass biotic extinction have affected shallow water taxa to a greater extent than those which lived in deeper water.