美国艾奥瓦州文尼希克Lagerstatte及其沉积环境  

The Winneshiek Lagersttte,Iowa,USA and Its Depositional Environments

作　　者：刘怀宝 R. M. McKay B. J. Witzke D. E. G. Briggs 

机构地区：[1]Iowa Department of Natural Resources, Geological and Water Survey, 109 Trowbridge Hall, Iowa City, IA 52242, USA [2]Department of Geology and Geophysics and Yale Peabody Museum of Natural History, Yale University, P.O. Box 208109, New Haven, CT 06520, USA

出　　处：《高校地质学报》2009年第3期285-295,共11页Geological Journal of China Universities

摘　　要：Lagersttte是指保存丰富或精美化石、因而具有特殊研究价值的化石层。这类地层所含的化石常具有经矿化的生物软体甚至未变实体,从而为古生物的分类学、组织学、形态学、解剖学、生态学、埋藏学等研究提供了极其难得的材料。近年来发现于美国艾奥瓦州的文尼希克化石层,以其特异保存的多门类不常见化石分子为特征,成为目前仅知的中奥陶世Lagersttte。这一生物群的发现不仅填补了化石记录中的一些空白,也为中奥陶世的生物辐射事件研究领域打开了一个在赤道附近非正常海洋环境中生存的生物群面貌窗口。而且,其中所含的不同类别矿化生物残留,在有机物的分解、置换以及生物成岩作用等研究中具有重要意义。初步研究表明,文尼希克生物群的生活环境与化石保存,可能与陨石撞击事件有关,从而为奥陶纪生物辐射事件的起因可能与太空星体爆裂有关的理论研究,提供了新的验证材料。Fossil Lagersttten are deposits containing abundant and/or exceptionally preserved fossils,often including soft-bodied tissue.Of these,Konservat-Lagersttten are especially important because they provide not only a much more complete record of the diversity and paleoecology of ancient communities,but also more detailed information on the taxonomy and anatomy of the biota compared to the normal shelly fossil record.However,Konservat-Lagersttten are rare because they require exceptional physical and chemical depositional conditions.Environmental conditions during the Cambrian may have been more favorable for the preservation of soft-bodied organisms than later in the Paleozoic,and such Lagersttten provide evidence of biodiversity changes during the Cambrian explosion.Although the Ordovician Radiation or Great Ordovician Biodiversification Event（GOBE） has been well documented,this is based mainly on the shelly fossil record because soft-bodied organisms are poorly represented during the 45 million years of the Ordovician.Only three Lagersttten,Beecher＇s Trilobite Bed in upper New York State,the Soom Shale in South Africa,and the recently recognized biota in Manitoba,Canada,approach the extent of soft-tissue preservation in Cambrian deposits.All the three Lagersttten are of Late Ordovicianage. The Winneshiek fauna was discovered recently near Decorah,northeast Iowa,USA（Fig.1） .It is preserved in a new stratigraphic unit which consists of greenish-brown to dark-gray sandy laminated shale with abundant organic carbon and pyrite（Fig.2） .The new fauna contains both invertebrate and vertebrate fossils;current recovery includes eurypterids and other chelicerates,phyllocarid crustaceans,ostracods,linguloid brachiopods,mollusks,isolated conodont elements and bedding plane assemblages,skeletal elements of jawless fish,various indeterminate fossil forms,and bromalites and other trace fossils（Fig.3） .Most of these fossils are extraordinarily preserved,some with soft tissues or body impressions

关 键 词：特异埋藏 文尼希克生物群 圣.彼得砂岩 奥陶纪生物辐射 星体爆裂事件 陨石坑 美国艾奥瓦州 

分 类 号：Q913.2[天文地球—古生物学与地层学]