内蒙古西乌旗地区早二叠世皱纹珊瑚化石组合及其地质意义

EARLY PERMIAN RUGOSE CORAL ASSEMBLAGE AND ITS GEOLOGICAL SIGNIFICANCES IN XIWUQI OF INNER MONGOLIA

基于生物地层学的研究,详细描述了内蒙古西乌旗地区早二叠世的皱纹珊瑚,建立了7个新种,划分了2个珊瑚组合:Lytvolasma-Cyathocarinia组合和Lytvolasma-Caninophyllum-Pseu dopolythecalis组合。前一组合主要为小型单体,无鳞板,隔壁加厚,外壁厚,一些分子具典型中柱的珊瑚类型;后一珊瑚化石组合表现为群体珊瑚和单体珊瑚混生融合。本区珊瑚动物群在早二叠世阿木山期混生类型为超覆型,在早二叠世包特格期混生类型为混合型。这种混生现象与石炭纪末-二叠纪初全球气候变冷事件相吻合,并反映了古气候暖-冷-暖的变化。同时也佐证了古亚洲洋洋壳的性质在稍早的时期已经发生了本质变化。此时海盆性状应该是岛弧浅海,而不是大洋。

Based on biostratigraphical discussion, the paper gives a detailed description to the rugose fauna of the early-Permian, including 7 new species. Two coral assemblages are divided:Lytvolasma-Cyathocarinia and Lytvolasma-Caninophyllum-Pseudopolythecalis.The first assemblage is mainly made up of minitype, monocase.Septa and their ektexines are all thickened; the second assemblage exhibits mixed fauna including colony and monocase coral. The paper also puts forward the overlapped type and mixed type of the mixed fauna in the area, and points out that the appearance of the mixed fauna in this area is consistent with the general decreased temperature from late Carboniferous to early Permian, and also reflects climate changes from warm to cold, then to warm again.The study also reveals that the nature of the Paleo-Asian oceanic crust had essentially changed a little before the early Permian: it was shallow sea in an arch-island environment, not an open sea.