老挝北部南莫溪结合带放射虫化石组合及其构造古地理意义

RADIOLARIAN BIOSTRATIGRAPHY AND TECTONIC PALEOGEOGRAPHIC SIGNIFICANCE IN NAMHI JUNCTION BELT, NORTHERN LAOS

南莫溪结合带位于老挝北部万象地区,是黎府缝合带的重要组成部分。本文结合区域地质调查开展剖面工作,采集了硅质岩样品进行放射虫化石鉴定,共鉴定出放射虫9属29种,包括中–晚泥盆世放射虫Radiobisphaera rozanovi,Trilonchevetusta和晚泥盆世放射虫Heleniforerobustum,以及晚泥盆世放射虫属种Triloncheminax (Hinde)等。建立了中–晚泥盆世Radiobisphaera rozanovi-Stigmosphaerostylus pusilla组合带、晚泥盆世Trilonche minax延限带和早石炭世Albaillella paradoxa-Archocyrtium riedeli组合带,探讨了南莫溪结合带的构造古地理特征。该成果进一步丰富了老挝北部黎府缝合带的古生物化石组成特征,对研究南莫溪结合带的演化历史具有重要的指示意义。

The Namhi junction belt, located in the Vientiane area of the northern Laos, is an important part of Loei Suture Zone. Samples were collected in the area of Namhi and 28 species in 9 genera of radiolarian were recognized,including the index fossils Radiobisphaera rozanovi, Trilonche Vetusta, Helenifore robustum and Trilonche minax.Three radiolarian assemblage zones were recognized, including Radiobisphaera rozanovi-Stigmosphaerostylus pusilla, Trilonche minax and Albaillella paradoxa-Archocyrtium riedeli, indicating the age of the expansion of the Namhi ocean is from the Middle Devonian to the Early Carboniferous. The tectonic paleogeographic characteristics of the Nahmi junction belt is also discussed. This study enriches and perfects the paleontological fossil composition characteristics of Loei suture zone in the northern Laos, which is of great significance to the study of the evolution history of Nahmi junction belt.