摘要:
通过野外剖面实测和镜下薄片观察,笔者发现米仓山南缘志留系罗惹坪组顶部发育多套风暴沉积,典型的风暴沉积构造,包括侵蚀构造、砾屑结构、粒序层理等发育,岩性主要为灰绿色泥页岩、浅灰色或灰色微晶灰岩和生屑微晶灰岩。该区风暴岩发育3种风暴沉积序列,且具有一定的继承性,为远源型,沉积环境为浅水陆棚;风暴岩的发现解释了该区罗惹坪组生物灰岩透镜体的成因,为区域地层等时对比提供了新的标尺,对于研究区古地理、古气候以及古扬子海盆演化提供了依据。研究表明南江地区在志留系罗惹坪组晚期沉积时,曾处于风暴频发低纬度地区。
Abstract:
Based on the outcrop measurement and indoor identification to the Luoreping Formation in southern Micangshan,it has been found that there are many tempestites in the Luoreping Formation of Middle Silurian in southern Micangshan, developing ditch structures, gravel-sized grain structures and graded bedding. The main lithology are mud shale, micrite and bioclastic limestone. There are three kinds of sedimentary sequences in the tempestites which show a certain inheritance. This is distal storm deposit and shallow shelf sedimentary environment. The discovery of storm-induced rocks in the area has explained the causes of the biological limestone lenticle, providing new standard for regional stratigraphic isochronous correlation and basis for the evolution of ancient geography, climate and Yangtze basin development. This study indicates that the later Luoreping Group sedimentation period in Nanjiang area has been in low latitude areas where storms frequently take place.
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