There are dozens of Microbially Induced Sedimentary Structures (MISS) in the red sandstone of Lower Triassic Liujiagou Formation in Yiyang area,Henan Province,including wrinkle structures,desiccation cracks and mat chips.According to the morphology evolution of MISS,it is divided into 4 different fabrics,namely wrinkle structures fabric,petees fabric,mini desiccation cracks fabric and large desiccation cracks fabric from bottom to top.They reflect the nuance palaeoenvironment and palaeoclimate:(1)wrinkle structures fabric reflects the warm moist suboxic sedimentary environment;(2) petees fabric reflects the warm moist oxygen-enriched sedimentary environment;(3)mini desiccation cracks fabric reflects the warm semi-arid suboxic sedimentary environment;(4) large desiccation cracks fabric reflects the hot semi-arid oxygen-enriched sedimentary environment.The geochemical information also indicates that the palaeoenvironment in the Early Triassic in Yiyang area changed from warm and moist suboxic to hot and semi-arid oxygen-enriched.In conclusion,the development and evolution of MISS in Yiyang area were a response to subtle changes of continental palaeoenvironment in the Early Triassic.%河南宜阳地区下三叠统刘家沟组红色砂岩中发育数十种微生物成因沉积构造(MISS),如皱饰构造、脱水裂痕、微生物席碎片等.按照其形态特征的演化可分为4个不同的组合,由下往上依次为皱饰构造组合、隆脊构造组合、小型脱水裂痕组合和大型脱水裂痕组合,其分别反映了不同的古环境与古气候:(1)皱饰构造组合反映了弱氧化的温暖、潮湿环境;(2)隆脊构造组合反映了富氧的温暖、潮湿环境;(3)小型脱水裂痕组合反映了弱氧化的温暖、半干旱环境;(4)大型脱水裂痕组合反映了富氧的炎热、半干旱—干旱环境.依据研究区的地球化学特征和岩石学特征,认为早三叠世宜阳地区的古环境由湿润、温暖、弱氧化向炎热、半干旱、富氧转变.两者比较表明,宜阳地区微生物成因沉积构造的发育与演化是对早三叠世陆相古环境细微变化的联动响应.
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