Barite from the Top Ediacaran Doushantuo Formation in the East Yangtze Gorges Area and Its Geological Implications
峡东伊迪卡拉纪陡山沱组顶部重晶石 特征与地质意义研究

Barite was found for the first time in the top part of the Ediacaran Doushantuo Formation in the Eastern Yangtze Gorges area. Macroscopic and microscopic sedimentary, mineralogical and geochemical features of the barite show an early diagenetic origin. Studies suggest that there occurred sea-level fall during the middle and the terminal Doushantuo depositional period, which caused slow depositional rates or pauses (or the major breaks) in the sedimentation and oxidation of buried organic materials and the input of mass terrigenous sediments. A turn-over of the deepwater environment related to the sea-level fall resulted in biotic extinction and radiation in early Ediacaran. Field observations in the study area revealed the sedimentary evidence of starvation sedimentation, depositional pause/break (or unconformity) within the bottom, interior and the top of the Doushantuo Formation, which challenges previous geochronology and biotic evolution in the Ediacaran Doushantuo Formation and is useful to decoding the Neoproterozoic Ediacaran geological history.