Journal of Sedimentary Research, 2006, v. 76, 978–995 Research Article DOI: 10.2110/jsr.2006.086 STRATIGRAPHY, SEDIMENTARY STRUCTURES, AND TEXTURES OF THE LATE NEOPROTEROZOIC DOUSHANTUO CAP CARBONATE IN SOUTH CHINA 1 2 3 4 4 GANQING JIANG, MARTIN J. KENNEDY, NICHOLAS CHRISTIE-BLICK, HUAICHUN WU, AND SHIHONG ZHANG 1Department of Geoscience, University of Nevada, Las Vegas, Nevada 89154-4010, U.S.A. , 2Department of Earth Sciences, University of California, Riverside, California 92521, U.S.A. , 3Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964-8000, U.S.A. 4School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China e-mail:
[email protected] ABSTRACT: The 3- to 5-m-thick Doushantuo cap carbonate in south China overlies the glaciogenic Nantuo Formation (ca. 635 Ma) and consists of laterally persistent, thinly laminated and normally graded dolomite and limestone indicative of relatively deep-water deposition, most likely below storm wave base. The basal portion of this carbonate contains a distinctive suite of closely associated tepee-like structures, stromatactis-like cavities, layer-parallel sheet cracks, and cemented breccias. The cores of tepees are composed of stacked cavities lined by cements and brecciated host dolomicrite. Onlap by laminated sediment indicates synsedimentary disruption of bedding that resulted in a positive seafloor expression. Cavities and sheet cracks contain internal sediments, and they are lined by originally aragonitic isopachous botryoidal cements with acicular radiating needles, now replaced by dolomite and silica. Pyrite and barite are common, and calcite is locally retained as a primary mineral.