Biological and Mineral Components of an Ancient Stromatolite: Gaoyuzhuang Formation, Mesoproterozoic of China
Lee Seong-Joo, Stjepko Golubic, 2000. "Biological and Mineral Components of an Ancient Stromatolite: Gaoyuzhuang Formation, Mesoproterozoic of China", Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World, John P. Grotzinger, Noel P. James
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Silicified Mesoproterozoic stratifom stromatolites of the ca. 1400 Ma Gaoyuzhuang Formation in northern China contain microbial fossils preserved in a synsedimentary context rich in carbonate precipitates. Benthic microbial fossils were preserved by early silicification in growth position. Carbonate precipitation took place concurrently with accumulation of fine-grained sediment, and within the time frame of microbial growth and movements. The kinetics of the sedimentary process is thus calibrated by the rates commensurate with the behavioral responses of ancient microorganisms. Since both mineral and organic components of these ancient stromatolites remained preserved, their mutual relationship could be assessed. Extensive microbial growth, mat formation, and accumulation of organic matter required time and indicated the extent of sedimentary pauses. Carbonate precipitation took place in the absence of microorganisms, inhibiting their successful colonization and growth. The interplay between biological and abiotic forces in the formation of Gaoyuzhuang stromatolite permits an approximation of actual rate of carbonate precipitation, which often exceeds that of microbial settlement and growth. The relationship between microbial growth and precipitates in stromatolites under study is generally antagonistic, indicating limited involvement of microbial activities in the precipitation process.
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Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World - Precambrian carbonates are usually regarded at the simple cousins of the sedimentary realm, composed of stromatolites and dolostones, texturally not challenging and commonly altered beyond recognition by the vagaries of time, diagenesis and metamorphism. However, these carbonates that formed deep in time are commonly exquisitely preserved and contain within them a record of the evolving young earth. SEPM Special Publication 67 explores these aspects. Resulting from a 1997 SEPM/CSPG symposium entitled? Precambrian Carbonates,? these 18 papers demonstrate the importance of understanding these rocks, since within them is contained a record of the early ocean, atmosphere, and biosphere.