Morphological Characteristics and Genesis of Molar-Tooth Structures Of Gaoyuzhuang Formation,Jixian Area

【摘要】：Molar-tooth(MT) is an enigmatic carbonate fabric composed of variously shaped cracks and voids filled with a characteristically uniform,equant microspar. MT widely distribute in Mesoproterozoic and early Neoproterozoic strata, where void-filling microspar and preserved carbonate. Detailed petrographic examination of MT structures from the esoproterozoic Gaoyuzhuang formation, Jixian,permits interpretation of the microscale relationship between crack morphology and lithologic,and potentially rheologic, variability of the surrounding substrate by tracing the distribution of petrographically distinctive MT microspar. That examination suggests that grain size, substrate lithology,and substrate cohesion all play critical roles in the development of MT. By contrast,the presence of a wide range of MT morphologies within petrographically homogeneous substrates,and an apparent relationship between crack diameter and sinuosity,suggest that the void-forming process itself also effected the final morphology of MT. On this basis,we discuss the significance of MT in the analysis of ancient marine environment.