The Growth Patterns and Mechanisms of Mud Cracks at Different Diagenetic Stages and Its Geological Significance

Key words: 
• mud crack /
• characteristic /
• growth pattern /
• geological model /
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Abstract: This paper discusses the growth stages, spatial structures, quantitative fitting relationships among various parameters, growth patterns and influencing factors of mud cracks by field survey, core observation and SEM analysis. The study shows that: (1) Mud crack growth can go through three stages, i.e. syndiagenetic stage, burial diagenetic stage (including early diagenetic stage, middlelate diagenetic stage) and epidiagenetic stage in turn. The number of mud cracks in different stages is represented as Σ syndiagenesis > Σ epidiagenesis > Σ burial diagenesis. (2) Mud crack growth has three models, such as unilateral growth model including linear growth pattern, curvilineal growth pattern and bifurcation growth pattern, multilateral growth model including intersectional growth pattern, join growth pattern and dispersed growth pattern, and mixed growth model including the combination of any patterns listed above. (3) Modern mud crack growth usually undergoes four stages, among which, sand beds in sandmud rhythmic strata can play a lubricative role on crack growth, and provide enough sandy sediments for filling cracks. (4) Mud crack growth usually produces bifurcation and bifurcation angle is mostly 120,  then 90, mainly related to sediment heterogeneity and released energy. (5) Factors affecting mud crack growth cover many aspects, that is to say, clay content and salinity can control the number of mud cracks in different areas, terrain can control mud crack morphology, and different sedimentary cycle can control the growth patterns and filling models of mud cracks. (6) Structure fractures can contribute to the growth and preservation of mud cracks, and they affect each other at different diagenetic stages. 