Hummocky cross-stratification and its formation : Approaches from flume experiments and field observation

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Hummocky cross-stratification(HCS)is a primary sedimentary structure and is observed in ancient shallow marine deposits of various geologic ages in many world localities. HCS is interpreted as a storm deposits formed by waves or combined oscillatory and unidirectional flows. The structure continues to be focus of ongoing debate regarding its mode of formation and paleohydrodynamic interpretation. In this research we try to clarify the depositional processes and formation of HCS based on two approaches, laboratory flume experiments and field observations.Following new achievements can be obtained and published the report of "Hummocky cross-stratification and its formation".1)HCS is formed under the two conditions, oscillatory and unidirectional flows.2)HCS has a wave-length from several cm to several tens m in natural condition.3)HCS is composed of a wide range in grain-size of coarse silt to granule.4)Typical HCS structure with hummocky and swaley forms was constructed under the condition of plane-bed antidune in upper flow-regime.5)Oscillatory HCS may be formed in a wide range of ripple, plane-bed and antidune fields.6)Discrete oscillatory HCS storm bed was formed during combined flows and following waning oscillatory flow conditions.