The presence of cyclicity is a recurring theme in strata of many types and ages, and deciphering possible forcing mechanisms has remained a challenge for stratigraphers. Utilizing a series of 1D flume experiments with constant fluid and sediment input, Muto et al. examine the nature and dynamics of cyclicity in deltaic deposits that arise solely through the dynamics of the delta itself. The experiments illustrate how periodic shifts in flow state (‘hydraulic jumps’) upstream of the topset-foreset break can lead to changes in amount and size of sediment deposited to the foreset, resulting in cyclic deposits even without variations in location of a feeder stream. They suggest several objective criteria that could be used in ancient strata to recognize comparable processes in the stratigraphic record.
The hydraulic autogenesis of distinct cyclicity in delta foreset bedding: flume experiments by Tetsuji Muto, Chizuru Yamagishi, Tomohiro Sekiguchi, Miwa Yokokawa and Gary Parker