Seasonal controls on the development and character of inclined heterolithic stratification in a tide-influenced, fluvially dominated channel, Fraser River, Canada

Inclined heterolithic stratification (IHS) is developed on an in-channel bar in the tide-influenced, fluvially dominated reach of the Fraser River, British Columbia, Canada. The vertical bar succession is characterized by a fining-upward profile with an increase in mud-bed thickness and content, from the shallow subtidal to the upper intertidal zone. There is an increase in the number of mud beds as well as their lateral continuity from the upstream to the downstream side of the bar. Sediment deposition is seasonally controlled, wherein sand deposition occurs during periods of high discharge (snowmelt-induced freshet), and mud is deposited during low discharge (ambient flow conditions). The seasonal cyclicity in sediment deposition is also observed in the ichnological character of the IHS. Mud beds are typically moderately to pervasively bioturbated (Bioturbation Index (BI) 2-5), and sand beds exhibit little to no bioturbation (BI 0-2).