Modern tidal rhythmites deposited in a deep-water estuary

The sedimentary record in Muir Inlet, a macrotidal fjord in Alaska, is dominated by cyclic silt-mud rhythmites. Couplet thicknesses vary systematically in a vertical sequence and reflect a semidiurnal tidal regime. Semimonthly, monthly, bimonthly, and annual cycles can be identified both visually in cores and by spectral frequency analysis. An average annual sedimentation of 22.5 cmyr^-1 occurs over a four-month meltwater season and is confirmed by ²¹⁰Pb dating. These modern deep-water tidal rhythmites can be used to verify interpretations made on ancient rhythmites in the stratigraphic record, and they also provide a dating tool to interpret high latitude successions for high-resolution climate change.