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 sys tematically in a vertical sequence and reflect a semidiurnal tidal reg ime. Semimonthly, monthly, bimonthly, and annual cycles can be identif ied both visually in cores and by spectral frequency analysis. An aver age annual sedimentation of 22.5 cm yr(-1) occurs over a four-month me ltwater season and is confirmed by Pb-210 dating. These modern deepwat er tidal rhythmites can be used to verify interpretations made on anci ent rhythmites in the stratigraphic record, and they also provide a da ting tool to interpret high latitude successions for high-resolution c limate change.