The Sedimentology, Stratigraphy, and Preservation of Intertidal Deposits in the Minas Basin System, Bay of Fundy

Intertidal sediments of the Minas Basin, a macrotidal estuary at the head of the Bay of Fundy, can be subdivided into six major facies: tidal marsh, beach, mudflat, sandflat, channel lag, and sandbar. Each is characterized by its grain size distributions, sedimentary structures, and biological communities. These sedimentary facies occur in three types of high-to-low tide zonation, depending on the local sediment source and wave and current energy. The Holocene stratigraphy presently preserved in the upper intertidal zone of Minas Basin consists of a relatively thin (on the average less than 1-2 m) wedge of sediment overlying bedrock. Only in a few sheltered locations, where deposits accumulate to several meters, is the marine transgressive stratigraphy well represented. The hypothetical progradational or marine regressive stratigraphy of upper intertidal sediments would probably resemble, from top to bottom, the high to low tide sequence of facies occurring today on sheltered tidal flats. Lebensspuren would provide the most reliable representation of the ecology of intertidal sediments in Minas Basin. They are useful in delineating communities as well as being sensitive indicators of sediment deposition. Microfauna are too easily transported or reworked. Field data from relict intertidal deposits (dated 2300-3400 yr. B.P.) indicate calcareous organism hard parts would probably provide a biased fossilized record. Indirect evidence is discussed, which suggest in situ dissolution of shells in certain intertidal sediments.