Abstract: Sediment Dynamics in Macrotidal Avon River Estuary, Nova Scotia

Joseph J. Lambiase

The hydraulic regime of the macrotidal Avon River estuary, part of the Bay of Fundy system, is dominated by a large tidal range (up to 15.6 m) that generates currents with speeds up to 2.1 m/sec. Maximum current speeds average 1.3 m/sec at the estuary head and 0.8 m/sec at the mouth.

The estuary contains six major intertidal sand bodies that range in length from 0.8 to 5.6 km. All six sand bodies are asymmetric in cross section; three form an ebb-tidal delta. Bedforms include ripples, dunes, and sandwaves.

Mean-grain size ranges between -1.2 and 3.2 ^phgr; sediment is finer and better sorted at the estuary head than at the mouth. Cumulative-curve dissection reveals a large traction population at the estuary mouth that is absent at the estuary head; 80% of all sediment at the estuary head is statistically identical to the sum of the intermittent suspension and suspension populations at the estuary mouth.

The inverse relation between current speed and mean-grain size results from hydraulic sorting at the estuary mouth. Sediment in the intermittent suspension and suspension populations is transported toward the estuary head where it is trapped by a flood-dominant hydraulic regime; sediment in the traction population remains at the estuary mouth.

In the Avon River estuary, the hydraulic environment is reflected more strongly in cumulative-curve shape than in mean-grain size.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC