2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 320-19
Presentation Time: 1:30 PM


SHCHEPETKINA, Alina1, GINGRAS, Murray2, ZONNEVELD, John-Paul3 and PEMBERTON, S. George2, (1)Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G 2E3, Canada, (2)Earth and Atmospheric Science, University of Alberta, 1-26 Earth Science Building, Edmonton, AB T6G 2E3, Canada, (3)Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada

Within the reaches of the Petitcodiac estuary abundant fluid mud containing 24-67% clay is observed. The considerable amounts of clay contribute to the formation of creeping fluid-mud sheets and viscous streams on the tidal flats. Larger proportions of silt and sand in the deposits with lesser amount of clay fraction (6-23%) are associated with the development and preservation of current ripples and erosional ripple ridges on the channel bed and tidal flats.

We further observe that clay flocs entangle silt- and even sand-sized grains while in suspension. In the process of settling, silt and plankton particles are efficiently swept from the water column. As a result, the flocculated sediments contain up to 75 % silt and 10-15% of diatoms. Flocculation aquarium experiments, using Petitcodiac sediments, confirm our field observations.

SEM and microscopic imaging of fluid mud show that a substantial amount of bioclastic material (articulated and detached diatom frustules) is present within the flocs. Moreover, extracellular polymeric substance (i.e. mucous) appears to play a role in floc growth and aggregation.