P. Traykovski, J. Irish and J. Lynch's STRATAFORM RESEARCH

Part of the ONR sponsored STRATAFORM project was designed to study the processes that control continental margin stratigraphy. In particular a series of observations were conducted on the Northern California continental shelf near the Eel river to examine flood deposits caused by winter storms. With this in mind the WHOI Ocean Acoustics Lab deployed several systems to observe sediment transport in the bottom boundary layer at the mud-sand transition in the winter of 1995-96, and over the entire water column on three positions on the STRATAFORM K-line in the winter of 1997-98.

The location of the 1995 and 1997 flood deposits is shown above (Data courtesy of R. Wheatcroft):

Here are some preliminary images from our 1995-96 Strataform deployment on the USGS Geoprobe tripod located at S50:

Overview of our data for the entire deployment.

A slightly more detailed look at the period between Feb. 4th and Feb. 11th. In particular notice how the thickness and concentration of the suspended mud layer is modulated by the tidal flow during the period from 2/08 to 2/10.

High frequency (2 Hz) Acoustic images of the mud layer present at on February 9th. On Jan 19th (left half of image) It appears the there is no high concentration (or perhaps a very dilute) mud layer present since "puffs" of sand with settling velocities of 0.5 to 1 cm/s are visible in the image. The constant layer (with some thickness modulation by surface gravity waves) that is visible on Feb. 9th (right half of image) is not typical of sand suspensions since the sediment does not settle out after a wave group has passed. We interpret this layer as a high concentration mud layer trapped in the wave boundary layer.

Here is a picture showing the equipment we deployed in the winter of 1997-98 at the Strataform site.
The Moorings at K 20, 40, and 60, and tripods at K 20, and 60 were sucessfully recovered. Unfortunately the tripod at K40 was buried in mud and broken and thus could not be recovered. Preliminary results should be available soon!