Overbank Flow
from a Sinuous Submarine Channel: Process and Product
Kane, Ian1, William. D.
McCaffrey1, Jeff Peakall1 (1)
Key differences between flow in subaerial
and submarine channels are 1) the absence of a free upper surface 2) a reduced
density difference between flow and ambient fluid and 3) the nature of overbank
flow. Super-elevated flow spilling from the channel builds levees through
deposition of sediment. This levee growth has implications for the downstream
evolution of, and deposition from, the within channel flow. Here we report
detailed experiments which examine this process. A series of experiments were
run in a tank 1.7 m2 and 1.5 m deep, with an inlet channel centered on one
face. An ‘incised' channel was cut out of acrylic sheets of varying thickness
so that the channel depth could be systematically altered. Suspensions of mixed
grain-size sediment (glass ballotini and silica flour) were mixed in a 10 liter
lock box and rapidly released. Ultrasonic velocity profiling and siphon
sampling were used to measure flow velocities and sediment concentrations
respectively. Post-flow sediment distributions were accurately mapped. Flows
were observed to follow the curved channel with very little overspill, even in
cases where the mean flow height was more than twice that of the levees. The
degree of overspill is quantified as a function of sediment stratification.
Comparison is made between experimental overbank deposits and data from an
ancient system, the Cretaceous Rosario Fm.,
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California