About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)


Journal of Sedimentary Research
Vol. 85 (2015), No. 8. (August), Pages 885-902
Research Articles

Flow Behavior of Ponded Turbidity Currents

Marco Patacci, Peter D.W. Haughton, William D. Mccaffrey


Sea-floor topography can constrict, deflect, or reflect turbidity currents resulting in a range of distinctive deposits. Where flows rebound off slopes and a suspension cloud collects in an enclosed basin, ponded or contained turbidites are deposited. Ponded turbidites have been widely recognized in slope mini-basins and on small, structurally confined basin floors in strike-slip and foreland-basin settings. They can have a variable internal structure the significance of which remains poorly understood in terms of flow behavior. New experiments demonstrate that the ponding process can comprise up to four phases: 1) cloud establishment, 2) inflation, 3) steady-state maintenance, and 4) collapse. The experiments explored the behavior of sustained turbidity currents draining into small basins and show that the ponded suspensions that form are characterized by an important internal interface; this divides a lower outbound-moving Previous HitlayerNext Hit from an upper return Previous HitlayerNext Hit. The basal Previous HitlayerNext Hit evolves to constant concentration and grain size, whereas the upper Previous HitlayerNext Hit is graded (concentration and grain size decrease upward). During the cloud inflation stage, the concentration and velocity profiles of the ponded suspension evolve, and this phase can dominate the resulting deposit. Outbound internal Previous HitwavesNext Hit can travel along the interface between the outbound and return layers and impinge against the confining slope, and their amplitude is highest when the density contrast between layers is greatest, e.g., when the input flows are thin and dense. The experiments show that flow reversals can arise in several ways (initial rebound, episodic collapse of the wedge of fluid above the counter slope, “grounding” of the internal velocity interface) and that despite steady input, velocities decay and the deposit grades upwards. Internal Previous HitwavesNext Hit emanate from the input point, i.e., do not form as reflections off the counter slope. The internal grain-size interface within the suspension may dictate textural trends in sands onlapping the confining slopes. Where flows are partially ponded, internal Previous HitwavesTop can generate pulsing overspill to basins down dip.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Protected Document: $10
Internal PDF Document: $14
Open PDF Document: $24