How is a turbidite actually deposited?

Area of Science:

• Geology
• Fluid Dynamics
• Sedimentology

Background:

• Turbidite deposition is traditionally modeled as a continuous process of sediment accumulation from waning density flows.
• Conceptual models envisage discrete events of continuous sediment accumulation at a falling rate.

Purpose of the Study:

• To investigate the fine-scale temporal dynamics of turbidite deposition.
• To challenge the traditional view of continuous sediment accumulation during turbidite events.

Main Methods:

• High-resolution computational fluid dynamics (CFD) simulations.
• Analysis of experimental turbidity currents with realistic grain-size composition.
• Comparison with rock-record examples.

Main Results:

• Turbidite deposition involves numerous brief episodes of nondeposition and transient erosion, not continuous accumulation.
• Hydraulic fluctuations, driven by Kelvin-Helmholtz waves, cause these interruptions in deposition.
• Experimental turbidity currents spent only 26-33% of their flow time depositing sediment.

Conclusions:

• The depositional timescale of a single turbidite is characterized by significant interruptions.
• The concept of stratigraphic incompleteness may extend to the depositional timescale of individual turbidites.
• Turbidity current dynamics are more complex than previously modeled, with implications for sedimentary records.