A sediment gravity flow is one of several types of sediment transport mechanisms, of which most geologists recognize four principal processes. These flows are differentiated by their dominant sediment support mechanisms, which can be difficult to distinguish as flows can be in transition from one type to the next as they evolve downslope.
This turbidite from the Devonian Becke-Oese Sandstone of Germany is an example of a deposit from a sediment gravity flow. Note the complete Bouma sequence.
Dish structures in the deposit (Bouma A, Lowe S3) of an ancient liquefied sediment flow preserved in outcrop.
Debris flows filling a gully after intense storms of 2010 in Ladakh in the Himalayas.
Debris flow deposit in outcrop showing free-floating large clasts suspended in a clay matrix.
A turbidite is the geologic deposit of a turbidity current, which is a type of amalgamation of fluidal and sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean.
Turbidites are deposited in the deep ocean troughs below the continental shelf, or similar structures in deep lakes, by underwater avalanches which slide down the steep slopes of the continental shelf edge. When the material comes to rest in the ocean trough, it is the sand and other coarse material which settles first followed by mud and eventually the very fine particulate matter. It is this sequence of deposition that creates the Bouma sequences that characterize these rocks.
Turbidite sequence. Carboniferous Ross Sandstone Formation (Namurian), County Clare, Western Ireland (USGS image)
Complete Bouma sequence in Devonian Sandstone (Becke-Oese Quarry, Germany)
Gorgoglione Flysch, Miocene, South Italy
