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
A turbidity current is most typically an underwater current of usually rapidly moving, sediment-laden water moving down a slope; although current research (2018) indicates that water-saturated sediment may be the primary actor in the process. Turbidity currents can also occur in other fluids besides water.
Turbidites are deposited in the deep ocean troughs below the continental shelf, or similar structures in deep lakes, by turbidity currents which slide down the slopes.
Longitudinal section through an underwater turbidity current
Turbidite interbedded with finegrained dusky-yellow sandstone and gray clay shale that occur in graded beds, Point Loma Formation, California.
