Turbidites and Turbidity Currents Flashcards

A high-velocity current that flows down gentle gradients because the sediment within it makes it denser than seawater.

An upward fining deposit of greywacke deposited from a turbidity current.

On the continental slope; flow from the continental shelf and deposited on the abyssal plain.

<p>Rivers deposit sediment on the continental shelf; if they are overloaded, or shaken by a small earthquake, the sediment rushes down the continental slope.</p> Signup and view all the answers

<p>70-90 km/h, due to high density and low friction with the surface of the continental slope.</p> Signup and view all the answers

<p>Submarine fans on the continental rise or ocean basins.</p> Signup and view all the answers

<p>It has a shallow incline of 4°, causing the flow to lose energy and slow down.</p> Signup and view all the answers

<p>The body is a mass of turbulent eddies, maintaining suspended particles.</p> Signup and view all the answers

<p>Because the body material travels faster than the head material; it is forced back and around, returning to the body.</p> Signup and view all the answers

<p>The idealized sequence of sedimentary layers and structures in a turbidite.</p> Signup and view all the answers

<p>Bouma sequence.</p> Signup and view all the answers

<p>A-E; A being deposited first.</p> Signup and view all the answers

<p>Coarse bed of pebble-granule size conglomerate, in a sandy matrix.</p> Signup and view all the answers

<p>Graded bedding, erosional base; high velocity.</p> Signup and view all the answers

<p>Coarse, then medium sandstone (greywacke).</p> Signup and view all the answers

<p>Parallel laminations, graded bedding; decreasing current.</p> Signup and view all the answers

<p>Sandstone (greywacke).</p> Signup and view all the answers

<p>Cross bedding (small-scale); decreasing current.</p> Signup and view all the answers

<p>Fine sandstone, then siltstone.</p> Signup and view all the answers

<p>Ripples, cross bedding (small scale); low velocity.</p> Signup and view all the answers

<p>Shale, may contain pelagic marine fossils like graptolites.</p> Signup and view all the answers

<p>Parallel laminations; interturbidite.</p> Signup and view all the answers

<p>Upwards fining.</p> Signup and view all the answers

<p>Because as the current loses energy, it deposits the coarsest material first, forming graded beds.</p> Signup and view all the answers

<p>Formed when spiral eddies develop in the flow; they scour elongate hollows in the underlying mud, which become shallower and wider down-current; they are preserved as casts.</p> Signup and view all the answers

<p>They open in the direction of flow.</p> Signup and view all the answers

<p>Erosion of the underlying sediment (if lithified) produces rip-up clasts.</p> Signup and view all the answers

<p>Indentations in underlying sediment caused by objects being carried along the bedload can be prod/bounce marks/linear grooves.</p> Signup and view all the answers

<p>Because the flow is high energy so has enough energy to carry 'tools'.</p> Signup and view all the answers

<p>When flows are deposited quickly on each other, they are still wet and soft; the density of the coarser sand sinks into the fine mud, producing load casts and flame structures.</p> Signup and view all the answers

<p>Flute cast.</p> Signup and view all the answers

<p>Rip-up clast.</p> Signup and view all the answers

<p>Tool mark.</p> Signup and view all the answers

<p>Load cast/flame structure.</p> Signup and view all the answers

<p>Top to bottom: E, D, C, B, A.</p> Signup and view all the answers