Sedimentary structures Flashcards
1
Q
Ripple marks
A
Sand grains transported by saltation in high energy environments
2
Q
Symmetrical Ripple Marks
A
Oscillating currents, most common on beaches
Tidal action moves sediment up and down (bi-directional flow)
3
Q
Asymmetrical Ripple Marks
A
Currents that travel in one direction (uni-directional flow)
Common in rivers, shallow seas and desert environments
4
Q
Graded bedding
A
Energy levels in water drop and sediment settles out of suspension
Found in sandstones and conglomerates
5
Q
Cross-bedding
A
Right way up when concave upwards
Flattens out at the base, cut out at the top due to erosion
6
Q
Dessication cracks
A
Form in clay-rich sediments
Has a v-shaped cross section
Loss of water from evaporation causes mud to contact.
Found in arid environments such as playa lakes
