sedimentary structures

Question 1

symmetrical ripple marks

Answer 1

form as sand grains are transported by saltation in high energy conditions. Bidirectional flow

Question 2

asymmetrical ripple marks

Answer 2

formed by currents that travel in one direction. Unidirectional flow

Question 3

cross bedding

Answer 3

unidirectional current moves sediment up shallow slopes, to avalanche down the steep side to rest.

Question 4

salt pseudomorphs

Answer 4

Halite crystals grow due to evaporation in an arid environment. these are later dissolved and refilled.

Question 5

imbricate structure

Answer 5

Pebbles rolled by a unidirectional current. Flattened pebbles stack against each other, arranged at right angles to direction of current.

Question 6

Graded bedding

Answer 6

largest and heaviest particles are able to settle out of suspensions first, followed by progressively finer material.

Question 7

desiccation cracks

Answer 7

form in clay rich sediments where loss of water causes shrinkage cracks to form. These polygons are later infilled by sediment.

Question 8

flute casts

Answer 8

found on the base of a bed as a result of erosion, usually from a turbidity flow. These are then filled with overlying sediment.

Question 9

what sedimentary structures are palaeocurrent indicators? x4

Answer 9

asymmetrical ripple marks
cross bedding
imbricate structure
flute casts

Question 10

what sedimentary structures are way up structures? x6

Answer 10

symmetrical ripple marks
asymmetrical ripple marks 
cross bedding 
graded bedding 
desiccation cracks 
flute casts

Question 11

which sedimentary structures form in high energy environments? x5

Answer 11

symmetrical ripple marks
asymmetrical ripple marks
cross bedding
imbricate structure 
flute casts

Question 12

which sedimentary structure is formed in low energy?

Answer 12

desiccation cracks

Question 13

which sedimentary structure is formed in variable energy?

Answer 13

graded bedding

Question 14

what environment do symmetrical ripple marks form in?

Answer 14

beaches

Question 15

what environments do asymmetrical ripple marks form in? x3

Answer 15

rivers, shallow seas, desert environment

Question 16

what environments does cross bedding form in? x3

Answer 16

desert, beach, river

Question 17

what environment do imbricate structures form in?

Answer 17

rivers

Question 18

what environments does graded bedding form in? x2

Answer 18

rivers into lakes

turbidity currents onto abyssal planes

Question 19

what environments do desiccation cracks form in? x2

Answer 19

playa lakes

arid areas

Question 20

what environments to flute casts form in? x4

Answer 20

beach/sea, rivers, turbidity