Sediment patterns (w7 handout)

Question 1

Tool marks

Answer 1

• made by string currents pushing rolling bouncing objects across the floor
• subsequent sedimentation infills scours –> marks at bottom of beds, “way up” indicator

Question 2

Flame structure/ Watre escape features

Answer 2

heavy, course grained sediment dumped on top of fine grained, wateer . filled sediment
water squeezed upwards and injected into the bed above
way up indicator

Question 3

Graded bedding

Answer 3

sediment deposited from a current that is slowing . down
largest grains are deposited first , smaller and smallere grains as the current dies away
way up indicator

Question 4

Flute casts

Answer 4

formed by strong currents scouring sediment from seafloor
subsequent sedimentation infills the scours
flute casts found bottom of beds and are a way- up and paleodirection indicator

Question 5

Crescent marks

Answer 5

formed b y strong currents flowing around obstacles in the sea floor
subsequent sedimentation infills the scours so crescent marks are found bottom of beds and are a way- up and paleodirection indicator

Question 6

Groove marks

Answer 6

formed by string currents pushing objects across the sea floor
subsequent sedimemntation infills the scours so grooves are found on bottom of beds and are a way up idicator
marks are symmetrical –> only sense of direction indicated