Studied by 3 people
unidirectional flow
fluid flows in consistent direction and sed structures form in response
flow separation
caused by obstacles on the bed due to lower pressure and pressure drag behind the object after a separation point
what does flow separation cause
differential erosion and deposition along a bed
origin of a ripple
cross beds
structures that can be used to infer the younging direction in sed sequence via stenos law of superposition
truncated tops and asymptotic toes
what structures occur when Fr<1
ripples, sand waves, dunes
what structures occur when Fr>1
plane flat beds
antidunes
chutes and pools
ripples
larger with larger grain sizes
dunes
larger with larger flow depths
upper stage plane beds
no flow separation since too turbulent
no leeward deposition
antidunes
form inphase with standing wave
low relief (~5 meter spacing)
migrate upstream
shallower with higher velocity
deeper with lower velocity
multidirectional flow
cause symmetrical waves
two distinct directions of unidirectional flow
herring bone
currents go in equal directions
positive relief
wave and current ripple bedforms
negative relief
fluid current makes holes
sole marks
features on bottom of beds that are molds or casts
flute casts
formed by eddies touching down bed bases and taper down current
tool marks
form from objects dragging along by current then molded
SECONDARY
------------
soft sediment deformation
forms from rapid sedimentation rates, leading to unstable sedimentary layer
water saturation leads to liquefaction
most common = load structures
ball and pillow
slumping
most extreme soft sediment deformation
soft layers are stuck together and preserved
burrows
soft sediment deformation
animals distrubing wet sediments
horizontal (sweeping)
vertical (pipes)
