SEDIMENTARY STRUCTURES
SEDIMENTARY STRUCTURES Large scale features Laminae < 1 cm, Beds > 1cm UPPER BEDDING : Rain print, Ripple marks, Mud cracks LOWER BEDDING - (Erosional structures) S cour marks : Flute cast : have a bulbous nose at their upstream end helps to infer paleocurrent direction Obstacle scour / Current crescent Longitudinal scour , Gutter casts Tool marks : Groove cast, Chevron marks, Prod casts, Bounce marks, Skip marks (Can’t identified in vertical section) SYN-DEPOSITIONAL : Graded bedding, Cross bedding/lamination POST DEPOSITIONAL/DEFORMATIONAL Load cast - gravitational instability Convolute bedding Dish and pillar structure - water escape structures, fluidisation Ball and pillow structure Slump structure BASED ON ENVIRONMENT Tidal : Herringbone, Sub-tidal : Double mud drapes Inter-tidal : Rain print, Mud crack, Adhesion ripple Storm : Hummocky cross Fluvial : Epsilon cross stratification TOP AND BOTTOM CRITERIA Oscillation ripple Load cast - soft sediment deformation...