5Sedimentary structures Stratification and bedforms:Bedding-plane markings:Bedding and lamination - Laminated bedding - Graded bedding - Massive (structureless) beddingBedformsIrregular stratificationGroove cast; striations, bounce, brush, prod, and roll markFlute castLoad castMudcracks and syneresis cracksOther structures: - Sedimentary sills and dykes
6BeddingBeds, or strata are tabular or lenticular layers of sedimentary rock that have lithologic, textural, or structural unity that clear distinguishes them from layers above and bellow.Groups of similar beds or cross beds are called bedsets.
7Description of bedding Thick bedsBeds that are 30–100 cm thick. Very thick beds are tens of m thick.Medium bedsBeds that are 10–30 cm thickThin bedsBeds that are less than 3 cmthickThinly laminated bedsBeds that are less than 0.3 cm thickRhythmic bedsA sequence of beds in which the contrast between adjacent beds is repeated periodically for a substantial thickness of strata
8Description of bedding Lateral continuityTermination - merging of bedding planes (pinch-out) - lateral gradation of composition (die out) - meeting of crosscutting features such as channel or unconformityParallel beddingWavy bedding
9Mechanisms of bedding formation sedimentation from suspensionhorizontal accretion from a moving bed load (bed load is a part of the stream load that moves on or immediately above the stream bed; stream load is all material that is transported by a stream)encroachment into the lee of an obstacle.
10Graded bedding Gradual change of grain size within a bed Commonly produced by turbidity currentsHelps to determine the base (lower surface) and the top (upper surface) of a bed
11GRADED BEDDINGTOPBOTTOMConglomeratesSandstonesUp The Section
12Bedforms – structures of the surface of a bed Cross-beddingRipple cross-laminationFlaser and lenticular bedding