Images On the Topic of sedimentary structures

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Load Casts at Pass Lueg

View looking up at the underside of a C unit in a Lofer cyclothem. The numerous bulbous forms which project downwards are called load casts. Load casts are often associated with turbidites. One bulb would be around 10-20 cm in diameter.

load cast sedimentary structures

Cross-sets

Sedimentary structures like these cross-sets form through the migration of sand dunes on the sea bottom under the action of a current. They can be used to infer flow directions and energy, and even aid in the interpretation of the general depositional system. Pleistocene calcarenites from Le Castella, Calabria, Italy.

sedimentary structures cross-stratification Pleistocene

Asymmetric ripples

Current ripples are small asymmetric bedforms generated by movement of fine-grained sediment under unidirectional currents. The presence of climbing ripple lamination indicates rapid deposition from a sediment-laden flow. Upward transition from planar lamination to current ripple lamination is indicative of flow deceleration. Sequence of sedimentary structures (cf. Bouma sequence), grain size decrease, and cyclical repetition of bedding points to deposition from turbidity currents. Photo taken at the Varvito Park, Ito, Brazil, with exposures of Permian strata from the Itararé Group. Scale in cm.

sedimentary structures ripples lamination rapid deposition, turbidites Permian

Climbing ripples

When a fluid laden with sediment rapidly drops some of its load as it is flowing, a sedimentary structure named "climbing ripple lamination" can form. It is characterized by superimposed ripple crests (or ripple cross-sets) migrating in the direction of flow. Photo taken at the Varvito Park, Ito, Brazil, with exposures of Permian strata from the Itararé Group. Scale in cm.

sedimentary structures ripples cross-lamination rapid deposition Permian

Mud cracks and ripples

On the surface of this Cretaceous mudstone bed from the Sousa Basin of Brazil, one can see both polygonal cracks (indicative of subaerial exposure) and wave ripples (indicative of a thin cover of water).

sedimentary structures Cretaceous