Bedding Plane Structures
Bedding Plane Structures are commonly used as paleocurrent indicators. They are formed when sediment has been deposited and then reworked and reshaped. They include:
- Sole markings form when an object gouges the surface of a sedimentary layer; this groove is later preserved as a cast when filled in by the layer above. They include:
- Flute casts are scours dug into soft, fine sediment which typically get filled by an overlying bed. Measuring the long axis of the flute cast gives the direction of flow, with the scoop-shaped end pointing in the upcurrent direction and the tapered end pointing downcurrent (paleoflow direction). The convexity of the flute cast also points stratigraphically down.
- Tool marks are a type of sole marking formed by grooves left in a bed by objects dragged along by a current. The average direction of these can be assumed to be the axis of flow direction.
- Mudcracks form when mud is dewatered, shrinks, and leaves a crack. This tells you that the mud was saturated with water and then exposed to air. Mudcracks curl upwards, so they can be used as geopetal structures. Syneresis cracks form in a similar way, with the exception that they are never exposed to air, instead being caused by changes in the salinity of the surrounding water.
- Raindrop impressions form on exposed sediment by raindrop impacts.
- Parting lineations are subtly aligned minerals that form in the lower part of the Upper Flow Regime within plane beds.
Read more about this topic: Sedimentary Structures
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