Within Bedding Structures
These structures are within sedimentary bedding and can help with the interpretation of depositional environment and paleocurrent directions. They are formed when the sediment is deposited.
- Cross bedding - This can include ripples and dunes, or any cross stratification caused by currents. The "cross" refers to the angle between flat bedding and the inclined bedding of the cross bed, typically about 34 degrees. Paleocurrents are best found from cross beds that have 3D architecture exposed so you can measure the axis of the trough of the cross bed.
- Hummocky cross-stratification is made up of undulating sets of cross-laminae that are concave-up (swales) and convex-up (hummocks). These cross-beds gently cut into each other with curved erosional surfaces. They form in shallow-water, storm-dominated environments. Strong storm-wave action erodes the seabed into low hummocks and swales that lack a specific orientation.
- Imbrication is the stacking of larger clasts in the direction of flow.
- Normal graded bedding occurs when current velocity changes and grains are progressively dropped out of the current. The most common place to find this is in a turbidite deposit. This can also be inverted, called reversed graded bedding, and is common in debris flows.
- Bioturbation - Biological stirring of sediment (i.e. burrowing); typical of shallow water, finer-grained sediment.
Read more about this topic: Sedimentary Structures
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