Friday Rocks #39: Soft Sediment Deformation and Flame Structures

[caption id="attachment_595" align="aligncenter" width="610"]Soft sediment deformation at Point Lobos, California Soft sediment deformation at Point Lobos, California[/caption]

This weeks photo comes from a spectacular outcrop at Point Lobos, California. If you are there, try to time it with low tide, or you'll miss this.

Soft sediment deformation occurs in unlithified sediments. Sometimes a trigger such as rapid loading by a mass wasting event or an earthquake is necessary to cause the deformation.

 

Flame structures (middle right in the photo) form when the overlying sediment (orange) is denser than the underlying sediment (black). This causes the overlying sediment to sink down into the low sediment, which pushes the lower sediment up. The structures formed resemble flames, hence the name.

Also in the photo (near the pointing finger) is a more competent sediment that was normal faulted as the unlithified sediment below it deformed. What other structures do you see in the photo?

Here's another shot of the flame structures.

[caption id="attachment_596" align="aligncenter" width="610"]Point Lobos Flame Structures Point Lobos Flame Structures[/caption]

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