Sole Markings

Image Courtesy of the British Geological Survey

Flute Casts

Sole marks are sedimentary structures found on the bases of certain strata that indicate small-scale (centimeter-scale) grooves or irregularities. This usually occurs at the interface of two differing lithologies. They are commonly preserved as casts of these indents on the bottom of the overlying bed (like flute casts). This is similar to casts and molds in fossil preservation. Occurring as they do only at the bottom of beds, and their distinctive shapes, they can make useful "way up" structures and paleocurrent indicators. Sole markings are found most commonly in turbidite deposits. Scour marks and Flute casts are scours dug into soft, fine sediment which typically get filled by an overlying bed (hence the name cast). Measuring the long axis of the flute cast gives the direction of flow, with the tapered end pointing toward the flow and the steep end up current. The concavity of the flute cast also points stratigraphically up. Tool marks are a type of sole marking formed by groves left in a bed by things like sticks being dragged along by a current. The average direction of these can be assumed to be the flow direction, though it is bimodal, so it could be either way along the mark. Load casts are blobs that form when a denser sediment slumps down on and into a less dense water-saturated sediment below. Groove casts form when high velocity flows, such as those associated with a turbidite, create a visible pattern on an underlying bed.

Photograph from Y. Tang et al., Geoscience Frontiers 3(5) (2012)

Flute Casts

Late Triassic

Zhuwo Formation

CHINA