A paleocurrent or paleocurrent indicator is a geological feature (typically a sedimentary structure) that helps one determine the direction of flowing water in the geologic past. This is an invaluable tool in the reconstruction of ancient depositional environments.[1]
There are two main types of paleocurrent indicators:
Unidirectional, which give a clear, single direction of flow
Bidirectional, which give a good linear direction, but it is unclear which direction along the linear trend the water flowed.
Paleocurrents are usually measured with an azimuth, or as a rake on a bedding plane, and displayed with a Rose Diagram to show the dominant direction(s) of flow. This is needed because in some depositional environments, like meandering rivers, the paleocurrent resulting from natural sinuosity has a natural variation of 180 degrees or more.[2]
Below are a partial list of common paleocurrent indicators:
Unidirectional
Flute cast, showing paleocurrent to the upper right of pic
Cross-bedding – the axis of a trough cross bed or the down-dip direction of a tabular cross bed point the direction of paleo flow.
Current ripple marks – will have the short side of the ripple pointing down stream.
Sole markings/flute casts – the short, steep side will point up stream, and the long, tapered side points down stream.
Imbrication – clasts line up in the direction of flow.
