Flute Casts

Flute casts are irregular ridges that display a marked asymmetry.  The asymmetry of these structures allows for determination of paleocurrent direction—flows originate from the direction of the steeper side of the flute.  Flute casts typically have a "pointy" end, oriented in the upstream direction, and a more gentle, flared end that merges downstream into the bed surface.  Flute casts along the base of a given bed are usually of approximately the same size, but between beds or formations, may vary greatly in size. 

	Large flutes along the Gaspe Peninsula, Quebec.  These are the largest flute casts I've ever seen.  Flow was from the top of the image toward the bottom, as indicated by the pointier end of the flutes, particularly those near the center of the image.  That's Jerry Middleton holding the ruler.
	Here's another bed from the same unit along the Gaspe. These flutes are oriented differently than those in the above image, and here flow is from the upper left toward the lower right.  This time, it's Orrin Pilkey for scale.
	These flute casts are closer to the usual size.  The flows that produced these flutes traveled from the right toward the left of the image.
	Here's a closer view of the flutes in the above image.  You can clearly see the asymmetry of the structures, and how the shape changes from a distinct point at the apex of the structure to a gentle flare at the downstream end.  These are classic.
	The base of the bed shown in this photo is more complexly deformed than the others on this page.  Many of the flutes are nearly superimposed on one another, but you can still determine paleoflow direction--in this case from right to left.
	This is a two-fer example.  The bed in the foreground shows really nice flute casts, showing flow from right to left.  The beds in the background contain a different type of sole marking, called wrinkle marks.
	This example shows flute casts on the base of several beds, but the difference here is that the flutes on different beds show different paleoflow directions.   The foreground bed gives flow directions from bottom to top, while the prominent background bed shows flow from right to left.
	This photo shows how concentrated flute casts can become on the base of some beds. The photo below shows a closer view of a portion of this bed.
	Blow-up of the above image showing concentration of flute casts.   These flutes show paleoflow from the right toward the left of the photo.
	Here's another sedimentary structure two-fer.  The large structure on the right side of the photo is a flute cast (shown enlarged in the photo below).  The smaller features are bounce marks, created by an object of some kind bouncing across the substrate.
	This is a closer view of the flute in the above image.  In this photograph, it's possible to get a sense of the flow regime that scoured the underlying bed on which this flute formed.  Look closely and you'll be able to see a kind of a swirling fabric, running from the lower edge of the flute, in a clockwise direction, across to the upper edge.  This fabric is best visible in roughly the center of the photo, and was likely created by swirling vortices in the turbulent erosive flows.
	This image shows a cross-sectional view of two separate flute casts.   The cut is perpendicular to the paleoflow direction, such that flow was coming toward you as you look at this photo.  Note the characteristic bulbous shape of these flutes.
	Another flute cast in cross section.  This image shows the marked asymmetry of these structures.  In this case, the steeper side is toward the left (toward the knife) and the flute merges into the base of the bed toward the right, indicating paleoflows from the left to the right.