8 April 2013

Nice plume

Posted by Callan Bentley

Another scene from the South Page Valley Martinsburg outcrop featured here last week: a slightly mud-bedecked example of plumose structure.

This plume occurs within a single graded bed (turbidite) of the Martinsburg Formation. It gets younger (paleo-up) to the right.

The joint propagation that the plumose structure records began somewhere vertically above the area of this photo, and advanced downward, with the plumes spreading out as it grew.

Note the different angles the subsidiary plumes / hackles make with respect to the “shaft” of the plume, depending on whether they advance (stratigraphically downward) left into the base of the graded bed, or (stratigraphically upward) right towards the muddier top of the bed.