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.
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.