Field Area 2: Swift Run Formation

Swift Run Formation
Our second field area required us to go on a hike off the beaten path.  I tredged through the woods, trying not to brush against any poison ivy.  This stop was to the Swift Run outcrop.  There are many different types of rocks here- sandstone, conglomerates and feldspathic wacke.  The feldspathic wacke was close to the source of from the Grenville orogeny.  It came from the deposition associated with the rift valley that became the Iapetus ocean.  We were to look for several primary and secondary structures.  Here’s what I found.

Primary Structures:

Here’s an example of some graded bedding going from coarse to fine.

Graded beds of the Swift Run Formation.

There was also cross bedding in the formation.

Cross bedding

The picture below shows rip up mud clasts.  These were areas of mud that got "ripped up" and deposited with the sands.

Rip Up Mud Clasts.  Photo courtesy of Laura Snyder.

I measured the orientation of the bedding and found it to be
-022°, 74°
-008°, 74°
-010°, 75°
-030°, 55°


Secondary Structures:
There were also areas of folding.

Fold found in swift run

Annotated fold

The picture below is of cleaving over printing the fold.  I took the orientation of the of the cleavage- 075°, 80°.

Cleavage

Extra Stop
Chillhowee Group
Since there was plenty of time left after our stop at Swift Run, we made an extra stop.  This one was to the Chilhowee group which is part of the Harpers formation.  The rocks here are meta-sedimentary.  Some structures seen here were plumose structures.

Plumos structure. Photo courtesy of Laura Snyder.

There was liesegang banding when iron from water stains the rock.

Liesagang banding

The bedding was orientated at 205°, 56° and the foliation was orientated at 025°, 29°.

Stereonet of bedding and foliation.