1. Skip to navigation
  2. Skip to content
  3. Skip to sidebar


Callan Bentley's Snapshots

Go to page:
  1. Small mica-rich clast

    Snapshot Title: Small mica-rich clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    w/ reaction halo



  2. Large, mica-rich clast

    Snapshot Title: Large, mica-rich clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    bearing a reaction halo around it



  3. Light-colored clast

    Snapshot Title: Light-colored clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Apparently well rounded.



  4. Hammerhead

    Snapshot Title: Hammerhead
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    for scale



  5. Shadow

    Snapshot Title: Shadow
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    of the GigaPan



  6. Fresh vs. weathered surfaces

    Snapshot Title: Fresh vs. weathered surfaces
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    This rock rusts!



  7. Lichen

    Snapshot Title: Lichen
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Not clasts



  8. Foliated clast

    Snapshot Title: Foliated clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Where the (coarser; gneissic) foliation internal to the clast is oblique to the regional foliation in the surrounding matrix.



  9. Quartz clast

    Snapshot Title: Quartz clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Oblique to foliation.



  10. Hammer for scale

    Snapshot Title: Hammer for scale
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Here's the top of the hammer handle.



  11. Weathered out clast

    Snapshot Title: Weathered out clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    You can see a little tail of relatively-unweathered biotite-rich clast to the right of the joint trace.



  12. Bird poop

    Snapshot Title: Bird poop
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Probably a heron.



  13. Recessive weathering

    Snapshot Title: Recessive weathering
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Some clasts are less chemically stable than the surrounding matrix, and weather out to make clast-shaped holes in the rock face.



  14. Another reaction halo

    Snapshot Title: Another reaction halo
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Rimming this mica-rich clast



  15. Felsic clast

    Snapshot Title: Felsic clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Mica poor, relative to matrix



  16. Reaction halo

    Snapshot Title: Reaction halo
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Where the clast reacted w/ surrounding matrix.



  17. Fishlike clast

    Snapshot Title: Fishlike clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Pointy tip and frayed tail



  18. Elongate, flat dark schist clasts

    Snapshot Title: Elongate, flat dark schist clasts
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    And chunkier light-colored clasts.



  19. Contrasting clasts

    Snapshot Title: Contrasting clasts
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Dark-colored, mica-rich clasts tend to be flattened parallel to the plane of foliation. Lighter colored clasts tend to be more chunky and equant.



  20. Sense of scale

    Snapshot Title: Sense of scale
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Tip of hammer (the only part that's in focus!)



  21. Chlorite clast weathering away

    Snapshot Title: Chlorite clast weathering away
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    more rapidly than surrounding rock.



  22. Fresher surface

    Snapshot Title: Fresher surface
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    The rusty, hydrolysed weathering rind has peeled off here, showing fresher (grayer) rock beneath.



  23. Recessive weathering

    Snapshot Title: Recessive weathering
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    of a chlorite-rich clast



  24. Mafic clast

    Snapshot Title: Mafic clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    No reaction rim, though



  25. Slickensides

    Snapshot Title: Slickensides
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Common feature in these rocks.



  26. Two squashed clasts

    Snapshot Title: Two squashed clasts
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Ellipsoidal.



  27. Light-colored clasts

    Snapshot Title: Light-colored clasts
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Some with reaction rims, others (milky quartz) with no obvious reaction rim.



  28. Clast

    Snapshot Title: Clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    of milky quartz



  29. Felsic clast

    Snapshot Title: Felsic clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Must be older than the Sykesville Formation that includes it.



  30. Big tabular clast

    Snapshot Title: Big tabular clast
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    A big slabby chunk of quartzite included in the metagraywacke/schist matrix.



  31. Hammer for scale

    Snapshot Title: Hammer for scale
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Here is the butt end of the hammer.



  32. Reaction rim

    Snapshot Title: Reaction rim
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Another signal of chemical re-equilibration between clast and matrix.



  33. Mafic clast w/ reaction rim

    Snapshot Title: Mafic clast w/ reaction rim
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Amphibolite?



  34. Milky quartz inclusions

    Snapshot Title: Milky quartz inclusions
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    exposed on the plane of foliation.



  35. Hammer for scale

    Snapshot Title: Hammer for scale
    Taken by: Callan Bentley

    Image: Sykesville Formation, Chain Bridge Flats, DC
    Image Owner: Callan Bentley



    Description:

    Top of the handle



  36. Students

    Snapshot Title: Students
    Taken by: Callan Bentley

    Image: Gastropod duplex w/ people for scale
    Image Owner: Callan Bentley



    Description:

    Zack, Matt, and Jake, checking out the structural geology.



  37. Percussion marks

    Snapshot Title: Percussion marks
    Taken by: Callan Bentley

    Image: Second Generation Quartz, Billy Goat Trail
    Image Owner: Marissa Dudek



    Description:

    Great examples.



  38. Percussion marks

    Snapshot Title: Percussion marks
    Taken by: Callan Bentley

    Image: Second Generation Quartz, Billy Goat Trail
    Image Owner: Marissa Dudek



    Description:

    Bouncing cobbles in the ancient Potomac River slammed into this postively-weathering vein to make these features.



  39. A closer look

    Snapshot Title: A closer look
    Taken by: Callan Bentley

    Image: Faulted- Tonoloway
    Image Owner: Alan Pitts



    Description:

    Details here:
    gigapan.com/gigapans/174628



  40. Slogan

    Snapshot Title: Slogan
    Taken by: Callan Bentley

    Image: Syncline Fold, Corridor H
    Image Owner: Marissa Dudek



    Description:

    Resolution's good enough to read off the fine print on the license plate.



Go to page: