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Shell Collage Excavated from Drum Cliff Member Matrix, Calvert County, Maryland

I_gotta_rock

Carefully exposed all of these with a dental pick from the lump of matrix in which they were encased. Nothing got moved, just glued insitu.

top: Scaphella virginiana

center left: Mariacolpus octonaria

center right: Ecphora megane

bottom left: arcadae indet. sp.

bottom right: Glossus sp.


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Calvert Cliffs

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Photo Information for Shell Collage Excavated from Drum Cliff Member Matrix, Calvert County, Maryland

Taken with Apple iPhone 5c

  • 4.1 mm
  • 1/20
  • f f/2.4
  • ISO 50
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Atsa nice, I'ma like!

Did you have to stabilize the matrix with anything? I figure it could fall apart easily if you can prep it out with a dental pick.

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31 minutes ago, Wrangellian said:

Atsa nice, I'ma like!

Did you have to stabilize the matrix with anything? I figure it could fall apart easily if you can prep it out with a dental pick.

Extremely easily! I lost innumerable shells trying to get them out of this matrix. This came off a corner of the block as I felt around. The lump came off with the Scaphella attached to matrix only at the aperture. I let it dry out a little bit so that I could scrape the sand away without it pulling at the shell material. When it was as good as I was going to get it without destroying it, I doused it with Paleobond so it didn't disintegrate when it dried completely. I dip fossils from this matrix in a bowl of diluted Elmer's glue instead sometimes, but only sturdier shells that I'm fairly sure will not dissolve when they get wet. I've lost a fair few shells just trying to rinse off the sand in still water, too.

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I didn't know the shells themselves would be so fragile, but that makes sense.

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4 hours ago, Wrangellian said:

I didn't know the shells themselves would be so fragile, but that makes sense.

The matrix is acidic. In some members of the formation, it is acidic enough to completely dissolve the shells so only impressions remain, or maybe impressions with white powder. This member isn't THAT acidic, so the shells remain, but most of them are soft and mushy or brittle, depending on their chemical makeup. Chesapectins and Ecphora survive because they are a different chemical composition than most of the others, so tend to last better. The mussels in the attached picture were in the next member up. As you can see, there is really not much left of the actual shells but a powdery coating over the molds.

IMG_2444.jpg

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I know what you mean, We've got an Oligocene formation over here that is much like that last pic. Shells are powdery.

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