Choptank Formation

Middle Miocene, 15 to 12 million years ago. Interbedded brown to yellow very fine-grained to fine-grained sand and gray to dark bluish-green argillaceous silt; locally indurated to calcareous sandstone; prominent shell beds; thickness 0 to 50 feet. (Source: USGS On-line Spatial Data)

The first four images are death assemblages from one layer. The matrix is a gray fine sandstone.

This specimen consist of Glossus fraterna (the clam) and Turritella plebia (the snail). Notice that both an individual clam and snail have been attacked by predatary snails.

This is the other side of the group with the same clam and snail.

The clams in this specimen are mostly Anadara staminea. There are two Astarte obruta at the top center and lower down to the right. Partialy hidden near the bottom of the first Astarte is an example of Corbula inaequalis. The holes in the Anadara specimen at the bottom center may be the result of borings by a demosponge.

This is a more diverse group and includes: Mercenaria plena; Corbula idonea; Ecphora tricostata; Lunatia heros; Chesapecten nefrens; Turritella plebia; Astarte obruta; Panope whitfieldi; and Glossus fraterna.

You can see in this group how broken up the shells are. Only a few are not broken or split.