Determination of Paleotemperature and Paleosalinity from

Shells of Mercenaria campechiensis from

Seahorse Key Midden, Cedar Key, Florida


LDEO Summer Intern Project: Andy Petter


Also: Peter deMenocal, Brad Linsley, Mary Elliot, Andrew Petter, Irvy Quitmeyer, Doug Jones



Cedar Key, Florida is located on the Gulf Coast between Pensacola and Tampa Bay. (Map) It was occupied year round by Gulf coastal Indians of the Weeden Island culture from 300-800 A.D. The Indians were hunters and gatherers who included fish and shellfish in their diets. After eating the fish, the bones and shells were deposited in a midden. The midden is valuable to archaeologists because it contains a stratigraphically constrained record of Indian life. The midden is valuable to paleoclimatists because the shells contain a climatic record of the environment that they grew in. Combined, these two records give us the ability to evaluate the influence of climate on Indian society, though no attempt to do this is made at this website.

We obtained 48 hard clam (Mercenaria campechiensis) shells from the Florida Musuem of Natural History that had been excavated from the Seahorse Key Midden. We prepared them for sampling by cutting out a 3-4 mm thick section running from the umbo to the ventral margin along the axis of maximum growth with a table saw. One side of the section was ground, flattened, and polished with various lapidary wheels. This side was glued to a 3" by 6", 1/4" thick glass slide with epoxy. A diamond grinding saw was then used to grind away the other side of the section until the section was 0.5-1.5 mm thick. This side was then flattened and polished in the same manner as the other side and the shell was ready for sampling.


Hard clams and the use of oxygen isotope ratios

Sampling techniques

What do we want to know?


Unanswered questions

Scanned images of clam cross-sections


Questions? E-mail Andy Petter at