M.A. Theses: David Bruce Saxon Maxwell, 1989

Growth Coloration: A Method for Determining the Season of Collection of Archaeological Shellfish

Marine bivalves are often studied as indicators of the season of occupation of coastal archaeological sites. Literature review shows that most studies are based upon faulty assumptions about shell growth. The potential of a recently introduced technique for determining the season of death of marine bivalves is examined and tested. The technique records season patterns in the growth coloration of the ventral margin of modern shells. The margin will appear either opaque or translucent when viewed in thin section. Ratios of opaque and translucent shells are recorded for each month of the year. An estimate of the season of death of prehistoric shells can be made through comparison with modern ratios.

Literature reviews of the mechanisms of shell growth, of types of archaeological analysis based upon shellfish remains and of previous archaeological studies of the season of death of marine bivalves are provided. Appropriate methods for collecting, sectioning, and analyzing modern comparative shells, as well as the time required for these activities, and the reliability of the results are discussed.

It can be concluded that the bivalve Protothaca staminea, common in archaeological sites in British Columbia, is the most useful species for archaeological season of death studies. This species displays the most distinctive seasonal change in growth coloration, and is the easiest to analyze in terms of time expenditure. Future researchers should concentrate on this species.