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Open Access Publications from the University of California

A Test of Three Shellfish Seasonality Methods: Preliminary Results


This paper reports preliminary results of investigations into the use of bivalves as seasonal indicators in archaeology. Specifically, it addresses three proposed methods used for deriving seasonality for the southern California coastal region (Drover 1974; Lyons 1978; Macko 1983) based on external shell features. Basic to each of these seasonality methods is the premise that each year, usually during winter, Chione species bivalves will form an externally visible growth-cessation band (often termed the "winter" or "annular" break ring or band) along the outermost margins of their shells. As the bivalve resumes growth during the remainder of the year, this "annular" band is incorporated as a feature of the external shell structure of the bivalve. It is assumed that these "annular" bands therefore are permanent marks recording each year in the life of a bivalve across the surface of its shell from the hinge to the margin, and that the growth between each band occurred in one year. Based on this premise, three methods (each simply variations on the same theme) have been proposed to obtain seasonal data from shell remains recovered from archaeological sites on the southern California coast. A fourth method (Weide 1969) employing Pismo clams is not considered here because that species is somewhat sparse in most southern California shell middens.

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